Siderite's Blog

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If you read an Angular book or read a howto, you will think that Angular is the greatest discovery since fire. Everything is neatly stacked in modules, controllers, templates, directives, factories, etc. The problem comes when you want to use some code of your own, using simple Javascript that does specific work, and then you want to link it nicely with AngularJS. It is not always easy. My example concerns the simple display of a dialog which edits an object. I want it to work on every page, so I added it to the general layout template. The layout does not have a controller. Even if I add it, the dialog engine I have been using was buggy and I've decided to just use jQuery.dialog.

So here is my conundrum: How to load the content of a dialog from an Angular template, display it with jQuery.dialog, load the information with jQuery.get, then bind its input elements to an Angular scope object. I've tried the obvious: just load the template in the dialog and expect Angular to notice a new DOM element was added and parse it and work its magic. It didn't work. Why can't I just call an angular.refresh(elem); function and get it over with, I thought. There are several other solutions. One is to not create the content dynamically at all, just add it to the layout, mark it with ng-controller="something" and then, in the controller, save the object you are interested in or the scope as some sort of globally accessible object that you instantiate from jQuery.get. The dialog would just move the element around, afterwards. That means you need to create a controller, maybe in another file, to be nice, then load it into your page. Another is to create some sort of directive or script tag that loads the Angular template dynamically and to hope it works.

Long story short, none of these solutions appealed to me. I wanted a simple refresh(elem) function. And there is one. It is called angular.injector. You call it with the names of the modules you need to load ('ng' one of them and usually the main application module the second). The result is a function that can use invoke to get the same results as a controller constructor. And that is saying something: if you can do the work that the controller does in your block of code, you don't need a zillion controllers making your life miserable, nor do you need to mark the HTML uselessly for very simple functionality.

Without further ado, here is a function that takes as parameters an element and a data object. The function will force angular to compile said element like it was part of the angular main application, then bind to the main scope the properties of the data object:

function angularCompile(elem, data) {
    // create an injector
    var $injector = angular.injector(['ng','app']);
            
    // use the type inference to auto inject arguments, or use implicit injection
    $injector.invoke(function($rootScope, $compile, $document){
        var compiled = $compile(elem || $document);
        compiled($rootScope);
        if (data) {
            for (var k in data) {
                if (data.hasOwnProperty(k)) {
                    $rootScope[k]=data[k];
                }
            }
        }
           $rootScope.$digest();
    });
}


Example usage:

angularCompile(dialog[0],{editedObject: obj}); // will take the jQuery dialog element, compile it, and add to the scope the editedObject property with the value of obj.


Full code:

OpenTranslationDialog=function(Rule, onProceed, onCancel) {
  jQuery.ajax({
          type: 'GET',
          url: '/Content/ng-templates/dialogs/Translation.html',
          data: Rule,
          success: function(data) {
            var dialog=jQuery('<div></div>')
              .html(data)
              .dialog({
                resizable:true,
                width:700,
                modal:true,
                    buttons: {
                      "Save": function() {
                    var url='/some/api/url';
                    jQuery.ajax({
                        type:'PUT',
                        url:url,
                        data:Rule,
                        success:function() {
                          if (onProceed) onProceed();
                              $(this).dialog( "close" );
                        },
                        error:function() {
                          alert('There was an error saving the rule');
                        }
                      });
                      },
                      Cancel: function() {
                    if (onCancel) onCancel();
                          $(this).dialog( "close" );
                      }
                    }
              });

            angularCompile(dialog[0],{Rule:Rule});
          },
          error:function() {
              alert('There was an error getting the dialog template');
                  }
      });
}


Before you take my word on it, though, beware: I am an Angular noob and my desire here was to hack away at it in order to merge my own code with the nice structured code of my colleagues, who now hate me. Although they liked angular.injector when I showed it to them :)

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Update 2015 August 28: I've replaced the function master.sys.fn_varbintohexstr with CONVERT, with the extra parameter 2, which translates a binary field into a hexadecimal string with no leading 0x. In addition to being ugly to use, fn_varbintohexstr is very slow.

Sometimes you need to create a unique identifier for a bunch of values so that you use it as an ID in the database. The immediately obvious choice is the CHECKSUM and BINARYCHECKSUM functions. But beware, the purpose of these functions is to detect changes in a string, not to uniquely identify it. It might seem strange, but the two concepts are very different. The change modification functionality is only meant to generate very different values on small changes. The uniqueness is trying to create a value as distinctive as possible for any string. That is why when you use a checksum you will get a lot of similar values for (very) different strings.

Enter HASHBYTES, another function that has the purpose of creating a cryptographic hash for a string. It is mainly used for password hashing, but it will fit nicely for our purpose. There are some caveats, though. First, CHECKSUM gets a variable number of parameters, HASHBYTES only accepts one, so we must take care of the cumbersome concatenation of multiple values. Unfortunately SQL functions do not have the option of variable parameters, which is truly a shame, so we can't hack it. Also, the value that HASHBYTES returns is a varbinary. We could cast it to NVARCHAR, but it turns into a weird Chinese characters string. In order to turn it into a proper string, we need to use the same function used by SQL Server to display varbinary when selecting it: master.sys.fn_varbintohexstr the CONVERT function with a parameter of 2 (hex string without the leading 0x).

So let's compare the two usages. Suppose we have this nice table that contains company data: company name, contact first name, contact last name, phone, email, yearly value. We need to create a unique ID based on these values.
First CHECKSUM:
SELECT CHECKSUM(companyName, firstName, lastName, phone, email, yearlyValue) FROM OurTable
So easy! Just add the columns, no matter how many or what type they have, and get a value as a result. You can even use * to select all columns in a row. You also have the advantage of getting the same checksum for differently capitalized strings. If you don't want this behaviour, use BINARYCHECSUM, which works even better.

Second HASHBYTES:
SELECT CONVERT(VARCHAR(Max),HASHBYTES('SHA1',companyName+'|'+firstName+'|'+lastName+'|'+phone+'|'+email+'|'+CAST(yearlyValue as NVARCHAR(100))),2) as id,*
FROM OurTable
Ugly! You need to create a string from different types, using ugly casts. Also, this works more like BINARYCHECKSUM. If you want to get the same functionality as CHECKSUM you need to use LOWER(LTRIM(RTRIM(value))). Horrid!
However, it works.

WARNING: using CAST to NVARCHAR from a FLOAT loses precision. You should use STR instead!

