#5: Ensure we don't execute WM_NCPAINT and WM_ERASEBKGND when active.

tom-englert · Mar 4, 2022 · d87ceed · d87ceed
1 parent 90384c2
commit d87ceed
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Showing 4 changed files with 43 additions and 2 deletions.
diff --git a/src/RegionToShare/MainWindow.xaml b/src/RegionToShare/MainWindow.xaml
@@ -1,7 +1,7 @@
 <Window x:Class="RegionToShare.MainWindow"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-        xmlns:wf="clr-namespace:System.Windows.Forms;assembly=System.Windows.Forms"
+        xmlns:local="clr-namespace:RegionToShare"
         Title="Region to Share" Height="450" Width="800" Background="Black" Foreground="White"
         MouseLeftButtonDown="Window_MouseLeftButtonDown">
   <Grid x:Name="ClientArea">
@@ -15,7 +15,7 @@
       </Grid>
     </Grid>
     <WindowsFormsHost x:Name="RenderTargetHost" Visibility="Collapsed">
-      <wf:Control x:Name="RenderTargetWindow" Visible="False" MouseClick="RenderTargetWindow_OnMouseClick" />
+      <local:RenderTarget x:Name="RenderTargetWindow" MouseClick="RenderTargetWindow_OnMouseClick" />
     </WindowsFormsHost>
   </Grid>
 </Window>
diff --git a/src/RegionToShare/MainWindow.xaml.cs b/src/RegionToShare/MainWindow.xaml.cs
@@ -1,5 +1,6 @@
 using System.Windows;
 using System.Windows.Input;
+using System.Windows.Interop;
 using System.Windows.Media;
 using System.Windows.Threading;
 using TomsToolbox.Wpf;
@@ -22,6 +23,9 @@ protected override void OnSourceInitialized(EventArgs e)
     {
         base.OnSourceInitialized(e);
 
+        var messageSource = (HwndSource)PresentationSource.FromDependencyObject(this);
+        messageSource.AddHook(WindowProc);
+
         _windowHandle = this.GetWindowHandle();
 
         var separationLayerWindow = new Window() { Background = (Brush)FindResource("HatchBrush"), WindowStyle = WindowStyle.None, ResizeMode = ResizeMode.NoResize, Title = "Region to Share - Separation Layer", ShowInTaskbar = false };
@@ -102,4 +106,18 @@ private void SendToBack()
         NativeMethods.SetWindowPos(_separationLayerHandle, NativeMethods.HWND_BOTTOM, 0, 0, 0, 0, NativeMethods.SWP_NOMOVE | NativeMethods.SWP_NOSIZE | NativeMethods.SWP_NOACTIVATE | NativeMethods.SWP_SHOWWINDOW);
         NativeMethods.SetWindowPos(_windowHandle, _separationLayerHandle, 0, 0, 0, 0, NativeMethods.SWP_NOMOVE | NativeMethods.SWP_NOSIZE | NativeMethods.SWP_NOACTIVATE);
     }
+
+    private IntPtr WindowProc(IntPtr windowHandle, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
+    {
+        switch (msg)
+        {
+            case NativeMethods.WM_NCPAINT:
+            // case NativeMethods.WM_PAINT:
+            case NativeMethods.WM_ERASEBKGND:
+                handled = _recordingWindow != null;
+                break;
+        }
+
+        return IntPtr.Zero;
+    }
 }
diff --git a/src/RegionToShare/NativeMethods.cs b/src/RegionToShare/NativeMethods.cs
@@ -20,6 +20,9 @@ internal static class NativeMethods
     [DllImport("user32.dll", SetLastError = true)]
     public static extern bool SetWindowPos(IntPtr hWnd, IntPtr hWndInsertAfter, int x, int y, int cx, int cy, uint uFlags);
 
+    public const int WM_PAINT = 0x000F;
+    public const int WM_ERASEBKGND = 0x0014;
+    public const int WM_NCPAINT = 0x0085;
     public const int WM_NCHITTEST = 0x0084;
     public const int CURSOR_SHOWING = 0x00000001;
 

diff --git a/src/RegionToShare/RenderTarget.cs b/src/RegionToShare/RenderTarget.cs
@@ -0,0 +1,20 @@
+using System.Windows.Forms;
+
+namespace RegionToShare
+{
+    public class RenderTarget : Control
+    {
+        public override bool PreProcessMessage(ref Message msg)
+        {
+            switch (msg.Msg)
+            {
+                case NativeMethods.WM_NCPAINT:
+                // case NativeMethods.WM_PAINT:
+                case NativeMethods.WM_ERASEBKGND:
+                    return true;
+            }
+
+            return base.PreProcessMessage(ref msg);
+        }
+    }
+}