[WTR][Skia] Draw repaint rects mask

https://bugs.webkit.org/show_bug.cgi?id=271236

Reviewed by Alejandro G. Castro.

* Tools/WebKitTestRunner/skia/TestInvocationSkia.cpp:
(WTR::TestInvocation::dumpPixelsAndCompareWithExpected):

Canonical link: https://commits.webkit.org/276391@main

Tools/WebKitTestRunner/skia/TestInvocationSkia.cpp

@@ -30,6 +30,7 @@
 #include "PixelDumpSupport.h"
 #include "PlatformWebView.h"
 #include "TestController.h"
+#include <skia/core/SkCanvas.h>
 #include <skia/core/SkStream.h>
 IGNORE_CLANG_WARNINGS_BEGIN("cast-align")
 #include <skia/encode/SkPngEncoder.h>
@@ -66,7 +67,7 @@ static void dumpPixmap(const SkPixmap& pixmap, const std::string& checksum)
     printPNG(data->bytes(), data->size(), checksum.c_str());
 }
 
-void TestInvocation::dumpPixelsAndCompareWithExpected(SnapshotResultType snapshotType, WKArrayRef, WKImageRef)
+void TestInvocation::dumpPixelsAndCompareWithExpected(SnapshotResultType snapshotType, WKArrayRef repaintRects, WKImageRef)
 {
     sk_sp<SkImage> image;
     switch (snapshotType) {
@@ -78,12 +79,27 @@ void TestInvocation::dumpPixelsAndCompareWithExpected(SnapshotResultType snapsho
         break;
     }
 
-    // FIXME: support repaint rects.
-
     SkPixmap pixmap;
     if (!image->peekPixels(&pixmap))
         return;
 
+    if (repaintRects) {
+        auto canvas = SkCanvas::MakeRasterDirect(image->imageInfo(), pixmap.writable_addr(), image->imageInfo().minRowBytes());
+        canvas->saveLayer(SkRect::MakeWH(image->width(), image->height()), nullptr);
+        canvas->drawColor(SkColor4f { 0, 0, 0, 0.66 });
+
+        SkPaint paint;
+        paint.setColor(SkColor4f { 0, 0, 0, 0 });
+        paint.setBlendMode(SkBlendMode::kSrc);
+
+        size_t count = WKArrayGetSize(repaintRects);
+        for (size_t i = 0; i < count; ++i) {
+            WKRect rect = WKRectGetValue(static_cast<WKRectRef>(WKArrayGetItemAtIndex(repaintRects, i)));
+            canvas->drawRect(SkRect::MakeXYWH(static_cast<float>(rect.origin.x), static_cast<float>(rect.origin.y), static_cast<float>(rect.size.width), static_cast<float>(rect.size.height)), paint);
+        }
+        canvas->restore();
+    }
+
     auto snapshotHash = computeSHA1HashStringForPixmap(pixmap);
     if (!compareActualHashToExpectedAndDumpResults(snapshotHash))
         dumpPixmap(pixmap, snapshotHash);