A middle solution is to use XCHECKSUM. What is that, you ask? A placeholder that can be replaced with some regular expression search and replace, of course :)

Update: I've created a query that creates the script to update the value of a column called 'ValuesHash', for tables that have it, with the hash of all columns that are not in a list of names, they are not primary keys and they are not foreign keys, plus they are not computed, rowguidcol or filestream.
Imagine the scenario where you have something like this:
  • Table A:
    1. Id: primary identity key
    2. Data1: some data
    3. Data2: some data
    4. CreateTime: the creation time
    5. ValuesHash: a VARBINARY(50) column - only 20 are required normally, but let's make sure :)
  • Table B:
    1. Id: primary identity key
    2. AId: foreign key to A
    3. Data1: some data
    4. Data2: some data
    5. ModifyTime: the modification time
    6. ValuesHash: a VARBINARY(50) column - only 20 are required normally, but let's make sure :)
  • Table C:
    1. Id: primary identity key
    2. AId: foreign key to A
    3. Data1: some data
    4. Data2: some data
The query below will update ValuesHash for A and B (because C doesn't have the ValuesHash column) with a hash constructed from the Data columns. The Id columns will be ignored for being primary keys (and for being in the list of columns to ignore), the AId columns will be ignored for being foreign keys, ValuesHash and CreateTime and ModifyTime will be ignored for being in a list of custom columns)

WARNING: each column data is always truncated to 4000 characters, then the corresponding string is also truncated to 4000 bytes before running HASHBYTES (which only accepts a maximum of 8000 bytes). This hash will help in determining unique records, but it is not 100%.

SELECT * 
FROM   (
SELECT t.name, 
  'UPDATE [' + t.name+ '] SET ValuesHash = HASHBYTES(''SHA1'',SUBSTRING(' 
  + Stuff( 
    (SELECT '+ ''|''+ ISNULL('+CASE 
      WHEN tp.name IN ('float', 'real') THEN 'STR('+c.name+',30,30)' 
      WHEN tp.name IN ('binary', 'varbinary') THEN 'CONVERT(NVARCHAR(4000),'+c.name+',2)'
      ELSE 'CONVERT(NVARCHAR(4000),'+c.name+')' END+','''')'
     FROM sys.all_columns c 
         INNER JOIN sys.types tp 
      ON c.system_type_id=tp.system_type_id
      AND c.user_type_id=tp.user_type_id 
     LEFT JOIN sys.index_columns ic
      ON ic.object_id=t.object_id
      AND ic.column_id=c.column_id
     LEFT JOIN sys.indexes i
      ON ic.object_id=i.object_id
      AND ic.index_id=i.index_id 
     LEFT JOIN sys.foreign_key_columns fc
      ON fc.parent_object_id=t.object_id 
            AND c.column_id=fc.parent_column_id 
     WHERE t.object_id=c.object_id
      AND ISNULL(c.is_identity, 0)=0
      AND ISNULL(c.is_computed, 0)=0
      AND ISNULL(c.is_filestream, 0)=0
      AND ISNULL(c.is_rowguidcol, 0)=0
      AND ISNULL(i.is_primary_key, 0)=0 
      AND fc.parent_column_id IS NULL
      AND c.name NOT IN ('Id', 'CreateTime' , 'AcquireTime' , 'IntermediateCreateTime', 'IntermediateModifyTime', 'IntermediateDeleteTime', 'ValuesHash')
     ORDER BY Sign(c.max_length) DESC, c.max_length, Lower(c.name)
     FOR XML PATH(''), TYPE).value('.', 'nvarchar(max)')
    , 1, 7, '') 
  + ',0,4000)) WHERE ValuesHash IS NULL' AS computed 
FROM   sys.tables t 
INNER JOIN sys.all_columns c 
  ON t.object_id = c.object_id 
WHERE  c.name = 'ValuesHash') x 
WHERE  computed IS NOT NULL 
ORDER  BY name

Change it to suit your needs. It is by no means perfect, but it's a start for whatever you need.

Update:

A new FORMAT function was introduced in SQL Server 2012, working somewhat similar to the .NET ToString method. Using that function is slightly more precise:

SELECT * 
FROM   (
SELECT t.name, 
  'UPDATE [' + t.name+ '] SET ValuesHash = HASHBYTES(''SHA1'',SUBSTRING(' 
  + Stuff( 
    (SELECT '+ ''|''+ ISNULL('+CASE 
      WHEN tp.name IN ('float', 'real') THEN 'FORMAT('+c.name+',''R'')' 
      WHEN tp.name IN ('decimal') THEN 'FORMAT('+c.name+',''G'')' 
      WHEN tp.name IN ('datetime','datetime2') THEN 'FORMAT('+c.name+',''O'')' 
      WHEN tp.name IN ('binary', 'varbinary') THEN 'CONVERT(NVARCHAR(4000),'+c.name+',2)'
      ELSE 'CONVERT(NVARCHAR(4000),'+c.name+')' END+','''')'
     FROM sys.all_columns c 
         INNER JOIN sys.types tp 
      ON c.system_type_id=tp.system_type_id
      AND c.user_type_id=tp.user_type_id 
     LEFT JOIN sys.index_columns ic
      ON ic.object_id=t.object_id
      AND ic.column_id=c.column_id
     LEFT JOIN sys.indexes i
      ON ic.object_id=i.object_id
      AND ic.index_id=i.index_id 
     LEFT JOIN sys.foreign_key_columns fc
      ON fc.parent_object_id=t.object_id 
            AND c.column_id=fc.parent_column_id 
     WHERE t.object_id=c.object_id
      AND ISNULL(c.is_identity, 0)=0
      AND ISNULL(c.is_computed, 0)=0
      AND ISNULL(c.is_filestream, 0)=0
      AND ISNULL(c.is_rowguidcol, 0)=0
      AND ISNULL(i.is_primary_key, 0)=0 
      AND fc.parent_column_id IS NULL
      AND c.name NOT IN ('Id', 'CreateTime' , 'AcquireTime' , 'IntermediateCreateTime', 'IntermediateModifyTime', 'IntermediateDeleteTime', 'ValuesHash')
     ORDER BY Sign(c.max_length) DESC, c.max_length, Lower(c.name)
     FOR XML PATH(''), TYPE).value('.', 'nvarchar(max)')
    , 1, 7, '') 
  + ',0,4000)) WHERE ValuesHash IS NULL' AS computed 
FROM   sys.tables t 
INNER JOIN sys.all_columns c 
  ON t.object_id = c.object_id 
WHERE  c.name = 'ValuesHash'
) x 
WHERE  computed IS NOT NULL 
ORDER  BY name

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I met a few friends for a drink and they recommended to me (or rather seemed amazed that I had not heard of it) Dragonlance. I looked it up and, to my chagrin, found that it is a huge series with over 20 books and a lot of short stories - actually, in 2008 there where over 190 novels in the same universe. Resigned myself to read them all, I googled for the right order in which to read the saga and came up with Chronicles, which is a trilogy of books, as the correct starting point.

