SCI32: Improve kPlayVMD rendering

1. Added a new game option for linear interpolation when scaling
   overlay-mode video in ScummVM builds with USE_RGB_COLOR;
2. Implemented SCI2.1-variant of the VMD player renderer (fixes
   Trac#9857), which bypasses the engine's normal rendering
   pipeline;
3. Improved accuracy of the SCI3-variant of the VMD player by
   writing HunkPalettes into the VMD's CelObjMem instead of
   submitting palettes directly to GfxPalette32.

1 files changed, 42 insertions, 0 deletions

diff --git a/engines/sci/graphics/helpers.h b/engines/sci/graphics/helpers.h
index 1da3749c90..52699c6242 100644
--- a/engines/sci/graphics/helpers.h
+++ b/engines/sci/graphics/helpers.h
@@ -187,6 +187,48 @@ inline void mulru(Common::Rect &rect, const Common::Rational &ratioX, const Comm
 	rect.bottom = mulru(rect.bottom - 1, ratioY, extra) + 1;
 }
 
+/**
+ * Determines the parts of `r` that aren't overlapped by `other`.
+ * Returns -1 if `r` and `other` have no intersection.
+ * Returns number of returned parts (in `outRects`) otherwise.
+ * (In particular, this returns 0 if `r` is contained in `other`.)
+ */
+inline int splitRects(Common::Rect r, const Common::Rect &other, Common::Rect(&outRects)[4]) {
+	if (!r.intersects(other)) {
+		return -1;
+	}
+
+	int splitCount = 0;
+	if (r.top < other.top) {
+		Common::Rect &t = outRects[splitCount++];
+		t = r;
+		t.bottom = other.top;
+		r.top = other.top;
+	}
+
+	if (r.bottom > other.bottom) {
+		Common::Rect &t = outRects[splitCount++];
+		t = r;
+		t.top = other.bottom;
+		r.bottom = other.bottom;
+	}
+
+	if (r.left < other.left) {
+		Common::Rect &t = outRects[splitCount++];
+		t = r;
+		t.right = other.left;
+		r.left = other.left;
+	}
+
+	if (r.right > other.right) {
+		Common::Rect &t = outRects[splitCount++];
+		t = r;
+		t.left = other.right;
+	}
+
+	return splitCount;
+}
+
 struct Buffer : public Graphics::Surface {
 	uint16 screenWidth;
 	uint16 screenHeight;