Add alpha blending support to surfaces
diff --git a/vncviewer/Surface_Win32.cxx b/vncviewer/Surface_Win32.cxx
index 5eea2d1..87b0cb2 100644
--- a/vncviewer/Surface_Win32.cxx
+++ b/vncviewer/Surface_Win32.cxx
@@ -89,6 +89,48 @@
DeleteDC(dstdc);
}
+void Surface::blend(int src_x, int src_y, int x, int y, int w, int h)
+{
+ // Compositing doesn't work properly for window DC:s
+ assert(false);
+}
+
+void Surface::blend(Surface* dst, int src_x, int src_y, int x, int y, int w, int h)
+{
+ HDC dstdc, srcdc;
+ BLENDFUNCTION blend;
+
+ dstdc = CreateCompatibleDC(NULL);
+ if (!dstdc)
+ throw rdr::SystemException("CreateCompatibleDC", GetLastError());
+ srcdc = CreateCompatibleDC(NULL);
+ if (!srcdc)
+ throw rdr::SystemException("CreateCompatibleDC", GetLastError());
+
+ if (!SelectObject(dstdc, dst->bitmap))
+ throw rdr::SystemException("SelectObject", GetLastError());
+ if (!SelectObject(srcdc, bitmap))
+ throw rdr::SystemException("SelectObject", GetLastError());
+
+ blend.BlendOp = AC_SRC_OVER;
+ blend.BlendFlags = 0;
+ blend.SourceConstantAlpha = 255;
+ blend.AlphaFormat = AC_SRC_ALPHA;
+
+ if (!AlphaBlend(dstdc, x, y, w, h, srcdc, src_x, src_y, w, h, blend)) {
+ // If the desktop we're rendering to is inactive (like when the screen
+ // is locked or the UAC is active), then GDI calls will randomly fail.
+ // This is completely undocumented so we have no idea how best to deal
+ // with it. For now, we've only seen this error and for this function
+ // so only ignore this combination.
+ if (GetLastError() != ERROR_INVALID_HANDLE)
+ throw rdr::SystemException("BitBlt", GetLastError());
+ }
+
+ DeleteDC(srcdc);
+ DeleteDC(dstdc);
+}
+
void Surface::alloc()
{
BITMAPINFOHEADER bih;