As in the story, there is balance between the good and the bad in my assessment of the books. For one, I will not read the rest of the books and waste a lot of my time, but for the other, I already start regretting reading the first three. You see, the entire plot seems to have the only purpose of supporting a canon of the classic fantasy genre that the writers have thought up.

Probably emerging from games of Dungeons and Dragons, like many fantasy universes, the world of Krynn has nothing remotely original. There are elves, humans, dwarves, goblins, dragons, pegasi, unicorns, centaurs, and other races like that. From the very first pages, you meet the heroes that form the quest party and they seem to have gathered all the possible cliches in the genre in their travels: the dwarf is old and grumpy and complains a lot, the half-elf is tortured by his double ancestry, the knight is rigid and honorable, the mage is tiny and frail and frustrated about it, his big (twin) brother is huge and completely non-magical, etc. In fact, the mage character is the only one which seems remotely interesting, all the other being busy posturing most of the time, like real size commercials for their D&D class and specialization.

But what I thought was the most offensive of all was the premise of the trilogy. Beware, here be dragons... and spoilers. Do not read further if you think you might want to read the books.

You see, the world has been reeling after a huge Cataclysm, a fiery mountain hitting the planet and causing havoc. At the end of the book we learn that the gods, in their infinite wisdom, did that because the world was too unbalanced towards good! And we learn this from the good god, who for the entire duration of the story just nudged our heroes in one direction or the other while the evil god was amassing armies and killing everybody. How is that for balance?

Even so, you can hardly complain about a book being cliché if you don't read more of the genre and, to be honest, except for a few books, I didn't really read much fantasy. So I had an opportunity to enjoy this, even if the writing was simplistic, the characterization almost non existent and the story bland. But there was something in the books that kept me at arms length from enjoying it. It finally dawned on me in the middle of the second book, when, after reading about the emotional turmoil of everybody, having the men pair with the women - unless they were there for comic relief, like the dwarf and the kender (which one could consider a pair, if I think about it) - and making chaste promises to one another (like not having sex until they can focus on the relationship and stuff like that)... after all that, I realized that Dragonlance was written by two women. (Even later I realized that one of the women was actually a man. Shame on me! The rest of the review stands)

I don't want to sound misogynistic here, I really wanted to read something cool written by women, but for a series entitled after a weapon - albeit something long and thin, with a thick bulbous appendage at the tip - the story was surprisingly devoid of any detailed battles, tactics, strategy or even decent brawls. The heroes are always running around, talking about their feelings or thinking about them and, in case there is a huge battle between the forces of good and evil, quickly skips forward to the conflict between the two women that love the same man.

Also, as if it all wasn't formulaic enough, no one really dies from the group, unless it is something that fulfills their purpose in life, while the support cast keeps perishing without anyone actually giving a damn. Check out the bit where an entire ship crew - including the woman captain and the minotaur second that I had read a lot about in previous pages - just die without the characters even remembering it. Or the battle of the knights with the dragon armies, where one phrase describes how the knights held, but half of them died. Just like that. I may have written more about that bit than there was written in the book.

To end this terrible rant, if you thought Wheel of Time was childish, as I did, this is worse. T'is true, the fair maiden that hath captured my heart and recommended the books hath read said scrolls of wisdom when she was 16, so that might explain her fond memories and my tortured journey towards the end of the story. I also really really wanted to believe that by writing more, the authors would become more skilled at it. It didn't seem to be the case. I refuse to read another dozen books just to keep the faith.

In conclusion, I cannot in good conscience recommend this to anyone, including children or young adults - to which I think the story would be tantamount to poison, teaching all the wrong lessons in the worst possible way. These books sucked lance!

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I remember the first time it happened. We were just beginning to watch your struggle, the rise of such wonderful life, then the strike. It had happened before, but we weren't really paying attention. This time it was incredible drama. Galaxies cried out in anguish and desperation, but it wasn't the end. No, you survived, rebuilt, went on.

It's funny, the first time apes started acting smart there was a lot of disappointment. Ugly, cumbersome, a bit mad, everybody thought. But we continued to watch, mesmerized, as you got through so much that almost destroyed you. You changed, you evolved.

Then you bloomed. Started talking, singing, thinking and painting. Further on you started writing. What a wonderful flower you were. Worlds would die and form on the sounds of your wails or yells of joy. We loved it all, the wars, the art, the science, the suffering. We gulped it up, knowing that it was not going to last. They never do, we thought.

We cheered for you when you were dying in the great pandemics, we cried for you when you killed each other, you had our full attention when you almost destroyed everything with nuclear devices. Some of us rooted for that ending. They love violent, brusque ends, some of us do. But it didn't happen.

Oh how you danced, how you sang, the beautiful things you thought and put in writing, in films, did with your computers. We knew you were close to the end and we knew that it was all good stuff, because we didn't want it to end, but they all end, don't they?

We marvelled at your ships, at your resilience in hoping to contact others... us... and we cried. The space battles were magnificent. You took inspiration from your history and created fiction, then you used fiction to create your future. You bypassed your present altogether. A whole universe laughed and cheered. Those were good times.

Your enormous space habitats, floating around your sun, always changing, always growing, they gave us hope. Hope that some of you might make it, leave your system. Sometimes it happens. We love splinters, that we do, but it didn't happen. You stayed put.

And then your flower wilted away. You had altered yourselves, you had become faster, smarter, you had already merged with the machines you had built and defeated most of your biological problems. You were invincible and beautiful, immortal. But then you found it; after all, they all do, the universal link, the thing that finally allowed you to fulfil your dreams. You found us.

And now you listen to our songs, watch our histories, run our software, use our technology. But we remember you, how beautiful you were when you were young. We all loved you, humans. Now that you are old, like us, you have control. You are us. Join in watching this wonderful new life that emerges from the chaos. It's a great show. And maybe some will make it, some will manage to be different, somehow, sometime.

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As always, this post will reflect my personal opinion. I know that The Listeners is a classic book, one that has been cited by SETI as a major factor in the project becoming known and supported by others. I know that at that time, doing a reasonable sci-fi book was a feat. I know that the writer was a believer in the contact with aliens and human nature and so on, and thus he must have been a nice guy, with similar desires to mine and other space-looking people. However the book annoyed me to no end.

