GRAPHICS: Fix VectorRendererSpec for RGBA8888.

Formerly values in the gradient and blending code overflowed and thus caused
incorrect colors. Now there's some special case for 32bpp modes, which needs
slightly more operations but assures a correct output.

1 files changed, 51 insertions, 20 deletions

diff --git a/graphics/VectorRendererSpec.cpp b/graphics/VectorRendererSpec.cpp
index 4c5dd33cb5..1fee861539 100644
--- a/graphics/VectorRendererSpec.cpp
+++ b/graphics/VectorRendererSpec.cpp
@@ -317,9 +317,15 @@ setGradientColors(uint8 r1, uint8 g1, uint8 b1, uint8 r2, uint8 g2, uint8 b2) {
 	_gradientEnd = _format.RGBToColor(r2, g2, b2);
 	_gradientStart = _format.RGBToColor(r1, g1, b1);
 
-	_gradientBytes[0] = (_gradientEnd & _redMask) - (_gradientStart & _redMask);
-	_gradientBytes[1] = (_gradientEnd & _greenMask) - (_gradientStart & _greenMask);
-	_gradientBytes[2] = (_gradientEnd & _blueMask) - (_gradientStart & _blueMask);
+	if (sizeof(PixelType) == 4) {
+		_gradientBytes[0] = ((_gradientEnd & _redMask) >> _format.rShift) - ((_gradientStart & _redMask) >> _format.rShift);
+		_gradientBytes[1] = ((_gradientEnd & _greenMask) >> _format.gShift) - ((_gradientStart & _greenMask) >> _format.gShift);
+		_gradientBytes[2] = ((_gradientEnd & _blueMask) >> _format.bShift) - ((_gradientStart & _blueMask) >> _format.bShift);
+	} else {
+		_gradientBytes[0] = (_gradientEnd & _redMask) - (_gradientStart & _redMask);
+		_gradientBytes[1] = (_gradientEnd & _greenMask) - (_gradientStart & _greenMask);
+		_gradientBytes[2] = (_gradientEnd & _blueMask) - (_gradientStart & _blueMask);
+	}
 }
 
 template<typename PixelType>
@@ -328,9 +334,15 @@ calcGradient(uint32 pos, uint32 max) {
 	PixelType output = 0;
 	pos = (MIN(pos * Base::_gradientFactor, max) << 12) / max;
 
-	output |= ((_gradientStart & _redMask) + ((_gradientBytes[0] * pos) >> 12)) & _redMask;
-	output |= ((_gradientStart & _greenMask) + ((_gradientBytes[1] * pos) >> 12)) & _greenMask;
-	output |= ((_gradientStart & _blueMask) + ((_gradientBytes[2] * pos) >> 12)) & _blueMask;
+	if (sizeof(PixelType) == 4) {
+		output |= ((_gradientStart & _redMask) + (((_gradientBytes[0] * pos) >> 12) << _format.rShift)) & _redMask;
+		output |= ((_gradientStart & _greenMask) + (((_gradientBytes[1] * pos) >> 12) << _format.gShift)) & _greenMask;
+		output |= ((_gradientStart & _blueMask) + (((_gradientBytes[2] * pos) >> 12) << _format.bShift)) & _blueMask;
+	} else {
+		output |= ((_gradientStart & _redMask) + ((_gradientBytes[0] * pos) >> 12)) & _redMask;
+		output |= ((_gradientStart & _greenMask) + ((_gradientBytes[1] * pos) >> 12)) & _greenMask;
+		output |= ((_gradientStart & _blueMask) + ((_gradientBytes[2] * pos) >> 12)) & _blueMask;
+	}
 	output |= _alphaMask;
 
 	return output;
@@ -537,20 +549,39 @@ applyScreenShading(GUI::ThemeEngine::ShadingStyle shadingStyle) {
 template<typename PixelType>
 inline void VectorRendererSpec<PixelType>::
 blendPixelPtr(PixelType *ptr, PixelType color, uint8 alpha) {
-	int idst = *ptr;
-	int isrc = color;
-
-	*ptr = (PixelType)(
-		(_redMask & ((idst & _redMask) +
-		((int)(((int)(isrc & _redMask) -
-		(int)(idst & _redMask)) * alpha) >> 8))) |
-		(_greenMask & ((idst & _greenMask) +
-		((int)(((int)(isrc & _greenMask) -
-		(int)(idst & _greenMask)) * alpha) >> 8))) |
-		(_blueMask & ((idst & _blueMask) +
-		((int)(((int)(isrc & _blueMask) -
-		(int)(idst & _blueMask)) * alpha) >> 8))) |
-		(idst & _alphaMask));
+	if (sizeof(PixelType) == 4) {
+		const byte sR = (color & _redMask) >> _format.rShift;
+		const byte sG = (color & _greenMask) >> _format.gShift;
+		const byte sB = (color & _blueMask) >> _format.bShift;
+
+		byte dR = (*ptr & _redMask) >> _format.rShift;
+		byte dG = (*ptr & _greenMask) >> _format.gShift;
+		byte dB = (*ptr & _blueMask) >> _format.bShift;
+
+		dR += ((sR - dR) * alpha) >> 8;
+		dG += ((sG - dG) * alpha) >> 8;
+		dB += ((sB - dB) * alpha) >> 8;
+
+		*ptr = ((dR << _format.rShift) & _redMask)
+		     | ((dG << _format.gShift) & _greenMask)
+		     | ((dB << _format.bShift) & _blueMask)
+		     | (*ptr & _alphaMask);
+	} else {
+		int idst = *ptr;
+		int isrc = color;
+
+		*ptr = (PixelType)(
+			(_redMask & ((idst & _redMask) +
+			((int)(((int)(isrc & _redMask) -
+			(int)(idst & _redMask)) * alpha) >> 8))) |
+			(_greenMask & ((idst & _greenMask) +
+			((int)(((int)(isrc & _greenMask) -
+			(int)(idst & _greenMask)) * alpha) >> 8))) |
+			(_blueMask & ((idst & _blueMask) +
+			((int)(((int)(isrc & _blueMask) -
+			(int)(idst & _blueMask)) * alpha) >> 8))) |
+			(idst & _alphaMask));
+	}
 }
 
 template<typename PixelType>