Bug 1127066 - Factor out code common to APZCCallbackHelper::UpdateRootFrame and UpdateSubFrame. r=kats

--HG--
extra : source : fe1ea639cdfde510a2bb51d2f113fb14809b6b43

gfx/layers/apz/util/APZCCallbackHelper.cpp

@@ -106,27 +106,18 @@ ScrollFrameTo(nsIScrollableFrame* aFrame, const CSSPoint& aPoint, bool& aSuccess
   return geckoScrollPosition;
 }
 
-void
-APZCCallbackHelper::UpdateRootFrame(nsIDOMWindowUtils* aUtils,
+/**
+ * Scroll the scroll frame associated with |aContent| to the scroll position
+ * requested in |aMetrics|.
+ * The scroll offset in |aMetrics| is updated to reflect the actual scroll
+ * position.
+ * The displayport stored in |aMetrics| is updated to reflect any difference
+ * between the requested and actual scroll positions.
+ */
+static void
+ScrollFrame(nsIContent* aContent,
             FrameMetrics& aMetrics)
 {
-    // Precondition checks
-    MOZ_ASSERT(aUtils);
-    MOZ_ASSERT(aMetrics.GetUseDisplayPortMargins());
-    if (aMetrics.GetScrollId() == FrameMetrics::NULL_SCROLL_ID) {
-        return;
-    }
-
-    // Set the scroll port size, which determines the scroll range. For example if
-    // a 500-pixel document is shown in a 100-pixel frame, the scroll port length would
-    // be 100, and gecko would limit the maximum scroll offset to 400 (so as to prevent
-    // overscroll). Note that if the content here was zoomed to 2x, the document would
-    // be 1000 pixels long but the frame would still be 100 pixels, and so the maximum
-    // scroll range would be 900. Therefore this calculation depends on the zoom applied
-    // to the content relative to the container.
-    CSSSize scrollPort = aMetrics.CalculateCompositedSizeInCssPixels();
-    aUtils->SetScrollPositionClampingScrollPortSize(scrollPort.width, scrollPort.height);
-
   // Scroll the window to the desired spot
   nsIScrollableFrame* sf = nsLayoutUtils::FindScrollableFrameFor(aMetrics.GetScrollId());
   bool scrollUpdated = false;
@@ -147,19 +138,17 @@ APZCCallbackHelper::UpdateRootFrame(nsIDOMWindowUtils* aUtils,
   }
 
   aMetrics.SetScrollOffset(actualScrollOffset);
+}
 
-    // The pres shell resolution is updated by the the async zoom since the
-    // last paint.
-    float presShellResolution = aMetrics.GetPresShellResolution()
-                              * aMetrics.GetAsyncZoom().scale;
-    aUtils->SetResolutionAndScaleTo(presShellResolution, presShellResolution);
-
-    // Finally, we set the displayport.
-    nsCOMPtr<nsIContent> content = nsLayoutUtils::FindContentFor(aMetrics.GetScrollId());
-    if (!content) {
+static void
+SetDisplayPortMargins(nsIDOMWindowUtils* aUtils,
+                      nsIContent* aContent,
+                      FrameMetrics& aMetrics)
+{
+  if (!aContent) {
     return;
   }
-    nsCOMPtr<nsIDOMElement> element = do_QueryInterface(content);
+  nsCOMPtr<nsIDOMElement> element = do_QueryInterface(aContent);
   if (!element) {
     return;
   }
@@ -174,7 +163,42 @@ APZCCallbackHelper::UpdateRootFrame(nsIDOMWindowUtils* aUtils,
   nsRect base(0, 0,
               baseCSS.width * nsPresContext::AppUnitsPerCSSPixel(),
               baseCSS.height * nsPresContext::AppUnitsPerCSSPixel());
-    nsLayoutUtils::SetDisplayPortBaseIfNotSet(content, base);
+  nsLayoutUtils::SetDisplayPortBaseIfNotSet(aContent, base);
+}
+
+void
+APZCCallbackHelper::UpdateRootFrame(nsIDOMWindowUtils* aUtils,
+                                    FrameMetrics& aMetrics)
+{
+  // Precondition checks
+  MOZ_ASSERT(aUtils);
+  MOZ_ASSERT(aMetrics.GetUseDisplayPortMargins());
+  if (aMetrics.GetScrollId() == FrameMetrics::NULL_SCROLL_ID) {
+    return;
+  }
+
+  // Set the scroll port size, which determines the scroll range. For example if
+  // a 500-pixel document is shown in a 100-pixel frame, the scroll port length would
+  // be 100, and gecko would limit the maximum scroll offset to 400 (so as to prevent
+  // overscroll). Note that if the content here was zoomed to 2x, the document would
+  // be 1000 pixels long but the frame would still be 100 pixels, and so the maximum
+  // scroll range would be 900. Therefore this calculation depends on the zoom applied
+  // to the content relative to the container.
+  // Note that this needs to happen before scrolling the frame (in UpdateFrameCommon),
+  // otherwise the scroll position may get clamped incorrectly.
+  CSSSize scrollPort = aMetrics.CalculateCompositedSizeInCssPixels();
+  aUtils->SetScrollPositionClampingScrollPortSize(scrollPort.width, scrollPort.height);
+
+  nsIContent* content = nsLayoutUtils::FindContentFor(aMetrics.GetScrollId());
+  ScrollFrame(content, aMetrics);
+
+  // The pres shell resolution is updated by the the async zoom since the
+  // last paint.
+  float presShellResolution = aMetrics.GetPresShellResolution()
+                            * aMetrics.GetAsyncZoom().scale;
+  aUtils->SetResolutionAndScaleTo(presShellResolution, presShellResolution);
+
+  SetDisplayPortMargins(aUtils, content, aMetrics);
 }
 