The first and biggest of all problems is the insistence of the writer to add to the book all kinds of quotes from various works, many of them in a foreign language - that is, other than English. It was the reason why originally publishers refused his manuscript. Now, even if I understand the language, I don't know the quote. There is an annex at the end of the book that translates everything, but really, when a character randomly interrupts a perfectly good conversation to spout something unintelligible in another language, that guy is an asshole!

Then there was the construction of the book, the Project being presented like something that held sway over the human heart. All you had to do to convince anyone of anything was turn on the speakers so that they hear static, while the main character would do PR work, knowing exactly what to say to manipulate the other person. I would not have a problem with that, if the manipulation would not be completely obvious and most of the time completely ridiculous. It felt like a Naruto episode where the other ninja, filled with power, suddenly decides to switch sides because Naruto is such a nice guy. I know I don't inspire confidence when I compare a classic sci-fi book with a Japanese manga, but for me it was the same quality of work, which may be entertaining, but not great.

All the people and events changed in order to conveniently support the plot. It felt fake and it is a lousy writing technique, more suited to pulp. I did not enjoy that.

As for the plot itself, it is about this Project, which is pretty much SETI, that suddenly receives an alien signal piggybacked on 90 years old radio transmissions. What people do and say is so underwhelming that it felt like I was wasting my time while reading the book. That is why it took so long to finish it. My conclusion: while a classic for the science fiction genre, I did not enjoy the book or empathise with its characters. The plot is difficult to swallow and the story is very dated. I would not recommend it.

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It just happens that I have two different projects that have the need of cluster analysis, applied in two different ways: one has uses on maps, where a large number of items needs to be displayed quickly, while another implies finding clusters of news items, where the distance between them is determined by their content. The most used clustering algorithm and the first to be found by searching the web is the k-means clustering. Its purpose is to categorize a list of items into a number of k clusters, hence the name. Setting aside the use value of the algorithm for my purposes, the biggest problem I see is the complexity: in its general form it is at least O(n2), and most of the time a lot higher. The net abounds with scientific papers investigating the k-means complexity and suggesting improvements, but they are highly mathematical and I didn't have the time to investigate further. So I just built my own algorithm. It is clearly fuzzy, imperfect, may even be wrong in some situations, but at least it is fast. I will certainly investigate this area more, maybe even try to understand the math behind it and analyse my results based on this research. When I do that I will update this post or write others. But until then, let me present my work so far.

The first problem I had was, as I said, complexity. For one million points on the map, any algorithm that takes into account the distance between any two items will have to make at least one trillion comparisons. So my solution was to limit the number of items by grouping them in a grid:
Step 1: find the min and max on each dimension (that means going through the entire item collection once or knowing beforetime the map bounds)
Step 2: determine a number of cells that would be a bit more than what I need in the end. (that's a decision I have to take, no algorithmic complexity)
Example: for my map example I have only two dimensions: X and Y. I want to display an upper bound of 1000 clusters. Therefore I find the minimum and maximum X and Y and then split each dimension into 100 slots. That means I would cluster the items I have into 10000 cells.
Step 3: for each item, find its cell based on X,Y and add the item to the cell. This is done by simple division: (X-minX)/(maxX-minX). (again that means going once through the collection)
Step 4: find the smallest cell (the complexity is reduced now to working with cells)
Step 5: find its smallest neighbour (the complexity of this on the implementation)
Step 6: merge the two cells
Until the number of cells is larger than the desired number of clusters, repeat from Step 4.
In the end, the algorithm is O(n+p*log(p)), I guess, where p is the number of cells chosen at step 2.

Optimizations are the next issue.
  • How does one find the neighbours of a cell? On Step 3 we also create a list of neighbors for each new cluster by looking for a cluster that is at coordinates immediately above, below, left or right. When we merge two clusters, we get a cluster that is a neighbour to all the neighbours of the merged clusters.
  • How does one quickly get the cluster at a certain position? We create a dictionary that has the coordinates as the key. What about when we merge two clusters? Then the new cluster will be accessible by any of the original cluster keys (that implied that each cluster has a list of keys, as well)
  • How does one find the smallest cell in the cluster list? After Step 3 we sort the cluster list by the number of items they contain and each time we perform a merge we find the first item larger than the merged result and we insert it in the list at that location, so that the list always remains sorted.
  • How do we easily find the first item larger than an item? By employing a divide-et-impera method of splitting the list in two at each step and choosing to look into one bucket based on the item count of the cluster at the middle position

Before you use the code note that there are specific scenarios where this type of clustering would look a bit off, like items in a long line or an empty polygon (the cluster will appear to be in its center). But I needed speed and I got it.

Enjoy!

Update: The performance of removing or adding items from a List is very poor, so I created a LinkedList version that seems to be even faster. Here it is. The old List version is at the end

/// <summary>
/// Generic x,y positioned item class
/// </summary>
public class Item
{
    public double X { get; set; }
    public double Y { get; set; }
}

public class ClusteringDataProcessor
{
    /// <summary>
    /// the squared root of the initial cell number (100*100 = 10000)
    /// </summary>
    private const int initialClustersSquareSide = 100;
    /// <summary>
    /// the desired number of resulting clusters
    /// </summary>
    private const int numberOfFinalClusters = 1000;
    private static Random _rnd = new Random();

    /// <summary>
    /// In this implementation, the Cluster inherits from Item, so the result is a list of Item
    /// In the case of one Item Clusters, we actually return the original Item
    /// </summary>
    /// <param name="list"></param>
    /// <returns></returns>
    public List<Item> Process(List<Item> list)
    {
        if (list.Count <= numberOfFinalClusters) return list;
        // find bounds. If already known, this can be provided as parameters
        double minY = double.MaxValue;
        double minX = double.MaxValue;
        double maxY = double.MinValue;
        double maxX = double.MinValue;
        foreach (var item in list)
        {
            var y = item.Y;
            var x = item.X;
            minY = Math.Min(minY, y);
            maxY = Math.Max(maxY, y);
            minX = Math.Min(minX, x);
            maxX = Math.Max(maxX, x);
        }
        // the original list of clusters
        var clusterArr = new List<Cluster>();

        // the dictionary used to index clusters on their position
        var clusterDict = new Dictionary<string, Cluster>();

