Programmatic control of virtual desktops in Windows 10
Solution 1:
The Windows SDK Support Team Blog posted a C# demo to switch Desktops via IVirtualDesktopManager:
[ComImport, InterfaceType(ComInterfaceType.InterfaceIsIUnknown), Guid("a5cd92ff-29be-454c-8d04-d82879fb3f1b")]
[System.Security.SuppressUnmanagedCodeSecurity]
public interface IVirtualDesktopManager
{
[PreserveSig]
int IsWindowOnCurrentVirtualDesktop(
[In] IntPtr TopLevelWindow,
[Out] out int OnCurrentDesktop
);
[PreserveSig]
int GetWindowDesktopId(
[In] IntPtr TopLevelWindow,
[Out] out Guid CurrentDesktop
);
[PreserveSig]
int MoveWindowToDesktop(
[In] IntPtr TopLevelWindow,
[MarshalAs(UnmanagedType.LPStruct)]
[In]Guid CurrentDesktop
);
}
[ComImport, Guid("aa509086-5ca9-4c25-8f95-589d3c07b48a")]
public class CVirtualDesktopManager
{
}
public class VirtualDesktopManager
{
public VirtualDesktopManager()
{
cmanager = new CVirtualDesktopManager();
manager = (IVirtualDesktopManager)cmanager;
}
~VirtualDesktopManager()
{
manager = null;
cmanager = null;
}
private CVirtualDesktopManager cmanager = null;
private IVirtualDesktopManager manager;
public bool IsWindowOnCurrentVirtualDesktop(IntPtr TopLevelWindow)
{
int result;
int hr;
if ((hr = manager.IsWindowOnCurrentVirtualDesktop(TopLevelWindow, out result)) != 0)
{
Marshal.ThrowExceptionForHR(hr);
}
return result != 0;
}
public Guid GetWindowDesktopId(IntPtr TopLevelWindow)
{
Guid result;
int hr;
if ((hr = manager.GetWindowDesktopId(TopLevelWindow, out result)) != 0)
{
Marshal.ThrowExceptionForHR(hr);
}
return result;
}
public void MoveWindowToDesktop(IntPtr TopLevelWindow, Guid CurrentDesktop)
{
int hr;
if ((hr = manager.MoveWindowToDesktop(TopLevelWindow, CurrentDesktop)) != 0)
{
Marshal.ThrowExceptionForHR(hr);
}
}
}
it includes the API to detect on which desktop the Window is shown and it can switch and move a Windows the a Desktop.
Solution 2:
Programmatic access to the virtual desktop feature is very limited, as Microsoft has only exposed the IVirtualDesktopManager COM interface. It does provide two key functions:
-
IVirtualDesktopManager::GetWindowDesktopIdallows you to retrieve the ID of a virtual desktop, based on a window that is already assigned to that desktop. -
IVirtualDesktopManager::MoveWindowToDesktopallows you to move a window to a specific virtual desktop.
Unfortunately, this is not nearly enough to accomplish anything useful. I've written some C# code based on the reverse-engineering work done by NickoTin. I can't read much of the Russian in his blog post, but his C++ code was pretty accurate.
I do need to emphasize that this code is not something you want to commit to in a product. Microsoft always feels free to change undocumented APIs whenever they feel like it. And there is a runtime risk as well: this code does not necessarily interact well when the user is tinkering with the virtual desktops. Always keep in mind that a virtual desktop can appear and disappear at any time, completely out of sync with your code.