 void
@@ -184,43 +208,13 @@ APZCCallbackHelper::UpdateSubFrame(nsIContent* aContent,
   // Precondition checks
   MOZ_ASSERT(aContent);
   MOZ_ASSERT(aMetrics.GetUseDisplayPortMargins());
-    if (aMetrics.GetScrollId() == FrameMetrics::NULL_SCROLL_ID) {
-        return;
+
+  // We don't currently support zooming for subframes, so nothing extra
+  // needs to be done beyond the tasks common to this and UpdateRootFrame.
+  ScrollFrame(aContent, aMetrics);
+  if (nsCOMPtr<nsIDOMWindowUtils> utils = GetDOMWindowUtils(aContent)) {
+    SetDisplayPortMargins(utils, aContent, aMetrics);
   }
-
-    nsCOMPtr<nsIDOMWindowUtils> utils = GetDOMWindowUtils(aContent);
-    if (!utils) {
-        return;
-    }
-
-    // We currently do not support zooming arbitrary subframes. They can only
-    // be scrolled, so here we only have to set the scroll position and displayport.
-
-    nsIScrollableFrame* sf = nsLayoutUtils::FindScrollableFrameFor(aMetrics.GetScrollId());
-    bool scrollUpdated = false;
-    CSSPoint actualScrollOffset = ScrollFrameTo(sf, aMetrics.GetScrollOffset(), scrollUpdated);
-
-    nsCOMPtr<nsIDOMElement> element = do_QueryInterface(aContent);
-    if (element) {
-        if (scrollUpdated) {
-            AdjustDisplayPortForScrollDelta(aMetrics, actualScrollOffset);
-        } else {
-            RecenterDisplayPort(aMetrics);
-        }
-        ScreenMargin margins = aMetrics.GetDisplayPortMargins();
-        utils->SetDisplayPortMarginsForElement(margins.left,
-                                               margins.top,
-                                               margins.right,
-                                               margins.bottom,
-                                               element, 0);
-        CSSRect baseCSS = aMetrics.CalculateCompositedRectInCssPixels();
-        nsRect base(0, 0,
-                    baseCSS.width * nsPresContext::AppUnitsPerCSSPixel(),
-                    baseCSS.height * nsPresContext::AppUnitsPerCSSPixel());
-        nsLayoutUtils::SetDisplayPortBaseIfNotSet(aContent, base);
-    }
-
-    aMetrics.SetScrollOffset(actualScrollOffset);
 }
 
 already_AddRefed<nsIDOMWindowUtils>