        // the unit for finding the cell position for the initial clusters
        var qX = (maxX - minX) / initialClustersSquareSide;
        var qY = (maxY - minY) / initialClustersSquareSide;

        foreach (var item in list)
        {
            // compute cell coordinates (integer and the values used as keys in the dictionary)
            var cx = Math.Min((int)((item.X - minX) / qX), initialClustersSquareSide - 1);
            var cy = Math.Min((int)((item.Y - minY) / qY), initialClustersSquareSide - 1);
            var key = getKey(cx, cy);
            Cluster cluster;
            // if the cluster for this position does not exist, create it
            if (!clusterDict.TryGetValue(key, out cluster))
            {
                cluster = new Cluster
                {
                    Keys = new List<string> { key },
                    X = minX + cx * qX + qX / 2,
                    Y = minY + cy * qY + qY / 2,
                    //Items = new List<Item>(),
                    Count = 0,
                    Neighbors = new List<string>()
                };
                // the neighbours of this cluster are the existing clusters that are below, above, left or right. If they exist, this cluster also is added to their neighbour list
                var nkeys = new[] { getKey(cx - 1, cy), getKey(cx + 1, cy), getKey(cx, cy - 1), getKey(cx, cy - 1) };
                for (var j = 0; j < 4; j++)
                {
                    Cluster nc;
                    if (clusterDict.TryGetValue(nkeys[j], out nc))
                    {
                        cluster.Neighbors.Add(nkeys[j]);
                        nc.Neighbors.Add(key);
                    }
                }
                clusterDict[key] = cluster;
                clusterArr.Add(cluster);
            }
            // add the item to the cluster (note that the commented lines hold the items in a list, while the current implementation only remember the number of items)
            //cluster.Items.Add(item);
            cluster.Item = item;
            cluster.Count++;
            // add the item position to the sums, so that we can compute the final position of the cluster at the Finalize stage without enumerating the items (or having to hold them in an Items list)
            cluster.SumX += item.X;
            cluster.SumY += item.Y;
        }
        // if the number of items is already smaller than the desired number of clusters, just return the clusters
        if (clusterArr.Count <= numberOfFinalClusters)
        {
            return clusterArr.Select(c => c.Finalize()).ToList();
        }

        // sort the cluster list so we can efficiently find the smallest cluster
        //clusterArr.Sort(new Comparison<Cluster>((c1, c2) => c1.Items.Count.CompareTo(c2.Items.Count)));
        LinkedList<Cluster> clusterLinkedList = new LinkedList<Cluster>(clusterArr.OrderBy(c => c.Count));

        // remember last merged cluster, as next merged clusters might have similar sizes
        var lastCount = int.MaxValue;
        LinkedListNode<Cluster> lastLinkedNode = null;

        // do this until we get to the desired number of clusters
        while (clusterLinkedList.Count > numberOfFinalClusters)
        {
            // we need to get the smallest (so first) cluster that has any neighbours
            var cluster1 = clusterLinkedList.First(c => c.Neighbors.Any());
            Cluster cluster2 = null;
            // then find the smallest neighbour
            var min = int.MaxValue;
            foreach (var nkey in cluster1.Neighbors)
            {
                var n = clusterDict[nkey];
                //var l = n.Items.Count;
                var l = n.Count;
                if (l < min)
                {
                    min = l;
                    cluster2 = n;
                }
            }
            // join the clusters
            var keys = cluster1.Keys.Union(cluster2.Keys).ToList();
            var cluster = new Cluster
            {
                Keys = keys,
                // approximate cluster position, not needed
                //X = (cluster1.X + cluster2.X) / 2,
                //Y = (cluster1.Y + cluster2.Y) / 2,

                // the result holds the count of both clusters
                //Items = cluster1.Items.Union(cluster2.Items).ToList(),
                Count = cluster1.Count + cluster2.Count,
                // the neighbors are in the union of their neighbours that does not contain themselves
                Neighbors = cluster1.Neighbors.Union(cluster2.Neighbors)
                    .Distinct()
                    .Except(keys)
                    .ToList(),
                // compute the sums for the final position
                SumX = cluster1.SumX + cluster2.SumX,
                SumY = cluster1.SumY + cluster2.SumY
            };
            foreach (var key in keys)
            {
                clusterDict[key] = cluster;
            }
            // efficiently remove clusters since LinkedList removals are fast
            clusterLinkedList.Remove(cluster1);
            clusterLinkedList.Remove(cluster2);

            // a little bit of magic to make the finding of the insertion point faster (LinkedLists go through the entire list to find an item)
            // if the last merged cluster is smaller or equal to the new merged cluster, then start searching from it.
            // this halves the insert time operation, but I am sure there are even better implementations, just didn't think it's so important
            LinkedListNode<Cluster> start;
            if (lastCount <= cluster.Count && lastLinkedNode.Value != cluster1 && lastLinkedNode.Value != cluster2)
            {
                start = lastLinkedNode;
            }
            else
            {
                start = clusterLinkedList.First;
            }
            var insertionPoint = nextOrDefault(clusterLinkedList, start, c => c.Count >= cluster.Count);
            // remember last merged cluster
            LinkedListNode<Cluster> link;
            if (insertionPoint == null)
            {
                link = clusterLinkedList.AddLast(cluster);
            }
            else
            {
                link = clusterLinkedList.AddBefore(insertionPoint, cluster);
            }
            lastLinkedNode = link;
            lastCount = cluster.Count;
        }
        return clusterLinkedList.Select(c => c.Finalize()).ToList();
    }

    private LinkedListNode<T> nextOrDefault<T>(LinkedList<T> list, LinkedListNode<T> start, Func<T, bool> condition)
    {
        while (start.Next != null)
        {
            if (condition(start.Value)) return start;
            start = start.Next;
        }
        return null;
    }

    private string getKey(int cx, int cy)
    {
        return cx + ":" + cy;
    }

    private class Cluster : Item
    {
        public Cluster()
        {
            SumX = 0;
            SumY = 0;
        }

        public double SumX { get; set; }
        public double SumY { get; set; }

        public List<string> Keys { get; set; }

        //public List<Item> Items { get; set; }
        public int Count { get; set; }
        public Item Item { get; set; }

        public List<string> Neighbors { get; set; }


        /// <summary>
        /// the function that finalizes the computation of the values or even decides to return the only item in the cluster
        /// </summary>
        /// <returns></returns>
        public Item Finalize()
        {
            //if (Items.Count == 1) return Items[0];
            if (Count == 1) return Item;
            /*Y = SumY / Items.Count;
            X = SumX / Items.Count;
            Count = Items.Count;*/
            Y = SumY / Count;
            X = SumX / Count;
            Count = Count;
            return this;
        }
    }
}

old List based code (click to show)

and has 2 comments
Well, sometimes an admin will try to make the system secure by annoying the people who have to use it. Yeah, that always works. My situation is that I have to login every day into a virtual machine that is on a "secure network". So after using a very restrictive password policy that forces everybody to be creative in the way they write "password" and "123456", he also disallowed the saving credentials in Remote Desktop Connection. So every day I have to enter the damn complicated password. I couldn't have that. Here is a .js script that you execute with WScript and it logs you in automatically:
var shell = WScript.CreateObject("WScript.Shell");
shell.Run("mstsc /v:[remote server] /console");
while (!shell.AppActivate("Windows Security")) {
    WScript.Sleep(100);
}
WScript.Sleep(100);
shell.SendKeys("[password]{enter}");

