join rects without gaps

While analyzing cursor rings, regions are built from text,
rects, and bitmaps to determine the areas inside and outside
the rings. These areas determine if the rings are fully visible,
and if they can be expanded into a larger bounds.

Empty input areas are defined only by rects drawn as their
background. In general, rects may be drawn as pieces that need
to be stitched together. Unlike glyphs, the stitching should
not allow gaps between rects.

By detecting gaps, and treating each unjoined rect as its own
area, a page with multiple successive input fields correctly
computes cursor rect bounds.

bug:3116242
Change-Id: If702b692c99c96c0188b42a638f750da12af6df4

1 files changed, 19 insertions, 1 deletions

diff --git a/WebKit/android/nav/CachedRoot.cpp b/WebKit/android/nav/CachedRoot.cpp
index 0c92498..d529a00 100644
--- a/WebKit/android/nav/CachedRoot.cpp
+++ b/WebKit/android/nav/CachedRoot.cpp
@@ -898,7 +898,11 @@ protected:
                 && mType != kDrawSprite_Type && mType != kDrawBitmap_Type)
             return false;
         if (mLayerTypes.isEmpty() || mLayerTypes.last() != mType
-            || !mAppendLikeTypes) {
+            || !mAppendLikeTypes
+            // if the last was a rect, and the current one is also a rect,
+            // but the two rects have a gap between, don't join them -- push
+            // an empty between them
+            || (mType == kDrawRect_Type && !joinable(rect))) {
             push(mType, mEmpty);
         }
         DBG_NAV_LOGD("RingCheck join %s (%d,%d,r=%d,b=%d) '%c'",
@@ -995,6 +999,20 @@ private:
         }
     }
 
+    bool joinable(const SkIRect& rect)
+    {
+        SkRegion region = mLayers.last();
+        if (!region.isRect())
+            return false;
+        const SkIRect& bounds1 = region.getBounds();
+        int area1 = bounds1.width() * bounds1.height();
+        area1 += rect.width() * rect.height();
+        region.op(rect, SkRegion::kUnion_Op);
+        const SkIRect& bounds2 = region.getBounds();
+        int area2 = bounds2.width() * bounds2.height();
+        return area2 <= area1;
+    }
+
     void popEmpty()
     {
         if (mLayerTypes.size() == 0)