Ticklish Techs

I created two DirectiveProcessor for Visual Studio to use in the T4 system. I added the classes to JaDAL hoping someone can use them in her project or use the code as an example when creating new DirectiveProcessors.

Let’s start with a short introduction to DirectiveProcessors. DirectiveProcessors are used in .tt-files to provide data to the template. The DirectiveProcessor can take parameters from the declaration in the .tt-file and adds some code to the compiled template. This code (often properties) can be used from within the template. For example the DSL Tools are generating one DirectiveProcessor for each DSL model. In a template form the DSL Tools you will see a line like the following:

<#@ Language1 processor=“Language1DirectiveProcessor”
requires=“fileName=’Sample.mydsl1′” #>

This line uses the Language1DirectiveProcessor and provides it with one parameter (fileName). The DirectiveProcessor adds code to the template to open the given file and creates (in this case) a ExampleModel-property to use in the template code.

I created two DirectiveProcessors to use the data of simple Xml-files and Visual Studio Project files in the templates. The code of the two DirectiveProcessors is very straight forward and maybe one could advance it (e.g. make it compatible with templates written in Visual Basic).

Using the XmlFileDirectiveProcessor

Add a line like the following to your .tt-file:

<#@ XmlFile processor=“XmlFileDirectiveProcessor” FileName=“example.xml” #>

Inside this template you can access the (full qualified) filename via the this.XmlFileName-Property and the Content of this file (as a XDocument) via the this.XmlFile-Property.

Using the VsProjectFileDirectiveProcessor

Add this line to your template:

<#@ ProjectFile processor=“VsProjectFileDirectiveProcessor” FileName=“x.csproj” #>

A property named this.ProjectFile will be added to the template. This property provides you with an instance of the VsProjectFile-class containing the project file contents. This class contains only very little functionality (feel free to add some more and submit it back to me!). Just take a look at the source code of this class. The method GetAllFiles() returns a string array of all files found in the project (supporting C++ and C# project files – .vcproj and .csproj).

Setup

An entry in the registry is needed to allow the T4 system to find custom DirectiveProcessors. Just add the following entries to your registry and don’t forget to point to the right location of the JaDAL.dll.

[HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\9.0Exp\
Configuration\TextTemplating\DirectiveProcessors\VsProjectFileDirectiveProcessor]
“Class”=”BenjaminSchroeter.Dsl.DirectiveProcessors.VsProjectFileDirectiveProcessor”
“CodeBase”=”D:\\JaDAL\\bin\\Debug\\JaDAL.dll”

[HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\9.0Exp\
Configuration\TextTemplating\DirectiveProcessors\XmlFileDirectiveProcessor]
“Class”=”BenjaminSchroeter.Dsl.DirectiveProcessors.XmlFileDirectiveProcessor”
“CodeBase”=”D:\\JaDAL\\bin\\Debug\\JaDAL.dll”

These registry keys are for the Experimental Hive of Visual Studio. To register the DirectiveProcessors for the normal Visual Studio instance the registry key starts with HKEY_LOCAL_MACHINE\Software\Microsoft\VisualStudio\9.0
\TextTemplating\DirectiveProcessors\

There was not that much going on here lately. Wolfram and I are very busy these days, but we didn’t forgot about the blog. There are many ideas for articles but to few spare time to write them. Fortunately this will become a little bit better in a few weeks.

For the meantime I build a nice tagcloud to remember you what’s usually going on her:

Produced with Wordle. Images of Wordles are licensed .

Stay tuned!

Every DSL you create with DSL Tools has a model explorer. This model explorer is a tool window in Visual Studio displaying the elements of your model in a hierarchical way. This is often a nice feature but sometimes a hierarchical view of your data is not appropriate. So I came to the question: How to remove the explorer from the generated code?

