/// <devdoc>
/// Selects a region as the current clipping region for the device context.
/// Remarks (From MSDN):
/// - Only a copy of the selected region is used. The region itself can be selected for any number of other device contexts or it can be deleted.
/// - The SelectClipRgn function assumes that the coordinates for a region are specified in device units.
/// - To remove a device-context's clipping region, specify a NULL region handle.
/// </devdoc>
public void SetClip(WindowsRegion region)
{
HandleRef hdc = new HandleRef(this, this.Hdc);
HandleRef hRegion = new HandleRef(region, region.HRegion);
IntUnsafeNativeMethods.SelectClipRgn(hdc, hRegion);
}
///<devdoc>
/// Creates a new clipping region from the intersection of the current clipping region and
/// the specified rectangle.
///</devdoc>
public void IntersectClip(WindowsRegion wr)
{
//if the incoming windowsregion is infinite, there is no need to do any intersecting.
if (wr.HRegion == IntPtr.Zero)
{
return;
}
WindowsRegion clip = new WindowsRegion(0, 0, 0, 0);
try {
int result = IntUnsafeNativeMethods.GetClipRgn(new HandleRef(this, this.Hdc), new HandleRef(clip, clip.HRegion));
// If the function succeeds and there is a clipping region for the given device context, the return value is 1.
if (result == 1)
{
Debug.Assert(clip.HRegion != IntPtr.Zero);
wr.CombineRegion(clip, wr, RegionCombineMode.AND); //1 = AND (or Intersect)
}
SetClip(wr);
}
finally {
clip.Dispose();
}
}
// Consider implementing a constructor that calls ExtCreateRegion(XFORM lpXform, DWORD nCount, RGNDATA lpRgnData) if needed.
/// <devdoc>
/// Creates a WindowsRegion from a region handle, if 'takeOwnership' is true, the handle is added to the HandleCollector
/// and is removed & destroyed on dispose.
/// </devdoc>
public static WindowsRegion FromHregion(IntPtr hRegion, bool takeOwnership) {
WindowsRegion wr = new WindowsRegion();
// Note: Passing IntPtr.Zero for hRegion is ok. GDI+ infinite regions will have hRegion == null.
// GDI's SelectClipRgn interprets null region handle as resetting the clip region (all region will be available for painting).
if( hRegion != IntPtr.Zero ) {
wr.nativeHandle = hRegion;
if (takeOwnership) {
wr.ownHandle = true;
System.Internal.HandleCollector.Add(hRegion, IntSafeNativeMethods.CommonHandles.GDI);
}
}
return wr;
}
/// <devdoc>
/// Creates a WindowsRegion from a System.Drawing.Region.
/// </devdoc>
public static WindowsRegion FromRegion(Region region, Graphics g)
{
if (region.IsInfinite(g))
{
// An infinite region would cover the entire device region which is the same as
// not having a clipping region. Observe that this is not the same as having an
// empty region, which when clipping to it has the effect of excluding the entire
// device region.
// To remove the clip region from a dc the SelectClipRgn() function needs to be
// called with a null region ptr - that's why we use the empty constructor here.
// GDI+ will return IntPtr.Zero for Region.GetHrgn(Graphics) when the region is
// Infinite.
return(new WindowsRegion());
}
return(WindowsRegion.FromHregion(region.GetHrgn(g), true));
}
// Consider implementing a constructor that calls ExtCreateRegion(XFORM lpXform, DWORD nCount, RGNDATA lpRgnData) if needed.
/// <devdoc>
/// Creates a WindowsRegion from a region handle, if 'takeOwnership' is true, the handle is added to the HandleCollector
/// and is removed & destroyed on dispose.
/// </devdoc>
public static WindowsRegion FromHregion(IntPtr hRegion, bool takeOwnership)
{
WindowsRegion wr = new WindowsRegion();
// Note: Passing IntPtr.Zero for hRegion is ok. GDI+ infinite regions will have hRegion == null.
// GDI's SelectClipRgn interprets null region handle as resetting the clip region (all region will be available for painting).
if (hRegion != IntPtr.Zero)
{
wr.nativeHandle = hRegion;
if (takeOwnership)
{
wr.ownHandle = true;
System.Internal.HandleCollector.Add(hRegion, IntSafeNativeMethods.CommonHandles.GDI);
}
}
return(wr);
}
/// <devdoc>
/// Combines region1 & region2 into this region. The regions cannot be null.
/// The three regions need not be distinct. For example, the sourceRgn1 can equal this region.
