Bug 1068525 - Ignore zoom level for AccessibleCaret. f=mtseng, r=roc

We want AccessibleCaret be of the same size regardless of the zoom
level. We simply divide the caret's width, height, margin-left, and the
text selection bar's margin-left by current zoom level.

The margin-left of the caret is adjusted from -23px to -23.5px for better
looking.

layout/base/AccessibleCaret.cpp

@@ -26,6 +26,11 @@ using namespace dom;
 
 NS_IMPL_ISUPPORTS(AccessibleCaret::DummyTouchListener, nsIDOMEventListener)
 
+float AccessibleCaret::sWidth = 0.0f;
+float AccessibleCaret::sHeight = 0.0f;
+float AccessibleCaret::sMarginLeft = 0.0f;
+float AccessibleCaret::sBarWidth = 0.0f;
+
 // -----------------------------------------------------------------------------
 // Implementation of AccessibleCaret methods
 
@@ -40,6 +45,15 @@ AccessibleCaret::AccessibleCaret(nsIPresShell* aPresShell)
   MOZ_ASSERT(mPresShell->GetCanvasFrame()->GetCustomContentContainer());
 
   InjectCaretElement(mPresShell->GetDocument());
+
+  static bool prefsAdded = false;
+  if (!prefsAdded) {
+    Preferences::AddFloatVarCache(&sWidth, "layout.accessiblecaret.width");
+    Preferences::AddFloatVarCache(&sHeight, "layout.accessiblecaret.height");
+    Preferences::AddFloatVarCache(&sMarginLeft, "layout.accessiblecaret.margin-left");
+    Preferences::AddFloatVarCache(&sBarWidth, "layout.accessiblecaret.bar.width");
+    prefsAdded = true;
+  }
 }
 
 AccessibleCaret::~AccessibleCaret()
@@ -215,13 +229,13 @@ AccessibleCaret::SetPosition(nsIFrame* aFrame, int32_t aOffset)
 
   mImaginaryCaretRect = imaginaryCaretRect;
 
-  // SetCaretElementPosition() and SetSelectionBarElementPosition() require the
+  // SetCaretElementStyle() and SetSelectionBarElementStyle() require the
   // input rect relative to container frame.
   nsRect imaginaryCaretRectInContainerFrame = imaginaryCaretRectInFrame;
   nsLayoutUtils::TransformRect(aFrame, CustomContentContainerFrame(),
                                imaginaryCaretRectInContainerFrame);
-  SetCaretElementPosition(imaginaryCaretRectInContainerFrame);
-  SetSelectionBarElementPosition(imaginaryCaretRectInContainerFrame);
+  SetCaretElementStyle(imaginaryCaretRectInContainerFrame);
+  SetSelectionBarElementStyle(imaginaryCaretRectInContainerFrame);
 
   return PositionChangedResult::Changed;
 }
@@ -236,7 +250,7 @@ AccessibleCaret::CustomContentContainerFrame() const
 }
 
 void
-AccessibleCaret::SetCaretElementPosition(const nsRect& aRect)
+AccessibleCaret::SetCaretElementStyle(const nsRect& aRect)
 {
   nsPoint position = CaretElementPosition(aRect);
   nsAutoString styleStr;
@@ -244,6 +258,12 @@ AccessibleCaret::SetCaretElementPosition(const nsRect& aRect)
                         nsPresContext::AppUnitsToIntCSSPixels(position.x),
                         nsPresContext::AppUnitsToIntCSSPixels(position.y));
 
+  float zoomLevel = GetZoomLevel();
+  styleStr.AppendPrintf(" width: %.2fpx; height: %.2fpx; margin-left: %.2fpx",
+                        sWidth / zoomLevel,
+                        sHeight / zoomLevel,
+                        sMarginLeft / zoomLevel);
+
   ErrorResult rv;
   CaretElement()->SetAttribute(NS_LITERAL_STRING("style"), styleStr, rv);
   MOZ_ASSERT(!rv.Failed());
@@ -252,13 +272,16 @@ AccessibleCaret::SetCaretElementPosition(const nsRect& aRect)
 }
 
 void
-AccessibleCaret::SetSelectionBarElementPosition(const nsRect& aRect)
+AccessibleCaret::SetSelectionBarElementStyle(const nsRect& aRect)
 {
   int32_t height = nsPresContext::AppUnitsToIntCSSPixels(aRect.height);
   nsAutoString barStyleStr;
   barStyleStr.AppendPrintf("margin-top: -%dpx; height: %dpx;",
                            height, height);
 
