c#winformswinapipinvokeuser32
Move window when external application's window moves
I've got an always on-top application (basically a status display) that I want to follow around another program and always sit just to the left of the minimize button.
I can get the Rect representing the "target" process using the following code which I can then pair with an offset to generate the initial position of my overlay.
Get the HWnd IntPtr:
private IntPtr HWnd = Process.GetProcessesByName("targetapplication")[0].MainWindowHandle;
Declare the function from user32.dll:
[DllImport("user32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool GetWindowRect(IntPtr hWnd, ref RECT lpRect);
And the appropriate struct:
[StructLayout(LayoutKind.Sequential)]
private struct RECT
{
public int Left;
public int Top;
public int Right;
public int Bottom;
}
And then call it on demand.
However, I would like to avoid constantly polling this value, so I would like to hook into the target application and respond whenever the target window is moved.
Looking around the user32.dll documentation, the only way I can see for doing this is using SetWindowsHookEx(). I'm not entirely sure of how I'd go about intercepting an event from here however.
I believe the target application is built off of WinForms but I cannot be sure. So solutions that let me respond to the target's Move event or directly to some Windows Message would both be useful.
Any ideas on how I can proceed?
Solution
A method to hook a Windows Form to another process (Notepad, in this case) and follow the movements of the process' Main Window, to create sort of a Toolbar that can interact with the process, using SetWinEventHook().
To get the hooked Window bounds, GetWindowRect() is not recommended. Better call DwmGetWindowAttribute() passing DWMWA_EXTENDED_FRAME_BOUNDS as the DWMWINDOWATTRIBUTE, which still returns a RECT. This because GetWindowRect() is not DpiAware and it may return a virtualized measure in some contexts, plus it includes the Window drop shadow in specific configurations.
Read more about DpiAwarenes, Screen layout and VirtualScreen here:
Using SetWindowPos with multiple monitors
Also refactored the Hook helper class and the NativeMethods declarations.
▶ To move to foreground the Tool Window, as in the animation, when the hooked Window becomes the Foreground Window, also hook the EVENT_SYSTEM_FOREGROUND event: you'll receive a notification when the Foreground Window changes, then compare with the handle of Window you're hooking.
A visual representation of the results:
The Form class initialization procedure:
using System.Diagnostics;
using System.Drawing;
using System.Linq;
using System.Runtime.InteropServices;
using System.Windows.Forms;
public partial class Form1 : Form
{
private IntPtr notepadhWnd;
private IntPtr hWinEventHook;
private Process targetProc = null;
protected Hook.WinEventDelegate WinEventDelegate;
static GCHandle GCSafetyHandle;
public Form1()
{
InitializeComponent();
WinEventDelegate = new Hook.WinEventDelegate(WinEventCallback);
GCSafetyHandle = GCHandle.Alloc(WinEventDelegate);
targetProc = Process.GetProcessesByName("notepad").FirstOrDefault(p => p != null);
try {
if (targetProc != null) {
