Tracking SelectionBounds for all RenderWidgets on the Browser Side (Aura Only)

content/browser/renderer_host/text_input_manager.h

Index: content/browser/renderer_host/text_input_manager.h
diff --git a/content/browser/renderer_host/text_input_manager.h b/content/browser/renderer_host/text_input_manager.h
index 2bb4c16d9e5f27f2f7b754f4f3676a54daa74c2e..9f7233343501ffd0fdc4da8242ab5d1548d201aa 100644
--- a/content/browser/renderer_host/text_input_manager.h
+++ b/content/browser/renderer_host/text_input_manager.h
@@ -6,10 +6,15 @@
 #define CONTENT_BROWSER_RENDERER_HOST_TEXT_INPUT_MANAGER_H__
 
 #include <unordered_map>
+#include <utility>
 
 #include "base/observer_list.h"
 #include "content/common/content_export.h"
 #include "content/common/text_input_state.h"
+#include "ui/gfx/geometry/rect.h"
+#include "ui/gfx/selection_bound.h"
+
+struct ViewHostMsg_SelectionBounds_Params;
 
 namespace content {
 
@@ -41,6 +46,10 @@ class CONTENT_EXPORT TextInputManager {
     virtual void OnImeCancelComposition(
         TextInputManager* text_input_manager,
         RenderWidgetHostViewBase* updated_view) {}
+    // Called when the selection bounds for the |updated_view| has changed.
+    virtual void OnSelectionBoundsChanged(
+        TextInputManager* text_input_manager,
+        RenderWidgetHostViewBase* updated_view) {}
   };
 
   TextInputManager();
@@ -59,6 +68,9 @@ class CONTENT_EXPORT TextInputManager {
   // dangling if the TextInputManager or |active_view_| might go away.
   const TextInputState* GetTextInputState();
 
+  // Returns the rect between selection bounds for the |active_view_|.
+  gfx::Rect GetSelectionBoundsRect();
+
   // ---------------------------------------------------------------------------
   // The following methods are called by RWHVs on the tab to update their IME-
   // related state.
@@ -71,6 +83,9 @@ class CONTENT_EXPORT TextInputManager {
   // the widget corresponding to |view|.
   void ImeCancelComposition(RenderWidgetHostViewBase* view);
 
+  void SelectionBoundsChanged(RenderWidgetHostViewBase* view,

[Charlie Reis, 2016/06/29 20:18:37]

Please add a comment about what selection bounds are.  It's a bit puzzling to me
that keyboard input triggers this, when it sounds like a gfx::Rect.

[EhsanK, 2016/06/30 00:24:45]

Good point.

This is not necessarily triggered by keyboard:
https://cs.chromium.org/chromium/src/content/renderer/render_widget.cc?sq=pac...

In aura, we use the selection bounds in determine the caret position for IME:
https://cs.chromium.org/chromium/src/content/browser/renderer_host/render_wid...
But there we use the type ui::SelectionBound which seems more relevant than
gfx::Rect. But why the bounds in IPC are of type gfx::Rect, I am not sure. Maybe
because InputMethod on ui/ side asks for a rect so initially they were
gfx::Rect? 

But apparently there has been movements in removing this IPC and use compositor
meta data. But IME (specifically for <webview>) has been a blocker for that. See
here:
https://cs.chromium.org/chromium/src/content/renderer/render_widget.cc?rcl=0&...

The rest of selection as I understand get updates through some compositing meta
data. That is as much as I could dig :P.

Finally, this update is only used by Mac and Aura.

+                              const ViewHostMsg_SelectionBounds_Params& params);
+
   // Registers the given |view| for tracking its TextInputState. This is called
   // by any view which has updates in its TextInputState (whether tab's RWHV or
   // that of a child frame). The |view| must unregister itself before being
@@ -100,6 +115,10 @@ class CONTENT_EXPORT TextInputManager {
       RenderWidgetHostViewBase* view);
 
  private:
+  template <class Value>
+  class ViewMap : public std::unordered_map<RenderWidgetHostViewBase*, Value> {
+  };
+
   void NotifyObserversAboutInputStateUpdate(RenderWidgetHostViewBase* view,
                                             bool did_update_state);
 
@@ -108,8 +127,14 @@ class CONTENT_EXPORT TextInputManager {
   // cannot have a |TextInputState.type| of ui::TEXT_INPUT_TYPE_NONE.
   RenderWidgetHostViewBase* active_view_;
 
-  std::unordered_map<RenderWidgetHostViewBase*, TextInputState>
-      text_input_state_map_;
+  ViewMap<TextInputState> text_input_state_map_;
+
+#if defined(USE_AURA)
+  // Maps a registered view to a pair of selection bounds where the first bound
+  // is selection anchor and the second is selection focus.
+  ViewMap<std::pair<gfx::SelectionBound, gfx::SelectionBound>>

[Charlie Reis, 2016/06/29 20:18:37]

I'm not a fan of using a map of pairs.  Can we have a struct rather than a pair
to make the members more explicit?

[EhsanK, 2016/06/30 00:24:45]

Acknowledged.

+      selection_bound_map_;
+#endif
 
   base::ObserverList<Observer> observer_list_;