public static void HandleWmPaint(ref Message m, Control control, Action <PaintEventArgs> paint)
{
var ps = new WinApi.PAINTSTRUCT();
bool needDisposeDc = false;
try {
Rectangle clip;
IntPtr dc;
if (m.WParam == IntPtr.Zero)
{
dc = WinApi.BeginPaint(new HandleRef(control, control.Handle), ref ps);
if (dc == IntPtr.Zero)
{
return;
}
needDisposeDc = true;
clip = new Rectangle(ps.rcPaint_left, ps.rcPaint_top, ps.rcPaint_right - ps.rcPaint_left, ps.rcPaint_bottom - ps.rcPaint_top);
}
else
{
dc = m.WParam;
clip = control.ClientRectangle;
}
if (clip.Width > 0 && clip.Height > 0)
{
try {
using (var bufferedGraphics = BufferedGraphicsManager.Current.Allocate(dc, control.ClientRectangle)) {
bufferedGraphics.Graphics.SetClip(clip);
using (var pevent = new PaintEventArgs(bufferedGraphics.Graphics, clip)) {
paint?.Invoke(pevent);
}
bufferedGraphics.Render();
}
} catch (Exception ex) {
// BufferContext.Allocate will throw out of memory exceptions
// when it fails to create a device dependent bitmap while trying to
// get information about the device we are painting on.
// That is not the same as a system running out of memory and there is a
// very good chance that we can continue to paint successfully. We cannot
// check whether double buffering is supported in this case, and we will disable it.
// We could set a specific string when throwing the exception and check for it here
// to distinguish between that case and real out of memory exceptions but we
// see no reasons justifying the additional complexity.
if (!(ex is OutOfMemoryException))
{
throw;
}
}
}
} finally {
if (needDisposeDc)
{
WinApi.EndPaint(new HandleRef(control, control.Handle), ref ps);
}
}
}
