/// <summary>
/// Creates a window handle for this window.
/// </summary>
public virtual void CreateHandle(CreateParams cp)
{
lock (this)
{
CheckReleased();
WindowClass windowClass = WindowClass.Create(cp.ClassName, (NativeMethods.ClassStyle)cp.ClassStyle);
lock (s_createWindowSyncObject)
{
// The CLR will sometimes pump messages while we're waiting on the lock.
// If a message comes through (say a WM_ACTIVATE for the parent) which
// causes the handle to be created, we can try to create the handle twice
// for NativeWindow. Check the handle again to avoid this.
if (Handle != IntPtr.Zero)
{
return;
}
windowClass._targetWindow = this;
IntPtr createResult = IntPtr.Zero;
int lastWin32Error = 0;
// Parking window dpi awarness context need to match with dpi awarenss context of control being
// parented to this parkign window. Otherwise, reparenting of control will fail.
using (DpiHelper.EnterDpiAwarenessScope(DpiAwarenessContext))
{
IntPtr modHandle = Kernel32.GetModuleHandleW(null);
// Older versions of Windows AV rather than returning E_OUTOFMEMORY.
// Catch this and then we re-throw an out of memory error.
try
{
// CreateWindowEx throws if WindowText is greater than the max
// length of a 16 bit int (32767).
// If it exceeds the max, we should take the substring....
if (cp.Caption != null && cp.Caption.Length > short.MaxValue)
{
cp.Caption = cp.Caption.Substring(0, short.MaxValue);
}
createResult = UnsafeNativeMethods.CreateWindowEx(
cp.ExStyle,
windowClass._windowClassName,
cp.Caption,
cp.Style,
cp.X,
cp.Y,
cp.Width,
cp.Height,
new HandleRef(cp, cp.Parent),
NativeMethods.NullHandleRef,
new HandleRef(null, modHandle),
cp.Param);
lastWin32Error = Marshal.GetLastWin32Error();
}
catch (NullReferenceException e)
{
throw new OutOfMemoryException(SR.ErrorCreatingHandle, e);
}
}
windowClass._targetWindow = null;
Debug.WriteLineIf(CoreSwitches.PerfTrack.Enabled, "Handle created of type '" + cp.ClassName + "' with caption '" + cp.Caption + "' from NativeWindow of type '" + GetType().FullName + "'");
if (createResult == IntPtr.Zero)
{
throw new Win32Exception(lastWin32Error, SR.ErrorCreatingHandle);
}
_ownHandle = true;
}
}
}