To use the code, create a new C# class library project. I'll first post ComInterop.cs, it contains the COM interface declarations that match NickoTin's C++ declarations:
using System;
using System.Runtime.InteropServices;
namespace Windows10Interop {
internal static class Guids {
public static readonly Guid CLSID_ImmersiveShell =
new Guid(0xC2F03A33, 0x21F5, 0x47FA, 0xB4, 0xBB, 0x15, 0x63, 0x62, 0xA2, 0xF2, 0x39);
public static readonly Guid CLSID_VirtualDesktopManagerInternal =
new Guid(0xC5E0CDCA, 0x7B6E, 0x41B2, 0x9F, 0xC4, 0xD9, 0x39, 0x75, 0xCC, 0x46, 0x7B);
public static readonly Guid CLSID_VirtualDesktopManager =
new Guid("AA509086-5CA9-4C25-8F95-589D3C07B48A");
public static readonly Guid IID_IVirtualDesktopManagerInternal =
new Guid("AF8DA486-95BB-4460-B3B7-6E7A6B2962B5");
public static readonly Guid IID_IVirtualDesktop =
new Guid("FF72FFDD-BE7E-43FC-9C03-AD81681E88E4");
}
[ComImport]
[InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
[Guid("FF72FFDD-BE7E-43FC-9C03-AD81681E88E4")]
internal interface IVirtualDesktop {
void notimpl1(); // void IsViewVisible(IApplicationView view, out int visible);
Guid GetId();
}
[ComImport]
[InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
[Guid("AF8DA486-95BB-4460-B3B7-6E7A6B2962B5")]
internal interface IVirtualDesktopManagerInternal {
int GetCount();
void notimpl1(); // void MoveViewToDesktop(IApplicationView view, IVirtualDesktop desktop);
void notimpl2(); // void CanViewMoveDesktops(IApplicationView view, out int itcan);
IVirtualDesktop GetCurrentDesktop();
void GetDesktops(out IObjectArray desktops);
[PreserveSig]
int GetAdjacentDesktop(IVirtualDesktop from, int direction, out IVirtualDesktop desktop);
void SwitchDesktop(IVirtualDesktop desktop);
IVirtualDesktop CreateDesktop();
void RemoveDesktop(IVirtualDesktop desktop, IVirtualDesktop fallback);
IVirtualDesktop FindDesktop(ref Guid desktopid);
}
[ComImport]
[InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
[Guid("a5cd92ff-29be-454c-8d04-d82879fb3f1b")]
internal interface IVirtualDesktopManager {
int IsWindowOnCurrentVirtualDesktop(IntPtr topLevelWindow);
Guid GetWindowDesktopId(IntPtr topLevelWindow);
void MoveWindowToDesktop(IntPtr topLevelWindow, ref Guid desktopId);
}
[ComImport]
[InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
[Guid("92CA9DCD-5622-4bba-A805-5E9F541BD8C9")]
internal interface IObjectArray {
void GetCount(out int count);
void GetAt(int index, ref Guid iid, [MarshalAs(UnmanagedType.Interface)]out object obj);
}
[ComImport]
[InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
[Guid("6D5140C1-7436-11CE-8034-00AA006009FA")]
internal interface IServiceProvider10 {
[return: MarshalAs(UnmanagedType.IUnknown)]
object QueryService(ref Guid service, ref Guid riid);
}
}
Next is Desktop.cs. It contains the friendly C# classes that you can use in your code:
using System;
using System.Runtime.InteropServices;
namespace Windows10Interop
{
public class Desktop {
public static int Count {
// Returns the number of desktops
get { return DesktopManager.Manager.GetCount(); }
}
public static Desktop Current {
// Returns current desktop
get { return new Desktop(DesktopManager.Manager.GetCurrentDesktop()); }
}
public static Desktop FromIndex(int index) {
// Create desktop object from index 0..Count-1
return new Desktop(DesktopManager.GetDesktop(index));
}
public static Desktop FromWindow(IntPtr hWnd) {
// Creates desktop object on which window <hWnd> is displayed
Guid id = DesktopManager.WManager.GetWindowDesktopId(hWnd);
return new Desktop(DesktopManager.Manager.FindDesktop(ref id));
}
public static Desktop Create() {
// Create a new desktop
return new Desktop(DesktopManager.Manager.CreateDesktop());
}
public void Remove(Desktop fallback = null) {
// Destroy desktop and switch to <fallback>
var back = fallback == null ? DesktopManager.GetDesktop(0) : fallback.itf;
DesktopManager.Manager.RemoveDesktop(itf, back);
}
public bool IsVisible {
// Returns <true> if this desktop is the current displayed one
