Fix macOS text composing

shell/platform/common/text_input_model.cc

@@ -69,15 +69,22 @@ void TextInputModel::BeginComposing() {
   composing_range_ = TextRange(selection_.start());
 }
 
-void TextInputModel::UpdateComposingText(const std::u16string& text) {
+void TextInputModel::UpdateComposingText(const std::u16string& text,
+                                         const TextRange& selection) {
   // Preserve selection if we get a no-op update to the composing region.
   if (text.length() == 0 && composing_range_.collapsed()) {
     return;
   }
-  DeleteSelected();
-  text_.replace(composing_range_.start(), composing_range_.length(), text);
+  const TextRange& rangeToDelete =
+      composing_range_.collapsed() ? selection_ : composing_range_;
+  text_.replace(rangeToDelete.start(), rangeToDelete.length(), text);
   composing_range_.set_end(composing_range_.start() + text.length());
-  selection_ = TextRange(composing_range_.end());
+  selection_ = TextRange(selection.start() + composing_range_.start(),
+                         selection.extent() + composing_range_.start());
+}
+
+void TextInputModel::UpdateComposingText(const std::u16string& text) {
+  UpdateComposingText(text, TextRange(text.length()));
 }
 
 void TextInputModel::UpdateComposingText(const std::string& text) {

shell/platform/common/text_input_model.h

@@ -57,12 +57,17 @@ class TextInputModel {
   // are restricted to the composing range.
   void BeginComposing();
 
-  // Replaces the composing range with new UTF-16 text.
+  // Replaces the composing range with new UTF-16 text, and sets the selection.
   //
-  // If a selection of non-zero length exists, it is deleted if the composing
-  // text is non-empty. The composing range is adjusted to the length of
-  // |text| and the selection base and offset are set to the end of the
-  // composing range.
+  // The given |text| replaces text within the current composing range, or the
+  // current selection if the text wasn't composing. The composing range is
+  // adjusted to the length of |text|, and the |selection| describes the new
+  // selection range, relative to the start of the new composing range.
+  void UpdateComposingText(const std::u16string& text,
+                           const TextRange& selection);
+
+  // Replaces the composing range with new UTF-16 text and sets the selection to
+  // the end of the composing text.
   void UpdateComposingText(const std::u16string& text);
 
   // Replaces the composing range with new UTF-8 text.

shell/platform/common/text_input_model_unittests.cc

@@ -403,6 +403,17 @@ TEST(TextInputModel, UpdateComposingRemovesLastComposingCharacter) {
   model->SetText("ACDE");
 }
 
+TEST(TextInputModel, UpdateSelectionWhileComposing) {
+  auto model = std::make_unique<TextInputModel>();
+  model->SetText("ABCDE");
+  model->BeginComposing();
+  model->SetComposingRange(TextRange(4, 5), 1);
+  model->UpdateComposingText(u"ぴょんぴょん", TextRange(3, 6));
+  EXPECT_STREQ(model->GetText().c_str(), "ABCDぴょんぴょん");
+  EXPECT_EQ(model->selection(), TextRange(7, 10));
+  EXPECT_EQ(model->composing_range(), TextRange(4, 10));
+}
+
 TEST(TextInputModel, AddCodePoint) {
   auto model = std::make_unique<TextInputModel>();
   model->AddCodePoint('A');

shell/platform/darwin/macos/framework/Source/FlutterTextInputPlugin.mm

@@ -67,9 +67,9 @@
 
 #pragma mark - Enums
 /**
- * The affinity of the current cursor position. If the cursor is at a position representing
- * a line break, the cursor may be drawn either at the end of the current line (upstream)
- * or at the beginning of the next (downstream).
+ * The affinity of the current cursor position. If the cursor is at a position
+ * representing a soft line break, the cursor may be drawn either at the end of
+ * the current line (upstream) or at the beginning of the next (downstream).
  */
 typedef NS_ENUM(NSUInteger, FlutterTextAffinity) {
   kFlutterTextAffinityUpstream,
@@ -852,19 +852,13 @@ - (void)setMarkedText:(id)string
 
   // Input string may be NSString or NSAttributedString.
   BOOL isAttributedString = [string isKindOfClass:[NSAttributedString class]];
-  std::string marked_text = isAttributedString ? [[string string] UTF8String] : [string UTF8String];
-  _activeModel->UpdateComposingText(marked_text);
-
-  // Update the selection within the marked text.
-  long signedLength = static_cast<long>(selectedRange.length);
-  long location = selectedRange.location + _activeModel->composing_range().base();
-  long textLength = _activeModel->text_range().end();
-
-  size_t base = std::clamp(location, 0L, textLength);
-  size_t extent = std::clamp(location + signedLength, 0L, textLength);
-  _activeModel->SetSelection(flutter::TextRange(base, extent));
+  const NSString* rawString = isAttributedString ? [string string] : string;
+  _activeModel->UpdateComposingText(
+      (const char16_t*)[rawString cStringUsingEncoding:NSUTF16StringEncoding],
+      flutter::TextRange(selectedRange.location, selectedRange.location + selectedRange.length));
 
