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.

1. Visual Studio tool windows
Author: Paul Eremeev
Date: 24.10.2012
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

2. 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
ProvideToolWindow attribute 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),

3. 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;

4. 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:MyToolwindowMyToolWindowControl.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.

5. 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.

6. 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;

7. 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)

8. {
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();

9. // 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
1. MSDN. Kinds of Windows.
2. MSDN. Tool Windows.
3. MSDN. Tool Window Essentials.
4. MSDN. Tool Window Walkthroughs.
5. MSDN. Arranging and Using Windows in Visual Studio.
6. MZ-Tools. HOWTO: Understanding toolwindow states in Visual Studio.
Other articles in this series
0. Introduction.
1. Creating, debugging and deploying extension packages for Microsoft Visual Studio
2005/2008/2010/2012.
2. Visual Studio Automation Object Model. EnvDTE interfaces.
3. Visual Studio commands.

10. 4. Visual Studio tool windows.
5. Integrating into Visual Studio settings.
6. Visual C++ project model.