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

components/arc/common/ime.mojom

Index: components/arc/common/ime.mojom
diff --git a/components/arc/common/ime.mojom b/components/arc/common/ime.mojom
index ae6d4e5bb9c79ba69be1ce09644b5f012b69be47..746274ef50b8577b515b04ec8de9e0b1792e408d 100644
--- a/components/arc/common/ime.mojom
+++ b/components/arc/common/ime.mojom
@@ -2,7 +2,7 @@
 // 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;
 
@@ -32,6 +32,12 @@ struct CursorRect {
   int32 bottom;
 };
 
+[MinVersion=5]
+struct TextRange {
+  uint32 start;
+  uint32 end;

[hidehiko, 2017/05/11 14:32:31]

Is |end| inclusive or exclusive? As this is interface between Chrome and ARC,
could you explicitly document it?

[yhanada, 2017/05/12 07:52:06]

Done.

+};
+
 // Represents a single segment of text currently composed by IME.
 struct CompositionSegment {
   // Start offset of the segment in UTF-16 index.
@@ -55,6 +61,12 @@ interface ImeHost {
 
   // 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.
+  [MinVersion=5] OnCursorRectChangedWithSurroundingText@4(

[hidehiko, 2017/05/11 14:32:31]

Could you document the args? Specifically what is the different between
|text_range| and |selection_range| passed here?

[kinaba, 2017/05/12 01:28:35]

Could you also add a comment why all these info are piggy-backed
into a single method?  (I.e., e.g., because Chrome OS IME tries
to retrieve these information synchronously, we need to update them
all at once to keep consistency, etc)

[yhanada, 2017/05/12 07:52:06]

Done.

+      CursorRect rect, TextRange text_range, string text_in_range,
+      TextRange selection_range);
 };
 
 // Next method ID: 6