/// </devdoc>
public IntNativeMethods.RegionFlags CombineRegion(WindowsRegion region1, WindowsRegion region2, RegionCombineMode mode)
{
return(IntUnsafeNativeMethods.CombineRgn(new HandleRef(this, this.HRegion), new HandleRef(region1, region1.HRegion), new HandleRef(region2, region2.HRegion), mode));
}
public static WindowsGraphics FromGraphics(Graphics g, ApplyGraphicsProperties properties)
{
Debug.Assert(g != null, "null Graphics object.");
//Debug.Assert( properties != ApplyGraphicsProperties.None, "Consider using other WindowsGraphics constructor if not preserving Graphics properties." );
WindowsRegion wr = null;
float[] elements = null;
Region clipRgn = null;
Matrix worldTransf = null;
if ((properties & ApplyGraphicsProperties.TranslateTransform) != 0 || (properties & ApplyGraphicsProperties.Clipping) != 0)
{
if (g.GetContextInfo() is object[] data && data.Length == 2)
{
clipRgn = data[0] as Region;
worldTransf = data[1] as Matrix;
}
if (worldTransf != null)
{
if ((properties & ApplyGraphicsProperties.TranslateTransform) != 0)
{
elements = worldTransf.Elements;
}
worldTransf.Dispose();
}
if (clipRgn != null)
{
if ((properties & ApplyGraphicsProperties.Clipping) != 0)
{
// We have to create the WindowsRegion and dipose the Region object before locking the Graphics object,
// in case of an unlikely exception before releasing the WindowsRegion, the finalizer will do it for us.
// (no try-finally block since this method is used frequently - perf).
// If the Graphics.Clip has not been set (Region.IsInfinite) we don't need to apply it to the DC.
if (!clipRgn.IsInfinite(g))
{
wr = WindowsRegion.FromRegion(clipRgn, g); // WindowsRegion will take ownership of the hRegion.
}
}
clipRgn.Dispose(); // Disposing the Region object doesn't destroy the hRegion.
}
}
WindowsGraphics wg = WindowsGraphics.FromHdc(g.GetHdc()); // This locks the Graphics object.
wg.graphics = g;
// Apply transform and clip
if (wr != null)
{
using (wr)
{
// If the Graphics object was created from a native DC the actual clipping region is the intersection
// beteween the original DC clip region and the GDI+ one - for display Graphics it is the same as
// Graphics.VisibleClipBounds.
wg.DeviceContext.IntersectClip(wr);
}
}
if (elements != null)
{
// elements (XFORM) = [eM11, eM12, eM21, eM22, eDx, eDy], eDx/eDy specify the translation offset.
wg.DeviceContext.TranslateTransform((int)elements[4], (int)elements[5]);
}
return(wg);
}
/// <devdoc>
/// Combines region1 & region2 into this region. The regions cannot be null.
/// The three regions need not be distinct. For example, the sourceRgn1 can equal this region.
/// </devdoc>
public IntNativeMethods.RegionFlags CombineRegion(WindowsRegion region1, WindowsRegion region2, RegionCombineMode mode) {
return IntUnsafeNativeMethods.CombineRgn(new HandleRef(this, this.HRegion), new HandleRef(region1, region1.HRegion), new HandleRef(region2, region2.HRegion), mode);
}
public void IntersectClip(WindowsRegion wr)
{
//if the incoming windowsregion is infinite, there is no need to do any intersecting.
if (wr.HRegion == IntPtr.Zero) {
return;
}
WindowsRegion clip = new WindowsRegion(0,0,0,0);
try {
int result = IntUnsafeNativeMethods.GetClipRgn(new HandleRef( this, this.Hdc), new HandleRef(clip, clip.HRegion));
// If the function succeeds and there is a clipping region for the given device context, the return value is 1.
if (result == 1) {
Debug.Assert(clip.HRegion != IntPtr.Zero);
wr.CombineRegion(clip, wr, RegionCombineMode.AND); //1 = AND (or Intersect)
}
SetClip(wr);
}
finally {
clip.Dispose();
}
}
public void SetClip(WindowsRegion region)
{
HandleRef hdc = new HandleRef(this, this.Hdc);
HandleRef hRegion = new HandleRef(region, region.HRegion);
IntUnsafeNativeMethods.SelectClipRgn(hdc, hRegion);
}
public void IntersectClip(WindowsRegion wr)
{
if (wr.HRegion != IntPtr.Zero)
{
using (WindowsRegion region = new WindowsRegion(0, 0, 0, 0))
{
if (IntUnsafeNativeMethods.GetClipRgn(new HandleRef(this, this.Hdc), new HandleRef(region, region.HRegion)) == 1)
{
wr.CombineRegion(region, wr, RegionCombineMode.AND);
}
this.SetClip(wr);
}
}
}