   if (_enableDeltaModel) {
+    std::string marked_text = [rawString UTF8String];
     [self updateEditStateWithDelta:flutter::TextEditingDelta(textBeforeChange,
                                                              selectionBeforeChange.collapsed()
                                                                  ? composingBeforeChange

shell/platform/darwin/macos/framework/Source/FlutterTextInputPluginTest.mm

@@ -945,8 +945,8 @@ - (bool)testOperationsThatTriggerDelta {
     @"deltaText" : @"marked text",
     @"deltaStart" : @(14),
     @"deltaEnd" : @(14),
-    @"selectionBase" : @(25),
-    @"selectionExtent" : @(25),
+    @"selectionBase" : @(14),
+    @"selectionExtent" : @(15),
     @"selectionAffinity" : @"TextAffinity.upstream",
     @"selectionIsDirectional" : @(false),
     @"composingBase" : @(14),
@@ -1030,7 +1030,7 @@ - (bool)testComposingWithDelta {
     @"deltaText" : @"m",
     @"deltaStart" : @(0),
     @"deltaEnd" : @(0),
-    @"selectionBase" : @(1),
+    @"selectionBase" : @(0),
     @"selectionExtent" : @(1),
     @"selectionAffinity" : @"TextAffinity.upstream",
     @"selectionIsDirectional" : @(false),
@@ -1060,8 +1060,8 @@ - (bool)testComposingWithDelta {
     @"deltaText" : @"ma",
     @"deltaStart" : @(0),
     @"deltaEnd" : @(1),
-    @"selectionBase" : @(2),
-    @"selectionExtent" : @(2),
+    @"selectionBase" : @(0),
+    @"selectionExtent" : @(1),
     @"selectionAffinity" : @"TextAffinity.upstream",
     @"selectionIsDirectional" : @(false),
     @"composingBase" : @(0),
@@ -1090,8 +1090,8 @@ - (bool)testComposingWithDelta {
     @"deltaText" : @"mar",
     @"deltaStart" : @(0),
     @"deltaEnd" : @(2),
-    @"selectionBase" : @(3),
-    @"selectionExtent" : @(3),
+    @"selectionBase" : @(0),
+    @"selectionExtent" : @(1),
     @"selectionAffinity" : @"TextAffinity.upstream",
     @"selectionIsDirectional" : @(false),
     @"composingBase" : @(0),
@@ -1120,8 +1120,8 @@ - (bool)testComposingWithDelta {
     @"deltaText" : @"mark",
     @"deltaStart" : @(0),
     @"deltaEnd" : @(3),
-    @"selectionBase" : @(4),
-    @"selectionExtent" : @(4),
+    @"selectionBase" : @(0),
+    @"selectionExtent" : @(1),
     @"selectionAffinity" : @"TextAffinity.upstream",
     @"selectionIsDirectional" : @(false),
     @"composingBase" : @(0),
@@ -1150,8 +1150,8 @@ - (bool)testComposingWithDelta {
     @"deltaText" : @"marke",
     @"deltaStart" : @(0),
     @"deltaEnd" : @(4),
-    @"selectionBase" : @(5),
-    @"selectionExtent" : @(5),
+    @"selectionBase" : @(0),
+    @"selectionExtent" : @(1),
     @"selectionAffinity" : @"TextAffinity.upstream",
     @"selectionIsDirectional" : @(false),
     @"composingBase" : @(0),
@@ -1180,8 +1180,8 @@ - (bool)testComposingWithDelta {
     @"deltaText" : @"marked",
     @"deltaStart" : @(0),
     @"deltaEnd" : @(5),
-    @"selectionBase" : @(6),
-    @"selectionExtent" : @(6),
+    @"selectionBase" : @(0),
+    @"selectionExtent" : @(1),
     @"selectionAffinity" : @"TextAffinity.upstream",
     @"selectionIsDirectional" : @(false),
     @"composingBase" : @(0),

shell/platform/windows/text_input_plugin.cc

@@ -197,9 +197,7 @@ void TextInputPlugin::ComposeChangeHook(const std::u16string& text,
   std::string text_before_change = active_model_->GetText();
   TextRange composing_before_change = active_model_->composing_range();
   active_model_->AddText(text);
-  cursor_pos += active_model_->composing_range().start();
-  active_model_->UpdateComposingText(text);
-  active_model_->SetSelection(TextRange(cursor_pos, cursor_pos));
+  active_model_->UpdateComposingText(text, TextRange(cursor_pos, cursor_pos));
   std::string text_after_change = active_model_->GetText();
   if (enable_delta_model) {
     TextEditingDelta delta = TextEditingDelta(