Adds DevTools commands for forced viewport override.

third_party/WebKit/Source/web/DevToolsEmulator.cpp

Index: third_party/WebKit/Source/web/DevToolsEmulator.cpp
diff --git a/third_party/WebKit/Source/web/DevToolsEmulator.cpp b/third_party/WebKit/Source/web/DevToolsEmulator.cpp
index 848f4e121489e3eb3daee48891475e134128abbc..e7965d6f8a34083d61235f713f707c375a80acad 100644
--- a/third_party/WebKit/Source/web/DevToolsEmulator.cpp
+++ b/third_party/WebKit/Source/web/DevToolsEmulator.cpp
@@ -11,6 +11,7 @@
 #include "core/page/Page.h"
 #include "core/style/ComputedStyle.h"
 #include "platform/RuntimeEnabledFeatures.h"
+#include "platform/geometry/FloatRect.h"
 #include "public/platform/WebLayerTreeView.h"
 #include "web/WebInputEventConversion.h"
 #include "web/WebLocalFrameImpl.h"
@@ -219,7 +220,7 @@ void DevToolsEmulator::enableDeviceEmulation(const WebDeviceEmulationParams& par
         disableMobileEmulation();
 
     m_webViewImpl->setCompositorDeviceScaleFactorOverride(params.deviceScaleFactor);
-    m_webViewImpl->setRootLayerTransform(WebSize(params.offset.x, params.offset.y), params.scale);
+    updateRootLayerTransform();
     // TODO(dgozman): mainFrameImpl() is null when it's remote. Figure out how
     // we end up with enabling emulation in this case.
     if (m_webViewImpl->mainFrameImpl()) {
@@ -238,8 +239,8 @@ void DevToolsEmulator::disableDeviceEmulation()
     m_webViewImpl->page()->settings().setDeviceScaleAdjustment(m_embedderDeviceScaleAdjustment);
     disableMobileEmulation();
     m_webViewImpl->setCompositorDeviceScaleFactorOverride(0.f);
-    m_webViewImpl->setRootLayerTransform(WebSize(0.f, 0.f), 1.f);
     m_webViewImpl->setPageScaleFactor(1.f);
+    updateRootLayerTransform();
     // mainFrameImpl() could be null during cleanup or remote <-> local swap.
     if (m_webViewImpl->mainFrameImpl()) {
         if (Document* document = m_webViewImpl->mainFrameImpl()->frame()->document())
@@ -319,6 +320,106 @@ void DevToolsEmulator::disableMobileEmulation()
         m_webViewImpl->mainFrameImpl()->frameView()->layout();
 }
 
+void DevToolsEmulator::setVisualTransformOverride(const WebFloatRect& area, float scale)
+{
+    GraphicsLayer* containerLayer = m_webViewImpl->page()->frameHost().visualViewport().containerLayer();
+    if (!m_visualTransformOverride) {
+        m_visualTransformOverride = VisualTransformOverride();
+        if (containerLayer)
+            m_visualTransformOverride->originalVisualViewportMasking = containerLayer->masksToBounds();
+    }
+
+    m_visualTransformOverride->area = area;
+    m_visualTransformOverride->scale = scale;
+
+    // Ensure that all content inside the area is painted.
+    if (m_webViewImpl->mainFrameImpl())
+        m_webViewImpl->mainFrameImpl()->frameView()->setVisibleContentRectForPainting(enclosingIntRect(area));
+
+    // Disable clipping on the visual viewport layer, to ensure the whole area is painted.
+    if (containerLayer)
+        containerLayer->setMasksToBounds(false);
+
+    // Move the correct (scaled) content area to show in the top left of the
+    // CompositorFrame via the root transform.
+    updateRootLayerTransform();
+}
+
+void DevToolsEmulator::clearVisualTransformOverride()
+{
+    if (!m_visualTransformOverride)
+        return;
+
+    bool originalMasking = m_visualTransformOverride->originalVisualViewportMasking;
+    m_visualTransformOverride = WTF::nullopt;
+
+    // Restore original state.
+    if (m_webViewImpl->mainFrameImpl())
+        m_webViewImpl->mainFrameImpl()->frameView()->resetVisibleContentRectForPainting();
+    GraphicsLayer* containerLayer = m_webViewImpl->page()->frameHost().visualViewport().containerLayer();
+    if (containerLayer)
+        containerLayer->setMasksToBounds(originalMasking);
+    updateRootLayerTransform();
+}
+
+void DevToolsEmulator::mainFrameScrollOrScaleChanged()
+{
+    // Visual transform override has to take current page scale and scroll
+    // offset into account. Update the transform if override is active.
+    if (m_visualTransformOverride)
+        updateRootLayerTransform();
+}
+
+void DevToolsEmulator::applyDeviceEmulationTransform(TransformationMatrix* transform)
+{
+    if (m_deviceMetricsEnabled) {
+        WebSize offset(m_emulationParams.offset.x, m_emulationParams.offset.y);
+        // Scale first, so that translation is unaffected.
+        transform->translate(offset.width, offset.height);
+        transform->scale(m_emulationParams.scale);
+        if (m_webViewImpl->mainFrameImpl())
+            m_webViewImpl->mainFrameImpl()->setInputEventsTransformForEmulation(offset, m_emulationParams.scale);
+    } else {
+        if (m_webViewImpl->mainFrameImpl())
+            m_webViewImpl->mainFrameImpl()->setInputEventsTransformForEmulation(WebSize(0, 0), 1.0);
+    }
+}
+
+void DevToolsEmulator::applyVisualTransformOverride(TransformationMatrix* transform)
+{
+    if (!m_visualTransformOverride)
+        return;
+
+    // Transform operations follow in reverse application.
+    // Last, scale positioned area according to override.
+    transform->scale(m_visualTransformOverride->scale);
+
+    // Translate while taking into account current scroll offset.
+    WebSize scrollOffset = m_webViewImpl->mainFrame()->scrollOffset();
+    WebFloatPoint visualOffset = m_webViewImpl->visualViewportOffset();
+    float scrollX = scrollOffset.width + visualOffset.x;
+    float scrollY = scrollOffset.height + visualOffset.y;
+    transform->translate(
+        -m_visualTransformOverride->area.x + scrollX,
+        -m_visualTransformOverride->area.y + scrollY);
+
+    // First, reverse page scale, so we don't have to take it into account for
+    // calculation of the translation.
+    transform->scale(1. / m_webViewImpl->pageScaleFactor());
+}
+
+void DevToolsEmulator::updateRootLayerTransform()
+{
+    TransformationMatrix transform;
+
+    // Apply device emulation transform first, so that it is affected by the
+    // visual transform override.
+    applyVisualTransformOverride(&transform);
+    applyDeviceEmulationTransform(&transform);
+
+    m_webViewImpl->setRootLayerTransform(transform);
+}
+
 void DevToolsEmulator::setTouchEventEmulationEnabled(bool enabled)
 {
     if (m_touchEventEmulationEnabled == enabled)