Visual Studio tool windows

24.10.2012 Paul Eremeev
This article is obsolete. You can read the new version of this article here.

Abstract

This article covers the extension of Visual Studio IDE through integration of a custom user toolwindow into the environment. Discussed are the issues of window registration and initialization in VSPackage and Add-In plug-in modules, hosting of user components and handling of window's events and states.

Introduction

Tool windows are child windows of Visual Studio MDI (Multiple Document Interface) interface and they are responsible for presenting various pieces of information to the user. Solution Explorer and Error List are the examples of tool windows. Usually tool windows' contents are not associated with any files and do not contain any editors, as separate document windows are reserved for such tasks.

For instance, PVS-Studio extension package integrates several tool windows into the IDE, with Output Window being the primary one. All other of its tool windows can be opened from this main window, as, for example, a search window for the grid. PVS-Studio Output Window itself can be opened from Visual Studio main menu (PVS-Studio -> Show PVS-Studio Output Window), but it also will be invoked automatically each time the analysis starts.

In most cases IDE creates and utilizes just a single instance for each one of its toolwindows, and this instance will be preserved until IDE itself needs to shut down. Therefore, pressing the 'close' button on a tool window does actually hide it, and when this window is invoked for the second time, it becomes visible again, thus preserving any data that it contained before being 'closed'. But still, is it possible to crate Multi-Instance toolwindows in the IDE, which are the windows that can exist in several instances at once. A toolwindow can also be associated with a certain UI context (as the so called dynamic window), and such window will be automatically displayed when the user enters this context.

Integration of a tool window into the IDE is supported by VSPackage and Add-In extensions (although the methods for it are different); it requires the specification of the window's initial settings and its registration in the system registry.

Registering and initializing user tool windows

A VSPackage project template that is installed together with Visual Studio SDK allows you to create a sample tool window in the extension project which this template generates. Such a project should already contain all of the basic components which will be described below, so it could be conveniently used as a sample for experimenting with Visual Studio toolwindow integration process for VSPackage plug-ins.

Registering, initializing and invoking a tool window in VSPackage

Registering a custom user window in the environment requires writing of the data that defines this window into a special section of Visual Studio registry hive. This process can be automated by generating a pkgdef file that can contain all of the required window registration information. The contents of this pkgdef files can be specified through special registration attributes of your Package subclass.

The immediate registration of a user-created tool window into VSPackage extension is handled by ProvideToolWindowattribute of Package subclass:

 [ProvideToolWindow(typeof(MyWindowPane), Orientation = 
ToolWindowOrientation.Right, Style = VsDockStyle.Tabbed, Window = 
Microsoft.VisualStudio.Shell.Interop.ToolWindowGuids.Outputwindow, 
MultiInstances = false, Transient = true, Width = 500, Height = 250, 
PositionX = 300, PositionY = 300)]

Let's examine several parameters of this attribute. The 'Typeof' parameter points to user implementation of the window's client area (a subclass of ToolWindowPane). The 'MultiInstances' parameter enables the Multi-Instance mode for a window, in which multiple instances of the window can be opened simultaneously. The Orientation, Size and Style parameters specify the initial position of a window when it is opened for the first time by the user. It should be noted that the position specified by these parameters will only be used once, when a tool window is displayed for the first time; at all of the subsequent iterations of opening this window, the IDE will be restoring its screen position from the previous one, that is the position before a window was closed. The 'Transient' parameter indicates whether the window will be automatically opened after Visual Studio environment is loaded in case it already have been opened during the previous session of the IDE.

It should also be remembered that the initialization of a user window by VSPackage (the initialization itself will be covered later) does not necessarily occur at the same moment as the initialization of a Package subclass for which we provided this registration attribute. For example, after implementing a tool window for PVS-Studio plug-in, we've encountered an issue in which our custom window was automatically opened (but not focused/displayed) and placed among other window tabs at the bottom of the main window, and it was done immediately after Visual Studio started up, even though we've passed the 'Transient=true' parameter to the ProvideToolWindow attribute. Although the plug-in itself is always initialized at IDE start-up, the window had not been fully initialized until after a first call to it, which was evident by the corrupted icon on aforementioned tab.

