1 files changed, 91 insertions, 0 deletions
diff --git a/chromium/third_party/WebKit/Source/core/rendering/ScrollBehavior.cpp b/chromium/third_party/WebKit/Source/core/rendering/ScrollBehavior.cpp
index d28c8e00b2e..d331f1dc07b 100644
--- a/chromium/third_party/WebKit/Source/core/rendering/ScrollBehavior.cpp
+++ b/chromium/third_party/WebKit/Source/core/rendering/ScrollBehavior.cpp
@@ -44,6 +44,8 @@
 #include "config.h"
 #include "core/rendering/ScrollBehavior.h"
 
+#include "platform/geometry/LayoutRect.h"
+
 namespace WebCore {
 
 const ScrollAlignment ScrollAlignment::alignCenterIfNeeded = { noScroll, alignCenter, alignToClosestEdge };
@@ -52,4 +54,93 @@ const ScrollAlignment ScrollAlignment::alignCenterAlways = { alignCenter, alignC
 const ScrollAlignment ScrollAlignment::alignTopAlways = { alignTop, alignTop, alignTop };
 const ScrollAlignment ScrollAlignment::alignBottomAlways = { alignBottom, alignBottom, alignBottom };
 
+#define MIN_INTERSECT_FOR_REVEAL 32
+
+LayoutRect ScrollAlignment::getRectToExpose(const LayoutRect& visibleRect, const LayoutRect& exposeRect, const ScrollAlignment& alignX, const ScrollAlignment& alignY)
+{
+    // Determine the appropriate X behavior.
+    ScrollBehavior scrollX;
+    LayoutRect exposeRectX(exposeRect.x(), visibleRect.y(), exposeRect.width(), visibleRect.height());
+    LayoutUnit intersectWidth = intersection(visibleRect, exposeRectX).width();
+    if (intersectWidth == exposeRect.width() || intersectWidth >= MIN_INTERSECT_FOR_REVEAL) {
+        // If the rectangle is fully visible, use the specified visible behavior.
+        // If the rectangle is partially visible, but over a certain threshold,
+        // then treat it as fully visible to avoid unnecessary horizontal scrolling
+        scrollX = getVisibleBehavior(alignX);
+    } else if (intersectWidth == visibleRect.width()) {
+        // If the rect is bigger than the visible area, don't bother trying to center. Other alignments will work.
+        scrollX = getVisibleBehavior(alignX);
+        if (scrollX == alignCenter)
+            scrollX = noScroll;
+    } else if (intersectWidth > 0) {
+        // If the rectangle is partially visible, but not above the minimum threshold, use the specified partial behavior
+        scrollX = getPartialBehavior(alignX);
+    } else {
+        scrollX = getHiddenBehavior(alignX);
+    }
+
+    if (scrollX == alignToClosestEdge) {
+        // Closest edge is the right in two cases:
+        // (1) exposeRect to the right of and smaller than visibleRect
+        // (2) exposeRect to the left of and larger than visibleRect
+        if ((exposeRect.maxX() > visibleRect.maxX() && exposeRect.width() < visibleRect.width())
+            || (exposeRect.maxX() < visibleRect.maxX() && exposeRect.width() > visibleRect.width())) {
+            scrollX = alignRight;
+        }
+    }
+
+    // Given the X behavior, compute the X coordinate.
+    LayoutUnit x;
+    if (scrollX == noScroll)
+        x = visibleRect.x();
+    else if (scrollX == alignRight)
+        x = exposeRect.maxX() - visibleRect.width();
+    else if (scrollX == alignCenter)
+        x = exposeRect.x() + (exposeRect.width() - visibleRect.width()) / 2;
+    else
+        x = exposeRect.x();
+
+    // Determine the appropriate Y behavior.
+    ScrollBehavior scrollY;
+    LayoutRect exposeRectY(visibleRect.x(), exposeRect.y(), visibleRect.width(), exposeRect.height());
+    LayoutUnit intersectHeight = intersection(visibleRect, exposeRectY).height();
+    if (intersectHeight == exposeRect.height()) {
+        // If the rectangle is fully visible, use the specified visible behavior.
+        scrollY = getVisibleBehavior(alignY);
+    } else if (intersectHeight == visibleRect.height()) {
+        // If the rect is bigger than the visible area, don't bother trying to center. Other alignments will work.
+        scrollY = getVisibleBehavior(alignY);
+        if (scrollY == alignCenter)
+            scrollY = noScroll;
+    } else if (intersectHeight > 0) {
+        // If the rectangle is partially visible, use the specified partial behavior
+        scrollY = getPartialBehavior(alignY);
+    } else {
+        scrollY = getHiddenBehavior(alignY);
+    }
+
+    if (scrollY == alignToClosestEdge) {
+        // Closest edge is the bottom in two cases:
+        // (1) exposeRect below and smaller than visibleRect
+        // (2) exposeRect above and larger than visibleRect
+        if ((exposeRect.maxY() > visibleRect.maxY() && exposeRect.height() < visibleRect.height())
+            || (exposeRect.maxY() < visibleRect.maxY() && exposeRect.height() > visibleRect.height())) {
+            scrollY = alignBottom;
+        }
+    }
+
+    // Given the Y behavior, compute the Y coordinate.
+    LayoutUnit y;
+    if (scrollY == noScroll)
+        y = visibleRect.y();
+    else if (scrollY == alignBottom)
+        y = exposeRect.maxY() - visibleRect.height();
+    else if (scrollY == alignCenter)
+        y = exposeRect.y() + (exposeRect.height() - visibleRect.height()) / 2;
+    else
+        y = exposeRect.y();
+
+    return LayoutRect(LayoutPoint(x, y), visibleRect.size());
+}
+
 }; // namespace WebCore