I could not find any option in the DSL design to remove the model explorer, but if you look at some of the .tt files you will find somewhere a query for this.Dsl.Explorer != null. For example in the package.tt file that generates the package.cs which is responsible for registering the tool window for the model explorer:

<#
    if(this.Dsl.Explorer != null)
    {
#>
    [VSShell::ProvideToolWindow(         typeof(<#= dslName #>ExplorerToolWindow),          MultiInstances = false,          Style = VSShell::VsDockStyle.Tabbed,          Orientation = VSShell::ToolWindowOrientation.Right,          Window = "{3AE79031-E1BC-11D0-8F78-00A0C9110057}")]
    [VSShell::ProvideToolWindowVisibility(         typeof(<#= dslName #>ExplorerToolWindow),          Constants.<#= dslName #>EditorFactoryId)]
<#
    }
#>

Even if I did not find any option to set the Dsl.Explorer property of the model to null (you did not see the Explorer property anywhere in the DSL diagram) it seems that the developers of the DSL Tools had this use case in mind.

To remove the Dsl.Explorer from your DSL model open the .dsl file with a text editor and go to the end. There you will find some XML tags like the following:

<Explorer ExplorerGuid="6c276297-6acd-4e9a-8740-b61ba834004b"  Title="HardwareDescription Explorer">
    <ExplorerBehaviorMoniker      Name="HardwareDescription/HardwareDescriptionExplorer" />
</Explorer>

Just delete these three lines and generate your code once again. Maybe you should reset your Experimental Hive, too.

I tested a DSL with a removed Model Explorer without any problems. It seems the developers of the DSL Tools did a very good job on the code generation templates . The generated ModelExplorer.cs file contains only a single line:

// This source file is empty because    this DSL does not define a model explorer.

That should be a good proof that a DSL can run without the model explorer even if it might be not supported by the DSL Tools.

We all know and love the foreach keyword in C# and use it for loops every day:

List<int> list = new List<int>();
/* fill the list */
foreach (int i in list)
    Console.WriteLine(i);

But the generic List<T> class contains a useful method for small loops, too. The method is called ForEach() and has only one parameter: an Action<T>.

delegates: Action<>, Func<> and Predicate<>

The Framework 3.5 defines a few generic delegate types for actions and functions. In this case a function is something that returns a value (think back to your math class) and actions are something that do not return a value but do something (maybe think back to physics class). All these delegates are defined with zero, one, two, three and four parameters:

public delegate voidAction();
public delegate voidAction<T>(T obj);
public delegate voidAction<T1, T2>(T1 arg1, T2 arg2);
public delegate voidAction<T1, T2, T3>(T1 arg1, T2 arg2, T3 arg3);
public delegate voidAction<T1, T2, T3, T4>(T1 arg1, T2 arg2, T3 arg3, T4 arg4);

public delegateTResult Func<TResult>();
public delegateTResult Func<T, TResult>(T arg);
public delegateTResult Func<T1, T2, TResult>(T1 arg1, T2 arg2);
public delegateTResult Func<T1, T2, T3, TResult>(T1 arg1, T2 arg2, T3 arg3);
public delegateTResult Func<T1, T2, T3, T4, TResult>(T1 arg1, T2 arg2, T3 arg3, T4 arg4);

And there is one more delegate. The Predicate<T> (philosophy class, you know). A predicate comes to a logical decision (true or false; bool return value) based on a single object:
public delegate bool Predicate<T>(T obj);

All these delegates are generic so you can use them in a type save way with the type parameters you need.

Back to the ForEach() method

As I explained above, the ForEach() method takes an Action<T> parameter. In my example this is an Action<int> delegate:

list.ForEach( delegate(int i) {Console.WriteLine(i);} );

This anonymous delegate declaration is not that nice, but we can use Lamda types here:

list.ForEach(i => Console.WriteLine(i));

But let’s take a look at the method we’re calling: void Console.WriteLine(int). That is exactly the definition of the needed Action here. So we can write the code line even shorter:

list.ForEach( Console.WriteLine );

I like this code. It is very short, elegant and readable. It says: “For each [entry of] the list: write it out”. Great.

There is a known issue in the current version of the DSL Tools while dealing with custom TypeConverters or custom TypeDescriptors:

1.10 TypeConverters and TypeDescriptors are not picked up during the build process or during toolbox initialization.
When adding a custom TypeConverter or TypeDescriptor and then building the DSL, the TypeConvertor or TypeDescriptor is not picked up. The workaround is to rebuild the solution with a clean build.

