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 112482)
+++ content/browser/accessibility/browser_accessibility.cc	(working copy)
@@ -133,8 +133,8 @@
   BrowserAccessibility* root = manager_->GetRoot();
   int scroll_x = 0;
   int scroll_y = 0;
-  root->GetIntAttribute(WebAccessibility::ATTR_DOC_SCROLLX, &scroll_x);
-  root->GetIntAttribute(WebAccessibility::ATTR_DOC_SCROLLY, &scroll_y);
+  root->GetIntAttribute(WebAccessibility::ATTR_SCROLL_X, &scroll_x);
+  root->GetIntAttribute(WebAccessibility::ATTR_SCROLL_Y, &scroll_y);
   bounds.Offset(-scroll_x, -scroll_y);
 
   return bounds;
@@ -163,6 +163,94 @@
   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;
+  }
+
+  int viewport_left = std::max(viewport.x(), 0);

[David Tseng, 2011/12/02 00:02:17]

Why isn't this std::max(viewport.x(), location_.x())?

[dmazzoni, 2011/12/03 00:37:10]

location_ is in global coordinates. We want things in local coordinates relative
to this container view.

However, you're right that this was inconsistent - where I had location_.right()
and location_.bottom() below, those should have been width and height instead.

I updated it to use Intersect instead, that's even more concise.

+  int viewport_top = std::max(viewport.y(), 0);

[David Tseng, 2011/12/02 00:02:17]

ditto.

+  int viewport_right = std::min(viewport.right(), location_.right());
+  int viewport_bottom = std::min(viewport.bottom(), location_.bottom());
+
+  int new_scroll_x = ComputeBestScrollOffset(

[David Tseng, 2011/12/02 00:02:17]

Did you try using Rect's as primitives to perform offset calculations? Perhaps
that might make this easier (i.e. getting the union of the focused rect and the
viewport rect).

[dmazzoni, 2011/12/03 00:37:10]

Used Intersect, above. Good idea.

I don't think there's a way to use it anymore and make it more concise.

+      scroll_x,
+      subfocus.x(), subfocus.right(),
+      focus.x(), focus.right(),
+      viewport_left, 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(),
+      viewport_top, 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_++;
 }