notepadhWnd = targetProc.MainWindowHandle;
if (notepadhWnd != IntPtr.Zero) {
uint targetThreadId = Hook.GetWindowThread(notepadhWnd);
hWinEventHook = Hook.WinEventHookOne(
NativeMethods.SWEH_Events.EVENT_OBJECT_LOCATIONCHANGE,
WinEventDelegate, (uint)targetProc.Id, targetThreadId);
var rect = Hook.GetWindowRectangle(notepadhWnd);
// Of course, set the Form.StartPosition to Manual
Location = new Point(rect.Right, rect.Top);
}
}
}
catch (Exception ex) {
// Log and message or
throw;
}
}
protected void WinEventCallback(
IntPtr hWinEventHook,
NativeMethods.SWEH_Events eventType,
IntPtr hWnd,
NativeMethods.SWEH_ObjectId idObject,
long idChild, uint dwEventThread, uint dwmsEventTime)
{
if (hWnd == notepadhWnd &&
eventType == NativeMethods.SWEH_Events.EVENT_OBJECT_LOCATIONCHANGE &&
idObject == (NativeMethods.SWEH_ObjectId)NativeMethods.SWEH_CHILDID_SELF)
{
var rect = Hook.GetWindowRectangle(hWnd);
Location = new Point(rect.Right, rect.Top);
}
}
protected override void OnFormClosing(FormClosingEventArgs e)
{
base.OnFormClosing(e);
if (!e.Cancel) {
if (GCSafetyHandle.IsAllocated) GCSafetyHandle.Free();
Hook.WinEventUnhook(hWinEventHook);
}
}
protected override void OnShown(EventArgs e)
{
if (targetProc == null) {
this.Hide();
MessageBox.Show("Notepad not found!", "Target Missing", MessageBoxButtons.OK, MessageBoxIcon.Hand);
this.Close();
}
else {
Size = new Size(50, 140);
targetProc.Dispose();
}
base.OnShown(e);
}
The support classes used to reference the Windows API methods:
using System.Runtime.InteropServices;
using System.Security.Permissions;
public class Hook
{
public delegate void WinEventDelegate(
IntPtr hWinEventHook,
NativeMethods.SWEH_Events eventType,
IntPtr hwnd,
NativeMethods.SWEH_ObjectId idObject,
long idChild,
uint dwEventThread,
uint dwmsEventTime
);
public static IntPtr WinEventHookRange(
NativeMethods.SWEH_Events eventFrom, NativeMethods.SWEH_Events eventTo,
WinEventDelegate eventDelegate,
uint idProcess, uint idThread)
{
return NativeMethods.SetWinEventHook(
eventFrom, eventTo,
IntPtr.Zero, eventDelegate,
idProcess, idThread,
NativeMethods.WinEventHookInternalFlags);
}
public static IntPtr WinEventHookOne(
NativeMethods.SWEH_Events eventId,
WinEventDelegate eventDelegate,
uint idProcess,
uint idThread)
{
return NativeMethods.SetWinEventHook(
eventId, eventId,
IntPtr.Zero, eventDelegate,
idProcess, idThread,
NativeMethods.WinEventHookInternalFlags);
}
public static bool WinEventUnhook(IntPtr hWinEventHook) =>
NativeMethods.UnhookWinEvent(hWinEventHook);
public static uint GetWindowThread(IntPtr hWnd)
{
return NativeMethods.GetWindowThreadProcessId(hWnd, IntPtr.Zero);
}
public static NativeMethods.RECT GetWindowRectangle(IntPtr hWnd)
{
NativeMethods.DwmGetWindowAttribute(hWnd,
NativeMethods.DWMWINDOWATTRIBUTE.DWMWA_EXTENDED_FRAME_BOUNDS,
out NativeMethods.RECT rect, Marshal.SizeOf<NativeMethods.RECT>());
return rect;
}
}
public static class NativeMethods
{
[StructLayout(LayoutKind.Sequential)]
public struct RECT
{
public int Left;
public int Top;
public int Right;
public int Bottom;
public Rectangle ToRectangle() => Rectangle.FromLTRB(Left, Top, Right, Bottom);
}
public static long SWEH_CHILDID_SELF = 0;
//SetWinEventHook() flags
public enum SWEH_dwFlags : uint
{