[see Known Issues for Microsoft Visual Studio 2008 SDK 1.0]

Some time ago I posted a workaround for this problem with the TypeConverter, but today a realized that this workaround does not work with the same issue for TypeDescriptors.

Imagine some class with the following attribute:

[TypeDescriptionProvider(typeof(MyClassTypeDescriptionProvider))]
public partial class MyClass : ModelElement
{}

The corresponding TypeDescriptor (provided by the MyClassTypeDescriptionProvider class) is loaded only the first time you build or rebuild your solution. Every time you start Visual Studio after that, this attribute seems to be ignored.

Fortunately there is another way to glue TypeDescriptors to your classes using a static method of the TypeDescriptor class at runtime:

TypeDescriptor.AddProvider(
   new MyClassTypeDescriptionProvider(), typeof(MyClass));

I think a good place for this code is the static constructor of the MyClass type:

partial class MyClass
{
    static MyClass()
    {
        TypeDescriptor.AddProvider(
            new MyClassTypeDescriptionProvider(),
            typeof(MyClass));
    }
}

Another interesting point is: Not only custom TypeDescriptors you write yourself are affected by this problem, also the TypeDescriptors that are generated by the DSL-Tools from your DslDefintion have to struggle with it:

In the DSL Explorer you can define custom TypeDescriptors for each Domain Class and each Shape. Even these TypeDescriptors will not be loaded after the first run. In other words: the definition of TypeDescriptors in the DSL Explorer is pretty useless as long as you do not add the three lines of code to each class. Of course this is something one can automate! I stole some code from PropertiesGrid.tt and added a few lines to create the RegisterTypeDescriptor.tt. Just add this file to your Dsl Project in the GeneratedCode folder and all TypeDescriptors defined in the DSL Explorer will be loaded every time you start your project.

As you know I was working with the DSL Tools in the past months. For some weeks I am writing the code generation for my project and I am struggling with new problems.

For some reason I want to know the filename of the model used in the tt-file. The default implementation provides you only with a reference to the model but with no chance to get its filename.

In your tt-file you will find something similar to

<#@ Language15 processor="Language15DirectiveProcessor"
     requires="fileName='Sample.mydsl1'" #>

This will use the Language15DirectiveProcessor to load the given file and provide your template with a global ExampleModel variable (of cause the name depends on your DSL and you can change it with the provides attribute in the tt-file).

To change the Language15DirectiveProcessor you can create a partial class in your DSL and add some code to it:

partial class Language15DirectiveProcessor
{
    protected override void GenerateTransformCode
     (string directiveName,
      StringBuilder codeBuffer,
      System.CodeDom.Compiler.CodeDomProvider languageProvider,
      IDictionary<string, string> requiresArguments,
      IDictionary<string, string> providesArguments)
      {
        base.GenerateTransformCode(directiveName,
                    codeBuffer, languageProvider,
                    requiresArguments, providesArguments);           

        codeBuffer.AppendFormat(
           "public string {1} = @\"{0}\";",
             requiresArguments["FileName"],
             providesArguments["FileName"]);

       codeBuffer.AppendLine();
    }

    protected override void InitializeProvidesDictionary
    (string directiveName,
      IDictionary<string, string> providesDictionary)
    {
        base.InitializeProvidesDictionary(directiveName,
                            providesDictionary);

        providesDictionary.Add("FileName","FileName");
    }
}

This adds a new global variable FileName to the tt and initializes it with the model file name.

Attention: You see the variable in this example is generated by writing a line of C# code to the codeBuffer. This may be a bad idea if you want to use this DirectiveProcessor for templates where the template language is set to VB. The better way is to create the code using the Emit and CodeDom API, but I was to lazy to do it that way.

If anybody ports this code to work with VB templates by using the CodeDom or plain VB code, please post a comment here.

Further reading: The process of creating your own DirectiveProcessor and everything you need to understand the code above can be found in the msdn: Creating Custom Text Template Directive Processors.