A dynamic visibility context can be specified for a window by the ProvideToolWindowVisibility attribute:

 [ProvideToolWindowVisibility(typeof(MyWindowPane), 
/*UICONTEXT_SolutionExists*/"f1536ef8-92ec-443c-9ed7-fdadf150da82")]

In this example, the window is set to be automatically displayed when the user enters the "Solution Exists" UI context. Take a note that each one of user's toolwindow requires a separate attribute and a window's type should be passed as a first argument to it.

The FindToolWindow method of a Package subclass can be utilized to create and display a toolwindow from a VSPackage extension. This method returns a reference to the specified toolwindow object, creating it if necessary (for instance, in case a single-instance window is called for a first time). Following is the example of invoking a single-instance toolwindow:

private void ShowMyWindow(object sender, EventArgs e)
{
  ToolWindowPane MyWindow = this.FindToolWindow(typeof(MyToolWindow), 
    0, true);
  if ((null == MyWindow) || (null == MyWindow.Frame))
  {
    throw new NotSupportedException(Resources.CanNotCreateWindow);
  }
  IVsWindowFrame windowFrame = (IVsWindowFrame) MyWindow.Frame;
  ErrorHandler.ThrowOnFailure(windowFrame.Show());
}

In this example, the window will be created in case it is called for the first time, or the window will be made visible in case it had been created before and then hidden. The FindToolWindow 's third argument of the bool type specifies whether a new instance of a window should be created if the method was unable to find an already existing one.

To create a Multi-Instance tool window, the CreateToolWindow method can be used. It allows the creation of a window with a pre-defined identifier. An example of invoking such window:

private void CreateMyWindow(object sender, EventArgs e)
{
  for (int i = 0; ; i++)
  {
    // Find existing windows.
    var currentWindow = 
      this.FindToolWindow(typeof(MyToolWindow), i, false);
    if (currentWindow == null)
    {
      // Create the window with the first free ID.
      var window = 
       (ToolWindowPane)this.CreateToolWindow(typeof(MyToolWindow), i);

      if ((null == window) || (null == window.Frame))
      {
        throw new 
          NotSupportedException(Resources.CanNotCreateWindow);
      }
      IVsWindowFrame windowFrame = (IVsWindowFrame)window.Frame;

      ErrorHandler.ThrowOnFailure(windowFrame.Show());
      break;
    }
  }
}

Note that in this example the FindToolWindow method receives 'false' value as its third argument, i.e. we are searching for an unoccupied index before initializing a new window instance.

As was mentioned above, the environment will preserve position of a window after it is closed. But if, for whatever reason, it is necessary to specify the size and position of a window, it could be achieved through the SetFramePos method of the IVsWindowFrame interface:

Guid gd = Guid.Empty;
windowFrame.SetFramePos(VSSETFRAMEPOS.SFP_fDockBottom, ref gd, 20, 20, 
  200, 200);

A call to the SetFramePos() should always be made only after the Show() method is executed.

Creating and invoking a window from Add-In extension

A user tool window can be initialized from an Add-In extension with the help of the EnvDTE Window2 interface:

public void OnConnection(object application, 
ext_ConnectMode connectMode, object addInInst, ref Array custom)
{
  _applicationObject = (DTE2)application;
  _addInInstance = (AddIn)addInInst;
  EnvDTE80.Windows2 window;
  AddIn add_in;
  object ctlobj = null;
  Window myWindow;

  // Get the window object
  add_in = _applicationObject.AddIns.Item(1);
  window = (Windows2)_applicationObject.Windows;

  // This section specifies the path and class name of the windows 
  // control that you want to host in the new tool window, as well as
  // its caption and a unique GUID.
  string assemblypath = "C:\\MyToolwindow\\MyToolWindowControl.dll";
  string classname = " MyToolWindowControl.MyUserControl";
  string guidpos = "{E87F0FC8-5330-442C-AF56-4F42B5F1AD11}";
  string caption = "My Window";

  // Creates the new tool window and inserts the user control into it.
  myWindow = window.CreateToolWindow2(add_in, assemblypath, 
  classname, caption, guidpos, ref ctlobj);
  myWindow.Visible = true;
}

In the example above, a user toolwindow was created using the MyToolWindowControl.MyUserControl as a client area control. The MyToolWindowControl.MyUserControl class could either be located in the same assembly as the add-in that initializes it, or it could be provided by a stand-alone assembly with a full COM visibility (though the 'Register for COM Interop' option in project settings). The regular composite UserControl subclass could be utilized as MyUserControl.