WINEVENT_OUTOFCONTEXT = 0x0000, // Events are ASYNC
WINEVENT_SKIPOWNTHREAD = 0x0001, // Don't call back for events on installer's thread
WINEVENT_SKIPOWNPROCESS = 0x0002, // Don't call back for events on installer's process
WINEVENT_INCONTEXT = 0x0004 // Events are SYNC, this causes your dll to be injected into every process
}
//SetWinEventHook() events
public enum SWEH_Events : uint
{
EVENT_MIN = 0x00000001,
EVENT_MAX = 0x7FFFFFFF,
EVENT_SYSTEM_SOUND = 0x0001,
EVENT_SYSTEM_ALERT = 0x0002,
EVENT_SYSTEM_FOREGROUND = 0x0003,
EVENT_SYSTEM_MENUSTART = 0x0004,
EVENT_SYSTEM_MENUEND = 0x0005,
EVENT_SYSTEM_MENUPOPUPSTART = 0x0006,
EVENT_SYSTEM_MENUPOPUPEND = 0x0007,
EVENT_SYSTEM_CAPTURESTART = 0x0008,
EVENT_SYSTEM_CAPTUREEND = 0x0009,
EVENT_SYSTEM_MOVESIZESTART = 0x000A,
EVENT_SYSTEM_MOVESIZEEND = 0x000B,
EVENT_SYSTEM_CONTEXTHELPSTART = 0x000C,
EVENT_SYSTEM_CONTEXTHELPEND = 0x000D,
EVENT_SYSTEM_DRAGDROPSTART = 0x000E,
EVENT_SYSTEM_DRAGDROPEND = 0x000F,
EVENT_SYSTEM_DIALOGSTART = 0x0010,
EVENT_SYSTEM_DIALOGEND = 0x0011,
EVENT_SYSTEM_SCROLLINGSTART = 0x0012,
EVENT_SYSTEM_SCROLLINGEND = 0x0013,
EVENT_SYSTEM_SWITCHSTART = 0x0014,
EVENT_SYSTEM_SWITCHEND = 0x0015,
EVENT_SYSTEM_MINIMIZESTART = 0x0016,
EVENT_SYSTEM_MINIMIZEEND = 0x0017,
EVENT_SYSTEM_DESKTOPSWITCH = 0x0020,
EVENT_SYSTEM_END = 0x00FF,
EVENT_OEM_DEFINED_START = 0x0101,
EVENT_OEM_DEFINED_END = 0x01FF,
EVENT_UIA_EVENTID_START = 0x4E00,
EVENT_UIA_EVENTID_END = 0x4EFF,
EVENT_UIA_PROPID_START = 0x7500,
EVENT_UIA_PROPID_END = 0x75FF,
EVENT_CONSOLE_CARET = 0x4001,
EVENT_CONSOLE_UPDATE_REGION = 0x4002,
EVENT_CONSOLE_UPDATE_SIMPLE = 0x4003,
EVENT_CONSOLE_UPDATE_SCROLL = 0x4004,
EVENT_CONSOLE_LAYOUT = 0x4005,
EVENT_CONSOLE_START_APPLICATION = 0x4006,
EVENT_CONSOLE_END_APPLICATION = 0x4007,
EVENT_CONSOLE_END = 0x40FF,
EVENT_OBJECT_CREATE = 0x8000, // hwnd ID idChild is created item
EVENT_OBJECT_DESTROY = 0x8001, // hwnd ID idChild is destroyed item
EVENT_OBJECT_SHOW = 0x8002, // hwnd ID idChild is shown item
EVENT_OBJECT_HIDE = 0x8003, // hwnd ID idChild is hidden item
EVENT_OBJECT_REORDER = 0x8004, // hwnd ID idChild is parent of zordering children
EVENT_OBJECT_FOCUS = 0x8005, // hwnd ID idChild is focused item
EVENT_OBJECT_SELECTION = 0x8006, // hwnd ID idChild is selected item (if only one), or idChild is OBJID_WINDOW if complex
EVENT_OBJECT_SELECTIONADD = 0x8007, // hwnd ID idChild is item added
EVENT_OBJECT_SELECTIONREMOVE = 0x8008, // hwnd ID idChild is item removed
EVENT_OBJECT_SELECTIONWITHIN = 0x8009, // hwnd ID idChild is parent of changed selected items
EVENT_OBJECT_STATECHANGE = 0x800A, // hwnd ID idChild is item w/ state change
EVENT_OBJECT_LOCATIONCHANGE = 0x800B, // hwnd ID idChild is moved/sized item
EVENT_OBJECT_NAMECHANGE = 0x800C, // hwnd ID idChild is item w/ name change
EVENT_OBJECT_DESCRIPTIONCHANGE = 0x800D, // hwnd ID idChild is item w/ desc change
EVENT_OBJECT_VALUECHANGE = 0x800E, // hwnd ID idChild is item w/ value change
EVENT_OBJECT_PARENTCHANGE = 0x800F, // hwnd ID idChild is item w/ new parent
EVENT_OBJECT_HELPCHANGE = 0x8010, // hwnd ID idChild is item w/ help change
EVENT_OBJECT_DEFACTIONCHANGE = 0x8011, // hwnd ID idChild is item w/ def action change
EVENT_OBJECT_ACCELERATORCHANGE = 0x8012, // hwnd ID idChild is item w/ keybd accel change
