[GTK][Skia] Add support for non-accelerated rendering

https://bugs.webkit.org/show_bug.cgi?id=270788

Reviewed by Adrian Perez de Castro.

GTK uses cairo for non-accelerated rendering, so we need to render the
ShareableBitmap with skia, but into a cairo surface.

* Source/WebCore/platform/graphics/skia/ShareableBitmapSkia.cpp:
(WebCore::ShareableBitmap::paint):
* Source/WebKit/UIProcess/cairo/BackingStoreCairo.cpp:
(WebKit::BackingStore::incorporateUpdate):
(WebKit::BackingStore::scroll):

Canonical link: https://commits.webkit.org/276018@main

Source/WebCore/platform/graphics/skia/ShareableBitmapSkia.cpp

@@ -62,9 +62,14 @@ void ShareableBitmap::paint(GraphicsContext& context, const IntPoint& dstPoint,
     paint(context, 1, dstPoint, srcRect);
 }
 
-void ShareableBitmap::paint(GraphicsContext&, float /*scaleFactor*/, const IntPoint&, const IntRect&)
+void ShareableBitmap::paint(GraphicsContext& context, float scaleFactor, const IntPoint& dstPoint, const IntRect& srcRect)
 {
-    notImplemented();
+    FloatRect scaledSrcRect(srcRect);
+    scaledSrcRect.scale(scaleFactor);
+    FloatRect scaledDestRect(dstPoint, srcRect.size());
+    scaledDestRect.scale(scaleFactor);
+    auto image = createPlatformImage(BackingStoreCopy::DontCopyBackingStore);
+    context.platformContext()->drawImageRect(image.get(), scaledSrcRect, scaledDestRect, { }, nullptr, { });
 }
 
 RefPtr<Image> ShareableBitmap::createImage()

Source/WebKit/UIProcess/cairo/BackingStoreCairo.cpp

@@ -40,6 +40,12 @@
 #include <WebCore/GraphicsContextCairo.h>
 #endif
 
+#if USE(SKIA)
+#include <WebCore/GraphicsContextSkia.h>
+#include <skia/core/SkCanvas.h>
+#include <skia/core/SkSurface.h>
+#endif
+
 namespace WebKit {
 using namespace WebCore;
 
@@ -99,9 +105,10 @@ void BackingStore::incorporateUpdate(UpdateInfo&& updateInfo)
 
     scroll(updateInfo.scrollRect, updateInfo.scrollOffset);
 
-#if USE(CAIRO)
     // Paint all update rects.
     IntPoint updateRectLocation = updateInfo.updateRectBounds.location();
+
+#if USE(CAIRO)
     GraphicsContextCairo graphicsContext(m_surface.get());
 
     // When m_webPageProxy.drawsBackground() is false, bitmap contains transparent parts as a background of the webpage.
@@ -114,7 +121,20 @@ void BackingStore::incorporateUpdate(UpdateInfo&& updateInfo)
         bitmap->paint(graphicsContext, m_deviceScaleFactor, updateRect.location(), srcRect);
     }
 #elif USE(SKIA)
-    notImplemented();
+    cairo_surface_flush(m_surface.get());
+    auto imageInfo = SkImageInfo::MakeN32Premul(cairo_image_surface_get_width(m_surface.get()), cairo_image_surface_get_height(m_surface.get()));
+    auto surface = SkSurfaces::WrapPixels(imageInfo, cairo_image_surface_get_data(m_surface.get()), cairo_image_surface_get_stride(m_surface.get()), nullptr);
+    GraphicsContextSkia graphicsContext(WTFMove(surface), RenderingMode::Unaccelerated, RenderingPurpose::ShareableLocalSnapshot);
+    graphicsContext.setCompositeOperation(WebCore::CompositeOperator::Copy);
+    for (const auto& updateRect : updateInfo.updateRects) {
+        IntRect srcRect(updateRect);
+        srcRect.move(-updateRectLocation.x(), -updateRectLocation.y());
+        bitmap->paint(graphicsContext, m_deviceScaleFactor, updateRect.location(), srcRect);
+
+        IntRect damage(updateRect.location(), srcRect.size());
+        damage.scale(m_deviceScaleFactor);
+        cairo_surface_mark_dirty_rectangle(m_surface.get(), damage.x(), damage.y(), damage.width(), damage.height());
+    }
 #endif
 }
 
@@ -132,12 +152,18 @@ void BackingStore::scroll(const IntRect& scrollRect, const IntSize& scrollOffset
     if (!m_scrollSurface)
         m_scrollSurface = createCairoImageSurfaceWithFastMalloc(m_size, m_deviceScaleFactor);
 
-#if USE(CAIRO)
+#if USE(SKIA)
+    auto copyRectFromOneSurfaceToAnother = [](cairo_surface_t* src, cairo_surface_t* dst, const IntSize& sourceOffset, const IntRect& rect) {
+        RefPtr<cairo_t> cr = adoptRef(cairo_create(dst));
+        cairo_set_operator(cr.get(), CAIRO_OPERATOR_SOURCE);
+        cairo_set_source_surface(cr.get(), src, sourceOffset.width(), sourceOffset.height());
+        cairo_rectangle(cr.get(), rect.x(), rect.y(), rect.width(), rect.height());
+        cairo_fill(cr.get());
+    };
+#endif
+
     copyRectFromOneSurfaceToAnother(m_surface.get(), m_scrollSurface.get(), scrollOffset, targetRect);
     copyRectFromOneSurfaceToAnother(m_scrollSurface.get(), m_surface.get(), { }, targetRect);
-#elif USE(SKIA)
-    // FIXME: move copyRectFromOneSurfaceToAnother to a different file if we really need this with skia.
-#endif
     m_scrolledHysteresis.impulse();
 }