Implementing a user toolwindow in a VSPackage module

Tool window consists of a frame border and a client area. A frame is provided by the environment and is responsible for performing docking with other interface objects of the environment, as well as for size and position of the window itself. A client area is a pane, controlled by a user, which houses the contents of a window. Tool windows can host user-created WinForms and WPF components and are capable of handling regular events, such as OnShow , OnMove, etc.

A user toolwindow, or its client area to be more precise, can be implemented by inheriting the class representing a standard empty IDE window — ToolWindowPane.

 [Guid("870ab1d8-b434-4e86-a479-e49b3c6797f0")]
public class MyToolWindow : ToolWindowPane
{

  public MyToolWindow():base(null)
  {
    this.Caption = Resources.ToolWindowTitle;
    this.BitmapResourceID = 301;
    this.BitmapIndex = 1;
    ...

  }

}

The Guid attribute is used to uniquely identify each custom user window. In case a plug-in module creates several windows of different types, each one of them should be identified by its own unique Guid. A ToolWIndowPane subclass can be subsequently modified and host user-controlled components.

Hosting user components

A base ToolWindowPane class implements an empty tool window of the environment. Inheriting form this class allows hosting user-created WinForms or WPF components.

Up until Visual Studio 2008 version, toolwindows only provided a native supported for WinForms user components, although it still was possible to host WPF components through the WPF Interoperability ElementHost object. Starting from Visual Studio 2010, toolwindows themselves are based on WPF technology, although they still provide a backward compatibility for hosting of WinForms components.

To host a user-created WinForms component inside a user toolwindow, the Window property of the ToolWindowPane base class should be overridden:

public MyUserControl control;

public MyToolWindow():base(null)
{
  this.Caption = Resources.ToolWindowTitle;
  this.BitmapResourceID = 301;
  this.BitmapIndex = 1;
  this.control = new MyUserControl();
}

public override IWin32Window Window
{
  get { return (IWin32Window)control; }
}

In the example above, the 'MyUserControl' object is a regular composite component of the System.Windows.Forms.UserControl type and it can host any other user component inside itself. UserControl can also host WPF components by using WPF ElementHost object.

Starting from Visual Studio 2010, WPF components can be hosted by tool windows natively. To do this, a reference to the WPF component should be passed to the 'Content' property of a base class:

public MyToolWindow():base(null)
{
  this.Caption = Resources.ToolWindowTitle;
  this.BitmapResourceID = 301;
  this.BitmapIndex = 1;
  base.Content = new MyWPFUserControl();
}

Please note that using the two methods described above simultaneously is not possible. When a reference to WPF component is assigned to the base.Content property, an overridden Window property is ignored.

The main PVS-Studio 'Output' window of our extension plug-in hosts a virtual grid based on SourceGrid open-source project. This window provides an interface for handling the results of static analysis. The grid itself is bound to a regular ADO.NET table of the System.Data.Datatable type, which is utilized for storing analysis results. Until 4.00 version of PVS-Studio extension, it utilized a regular IDE 'Error List' window, but as the analyzer evolved, the capabilities of this default window became insufficient. Apart from being un-extendable with such specific static analysis UI elements as, for example, false positive suppression and filtering mechanisms, the Error List is itself basically a 'real' grid, as it stores all of the displayed elements inside itself. Therefore, this grid only permits an adequate handling of 1-2k messages at a time, performance wise, as a greater number of messages already can cause quite a noticeable lag to the environment's UI. On the other hand, our own practice of using static analysis on relatively large projects, such as Chromium or LLVM, demonstrated that a total number of diagnostic messages (taking into account all of the marked false alarms and low-lever user diagnostics as well) could easily reach tens of thousands or even more.

