// Due to a problem with calling DeleteObject() on currently selected GDI objects,
// we now track the initial set of objects when a DeviceContext is created. Then,
// we also track which objects are currently selected in the DeviceContext. When
// a currently selected object is disposed, it is first replaced in the DC and then
// deleted.
private void CacheInitialState()
{
Debug.Assert(this.hDC != IntPtr.Zero, "Cannot get initial state without a valid HDC");
hCurrentPen = hInitialPen = IntUnsafeNativeMethods.GetCurrentObject(new HandleRef(this, hDC), IntNativeMethods.OBJ_PEN);
hCurrentBrush = hInitialBrush = IntUnsafeNativeMethods.GetCurrentObject(new HandleRef(this, hDC), IntNativeMethods.OBJ_BRUSH);
hCurrentBmp = hInitialBmp = IntUnsafeNativeMethods.GetCurrentObject(new HandleRef(this, hDC), IntNativeMethods.OBJ_BITMAP);
hCurrentFont = hInitialFont = IntUnsafeNativeMethods.GetCurrentObject(new HandleRef(this, hDC), IntNativeMethods.OBJ_FONT);
}
/// <summary>
/// Creates a WindowsFont from the font selected in the supplied dc.
/// </summary>
public static WindowsFont FromHdc(IntPtr hdc)
{
IntPtr hFont = IntUnsafeNativeMethods.GetCurrentObject(new HandleRef(null, hdc), IntNativeMethods.OBJ_FONT);
// don't call DeleteObject on handle from GetCurrentObject, it is the one selected in the hdc.
return(FromHfont(hFont));
}
public static WindowsBrush FromDC(DeviceContext dc)
{
IntPtr hBrush = IntUnsafeNativeMethods.GetCurrentObject(new HandleRef(null, dc.Hdc), IntNativeMethods.OBJ_BRUSH);
IntNativeMethods.LOGBRUSH logBrush = new IntNativeMethods.LOGBRUSH();
IntUnsafeNativeMethods.GetObject(new HandleRef(null, hBrush), logBrush);
// don't call DeleteObject on handle from GetCurrentObject, it is the one selected in the hdc.
return(WindowsBrush.FromLogBrush(dc, logBrush));
}
internal void DisposeFont(bool disposing)
{
if (disposing)
{
DeviceContexts.RemoveDeviceContext(this);
}
if (selectedFont != null && selectedFont.Hfont != IntPtr.Zero)
{
IntPtr hCurrentFont = IntUnsafeNativeMethods.GetCurrentObject(new HandleRef(this, hDC), IntNativeMethods.OBJ_FONT);
if (hCurrentFont == selectedFont.Hfont)
{
// select initial font back in
IntUnsafeNativeMethods.SelectObject(new HandleRef(this, this.Hdc), new HandleRef(null, hInitialFont));
hCurrentFont = hInitialFont;
}
selectedFont.Dispose(disposing);
selectedFont = null;
}
}