EVENT_OBJECT_INVOKED = 0x8013, // hwnd ID idChild is item invoked
EVENT_OBJECT_TEXTSELECTIONCHANGED = 0x8014, // hwnd ID idChild is item w? test selection change
EVENT_OBJECT_CONTENTSCROLLED = 0x8015,
EVENT_SYSTEM_ARRANGMENTPREVIEW = 0x8016,
EVENT_OBJECT_END = 0x80FF,
EVENT_AIA_START = 0xA000,
EVENT_AIA_END = 0xAFFF
}
//SetWinEventHook() Object Ids
public enum SWEH_ObjectId : long
{
OBJID_WINDOW = 0x00000000,
OBJID_SYSMENU = 0xFFFFFFFF,
OBJID_TITLEBAR = 0xFFFFFFFE,
OBJID_MENU = 0xFFFFFFFD,
OBJID_CLIENT = 0xFFFFFFFC,
OBJID_VSCROLL = 0xFFFFFFFB,
OBJID_HSCROLL = 0xFFFFFFFA,
OBJID_SIZEGRIP = 0xFFFFFFF9,
OBJID_CARET = 0xFFFFFFF8,
OBJID_CURSOR = 0xFFFFFFF7,
OBJID_ALERT = 0xFFFFFFF6,
OBJID_SOUND = 0xFFFFFFF5,
OBJID_QUERYCLASSNAMEIDX = 0xFFFFFFF4,
OBJID_NATIVEOM = 0xFFFFFFF0
}
public enum DWMWINDOWATTRIBUTE : uint
{
DWMWA_NCRENDERING_ENABLED = 1, // [get] Is non-client rendering enabled/disabled
DWMWA_NCRENDERING_POLICY, // [set] DWMNCRENDERINGPOLICY - Non-client rendering policy - Enable or disable non-client rendering
DWMWA_TRANSITIONS_FORCEDISABLED, // [set] Potentially enable/forcibly disable transitions
DWMWA_ALLOW_NCPAINT, // [set] Allow contents rendered In the non-client area To be visible On the DWM-drawn frame.
DWMWA_CAPTION_BUTTON_BOUNDS, // [get] Bounds Of the caption button area In window-relative space.
DWMWA_NONCLIENT_RTL_LAYOUT, // [set] Is non-client content RTL mirrored
DWMWA_FORCE_ICONIC_REPRESENTATION, // [set] Force this window To display iconic thumbnails.
DWMWA_FLIP3D_POLICY, // [set] Designates how Flip3D will treat the window.
DWMWA_EXTENDED_FRAME_BOUNDS, // [get] Gets the extended frame bounds rectangle In screen space
DWMWA_HAS_ICONIC_BITMAP, // [set] Indicates an available bitmap When there Is no better thumbnail representation.
DWMWA_DISALLOW_PEEK, // [set] Don't invoke Peek on the window.
DWMWA_EXCLUDED_FROM_PEEK, // [set] LivePreview exclusion information
DWMWA_CLOAK, // [set] Cloak Or uncloak the window
DWMWA_CLOAKED, // [get] Gets the cloaked state Of the window. Returns a DWMCLOACKEDREASON object
DWMWA_FREEZE_REPRESENTATION, // [set] BOOL, Force this window To freeze the thumbnail without live update
PlaceHolder1,
PlaceHolder2,
PlaceHolder3,
DWMWA_ACCENTPOLICY = 19
}
public static SWEH_dwFlags WinEventHookInternalFlags =
SWEH_dwFlags.WINEVENT_OUTOFCONTEXT |
SWEH_dwFlags.WINEVENT_SKIPOWNPROCESS |
SWEH_dwFlags.WINEVENT_SKIPOWNTHREAD;
[DllImport("dwmapi.dll", SetLastError = true)]
internal static extern int DwmGetWindowAttribute(IntPtr hwnd, DWMWINDOWATTRIBUTE dwAttribute, out RECT pvAttribute, int cbAttribute);
[DllImport("user32.dll", SetLastError = true)]
internal static extern uint GetWindowThreadProcessId(IntPtr hWnd, out uint lpdwProcessId);
[DllImport("user32.dll")]
internal static extern uint GetWindowThreadProcessId(IntPtr hWnd, IntPtr voidProcessId);
[DllImport("user32.dll", SetLastError = false)]
internal static extern IntPtr SetWinEventHook(
SWEH_Events eventMin,
SWEH_Events eventMax,
IntPtr hmodWinEventProc,
Hook.WinEventDelegate lpfnWinEventProc,
uint idProcess, uint idThread,
SWEH_dwFlags dwFlags);
[DllImport("user32.dll", SetLastError = false)]
internal static extern bool UnhookWinEvent(IntPtr hWinEventHook);
}