get { return object.ReferenceEquals(itf, DesktopManager.Manager.GetCurrentDesktop()); }
}
public void MakeVisible() {
// Make this desktop visible
DesktopManager.Manager.SwitchDesktop(itf);
}
public Desktop Left {
// Returns desktop at the left of this one, null if none
get {
IVirtualDesktop desktop;
int hr = DesktopManager.Manager.GetAdjacentDesktop(itf, 3, out desktop);
if (hr == 0) return new Desktop(desktop);
else return null;
}
}
public Desktop Right {
// Returns desktop at the right of this one, null if none
get {
IVirtualDesktop desktop;
int hr = DesktopManager.Manager.GetAdjacentDesktop(itf, 4, out desktop);
if (hr == 0) return new Desktop(desktop);
else return null;
}
}
public void MoveWindow(IntPtr handle) {
// Move window <handle> to this desktop
DesktopManager.WManager.MoveWindowToDesktop(handle, itf.GetId());
}
public bool HasWindow(IntPtr handle) {
// Returns true if window <handle> is on this desktop
return itf.GetId() == DesktopManager.WManager.GetWindowDesktopId(handle);
}
public override int GetHashCode() {
return itf.GetHashCode();
}
public override bool Equals(object obj) {
var desk = obj as Desktop;
return desk != null && object.ReferenceEquals(this.itf, desk.itf);
}
private IVirtualDesktop itf;
private Desktop(IVirtualDesktop itf) { this.itf = itf; }
}
internal static class DesktopManager {
static DesktopManager() {
var shell = (IServiceProvider10)Activator.CreateInstance(Type.GetTypeFromCLSID(Guids.CLSID_ImmersiveShell));
Manager = (IVirtualDesktopManagerInternal)shell.QueryService(Guids.CLSID_VirtualDesktopManagerInternal, Guids.IID_IVirtualDesktopManagerInternal);
WManager = (IVirtualDesktopManager)Activator.CreateInstance(Type.GetTypeFromCLSID(Guids.CLSID_VirtualDesktopManager));
}
internal static IVirtualDesktop GetDesktop(int index) {
int count = Manager.GetCount();
if (index < 0 || index >= count) throw new ArgumentOutOfRangeException("index");
IObjectArray desktops;
Manager.GetDesktops(out desktops);
object objdesk;
desktops.GetAt(index, Guids.IID_IVirtualDesktop, out objdesk);
Marshal.ReleaseComObject(desktops);
return (IVirtualDesktop)objdesk;
}
internal static IVirtualDesktopManagerInternal Manager;
internal static IVirtualDesktopManager WManager;
}
}
And finally a little test WinForms project that I used to test the code. Just drop 4 buttons on a form and name them buttonLeft/Right/Create/Destroy:
using Windows10Interop;
using System.Diagnostics;
...
public partial class Form1 : Form {
public Form1() {
InitializeComponent();
}
private void buttonRight_Click(object sender, EventArgs e) {
var curr = Desktop.FromWindow(this.Handle);
Debug.Assert(curr.Equals(Desktop.Current));
var right = curr.Right;
if (right == null) right = Desktop.FromIndex(0);
if (right != null) {
right.MoveWindow(this.Handle);
right.MakeVisible();
this.BringToFront();
Debug.Assert(right.IsVisible);
}
}
private void buttonLeft_Click(object sender, EventArgs e) {
var curr = Desktop.FromWindow(this.Handle);
Debug.Assert(curr.Equals(Desktop.Current));
var left = curr.Left;
if (left == null) left = Desktop.FromIndex(Desktop.Count - 1);
if (left != null) {
left.MoveWindow(this.Handle);
left.MakeVisible();
this.BringToFront();
Debug.Assert(left.IsVisible);
}
}
private void buttonCreate_Click(object sender, EventArgs e) {
var desk = Desktop.Create();
desk.MoveWindow(this.Handle);
desk.MakeVisible();
Debug.Assert(desk.IsVisible);
Debug.Assert(desk.Equals(Desktop.Current));
}
private void buttonDestroy_Click(object sender, EventArgs e) {
var curr = Desktop.FromWindow(this.Handle);
var next = curr.Left;
if (next == null) next = curr.Right;
if (next != null && next != curr) {
next.MoveWindow(this.Handle);
curr.Remove(next);
Debug.Assert(next.IsVisible);
}
}
}
The only real quirk I noticed while testing this is that moving a window from one desktop to another can move it to the bottom of the Z-order when you first switch the desktop, then move the window. No such problem if you do it the other way around.