Initial implementation of IAccessible2 scrollTo and setTextSelection and

content/browser/accessibility/browser_accessibility.cc

Index: content/browser/accessibility/browser_accessibility.cc
===================================================================
--- content/browser/accessibility/browser_accessibility.cc	(revision 112818)
+++ content/browser/accessibility/browser_accessibility.cc	(working copy)
@@ -163,6 +163,92 @@
   return this;
 }
 
+void BrowserAccessibility::ScrollToMakeVisible(const gfx::Rect& subfocus,
+                                               const gfx::Rect& focus,
+                                               const gfx::Rect& viewport) {
+  int scroll_x = 0;
+  int scroll_x_min = 0;
+  int scroll_x_max = 0;
+  int scroll_y = 0;
+  int scroll_y_min = 0;
+  int scroll_y_max = 0;
+  if (!GetIntAttribute(WebAccessibility::ATTR_SCROLL_X, &scroll_x) ||
+      !GetIntAttribute(WebAccessibility::ATTR_SCROLL_X_MIN, &scroll_x_min) ||
+      !GetIntAttribute(WebAccessibility::ATTR_SCROLL_X_MAX, &scroll_x_max) ||
+      !GetIntAttribute(WebAccessibility::ATTR_SCROLL_Y, &scroll_y) ||
+      !GetIntAttribute(WebAccessibility::ATTR_SCROLL_Y_MIN, &scroll_y_min) ||
+      !GetIntAttribute(WebAccessibility::ATTR_SCROLL_Y_MAX, &scroll_y_max)) {
+    return;
+  }
+
+  gfx::Rect final_viewport(0, 0, location_.width(), location_.height());
+  final_viewport.Intersect(viewport);
+
+  int new_scroll_x = ComputeBestScrollOffset(
+      scroll_x,
+      subfocus.x(), subfocus.right(),
+      focus.x(), focus.right(),
+      final_viewport.x(), final_viewport.right());
+  new_scroll_x = std::max(new_scroll_x, scroll_x_min);
+  new_scroll_x = std::min(new_scroll_x, scroll_x_max);
+
+  int new_scroll_y = ComputeBestScrollOffset(
+      scroll_y,
+      subfocus.y(), subfocus.bottom(),
+      focus.y(), focus.bottom(),
+      final_viewport.y(), final_viewport.bottom());
+  new_scroll_y = std::max(new_scroll_y, scroll_y_min);
+  new_scroll_y = std::min(new_scroll_y, scroll_y_max);
+
+  manager_->ChangeScrollPosition(*this, new_scroll_x, new_scroll_y);
+}
+
+// static
+int BrowserAccessibility::ComputeBestScrollOffset(
+    int current_scroll_offset,
+    int subfocus_min, int subfocus_max,
+    int focus_min, int focus_max,
+    int viewport_min, int viewport_max) {
+  int viewport_size = viewport_max - viewport_min;
+
+  // If the focus size is larger than the viewport size, shrink it in the
+  // direction of subfocus.
+  if (focus_max - focus_min > viewport_size) {
+    // Subfocus must be within focus:
+    subfocus_min = std::max(subfocus_min, focus_min);
+    subfocus_max = std::min(subfocus_max, focus_max);
+
+    // Subfocus must be no larger than the viewport size; favor top/left.
+    if (subfocus_max - subfocus_min > viewport_size)
+      subfocus_max = subfocus_min + viewport_size;
+
+    if (subfocus_min + viewport_size > focus_max) {
+      focus_min = focus_max - viewport_size;
+    } else {
+      focus_min = subfocus_min;
+      focus_max = subfocus_min + viewport_size;
+    }
+  }
+
+  // Exit now if the focus is already within the viewport.
+  if (focus_min - current_scroll_offset >= viewport_min &&
+      focus_max - current_scroll_offset <= viewport_max) {
+    return current_scroll_offset;
+  }
+
+  // Scroll left if we're too far to the right.
+  if (focus_max - current_scroll_offset > viewport_max)
+    return focus_max - viewport_max;
+
+  // Scroll right if we're too far to the left.
+  if (focus_min - current_scroll_offset < viewport_min)
+    return focus_min - viewport_min;
+
+  // This shouldn't happen.
+  NOTREACHED();
+  return current_scroll_offset;
+}
+
 void BrowserAccessibility::InternalAddReference() {
   ref_count_++;
 }