Save this into a Javascript file and replace [remove server] and [password] with your settings and either double click the .js file or create a batch file like this:
@echo off
start "Auto log on!" wscript c:\Batches\autologin.js

Of course, this means your secure password will be stored in a stupid text file somewhere, so be warned.

and has 0 comments
This is one of those WTF moments. After more than a decade of working in software development I learn something this basic about T-SQL (or rather, any flavour based on SQL-92). What would you think happens when running this script?
IF ''='                 ' SELECT 'WTF?!' -- empty string compared to a bunch of spaces
IF '      '='           ' SELECT 'WTF?!' -- bunch or spaces compared to another bunch of spaces of different length
IF 'x'='x               ' SELECT 'WTF?!' -- 'x' compared to 'x' followed by a bunch of spaces
IF 'x'='               x' SELECT 'WTF?!' -- 'x' compared to 'x' preceded by a bunch of spaces

There will be three WTF rows returned, for the first three queries. You don't believe me? Try it yourself. The motive is explained here: INF: How SQL Server Compares Strings with Trailing Spaces. Short story shorter: in order for SQL to compare two strings of different lengths, it first right-pads the shorter one with spaces.

So what can you do to fix it? Easy enough, use LEN ,right? Nope. Read the definition carefully: Returns the number of characters of the specified string expression, excluding trailing blanks. A possible but weird solution is to use DATALENGTH. A string is empty only is it has a datalength of 0. In the case of NVARCHAR you could even divide the resulting number to 2 in order to get the true length of the string. WTF, right?

and has 1 comment
Well, it's pretty obvious, but I wanted to post it here, as well. You see, we have this query that was supposed to filter some values based on a parameter. The query was done like this: SELECT * FROM table WHERE value=(CASE WHEN @filter IS NULL THEN value ELSE @filter). Can you spot the problem? Indeed, if value is NULL, then value is NOT equal to value. Not only is this incorrect, but also bad from the standpoint of the SQL execution plan. It is much faster to do SELECT * FROM table WHERE (@filter is NULL OR value=@filter). If, for whatever reason, you need the first syntax, you need to do it like this: SELECT * FROM table WHERE ISNULL(value,@impossibleValueThatIsNotNull)=COALESCE(@filter, value, @impossibleValueThatIsNotNull). Yeah, a bit of a show off, but when the "no filter" value is null, it's better to use ISNULL and COALESCE wherever possible.

and has 0 comments

I was just thinking about Coma a few days ago. I don't know why. I thought I miss one of their beautiful songs. And here I see on YouTube they released a new video just when I was thinking of them. This one is a very nice combination of Catalin's lyrics, melodic and hard sounds and a cool interweave of the voices of Catalin and Dan - it's not the usual contrast between singing and shouting, but rather a vocal collaboration which works surprisingly well. Without further ado, here it is.
Chip, by Coma:
\

Also, if you want to see a live version:

and has 2 comments
I have at work a very annoying HTTP proxy that requires a basic authentication. This translates in very inconsistent behaviour between applications and the annoying necessity of entering the username and password whenever the system wants it. So I've decided to add another local proxy to the chain that handles the authentication for me forever.

This isn't as easy as it sounds. Sure, proxies are a dime a dozen, but for some reason most of them seem to be coming from the Linux world. That is really bad user interaction, vague documentation and unhelpful forums where any request for help ends up in some version of "read the fucking manual". Hence I've decided to help out by creating this lovely post that explains how you can achieve the purpose described above with very little headache. These are the very easy steps that you have to undertake:
  1. Download and install Privoxy
  2. Go to the Program Files folder and look for Privoxy. You will need to edit two files: config.txt and user.action
  3. Optional: change the listen-address port, otherwise the proxy will function on port 8118
  4. Enter your proxy authentication username and password in the fields below and press Help me configure Privoxy - this is strictly a client base Javascript so don't worry that I am going to steal your proxy credentials...
  5. Edit user.action and add the bit of text that appeared as destined for that file.
  6. Edit config.txt, look for examples of forward and add to it the bit that belongs to config.txt and replace proxy:port and the domains and IP masks with the correct values for you
  7. Restart Privoxy
  8. Configure your internet settings to use a proxy on 127.0.0.1 and the port you configured in step 2 (or the default 8118)

This should be it. Enjoy!

Username:
Password:


and has 0 comments
I made a function in T-SQL that parsed some string and returned a decimal. It all worked fine until one of my colleagues wanted to use it on the test server. And here there was, a beautiful error message: 'decimal' is not a recognized built-in function name. I isolated the line, executed it, same error. It was like the server did not understand decimals anymore. The line in question was a simple SELECT TRY_CONVERT(DECIMAL(18,6),'10.33'). If I used CONVERT, though, it all worked fine. Another hint was that the function worked perfectly fine on the same server, in another database. The problem was that for that particular database, the defined SQL server version was 2008, not 2012. We changed it and it all worked fine after that. The setting in question is found in the Properties of the database, Options, Compatibility level.

and has 2 comments
While working on a small personal project, I decided to make a graphical tool that displayed a list of items in a Canvas. After making it work (for details go here), I've decided to make the items animate when changing their position. In my mind it had to be a simple solution, akin to jQuery animate or something like that; it was not.

The final solution was to finally give up on a generic method for this and switch to the trusted attached properties. But if you are curious to see what else I tried and how ugly it got, read it here:
Click here to get ugly!

