Fixing Canvas2DLayerBridge to handle lost graphics contexts

Source/core/platform/graphics/chromium/Canvas2DLayerBridge.cpp

Index: Source/core/platform/graphics/chromium/Canvas2DLayerBridge.cpp
diff --git a/Source/core/platform/graphics/chromium/Canvas2DLayerBridge.cpp b/Source/core/platform/graphics/chromium/Canvas2DLayerBridge.cpp
index 8715c44be61a490d0efe6489bddff8c640e9290d..649a23690992e6b5b57bf96322cdd411f1eacbbe 100644
--- a/Source/core/platform/graphics/chromium/Canvas2DLayerBridge.cpp
+++ b/Source/core/platform/graphics/chromium/Canvas2DLayerBridge.cpp
@@ -34,6 +34,7 @@
 #include "core/platform/graphics/GraphicsContext3D.h"
 #include "core/platform/graphics/chromium/Canvas2DLayerManager.h"
 #include "core/platform/graphics/chromium/GraphicsLayerChromium.h"
+#include "core/platform/graphics/gpu/SharedGraphicsContext3D.h"
 #include <public/Platform.h>
 #include <public/WebCompositorSupport.h>
 #include <public/WebGraphicsContext3D.h>
@@ -44,6 +45,36 @@ using WebKit::WebTextureUpdater;
 
 namespace WebCore {
 
+static SkSurface* createSurface(GraphicsContext3D* context3D, const IntSize& size)
+{
+    ASSERT(!context3D->webContext()->isContextLost());
+    GrContext* gr = context3D->grContext();
+    if (!gr)
+        return 0;
+    gr->resetContext();
+    SkImage::Info info;
+    info.fWidth = size.width();
+    info.fHeight = size.height();
+    info.fColorType = SkImage::kPMColor_ColorType;
+    info.fAlphaType = SkImage::kPremul_AlphaType;
+    return SkSurface::NewRenderTarget(gr, info);
+}
+
+PassOwnPtr<Canvas2DLayerBridge> Canvas2DLayerBridge::create(PassRefPtr<GraphicsContext3D> context, const IntSize& size, OpacityMode opacityMode, ThreadMode threading)
+{
+    SkAutoTUnref<SkSurface> surface(createSurface(context.get(), size));
+    if (!surface.get())
+        return 0;
+    SkDeferredCanvas* canvas = new SkDeferredCanvas(surface);
+    return adoptPtr(new Canvas2DLayerBridge(context, canvas, opacityMode, threading));
+}
+
+PassOwnPtr<Canvas2DLayerBridge> Canvas2DLayerBridge::create(PassRefPtr<GraphicsContext3D> context, SkDeferredCanvas* canvas, OpacityMode opacityMode, ThreadMode threading)
+{
+    // Factory overload used for unit testing

[Stephen White, 2013/05/28 14:23:10]

Nit: this comment should probably be in the header, to be more easily noticed.

+    return adoptPtr(new Canvas2DLayerBridge(context, canvas, opacityMode, threading));
+}
+
 Canvas2DLayerBridge::Canvas2DLayerBridge(PassRefPtr<GraphicsContext3D> context, SkDeferredCanvas* canvas, OpacityMode opacityMode, ThreadMode threadMode)
     : m_canvas(canvas)
     , m_context(context)
@@ -97,6 +128,13 @@ void Canvas2DLayerBridge::limitPendingFrames()
 
 void Canvas2DLayerBridge::prepareForDraw()
 {
+    if (!isValid()) {
+        if (m_canvas) {
+            // drop pending commands because there is no surface to draw to
+            m_canvas->silentFlush();
+        }
+        return;
+    }
 #if !ENABLE(CANVAS_USES_MAILBOX)
     m_layer->willModifyTexture();
 #endif
@@ -143,6 +181,8 @@ void Canvas2DLayerBridge::flush()
 
 unsigned Canvas2DLayerBridge::prepareTexture(WebTextureUpdater& updater)
 {
+    if (!isValid())
+        return 0;
 #if ENABLE(CANVAS_USES_MAILBOX)
     ASSERT_NOT_REACHED();
     return 0;
@@ -166,12 +206,50 @@ unsigned Canvas2DLayerBridge::prepareTexture(WebTextureUpdater& updater)
 
 WebGraphicsContext3D* Canvas2DLayerBridge::context()
 {
+    ASSERT(m_context.get());
     return m_context->webContext();
 }
 
+bool Canvas2DLayerBridge::isValid()
+{
+    RefPtr<GraphicsContext3D> sharedContext = SharedGraphicsContext3D::get();
+    if (!sharedContext || sharedContext->webContext()->isContextLost()) {
+        // Context was lost since last call to isValid and
+        // SharedGraphicsContext3D has not recovered.
+        m_context.clear();
+        m_layer->clearTexture();
+        return false;
+    }
+    if (m_context != sharedContext) {
+        ASSERT(sharedContext.get());
+        // Old context was lost and sharedContext has recovered.
+        // Use the new context to recover the layer
+        m_context = sharedContext;
+        m_layer->clearTexture();
+        IntSize size(m_canvas->getTopDevice()->width(), m_canvas->getTopDevice()->height());
+        SkAutoTUnref<SkSurface> surface(createSurface(m_context.get(), size));
+        if (surface.get()) {
+            m_canvas->setSurface(surface.get());
+            // FIXME: draw sad canvas picture into new buffer crbug.com/243842
+        } else {
+            // Surface allocation failed. Reset m_context to trigger subsequent retry
+            m_context.clear();
+            return false;
+        }
+#if !ENABLE(CANVAS_USES_MAILBOX)
+        GrRenderTarget* renderTarget = reinterpret_cast<GrRenderTarget*>(m_canvas->getDevice()->accessRenderTarget());
+        if (renderTarget)
+            m_layer->setTextureId(renderTarget->asTexture()->getTextureHandle());

[Stephen White, 2013/05/28 14:23:10]

Not new to this patch, but I see this code in four different places now in this
file (constructor, backBufferTexture(), prepareTexture(), here). IWBN to
refactor them.

+#endif
+    }
+    return true;
+}
+
 bool Canvas2DLayerBridge::prepareMailbox(WebKit::WebExternalTextureMailbox* outMailbox)
 {
 #if ENABLE(CANVAS_USES_MAILBOX)
+    if (!m_canvas.get() || !isValid())
+        return false;
     // Release to skia textures that were previouosly released by the
     // compositor. We do this before acquiring the next snapshot in
     // order to cap maximum gpu memory consumption.