Fix macOS text composing

Author: LongCatIsLooong

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,
+                                         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 +57,16 @@ 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, 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/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,
@@ -523,20 +523,19 @@ - (NSDictionary*)editingState {
     return nil;
   }
 
-  NSString* const textAffinity = [self textAffinityString];
-
-  int composingBase = _activeModel->composing() ? _activeModel->composing_range().base() : -1;
-  int composingExtent = _activeModel->composing() ? _activeModel->composing_range().extent() : -1;
-
-  return @{
+  NSDictionary* const dictionary = @{
     kSelectionBaseKey : @(_activeModel->selection().base()),
     kSelectionExtentKey : @(_activeModel->selection().extent()),
-    kSelectionAffinityKey : textAffinity,
-    kSelectionIsDirectionalKey : @NO,
-    kComposingBaseKey : @(composingBase),
-    kComposingExtentKey : @(composingExtent),
+    kSelectionAffinityKey : [self textAffinityString],
     kTextKey : [NSString stringWithUTF8String:_activeModel->GetText().c_str()] ?: [NSNull null],
   };
+  if (!_activeModel->composing()) {
+    return dictionary;
+  }
+  NSMutableDictionary* mutableDictionary = [dictionary mutableCopy];
+  mutableDictionary[kComposingBaseKey] = @(_activeModel->composing_range().base());
+  mutableDictionary[kComposingExtentKey] = @(_activeModel->composing_range().extent());
+  return mutableDictionary;
 }
 
 - (void)updateEditState {
@@ -852,19 +851,13 @@ - (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/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(