/// <summary>
/// Gets an <see cref="Graphics"/> based off of the primary display.
/// </summary>
/// <remarks>
/// Use in a using statement for proper cleanup.
///
/// When disposed the <see cref="Graphics"/> object will be disposed and the underlying <see cref="Gdi32.HDC"/>
/// will be returned to the cache. Do NOT change the state of the underlying DC (clipping, selecting objects
/// into it) without restoring the state. If you must pass the scope to another method it must be passed by
/// reference or you risk double disposal and accidentally returning extra copies to the cache.
/// </remarks>
public static ScreenGraphicsScope GetScreenDCGraphics()
{
ScreenDcCache.ScreenDcScope scope = GetScreenHdc();
try
{
return(new ScreenGraphicsScope(ref scope));
}
catch (OutOfMemoryException)
{
// GDI+ throws OOM if it can't confirm a valid HDC. We'll throw a more meaningful error here
// for easier diagnosis.
if (scope.HDC.IsNull)
{
throw new ArgumentNullException("hdc");
}
Gdi32.OBJ type = Gdi32.GetObjectType(scope.HDC);
if (type == Gdi32.OBJ.DC ||
type == Gdi32.OBJ.ENHMETADC ||
type == Gdi32.OBJ.MEMDC ||
type == Gdi32.OBJ.METADC)
{
// Not sure what is wrong in this case, throw the original.
throw;
}
throw new InvalidOperationException(string.Format(SR.InvalidHdcType, type));
}
}
/// <summary>
/// Internal version of constructor for performance. We try to avoid getting the graphics object until needed.
/// </summary>
public DrawingEventArgs(
Gdi32.HDC dc,
Rectangle clipRect,
DrawingEventFlags flags)
{
ArgumentValidation.ThrowIfNull(dc);
#if DEBUG
Gdi32.OBJ type = Gdi32.GetObjectType(dc);
Debug.Assert(type == Gdi32.OBJ.DC ||
type == Gdi32.OBJ.ENHMETADC ||
type == Gdi32.OBJ.MEMDC ||
type == Gdi32.OBJ.METADC);
#endif
_hdc = dc;
_graphics = null;
_oldPalette = default;
Flags = flags;
ClipRectangle = clipRect;
}
/// <summary>
/// Internal version of constructor for performance. We try to avoid getting the graphics object until needed.
/// </summary>
public DrawingEventArgs(
Gdi32.HDC dc,
Rectangle clipRect,
DrawingEventFlags flags)
{
if (dc.IsNull)
{
throw new ArgumentNullException(nameof(dc));
}
#if DEBUG
Gdi32.OBJ type = Gdi32.GetObjectType(dc);
Debug.Assert(type == Gdi32.OBJ.DC ||
type == Gdi32.OBJ.ENHMETADC ||
type == Gdi32.OBJ.MEMDC ||
type == Gdi32.OBJ.METADC);
#endif
_hdc = dc;
_graphics = null;
_oldPalette = default;
Flags = flags;
ClipRectangle = clipRect;
}
