Implement GetTextFromRange(), GetTextRange() and GetSelectionRange() for ArcImeService.

components/arc/common/ime.mojom

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Next MinVersion: 5
+// Next MinVersion: 6
 
 module arc.mojom;
 
 import "screen_rect.mojom";
 
 // Represents the type of text input field currently focused.
 [Extensible]
 enum TextInputType {
   NONE,
   TEXT,
   PASSWORD,
   SEARCH,
   EMAIL,
   NUMBER,
   TELEPHONE,
   URL,
   DATE,
   TIME,
   DATETIME,
 };
 
 // Represents the text insertion points in the container screen coordinates.
 struct CursorRect {
   int32 left;
   int32 top;
   int32 right;
   int32 bottom;
 };
 
+// Represents the range in the text. It is an open interval [start, end).
+[MinVersion=5]
+struct TextRange {
+  // Start offset in UTF-16 index.
+  uint32 start;
+  // End offset in UTF-16 index.
+  uint32 end;
+};
+
 // Represents a single segment of text currently composed by IME.
 struct CompositionSegment {
   // Start offset of the segment in UTF-16 index.
   uint32 start_offset;
   // End offset of the segment in UTF-16 index.
   uint32 end_offset;
   // Indicates that this segment should be emphasized.
   bool emphasized;
 };
 
 // Next method ID: 4
 interface ImeHost {
   // Notifies Chrome that the text input focus is changed.
   OnTextInputTypeChanged@0(TextInputType type);
 
   // Notifies Chrome that the cursor poisition has changed.
   OnCursorRectChanged@1(CursorRect rect);
 
   // Notifies Chrome that the current composition is canceled.
   [MinVersion=1] OnCancelComposition@2();
 
   // Show virtual keyboard of Chrome OS if needed.
   [MinVersion=2] ShowImeIfNeeded@3();
+
+  // Notifies Chrome that the cursor position has changed and
+  // also sends surrounding text.
+  //
+  // |text_range|, |text_in_range| and |selection_range| are piggy-backed
+  // into this method because Chrome OS IME tries to retrieve these information
+  // synchronously, so we need to update them all at once to keep consistency.
+  [MinVersion=5] OnCursorRectChangedWithSurroundingText@4(
+      CursorRect rect,           // The cursor position.

[hidehiko, 2017/05/16 10:08:59]

Optional: How about using Rect in ui/gfx/geometry/mojo/geometry.mojom, then?

+      TextRange text_range,      // The range of |text_in_range| in the current

[hidehiko, 2017/05/16 10:08:59]

Ditto, for ui/gfx/range/mojo/range.mojom.

+                                 // text in the editor.
+      string text_in_range,      // The text around the cursor.
+      TextRange selection_range  // The range of the selected text
+                                 // in the current text in the editor.
+      );
 };
 
 // Next method ID: 6
 interface ImeInstance {
   Init@0(ImeHost host_ptr);
 
   // Sets composition text and attributes requested by the host IME.
   SetCompositionText@1(string text, array<CompositionSegment> segments);
 
   // Commits the last set composition text and clears the composition.
   ConfirmCompositionText@2();
 
   // Commits the specified text and clears the composition.
   InsertText@3(string text);
 
   // Informs the virtual keyboard bounds on screen is changing.
   // |new_bounds| Represents a ChromeOS virtual keyboard bounds in ChromeOS
   // screen coordinate, physical pixel as a unit.
   // When all members are zero value, virtual keyboard is being hidden.
   [MinVersion=3] OnKeyboardBoundsChanging@4(ScreenRect new_bounds);
 
   // Deletes current selection plus the specified number of char16 values
   // before and after selection or caret.
   [MinVersion=4] ExtendSelectionAndDelete@5(uint64 before, uint64 after);
 };