Therefore, by implementing a custom output window, based on virtual grid that is connected to a DB table, PVS-Studio is able to display and provide convenient handling for hundreds of thousands of diagnostic messages at once. Also, the ability for a convenient and flexible filtering of the analysis results is quite an important aspect of handling a static analyzer, as the manual examination even of only such a "tiny" amount of messages as 1-2k is nearly impossible for a single user. The storage of analysis results in a Datatable object by itself provides quite a convenient filtering mechanism based on a simple SQL queries, even more so because the results of such queries become visible immediately inside the bound virtual grid.

Handling tool windows events

A client area of a tool window (represented by our ToolWindowPane subclass) can process the regular events of user-interface interactions. The IVsWindowFrameNotify3 interface can be used for subscribing to window events. Let's provide an example of implementing this interface:

public sealed class WindowStatus: IVsWindowFrameNotify3
{
  // Private fields to keep track of the last known state
  private int x = 0;
  private int y = 0;
  private int width = 0;
  private int height = 0;
  private bool dockable = false;

  #region Public properties
            
  // Return the current horizontal position of the window
  public int X
  {
    get { return x; }
  }
            
  // Return the current vertical position of the window
  public int Y
  {
    get { return y; }
  }

  // Return the current width of the window
  public int Width
  {
    get { return width; }
  }

  // Return the current height of the window
  public int Height
  {
    get { return height; }
  }
            
  // Is the window dockable
  public bool IsDockable
  {
    get { return dockable; }
  }

  #endregion

  public WindowStatus()
  {}

  #region IVsWindowFrameNotify3 Members
  // This is called when the window is being closed
  public int OnClose(ref uint pgrfSaveOptions)
  {
    return Microsoft.VisualStudio.VSConstants.S_OK;
  }

  // This is called when a window "dock state" changes. 
  public int OnDockableChange(int fDockable, int x, int y, int w, 
  int h)
  {
    this.x = x;
    this.y = y;
    this.width = w;
    this.height = h;
    this.dockable = (fDockable != 0);
                
    return Microsoft.VisualStudio.VSConstants.S_OK;
  }

  // This is called when the window is moved
  public int OnMove(int x, int y, int w, int h)
  {
    this.x = x;
    this.y = y;
    this.width = w;
    this.height = h;

    return Microsoft.VisualStudio.VSConstants.S_OK;
  }

  // This is called when the window is shown or hidden
  public int OnShow(int fShow)
  {
    return Microsoft.VisualStudio.VSConstants.S_OK;
  }

  /// This is called when the window is resized
  public int OnSize(int x, int y, int w, int h)
  {
    this.x = x;
    this.y = y;
    this.width = w;
    this.height = h;
    return Microsoft.VisualStudio.VSConstants.S_OK;
  }

  #endregion

}

As evident by this sample code above, the WindowsStatus class implementing the interface is able to process such window state changes, as the alterations in window's size, position, visibility properties and so on. Now, let's subscribe our window for handling these events. It requires the OnToolWindowCreated method to be overridden in our ToolWindowPane subclass:

public class MyToolWindow: ToolWindowPane
{
  public override void OnToolWindowCreated()
  {
    base.OnToolWindowCreated();

    // Register to the window events
    WindowStatus windowFrameEventsHandler = new WindowStatus();

ErrorHandler.ThrowOnFailure(
  ((IVsWindowFrame)this.Frame).SetProperty(
  (int)__VSFPROPID.VSFPROPID_ViewHelper, 
  (IVsWindowFrameNotify3)windowFrameEventsHandler));
  }

  ...
}

Controlling window state

A window state can be controlled through event handlers of our IVsWindowFrameNotify3 implementation.

The 'OnShow' method notifies the extension package about changes in tool window's visibility state, allowing to track the appearance of the window to a user, when, for example, user switches windows by clicking on window tabs. Current visibility state could be obtained by the fShow parameter, which corresponds to the __FRAMESHOW list.

The 'OnClose' method notifies about the closure of a window frame, allowing to define IDE behavior in case ofthis event with the pgrfSaveOptions parameter, which controls the default document saving dialog (__FRAMECLOSE).

The OnDockableChange method informs the package on window's docking status changes. The fDockable parameter indicates whether a window is docked to another one; other parameters control window's size and position before and after the docking event.

The parameters of 'OnMove' and 'OnSize' methods provide window's coordinates and size while it is being dragged of resized.

References

Other articles in this series