Allow objects without scrollbars to be scrollable

Source/core/platform/ScrollableArea.cpp

Index: Source/core/platform/ScrollableArea.cpp
diff --git a/Source/core/platform/ScrollableArea.cpp b/Source/core/platform/ScrollableArea.cpp
index 0f02cf04bc2b3ff3a325ea00e11de5e29b5a5752..0bd73b2f0a8b9761ce9b7fa75b10874f27006816 100644
--- a/Source/core/platform/ScrollableArea.cpp
+++ b/Source/core/platform/ScrollableArea.cpp
@@ -94,24 +94,38 @@ bool ScrollableArea::scroll(ScrollDirection direction, ScrollGranularity granula
         scrollbar = horizontalScrollbar();
     }
 
-    if (!scrollbar)
+    if (!isScrollable(orientation))
         return false;
 
     float step = 0;
-    switch (granularity) {
-    case ScrollByLine:
-        step = scrollbar->lineStep();
-        break;
-    case ScrollByPage:
-        step = scrollbar->pageStep();
-        break;
-    case ScrollByDocument:
-        step = scrollbar->totalSize();
-        break;
-    case ScrollByPixel:
-    case ScrollByPrecisePixel:
-        step = scrollbar->pixelStep();
-        break;
+
+    if (scrollbar) {
+        switch (granularity) {
+        case ScrollByLine:
+            step = scrollbar->lineStep();
+            break;
+        case ScrollByPage:
+            step = scrollbar->pageStep();
+            break;
+        case ScrollByDocument:
+            step = scrollbar->totalSize();
+            break;
+        case ScrollByPixel:
+        case ScrollByPrecisePixel:
+            step = scrollbar->pixelStep();
+            break;
+        }
+    } else {
+        // TODO: Where should we get the step sizes here?

[aelias_OOO_until_Jul13, 2013/06/18 00:54:47]

It looks like the step sizes should be moved out of the scrollbar object as
well.  How about making them part of the ScrollableArea?

[bokan, 2013/06/18 23:03:27]

Done, though ScrollableArea has a compile time assert about keeping its size
small. Is it ok that we're adding 24 bytes to the class size?

[aelias_OOO_until_Jul13, 2013/06/19 02:55:24]

Ah, no, that's not okay, sorry about that suggestion.

It looks like we could make the "step" information virtual getters in
ScrollableArea and have the subclasses implement them.  We could avoid separate
storage entirely and compute them on the fly in the getters.

[bokan, 2013/06/19 18:57:00]

Done.

+        switch (granularity) {
+        case ScrollByLine:
+        case ScrollByPage:
+        case ScrollByDocument:
+        case ScrollByPixel:
+        case ScrollByPrecisePixel:
+            step = 1.0f;
+            break;
+        }
     }
 
     if (direction == ScrollUp || direction == ScrollLeft)
@@ -364,13 +378,6 @@ void ScrollableArea::serviceScrollAnimations()
         scrollAnimator->serviceScrollAnimations();
 }
 
-IntPoint ScrollableArea::scrollPosition() const
-{
-    int x = horizontalScrollbar() ? horizontalScrollbar()->value() : 0;
-    int y = verticalScrollbar() ? verticalScrollbar()->value() : 0;
-    return IntPoint(x, y);
-}
-
 IntPoint ScrollableArea::minimumScrollPosition() const
 {
     return IntPoint();