Fixed the last (?) glitches around the mouse cursor [*] in aspect-ratio

correction mode by making sure that dirty rects always start on a line
that won't have its colours changed by the stretching function. This was
probably only noticeable when using the 1x scaler.

[*] Actually, the glitches weren't specific to the mouse cursor, but it was
    useful for triggering them.

svn-id: r8621

3 files changed, 17 insertions, 0 deletions

diff --git a/backends/sdl/sdl-common.cpp b/backends/sdl/sdl-common.cpp
index cd3b99430c..63e949fede 100644
--- a/backends/sdl/sdl-common.cpp
+++ b/backends/sdl/sdl-common.cpp
@@ -286,6 +286,9 @@ void OSystem_SDL_Common::add_dirty_rect(int x, int y, int w, int h) {
 		if (h > _screenHeight - y) {
 			h = _screenHeight - y;
 		}
+
+		if (_adjustAspectRatio)
+			makeRectStretchable(x, y, w, h);
 	
 		r->x = x;
 		r->y = y;
diff --git a/common/scaler.cpp b/common/scaler.cpp
index 65c4380266..a0a49ad5eb 100644
--- a/common/scaler.cpp
+++ b/common/scaler.cpp
@@ -683,6 +683,18 @@ static inline void interpolate5Line(uint16 *dst, const uint16 *srcA, const uint1
 #endif
 }
 
+void makeRectStretchable(int &x, int &y, int &w, int &h) {
+	int m = real2Aspect(y) % 6;
+
+	// Ensure that the rect will start on a line that won't have its
+	// colours changed by the stretching function.
+
+	if (m != 0 && m != 5) {
+		y -= m;
+		h += m;
+	}
+}
+
 /**
  * Stretch a 16bpp image vertically by factor 1.2. Used to correct the
  * aspect-ratio in games using 320x200 pixel graphics with non-qudratic
diff --git a/common/scaler.h b/common/scaler.h
index b8000ddccd..2c1b73b9d0 100644
--- a/common/scaler.h
+++ b/common/scaler.h
@@ -49,6 +49,8 @@ FORCEINLINE int aspect2Real(int y) {
 	return (y * 5 + 3) / 6;
 }
 
+extern void makeRectStretchable(int &x, int &y, int &w, int &h);
+
 extern int stretch200To240(uint8 *buf, uint32 pitch, int width, int height, int srcX, int srcY, int origSrcY);
 
 enum {