Bug 488901. When an element's size changes and it has borders, we don't necessarily need to invalidate the entire border-box --- if there is no right or bottom border, and other conditions are met. r+sr=dbaron

--HG--
extra : rebase_source : 24306ec844dab873cc9b580f32a383f0ccb769a5

layout/base/nsLayoutUtils.cpp

@@ -3060,6 +3060,44 @@ nsLayoutUtils::HasNonZeroCorner(const nsStyleCorners& aCorners)
   return PR_FALSE;
 }
 
+// aCorner is a "full corner" value, i.e. NS_CORNER_TOP_LEFT etc
+static PRBool IsCornerAdjacentToSide(PRUint8 aCorner, PRUint8 aSide)
+{
+  PR_STATIC_ASSERT(NS_SIDE_TOP == NS_CORNER_TOP_LEFT);
+  PR_STATIC_ASSERT(NS_SIDE_RIGHT == NS_CORNER_TOP_RIGHT);
+  PR_STATIC_ASSERT(NS_SIDE_BOTTOM == NS_CORNER_BOTTOM_RIGHT);
+  PR_STATIC_ASSERT(NS_SIDE_LEFT == NS_CORNER_BOTTOM_LEFT);
+  PR_STATIC_ASSERT(NS_SIDE_TOP == ((NS_CORNER_TOP_RIGHT - 1)&3));
+  PR_STATIC_ASSERT(NS_SIDE_RIGHT == ((NS_CORNER_BOTTOM_RIGHT - 1)&3));
+  PR_STATIC_ASSERT(NS_SIDE_BOTTOM == ((NS_CORNER_BOTTOM_LEFT - 1)&3));
+  PR_STATIC_ASSERT(NS_SIDE_LEFT == ((NS_CORNER_TOP_LEFT - 1)&3));
+
+  return aSide == aCorner || aSide == ((aCorner - 1)&3);
+}
+
+/* static */ PRBool
+nsLayoutUtils::HasNonZeroCornerOnSide(const nsStyleCorners& aCorners,
+                                      PRUint8 aSide)
+{
+  PR_STATIC_ASSERT(NS_CORNER_TOP_LEFT_X/2 == NS_CORNER_TOP_LEFT);
+  PR_STATIC_ASSERT(NS_CORNER_TOP_LEFT_Y/2 == NS_CORNER_TOP_LEFT);
+  PR_STATIC_ASSERT(NS_CORNER_TOP_RIGHT_X/2 == NS_CORNER_TOP_RIGHT);
+  PR_STATIC_ASSERT(NS_CORNER_TOP_RIGHT_Y/2 == NS_CORNER_TOP_RIGHT);
+  PR_STATIC_ASSERT(NS_CORNER_BOTTOM_RIGHT_X/2 == NS_CORNER_BOTTOM_RIGHT);
+  PR_STATIC_ASSERT(NS_CORNER_BOTTOM_RIGHT_Y/2 == NS_CORNER_BOTTOM_RIGHT);
+  PR_STATIC_ASSERT(NS_CORNER_BOTTOM_LEFT_X/2 == NS_CORNER_BOTTOM_LEFT);
+  PR_STATIC_ASSERT(NS_CORNER_BOTTOM_LEFT_Y/2 == NS_CORNER_BOTTOM_LEFT);
+
+  NS_FOR_CSS_HALF_CORNERS(corner) {
+    // corner is a "half corner" value, so dividing by two gives us a
+    // "full corner" value.
+    if (NonZeroStyleCoord(aCorners.Get(corner)) &&
+        IsCornerAdjacentToSide(corner/2, aSide))
+      return PR_TRUE;
+  }
+  return PR_FALSE;
+}
+
 /* static */ nsTransparencyMode
 nsLayoutUtils::GetFrameTransparency(nsIFrame* aFrame) {
   if (aFrame->GetStyleContext()->GetStyleDisplay()->mOpacity < 1.0f)

layout/base/nsLayoutUtils.h

@@ -943,6 +943,13 @@ public:
    */
   static PRBool HasNonZeroCorner(const nsStyleCorners& aCorners);
 
+  /**
+   * Determine if there is any corner radius on corners adjacent to the
+   * given side.
+   */
+  static PRBool HasNonZeroCornerOnSide(const nsStyleCorners& aCorners,
+                                       PRUint8 aSide);
+
   /**
    * Determine if a widget is likely to require transparency or translucency.
    *   @param aFrame the frame of a <window>, <popup> or <menupopup> element.

layout/generic/nsFrame.cpp

@@ -4051,11 +4051,22 @@ nsIFrame::CheckInvalidateSizeChange(const nsRect& aOldRect,
     return;
   }
 
-  // Invalidate the old frame borders if the frame has borders. Those borders
-  // may be moving.
+  // Invalidate the old frame border box if the frame has borders. Those
+  // borders may be moving.
   const nsStyleBorder* border = GetStyleBorder();
   NS_FOR_CSS_SIDES(side) {
     if (border->GetActualBorderWidth(side) != 0) {
+      if ((side == NS_SIDE_LEFT || side == NS_SIDE_TOP) &&
+          !nsLayoutUtils::HasNonZeroCornerOnSide(border->mBorderRadius, side) &&
+          !border->GetBorderImage() &&
+          border->GetBorderStyle(side) == NS_STYLE_BORDER_STYLE_SOLID) {
+        // We also need to be sure that the bottom-left or top-right
+        // corner is simple. For example, if the bottom or right border
+        // has a different color, we would need to invalidate the corner
+        // area. But that's OK because if there is a right or bottom border,
+        // we'll invalidate the entire border-box here anyway.
+        continue;
+      }
       Invalidate(nsRect(0, 0, aOldRect.width, aOldRect.height));
       return;
     }

layout/style/nsStyleStruct.h

@@ -578,7 +578,7 @@ struct nsStyleBorder {
     return mComputedBorder;
   }
 
-  // Get the actual border width for a particular side, in twips.  Note that
+  // Get the actual border width for a particular side, in appunits.  Note that
   // this is zero if and only if there is no border to be painted for this
   // side.  That is, this value takes into account the border style and the
   // value is rounded to the nearest device pixel by NS_ROUND_BORDER_TO_PIXELS.