+  float zoomLevel = GetZoomLevel();
+  barStyleStr.AppendPrintf(" width: %.2fpx;", sBarWidth / zoomLevel);
+
   ErrorResult rv;
   SelectionBarElement()->SetAttribute(NS_LITERAL_STRING("style"), barStyleStr, rv);
   MOZ_ASSERT(!rv.Failed());
@@ -266,4 +289,16 @@ AccessibleCaret::SetSelectionBarElementPosition(const nsRect& aRect)
   AC_LOG("Set bar style: %s", NS_ConvertUTF16toUTF8(barStyleStr).get());
 }
 
+float
+AccessibleCaret::GetZoomLevel()
+{
+  // Full zoom on desktop.
+  float fullZoom = mPresShell->GetPresContext()->GetFullZoom();
+
+  // Pinch-zoom on B2G.
+  float resolution = mPresShell->GetCumulativeResolution();
+
+  return fullZoom * resolution;
+}
+
 } // namespace mozilla

layout/base/AccessibleCaret.h

@@ -129,8 +129,11 @@ public:
 
 private:
   // Argument aRect should be relative to CustomContentContainerFrame().
-  void SetCaretElementPosition(const nsRect& aRect);
-  void SetSelectionBarElementPosition(const nsRect& aRect);
+  void SetCaretElementStyle(const nsRect& aRect);
+  void SetSelectionBarElementStyle(const nsRect& aRect);
+
+  // Get current zoom level.
+  float GetZoomLevel();
 
   // Element which contains the caret image for 'Contains' test.
   dom::Element* CaretImageElement() const
@@ -202,6 +205,12 @@ private:
   // the caret.
   nsRefPtr<DummyTouchListener> mDummyTouchListener{new DummyTouchListener()};
 
+  // Static class variables
+  static float sWidth;
+  static float sHeight;
+  static float sMarginLeft;
+  static float sBarWidth;
+
 }; // class AccessibleCaret
 
 } // namespace mozilla

layout/style/ua.css

@@ -321,12 +321,6 @@ div:-moz-native-anonymous.moz-accessiblecaret > div.bar {
   z-index: 2147483647;
 }
 
-div:-moz-native-anonymous.moz-accessiblecaret {
-  width: 44px;
-  height: 47px;
-  margin-left: -23px;
-}
-
 div:-moz-native-anonymous.moz-accessiblecaret > div.image {
   background-position: center center;
   background-size: 100% 100%;
@@ -340,7 +334,6 @@ div:-moz-native-anonymous.moz-accessiblecaret > div.image {
 
 div:-moz-native-anonymous.moz-accessiblecaret > div.bar {
   margin-left: 49%;
-  width: 2px;
   background-color: #008aa0;
 }
 

modules/libpref/init/all.js

@@ -4606,6 +4606,12 @@ pref("caret.manages-android-actionbar", false);
 // New implementation to unify touch-caret and selection-carets.
 pref("layout.accessiblecaret.enabled", false);
 
+// CSS attributes of the AccessibleCaret in CSS pixels.
+pref("layout.accessiblecaret.width", "44.0");
+pref("layout.accessiblecaret.height", "47.0");
+pref("layout.accessiblecaret.margin-left", "-23.5");
+pref("layout.accessiblecaret.bar.width", "2.0");
+
 // Timeout in milliseconds to hide the accessiblecaret under cursor mode while
 // no one touches it. Set the value to 0 to disable this feature.
 pref("layout.accessiblecaret.timeout_ms", 3000);