One of my DSLs uses many black connectors laying all over the screen. Every time I try to follow one connector I select it to change the border and to see a difference between all connectors. A colleague saw this design and asks me to implement a mouse over feedback for these connectors since all shapes have already such a visual feedback. The color of shapes changes a little bit if the mouse is over the shape. I had no idea how this should work for connectors…

First I take a look on the properties of the connector in the DSL designer and while searching I observed something: The DSL designer has this behavior on all connectors! I don’t have to write code for the MouseOver-event, but I have to figure out how to activate this behavior on my DSL editor.

For my surprise, the connectors on a newly created example language have a mouse over feedback, too. After playing around with some properties I was faced to a interesting fact: The mouse over feedback works pretty good for all connectors but black ones. I had no idea what’s going on.

Long story short: With Reflector I found one interesting method in the ShapeElement class: ModifyLuminosity(). The documentation is very clear:

"Calculates the luminosity of the highlight for the shape."

"The formula that creates luminosity. By default, the formula is: if luminosity is >= 160, then luminosity = luminosity * 0.9; otherwise, luminosity = luminosity + 40."

The luminosity of a black connector is 0 so the new luminosity will be 40. But for the color black you hardly see a difference between 0 and 40. But with this knowledge you can override the method in the connector class like this:

protected override int ModifyLuminosity
              (int currentLuminosity, DiagramClientView view)
{
  if(!view.HighlightedShapes.Contains(new DiagramItem(this)))
     return currentLuminosity;

 return 130;
}

The value 130 on a black connector works pretty good for me. Just try a few values und find a value you like.

Visual Studio 2005 had a known issue with the setup project and the RemovePreviousVersions option if the version number of your software is less than 1.0. This was a problem for me every time I released a new version of PhotoTagStudio. Like most small open source projects I won’t call it 1.0 (the current version is 0.7).

I described the problem and a workaround using the tool orca.exe. Every time I build a new setup I had to patch the setup. Last week I switched my PhotoTagStudio project to Visual Studio 2008 and created a new release. While patching the created msi I discovered that there is no need to do it that way any more. The problem seems to be fixed in the Visual Studio 2008 release!

Great work Microsoft!

In To restrict dynamically the usage of Domain Properties in DSL Models I described a way to restrict the usage of certain domain properties by the user. You can define different modes for your editor and thus allow or prevent the usage of domain properties via attributes on your domain classes. The technique is described in the linked article and the code is released as part of JaDAL – Just another DSL-Tools Addon Library.

This is a pretty static way to control the domain properties. You have to define a few modes and decide at design time the visible and active properties for each mode. Sometimes you need a more dynamic way: So I introduced another attribute CustomRestrictedPropertyAttribute and an interface ISupportsUserRestrictions. If this attribute is present, the library will call the GetRestriction() method of this interface and your user code can decide whenever the domain property will be visible, hidden or read only.

I built a small example: a domain class contains a few properties: CustomPropery, CustomPropertyVisible and CustomPropertyReadOnly. The two flags cause the first property to be visible, hidden or read only in the properties window.

[CustomRestrictedProperty("CustomProperty")]
partial class ExampleElement : ISupportsUserRestrictions
{
    public Restriction GetRestriction(string property)
    {
        if (property == "CustomProperty")
        {
            if (!this.CustomPropertyVisible)
                return Restriction.Hidden;

            if (this.CustumPropertyReadOnly)
                return Restriction.ReadOnly;

            return Restriction.Full;
        }

        return Restriction.Full;
    }
}

This example can be downloaded as part of the JaDAL source code. Currently you have to catch the code directly from the Source Code tab at CodePlex since it isn’t part of the latest Release yet.

Over the time I build some libraries that enhance the Microsoft DSL Tools framework and post them here. I wrote a number of articles and for many of them I provided a download with source code or examples.

However we all know: zip files are a bad version management system!

I decided to put all these code together and compose a single library with addons for the DSL Tools, name it “JaDAL – Just another DSL-Tools Addon Library” and publish it at CodePlex. I will continue to write articles here, but now you can always find the latest code at CodePlex.

If you are interested in my work with the DSL Tools, just take a look at JaDAL.