Support multisampled Bresenham lines

src/Device/PixelProcessor.cpp

@@ -192,6 +192,8 @@ namespace sw
 
 		state.multiSample = static_cast<unsigned int>(context->sampleCount);
 		state.multiSampleMask = context->multiSampleMask;
+		state.multiSampledBresenham = (state.multiSample > 1) && context->isDrawLine(true) &&
+		                              (context->lineRasterizationMode == VK_LINE_RASTERIZATION_MODE_BRESENHAM_EXT);
 
 		if(state.multiSample > 1 && context->pixelShader)
 		{

src/Device/PixelProcessor.hpp

@@ -81,6 +81,7 @@ namespace sw
 			VkFormat targetFormat[RENDERTARGETS];
 			unsigned int multiSample;
 			unsigned int multiSampleMask;
+			bool multiSampledBresenham;
 			bool alphaToCoverage;
 			bool centroid;
 			VkFrontFace frontFace;

src/Device/QuadRasterizer.cpp

@@ -180,7 +180,8 @@ namespace sw
 					{
 						if (state.multiSampleMask & (1<<q))
 						{
-							Short4 mask = CmpGT(xxxx, xLeft[q]) & CmpGT(xRight[q], xxxx);
+							unsigned int i = state.multiSampledBresenham ? 0 : q;
+							Short4 mask = CmpGT(xxxx, xLeft[i]) & CmpGT(xRight[i], xxxx);
 							cMask[q] = SignMask(PackSigned(mask, mask)) & 0x0000000F;
 						}
 						else

src/Device/Renderer.cpp

@@ -814,14 +814,7 @@ namespace sw
 			return false;
 		}
 
-		// We use rectangular lines for non-Bresenham lines (cf. 'strictLines'),
-		// and for Bresenham lines when multiSampling is enabled.
-		// FIXME(b/142965928): Bresenham lines should render the same with or without
-		//                     multisampling, which will require a special case in the
-		//                     code when multisampling is on. For now, we just use
-		//                     rectangular lines when multisampling is enabled.
-		if((draw.setupState.multiSample > 1) ||
-		   (draw.lineRasterizationMode != VK_LINE_RASTERIZATION_MODE_BRESENHAM_EXT))
+		if(draw.lineRasterizationMode != VK_LINE_RASTERIZATION_MODE_BRESENHAM_EXT)
 		{
 			// Rectangle centered on the line segment