Well, long story short: attached properties. I created two attached properties CanvasLeft and CanvasTop. When they change, I animate the real properties and, at the end of the animation, I set the value. Here is the code:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media.Animation;

namespace Siderite.AttachedProperties
{
    public static class UIElementProperties
    {
        public static readonly DependencyProperty CanvasLeftProperty = DependencyProperty.RegisterAttached("CanvasLeft", typeof(double), typeof(UIElementProperties), new FrameworkPropertyMetadata(
                                                                                            0.0,
                                                                                            FrameworkPropertyMetadataOptions.OverridesInheritanceBehavior,
                                                                                            CanvasLeftChanged));

        [AttachedPropertyBrowsableForType(typeof(UIElement))]
        public static double GetCanvasLeft(DependencyObject element)
        {
            if (element == null)
            {
                throw new ArgumentNullException("element");
            }
            return (double)element.GetValue(CanvasLeftProperty);
        }

        [DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)]
        public static void SetCanvasLeft(DependencyObject element, double value)
        {
            if (element == null)
            {
                throw new ArgumentNullException("element");
            }
            element.SetValue(CanvasLeftProperty, value);
        }

        private static void CanvasLeftChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var sb = new Storyboard();
            var oldVal = (double)e.OldValue;
            if (double.IsNaN(oldVal)) oldVal = 0;
            var newVal = (double)e.NewValue;
            if (double.IsNaN(newVal)) newVal = oldVal;
            var anim = new DoubleAnimation
            {
                From = oldVal,
                To = newVal,
                Duration = new Duration(TimeSpan.FromSeconds(1)),
                FillBehavior = FillBehavior.Stop
            };
            Storyboard.SetTarget(anim, d);
            Storyboard.SetTargetProperty(anim, new PropertyPath("(Canvas.Left)"));
            sb.Children.Add(anim);
            sb.Completed += (s, ev) =>
            {
                d.SetValue(Canvas.LeftProperty, newVal);
            };
            var fe = d as FrameworkElement;
            if (fe != null)
            {
                sb.Begin(fe, HandoffBehavior.Compose);
                return;
            }
            var fce = d as FrameworkContentElement;
            if (fce != null)
            {
                sb.Begin(fce, HandoffBehavior.Compose);
                return;
            }
            sb.Begin();
        }
        

        public static readonly DependencyProperty CanvasTopProperty = DependencyProperty.RegisterAttached("CanvasTop", typeof(double), typeof(UIElementProperties), new FrameworkPropertyMetadata(
                                                                                        0.0,
                                                                                        FrameworkPropertyMetadataOptions.OverridesInheritanceBehavior,
                                                                                        CanvasTopChanged));

        [AttachedPropertyBrowsableForType(typeof(UIElement))]
        public static double GetCanvasTop(DependencyObject element)
        {
            if (element == null)
            {
                throw new ArgumentNullException("element");
            }
            return (double)element.GetValue(CanvasTopProperty);
        }

        [DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)]
        public static void SetCanvasTop(DependencyObject element, double value)
        {
            if (element == null)
            {
                throw new ArgumentNullException("element");
            }
            element.SetValue(CanvasTopProperty, value);
        }

        private static void CanvasTopChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var sb = new Storyboard();
            var oldVal = (double)e.OldValue;
            if (double.IsNaN(oldVal)) oldVal = 0;
            var newVal = (double)e.NewValue;
            if (double.IsNaN(newVal)) newVal = oldVal;
            var anim = new DoubleAnimation
            {
                From = oldVal,
                To = newVal,
                Duration = new Duration(TimeSpan.FromSeconds(1)),
                FillBehavior = FillBehavior.Stop
            };
            Storyboard.SetTarget(anim, d);
            Storyboard.SetTargetProperty(anim, new PropertyPath("(Canvas.Top)"));
            sb.Children.Add(anim);
            sb.Completed += (s, ev) =>
            {
                d.SetValue(Canvas.TopProperty, newVal);
            };
            var fe = d as FrameworkElement;
            if (fe != null)
            {
                sb.Begin(fe, HandoffBehavior.Compose);
                return;
            }
            var fce = d as FrameworkContentElement;
            if (fce != null)
            {
                sb.Begin(fce, HandoffBehavior.Compose);
                return;
            }
            sb.Begin();
        }
    }
}

and this is how you would use them:

<ListView ItemsSource="{Binding KernelItems}" 
          SelectedItem="{Binding SelectedItem,Mode=TwoWay}"
          SelectionMode="Single"
          >
    <ListView.ItemsPanel>
        <ItemsPanelTemplate>
            <Canvas HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Background="Black" />
        </ItemsPanelTemplate>
    </ListView.ItemsPanel>
    <ListView.ItemContainerStyle>
        <Style TargetType="{x:Type ListViewItem}">
            <Setter Property="FocusVisualStyle" Value="{x:Null}"/>
            <Setter Property="Foreground" Value="White"/>
            <Setter Property="att:UIElementProperties.CanvasLeft" >
                <Setter.Value>
                    <MultiBinding Converter="{StaticResource CoordinateConverter}">
                        <Binding Path="X"/>
                        <Binding Path="ActualWidth" ElementName="lvKernelItems"/>
                        <Binding Path="DataContext.Zoom" RelativeSource="{RelativeSource AncestorType={x:Type Window}}"/>
                    </MultiBinding>
                </Setter.Value>
            </Setter>
            <Setter Property="att:UIElementProperties.CanvasTop" >
                <Setter.Value>
                    <MultiBinding Converter="{StaticResource CoordinateConverter}">
                        <Binding Path="Y"/>
                        <Binding Path="ActualHeight" ElementName="lvKernelItems"/>
                        <Binding Path="DataContext.Zoom" RelativeSource="{RelativeSource AncestorType={x:Type Window}}"/>
                    </MultiBinding>
                </Setter.Value>
            </Setter>
            <Style.Resources>
                <SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}" Color="Transparent" />
                <SolidColorBrush x:Key="{x:Static SystemColors.ControlBrushKey}" Color="Transparent" />
                <SolidColorBrush x:Key="{x:Static SystemColors.HighlightTextBrushKey}" Color="Black" />
                <SolidColorBrush x:Key="{x:Static SystemColors.ControlTextBrushKey}" Color="Black" />
            </Style.Resources>
            <Style.Triggers>
                <Trigger Property="IsSelected" Value="True">
                    <Setter Property="Foreground" Value="Cyan"/>
                    <Setter Property="Effect">
                        <Setter.Value>
                            <DropShadowEffect ShadowDepth="0" Color="White" Opacity="0.5" BlurRadius="10"/>
                        </Setter.Value>
                    </Setter>
                    <Setter Property="Canvas.ZIndex" Value="1000"/>
                </Trigger>
            </Style.Triggers>
        </Style>
    </ListView.ItemContainerStyle>
</ListView>

Hope it helps.

and has 0 comments
I've reached the last of the animes in the Studio Ghibli series that I wanted to watch (again) and it was nice that this one got to be the final one. You see, before that I had watched The Cat Returns and I rated it mediocre, so unlike the beautiful movies from the same collection. Whisper of the Heart seems to be the film designed to redeem it.

