8256331: Lanai: DrawImage/IncorrectAlphaSurface2SW fails

Author: Alexey Ushakov

src/java.desktop/macosx/native/libawt_lwawt/awt/common.h

@@ -112,7 +112,6 @@ struct TxtFrameUniforms {
     vector_float4 color;
     int mode; // NOTE: consider to use bit fields
     int isSrcOpaque;
-    int isSrcPremult;
     int isDstOpaque;
     float extraAlpha;
 };

src/java.desktop/macosx/native/libawt_lwawt/awt/shaders.metal

@@ -244,10 +244,6 @@ fragment half4 frag_txt(
         return half4(c.r, c.g, c.b , c.a);
     }
 
-    if (uniforms.isSrcPremult) {
-        pixelColor.rgb /= srcA;
-    }
-
     return half4(pixelColor.r,
                  pixelColor.g,
                  pixelColor.b, srcA)*uniforms.extraAlpha;

src/java.desktop/macosx/native/libawt_lwawt/java2d/metal/MTLBlitLoops.m

@@ -649,6 +649,18 @@ jboolean clipDestCoords(
     SurfaceData_InvokeUnlock(env, srcOps, &srcInfo);
 }
 
+void copyFromMTLBuffer(void *pDst, id<MTLBuffer> srcBuf, jint offset, jint len, BOOL convertFromArgbPre) {
+    char *pSrc = (char*)srcBuf.contents + offset;
+    if (convertFromArgbPre) {
+        jint pixelLen = len>>2;
+        for (int i = 0; i < pixelLen; i++) {
+            LoadIntArgbPreTo1IntArgb((jint*)pSrc, 0, i, ((jint*)pDst)[i]);
+        }
+    } else {
+        memcpy(pDst, pSrc, len);
+    }
+}
+
 /**
  * Specialized blit method for copying a native MTL "Surface" (pbuffer,
  * window, etc.) to a system memory ("Sw") surface.
@@ -719,7 +731,7 @@ jboolean clipDestCoords(
             // Metal texture is (0,0) at left-top
             srcx = srcOps->xOffset + srcx;
             srcy = srcOps->yOffset + srcy;
-            const int srcLength = width * height * 4; // NOTE: assume that src format is MTLPixelFormatBGRA8Unorm
+            const int byteLength = width * height * 4; // NOTE: assume that src format is MTLPixelFormatBGRA8Unorm
 
             // Create MTLBuffer (or use static)
             MTLRasterFormatInfo rfi = RasterFormatInfos[dsttype];
@@ -771,27 +783,28 @@ jboolean clipDestCoords(
                                toBuffer:mtlbuf
                       destinationOffset:0 /*offset already taken in: pDst = PtrAddBytes(pDst, dstx * dstInfo.pixelStride)*/
                  destinationBytesPerRow:width*4
-               destinationBytesPerImage:width * height*4];
+               destinationBytesPerImage:byteLength];
             [blitEncoder endEncoding];
 
             // Commit and wait for reading complete
             [cb commit];
             [cb waitUntilCompleted];
 
             // Perform conversion if necessary
+            BOOL convertFromPre = !RasterFormatInfos[dsttype].isPremult && !srcOps->isOpaque;
             if (directCopy) {
                 if ((dstInfo.scanStride == width * dstInfo.pixelStride) &&
                     (height == (dstInfo.bounds.y2 - dstInfo.bounds.y1))) {
                     // mtlbuf.contents have same dimensions as of pDst
-                    memcpy(pDst, mtlbuf.contents, srcLength);
+                    copyFromMTLBuffer(pDst, mtlbuf, 0, byteLength, convertFromPre);
                 } else {
                     // mtlbuf.contents have smaller dimensions than pDst
                     // copy each row from mtlbuf.contents at appropriate position in pDst
                     // Note : pDst is already addjusted for offsets using PtrAddBytes above
 
                     int rowSize = width * dstInfo.pixelStride;
                     for (int y = 0; y < height; y++) {
-                        memcpy(pDst, mtlbuf.contents + (y * rowSize), rowSize);
+                        copyFromMTLBuffer(pDst, mtlbuf, y * rowSize, rowSize, convertFromPre);
                         pDst = PtrAddBytes(pDst, dstInfo.scanStride);
                     }
                 }

src/java.desktop/macosx/native/libawt_lwawt/java2d/metal/MTLPaints.m

@@ -867,9 +867,7 @@ static void setTxtUniforms(
         id<MTLRenderCommandEncoder> encoder, int color, int mode, int interpolation, bool repeat, jfloat extraAlpha,
         const SurfaceRasterFlags * srcFlags, const SurfaceRasterFlags * dstFlags
 ) {
-    struct TxtFrameUniforms uf = {
-      RGBA_TO_V4(color), mode, srcFlags->isOpaque, srcFlags->isPremultiplied,
-      dstFlags->isOpaque, extraAlpha};
+    struct TxtFrameUniforms uf = {RGBA_TO_V4(color), mode, srcFlags->isOpaque, dstFlags->isOpaque, extraAlpha};
     [encoder setFragmentBytes:&uf length:sizeof(uf) atIndex:FrameUniformBuffer];
 
     setSampler(encoder, interpolation, repeat);