Remove special no-op rule from TipInputModeManager::OnSetFocus

With this commit, one remaining behavior difference between Mozc
and MS-IME in Windows 11 22H2 will be addressed.

Mozc has had a special no-op rule when switching input focus and the
InputScope specified in the newly focused field is the same as the one
that was previously observed in the same process.  MS-IME, on the other
hand, does not have such a special no-op rule and always updates its
input mode upon switching input focus.

For better app compatibility, let's make it compatible with MS-IME's.

Closes google#826.

PiperOrigin-RevId: 574371235

docs/design_doc/input_scope.md

@@ -96,6 +96,7 @@ Release History
   * 1.11.1490.10x: Initial release
   * 2.29.5250.10x
     * [#818](https://github.com/google/mozc/issues/818): Remapped `IS_ALPHANUMERIC_HALFWIDTH` to direct mode
+    * [#826](https://github.com/google/mozc/issues/826): Reflect `InputFocus` on every focus change.
 
 Reference
 ---------

src/win32/tip/tip_input_mode_manager.cc

@@ -217,11 +217,6 @@ TipInputModeManager::Action TipInputModeManager::OnSetFocus(
     }
   }
 
-  if (!new_input_scopes.empty() && (new_input_scopes == input_scope_)) {
-    // The same input scope is specified. Use the previous mode.
-    return kDoNothing;
-  }
-
   input_scope_ = std::move(new_input_scopes);
   mozc_state_ = GetOverriddenState(tsf_state_, input_scopes);
   if ((mozc_state_.open_close != prev_effective.open_close) ||

src/win32/tip/tip_input_mode_manager_test.cc

@@ -292,6 +292,38 @@ TEST(TipInputModeManagerTest, HonorOpenCloseModeFromApps_Issue8661096) {
   EXPECT_TRUE(input_mode_manager.GetTsfOpenClose());
 }
 
+TEST(TipInputModeManagerTest, InputScopeOnSetFocus_GitHubIssue826) {
+  TipInputModeManager input_mode_manager(GetThreadLocalMode());
+
+  // Initialize (Off + Hiragana)
+  input_mode_manager.OnInitialize(false, kNativeHiragana);
+
+  // SetFocus (Off + Hiragana)
+  std::vector<InputScope> input_scope_email = {IS_EMAIL_SMTPEMAILADDRESS};
+  auto action =
+      input_mode_manager.OnSetFocus(false, kNativeHiragana, input_scope_email);
+  EXPECT_EQ(action, TipInputModeManager::kDoNothing);
+  EXPECT_FALSE(input_mode_manager.IsIndicatorVisible());
+  EXPECT_FALSE(input_mode_manager.GetEffectiveOpenClose());
+  EXPECT_EQ(input_mode_manager.GetEffectiveConversionMode(),
+            TipInputModeManager::kHiragana);
+
+  // On -> (On + Hiragana)
+  input_mode_manager.OnReceiveCommand(true, TipInputModeManager::kHiragana,
+                                      TipInputModeManager::kHiragana);
+  EXPECT_TRUE(input_mode_manager.GetEffectiveOpenClose());
+  EXPECT_TRUE(input_mode_manager.IsIndicatorVisible());
+
+  // SetFocus again with the same InputScope -> (Off + Hiragana)
+  action =
+      input_mode_manager.OnSetFocus(true, kNativeHiragana, input_scope_email);
+  EXPECT_EQ(action, TipInputModeManager::kUpdateUI);
+  EXPECT_TRUE(input_mode_manager.IsIndicatorVisible());
+  EXPECT_FALSE(input_mode_manager.GetEffectiveOpenClose());
+  EXPECT_EQ(input_mode_manager.GetEffectiveConversionMode(),
+            TipInputModeManager::kHiragana);
+}
+
 }  // namespace
 }  // namespace tsf
 }  // namespace win32