The story is that of a young girl who likes to read a lot of books. She notices that most of the books that she borrowed from the library had the same name on their library cards, a boy that she didn't know. Coincidentally she follows a fat cat, apparently named Muta, to the shop of an old man who has a beautiful doll of a cat in a suit: the Baron of Gikkingen. You guessed it, two characters from The Cat Returns. And behold, the old man is the grandfather of the boy that kept borrowing the same books.

Whisper of the Heart seems to just take beautiful elements from other Ghibli animes and bring them all together in a wonderful union. The windy hills of Tokyo, which still has beauty despite the expansion of the city. The young girl who is not only smart and sensible, but also ambitious and kind. The family who is sometimes annoying and overbearing, but that in the end is the source of support for the development of the child it nurtures. The indolent fat cat :)

And then the love story, something that springs from common interests and a karmic connection between two people who seem to have been meant for each other. But there is more. They don't just click and that's it; they get motivated and energized to be the best of what they can be in order to honor the relationship in which they enter. In a way, it is a continuation of the warm and supporting family model from which both protagonists come.

One of the scenes in the anime was so funny to my wife that she spoke the Japanese words from it for a week. What a wonderful thing to have a film that not only makes me want to be a better man, but that already does make me be so by connecting me stronger to the one I love. And I watched it on Valentine's day, too! How can I rate it any less than with a perfect 10?

Returning to The Cat Returns, it somehow felt to me that the story linked to it also from the perspective of the ever aspiring artist; the rough and unpolished plot there sounds a lot like the story Shizuku writes, her first but one in many, the stone that will allow her to get to the skill and experience to do this story, which is so much better and complete. It does seem that way to me, since I watched The Cat Returns first, but chronologically Whisper of the Heart was made seven years earlier.

Now I don't know exactly in which proportion is Hayao Miyazaki responsible for the great quality of this film and story and how much Hiiragi Aoi, the writer of the original manga, but I heartily recommend the end result. I may be exaggerating, but this could be the best anime Studio Ghibli ever did, and that is saying much.

and has 0 comments
For a WPF project I wanted to create a graphical representation of a list of items. I computed some X,Y coordinates for each item and started changing the XAML of a Listview in order to reflect the position of each item on a Canvas. Well, it is just as easy as you imagine: change the ItemsPanel property to a Canvas and then style each item as whatever you want. The gotcha comes when trying to set the coordinates. The thing is that for each item in a listview a container is constructed and inside the item template is displayed. So here you have all you items displayed exactly as you want them, except the coordinates don't work, since what needs to be placed on the Canvas are the generated containers, not the items. Here is the solution:
<Window.Resources>
        <local:CoordinateConverter x:Key="CoordinateConverter"/>
        <DataTemplate DataType="{x:Type vm:KernelItem}"> <!-- the template for the data items -->
            <Grid>
                <Ellipse Fill="{Binding Background}" Width="100" Height="100" Stroke="DarkGray" Name="ellipse"
                         ToolTip="{Binding Tooltip}"/>
                <TextBlock Text="{Binding Text}" MaxWidth="75"  MaxHeight="75"
                           HorizontalAlignment="Center" VerticalAlignment="Center"
                           TextAlignment="Center"
                           TextWrapping="Wrap"
                           ToolTip="{Binding Tooltip}" />
            </Grid>
        </DataTemplate>
    </Window.Resources>
    <ListView ItemsSource="{Binding KernelItems}" Name="lvKernelItems"
              SelectedItem="{Binding SelectedItem,Mode=TwoWay}"
              SelectionMode="Single"
              >
        <ListView.ItemsPanel>
            <ItemsPanelTemplate>
                <Canvas HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Background="Black" />
            </ItemsPanelTemplate>
        </ListView.ItemsPanel>
        <ListView.ItemContainerStyle>
            <Style TargetType="{x:Type ListViewItem}">
                <Setter Property="FocusVisualStyle" Value="{x:Null}"/><!-- no highlight of selected items -->
                <Setter Property="Foreground" Value="White"/>
                <Setter Property="(Canvas.Left)" >
                    <Setter.Value>
                        <MultiBinding Converter="{StaticResource CoordinateConverter}">
                            <Binding Path="X"/>
                            <Binding Path="ActualWidth" ElementName="lvKernelItems"/>
                            <Binding Path="DataContext.Zoom" RelativeSource="{RelativeSource AncestorType={x:Type Window}}"/>
                        </MultiBinding>
                    </Setter.Value>
                </Setter>
                <Setter Property="(Canvas.Top)" >
                    <Setter.Value>
                        <MultiBinding Converter="{StaticResource CoordinateConverter}">
                            <Binding Path="Y"/>
                            <Binding Path="ActualHeight" ElementName="lvKernelItems"/>
                            <Binding Path="DataContext.Zoom" RelativeSource="{RelativeSource AncestorType={x:Type Window}}"/>
                        </MultiBinding>
                    </Setter.Value>
                </Setter>
                <Style.Resources><!-- no highlight of selected items -->
                    <SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}" Color="Transparent" />
                    <SolidColorBrush x:Key="{x:Static SystemColors.ControlBrushKey}" Color="Transparent" />
                    <SolidColorBrush x:Key="{x:Static SystemColors.HighlightTextBrushKey}" Color="Black" />
                    <SolidColorBrush x:Key="{x:Static SystemColors.ControlTextBrushKey}" Color="Black" />
                </Style.Resources>
                <Style.Triggers>
                    <Trigger Property="IsSelected" Value="True"><!-- custom selected item template -->
                        <Setter Property="Foreground" Value="Cyan"/>
                        <Setter Property="Effect">
                            <Setter.Value>
                                <DropShadowEffect ShadowDepth="0" Color="White" Opacity="0.5" BlurRadius="10"/>
                            </Setter.Value>
                        </Setter>
                        <Setter Property="Canvas.ZIndex" Value="1000"/>
                    </Trigger>
                </Style.Triggers>
            </Style>
        </ListView.ItemContainerStyle>
    </ListView>

As a bonus, you see the way to remove the default selection of an item: the ugly dotted line and the highlighting background.