Bug 1270019 - Add a SetRestoreResolution API for fennec's SessionRestore to use. r=rbarker

MozReview-Commit-ID: 7WqmgAkFItQ

dom/base/nsDOMWindowUtils.cpp

@@ -496,6 +496,19 @@ nsDOMWindowUtils::SetResolutionAndScaleTo(float aResolution)
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsDOMWindowUtils::SetRestoreResolution(float aResolution)
+{
+  nsIPresShell* presShell = GetPresShell();
+  if (!presShell) {
+    return NS_ERROR_FAILURE;
+  }
+
+  presShell->SetRestoreResolution(aResolution);
+
+  return NS_OK;
+}
+
 NS_IMETHODIMP
 nsDOMWindowUtils::GetResolution(float* aResolution)
 {

dom/interfaces/base/nsIDOMWindowUtils.idl

@@ -222,6 +222,13 @@ interface nsIDOMWindowUtils : nsISupports {
    */
   void setResolutionAndScaleTo(in float aResolution);
 
+  /**
+   * Set a resolution on the presShell which is the "restored" from history.
+   * This resolution should be used when painting for the first time. Calling
+   * this too late may have no effect.
+   */
+  void setRestoreResolution(in float aResolution);
+
   /**
    * Whether the resolution has been set by the user.
    * This gives a way to check whether the provided resolution is the default

layout/base/MobileViewportManager.cpp

@@ -84,6 +84,12 @@ MobileViewportManager::Destroy()
   mPresShell = nullptr;
 }
 
+void
+MobileViewportManager::SetRestoreResolution(float aResolution)
+{
+  mRestoreResolution = Some(aResolution);
+}
+
 void
 MobileViewportManager::RequestReflow()
 {
@@ -145,6 +151,22 @@ MobileViewportManager::SetInitialViewport()
   RefreshViewportSize(false);
 }
 
+CSSToScreenScale
+MobileViewportManager::ClampZoom(const CSSToScreenScale& aZoom,
+                                 const nsViewportInfo& aViewportInfo)
+{
+  CSSToScreenScale zoom = aZoom;
+  if (zoom < aViewportInfo.GetMinZoom()) {
+    zoom = aViewportInfo.GetMinZoom();
+    MVM_LOG("%p: Clamped to %f\n", this, zoom.scale);
+  }
+  if (zoom > aViewportInfo.GetMaxZoom()) {
+    zoom = aViewportInfo.GetMaxZoom();
+    MVM_LOG("%p: Clamped to %f\n", this, zoom.scale);
+  }
+  return zoom;
+}
+
 CSSToScreenScale
 MobileViewportManager::UpdateResolution(const nsViewportInfo& aViewportInfo,
                                         const ScreenIntSize& aDisplaySize,
@@ -156,18 +178,18 @@ MobileViewportManager::UpdateResolution(const nsViewportInfo& aViewportInfo,
   LayoutDeviceToLayerScale res(mPresShell->GetResolution());
 
   if (mIsFirstPaint) {
-    CSSToScreenScale defaultZoom = aViewportInfo.GetDefaultZoom();
-    MVM_LOG("%p: default zoom from viewport is %f\n", this, defaultZoom.scale);
-    if (!aViewportInfo.IsDefaultZoomValid()) {
-      defaultZoom = MaxScaleRatio(ScreenSize(aDisplaySize), aViewport);
-      MVM_LOG("%p: Intrinsic computed zoom is %f\n", this, defaultZoom.scale);
-      if (defaultZoom < aViewportInfo.GetMinZoom()) {
-        defaultZoom = aViewportInfo.GetMinZoom();
-        MVM_LOG("%p: Clamped to %f\n", this, defaultZoom.scale);
-      }
-      if (defaultZoom > aViewportInfo.GetMaxZoom()) {
-        defaultZoom = aViewportInfo.GetMaxZoom();
-        MVM_LOG("%p: Clamped to %f\n", this, defaultZoom.scale);
+    CSSToScreenScale defaultZoom;
+    if (mRestoreResolution) {
+      defaultZoom = CSSToScreenScale(mRestoreResolution.value() * cssToDev.scale);
+      MVM_LOG("%p: restored zoom is %f\n", this, defaultZoom.scale);
+      defaultZoom = ClampZoom(defaultZoom, aViewportInfo);
+    } else {
+      defaultZoom = aViewportInfo.GetDefaultZoom();
+      MVM_LOG("%p: default zoom from viewport is %f\n", this, defaultZoom.scale);
+      if (!aViewportInfo.IsDefaultZoomValid()) {
+        defaultZoom = MaxScaleRatio(ScreenSize(aDisplaySize), aViewport);
+        MVM_LOG("%p: Intrinsic computed zoom is %f\n", this, defaultZoom.scale);
+        defaultZoom = ClampZoom(defaultZoom, aViewportInfo);
       }
     }
     MOZ_ASSERT(aViewportInfo.GetMinZoom() <= defaultZoom &&

layout/base/MobileViewportManager.h

@@ -27,6 +27,11 @@ public:
                         nsIDocument* aDocument);
   void Destroy();
 
+  /* Provide a resolution to use during the first paint instead of the default
+   * resolution computed from the viewport info metadata. This is in the same
+   * "units" as the argument to nsDOMWindowUtils::SetResolutionAndScaleTo. */
+  void SetRestoreResolution(float aResolution);
+
   /* Notify the MobileViewportManager that a reflow was requested in the
    * presShell.*/
   void RequestReflow();
@@ -49,6 +54,10 @@ private:
   /* Secondary main helper method to update just the SPCSPS. */
   void RefreshSPCSPS();
 
+  /* Helper to clamp the given zoom by the min/max in the viewport info. */
+  mozilla::CSSToScreenScale ClampZoom(const mozilla::CSSToScreenScale& aZoom,
+                                      const nsViewportInfo& aViewportInfo);
+
   /* Updates the presShell resolution and returns the new zoom. */
   mozilla::CSSToScreenScale UpdateResolution(const nsViewportInfo& aViewportInfo,
                                              const mozilla::ScreenIntSize& aDisplaySize,
@@ -67,6 +76,7 @@ private:
   bool mPainted;
   mozilla::LayoutDeviceIntSize mDisplaySize;
   mozilla::CSSSize mMobileViewportSize;
+  mozilla::Maybe<float> mRestoreResolution;
 };
 
 #endif

layout/base/nsIPresShell.h

@@ -1435,6 +1435,12 @@ public:
    */
   virtual bool ScaleToResolution() const = 0;
 
+  /**
+   * Used by session restore code to restore a resolution before the first
+   * paint.
+   */
+  virtual void SetRestoreResolution(float aResolution) = 0;
+
   /**
    * Returns whether we are in a DrawWindow() call that used the
    * DRAWWINDOW_DO_NOT_FLUSH flag.

layout/base/nsPresShell.cpp

@@ -5565,6 +5565,13 @@ float PresShell::GetCumulativeNonRootScaleResolution()
   return resolution;
 }
 
+void PresShell::SetRestoreResolution(float aResolution)
+{
+  if (mMobileViewportManager) {
+    mMobileViewportManager->SetRestoreResolution(aResolution);
+  }
+}
+
 void PresShell::SetRenderingState(const RenderingState& aState)
 {
   if (mRenderFlags != aState.mRenderFlags) {

layout/base/nsPresShell.h

@@ -232,6 +232,7 @@ public:
   virtual bool ScaleToResolution() const override;
   virtual float GetCumulativeResolution() override;
   virtual float GetCumulativeNonRootScaleResolution() override;
+  virtual void SetRestoreResolution(float aResolution) override;
 
   //nsIViewObserver interface