Tracking SelectionBounds for all RenderWidgets on the Browser Side (Mac)

content/browser/renderer_host/text_input_manager.cc

Index: content/browser/renderer_host/text_input_manager.cc
diff --git a/content/browser/renderer_host/text_input_manager.cc b/content/browser/renderer_host/text_input_manager.cc
index aa2522f91ca74f1272bd1cbd63eff233b51f6607..7c648278fbc17a926c1bb5842415a9bbdc3c1ef0 100644
--- a/content/browser/renderer_host/text_input_manager.cc
+++ b/content/browser/renderer_host/text_input_manager.cc
@@ -61,13 +61,12 @@ const TextInputState* TextInputManager::GetTextInputState() const {
   return !!active_view_ ? &text_input_state_map_.at(active_view_) : nullptr;
 }
 
-gfx::Rect TextInputManager::GetSelectionBoundsRect() const {
-  if (!active_view_)
-    return gfx::Rect();
-
-  return gfx::RectBetweenSelectionBounds(
-      selection_region_map_.at(active_view_).anchor,
-      selection_region_map_.at(active_view_).focus);
+const TextInputManager::SelectionRegion* TextInputManager::GetSelectionRegion(
+    RenderWidgetHostViewBase* view) const {
+  DCHECK(!view || IsRegistered(view));
+  if (!view)
+    view = active_view_;
+  return view ? &selection_region_map_.at(view) : nullptr;
 }
 
 const TextInputManager::CompositionRangeInfo*
@@ -149,14 +148,14 @@ void TextInputManager::SelectionBoundsChanged(
     RenderWidgetHostViewBase* view,
     const ViewHostMsg_SelectionBounds_Params& params) {
   DCHECK(IsRegistered(view));
-
-// TODO(ekaramad): Implement the logic for other platforms (crbug.com/578168).
+  // Converting the anchor point to root's coordinate space (for child frame
+  // views).
+  gfx::Point anchor_origin_transformed =
+      view->TransformPointToRootCoordSpace(params.anchor_rect.origin());
 #if defined(USE_AURA)
   gfx::SelectionBound anchor_bound, focus_bound;
-  // Converting the points to the |view|'s root coordinate space (for child
-  // frame views).
-  anchor_bound.SetEdge(gfx::PointF(view->TransformPointToRootCoordSpace(
-                           params.anchor_rect.origin())),
+
+  anchor_bound.SetEdge(gfx::PointF(anchor_origin_transformed),
                        gfx::PointF(view->TransformPointToRootCoordSpace(
                            params.anchor_rect.bottom_left())));
   focus_bound.SetEdge(gfx::PointF(view->TransformPointToRootCoordSpace(
@@ -193,10 +192,19 @@ void TextInputManager::SelectionBoundsChanged(
 
   selection_region_map_[view].anchor = anchor_bound;
   selection_region_map_[view].focus = focus_bound;
-
+#else
+  if (params.anchor_rect == params.focus_rect) {

[erikchen, 2016/08/17 23:31:16]

When this condition evaluates to false, why don't we need to update caret_rect?
I'm having trouble understanding the relationship between
params.anchor_rect/params.focus_rect and ....caret_rect and
first_selection_rect. Is there documentation/design doc somewhere I can look
into?

[EhsanK, 2016/08/22 14:48:28]

Sadly, I don't know of any. But here is what I figured out:
anchor_rect: First point of entry for selection.
focus_rect: the end of selection, i.e., were caret is now.

When the condition is true there is actually no selection (highlighted text)
which is where the caret is. Hence the caret_rect update.

For the most part, first_selection_rect is pretty much equal to caret_rect. The
only exception I found so far is Katakana IME (Japanese). For this IME, we have
a sequence of 'composition clauses' of different length. If during composition
we use the arrow keys to move in between them, the first selection rect will be
different than caret rect (it will be the beginning of the clause).

+    selection_region_map_[view].caret_rect.set_origin(
+        anchor_origin_transformed);
+    selection_region_map_[view].caret_rect.set_size(params.anchor_rect.size());
+  }
+  selection_region_map_[view].first_selection_rect.set_origin(
+      anchor_origin_transformed);
+  selection_region_map_[view].first_selection_rect.set_size(
+      params.anchor_rect.size());
+#endif  // USE_AURA
   FOR_EACH_OBSERVER(Observer, observer_list_,
                     OnSelectionBoundsChanged(this, view));
-#endif
 }
 
 // TODO(ekaramad): We use |range| only on Mac OS; but we still track its value