Allow IME to insert zero-length composition string.

Some IMEs and Windows OS dictation will either insert zero-length text
or delete existing composition text to commit active composition.
Therefore, we should allow IMEs to cancel composition by committing zero
length text.

Bug: 1091069
Change-Id: I99cb213dc2ba1965abfa88ccf6858b89bd7e82df
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2233234
Commit-Queue: Siye Liu <siliu@microsoft.com>
Reviewed-by: Yohei Yukawa <yukawa@chromium.org>
Cr-Commit-Position: refs/heads/master@{#776198}

ui/base/ime/win/tsf_text_store.cc

@@ -647,9 +647,7 @@ HRESULT TSFTextStore::RequestLock(DWORD lock_flags, HRESULT* result) {
   // 3. User commits current composition text.
   if (((new_composition_start > last_composition_start &&
         text_input_client_->HasCompositionText()) ||
-       (wparam_keydown_fired_ == 0 && !has_composition_range_ &&
-        !text_input_client_->HasCompositionText()) ||
-       (wparam_keydown_fired_ != 0 && !has_composition_range_)) &&
+       !has_composition_range_) &&
       text_input_client_) {
     CommitTextAndEndCompositionIfAny(last_composition_start,
                                      new_composition_start);
@@ -1355,8 +1353,11 @@ void TSFTextStore::CommitTextAndEndCompositionIfAny(size_t old_size,
             : new_committed_string_size);
     // TODO(crbug.com/978678): Unify the behavior of
     //     |TextInputClient::InsertText(text)| for the empty text.
-    if (!new_committed_string.empty())
+    if (!new_committed_string.empty()) {
       text_input_client_->InsertText(new_committed_string);
+    } else {
+      text_input_client_->ClearCompositionText();
+    }
     // Notify accessibility about this committed composition
     text_input_client_->SetActiveCompositionForAccessibility(
         replace_text_range_, new_committed_string,

ui/base/ime/win/tsf_text_store_unittest.cc

@@ -3394,5 +3394,92 @@ TEST_F(TSFTextStoreTest, RegressionTest7) {
   EXPECT_EQ(S_OK, result);
 }
 
+// regression tests for crbug.com/1091069.
+// We should allow inserting empty compositon string to cancel composition.
+class RegressionTest8Callback : public TSFTextStoreTestCallback {
+ public:
+  explicit RegressionTest8Callback(TSFTextStore* text_store)
+      : TSFTextStoreTestCallback(text_store) {}
+
+  HRESULT LockGranted1(DWORD flags) {
+    SetTextTest(0, 0, L"bbbb", S_OK);
+    SetSelectionTest(0, 4, S_OK);
+
+    text_spans()->clear();
+    ImeTextSpan text_span_1;
+    text_span_1.start_offset = 0;
+    text_span_1.end_offset = 4;
+    text_span_1.underline_color = SK_ColorBLACK;
+    text_span_1.thickness = ImeTextSpan::Thickness::kThin;
+    text_span_1.background_color = SK_ColorTRANSPARENT;
+    text_spans()->push_back(text_span_1);
+
+    *edit_flag() = true;
+    *composition_start() = 0;
+    composition_range()->set_start(0);
+    composition_range()->set_end(4);
+    *has_composition_range() = true;
+
+    text_store_->OnKeyTraceDown(65u, 1966081u);
+    return S_OK;
+  }
+
+  void SetCompositionText1(const ui::CompositionText& composition) {
+    EXPECT_EQ(L"bbbb", composition.text);
+    EXPECT_EQ(0u, composition.selection.start());
+    EXPECT_EQ(4u, composition.selection.end());
+    ASSERT_EQ(1u, composition.ime_text_spans.size());
+    EXPECT_EQ(0u, composition.ime_text_spans[0].start_offset);
+    EXPECT_EQ(4u, composition.ime_text_spans[0].end_offset);
+    SetHasCompositionText(true);
+  }
+
+  HRESULT LockGranted2(DWORD flags) {
+    GetTextTest(0, -1, L"bbbb", 4);
+    SetTextTest(0, 4, L"", S_OK);
+
+    text_spans()->clear();
+    *edit_flag() = true;
+    *composition_start() = 0;
+    composition_range()->set_start(0);
+    composition_range()->set_end(0);
+
+    *has_composition_range() = false;
+    text_store_->OnKeyTraceUp(65u, 1966081u);
+    return S_OK;
+  }
+
+  void ClearCompositionText2() { EXPECT_EQ(false, *has_composition_range()); }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(RegressionTest8Callback);
+};
+
+TEST_F(TSFTextStoreTest, RegressionTest8) {
+  RegressionTest8Callback callback(text_store_.get());
+  EXPECT_CALL(text_input_client_, SetCompositionText(_))
+      .WillOnce(
+          Invoke(&callback, &RegressionTest8Callback::SetCompositionText1));
+
+  EXPECT_CALL(text_input_client_, ClearCompositionText())
+      .WillOnce(
+          Invoke(&callback, &RegressionTest8Callback::ClearCompositionText2));
+
+  EXPECT_CALL(*sink_, OnLockGranted(_))
+      .WillOnce(Invoke(&callback, &RegressionTest8Callback::LockGranted1))
+      .WillOnce(Invoke(&callback, &RegressionTest8Callback::LockGranted2));
+
+  ON_CALL(text_input_client_, HasCompositionText())
+      .WillByDefault(
+          Invoke(&callback, &TSFTextStoreTestCallback::HasCompositionText));
+
+  HRESULT result = kInvalidResult;
+  EXPECT_EQ(S_OK, text_store_->RequestLock(TS_LF_READWRITE, &result));
+  EXPECT_EQ(S_OK, result);
+  result = kInvalidResult;
+  EXPECT_EQ(S_OK, text_store_->RequestLock(TS_LF_READWRITE, &result));
+  EXPECT_EQ(S_OK, result);
+}
+
 }  // namespace
 }  // namespace ui