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Prevent external updates during composition/focus #6237

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34 changes: 32 additions & 2 deletions sdk/python/packages/flet-code-editor/src/flutter/flet_code_editor/lib/src/code_editor.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,8 @@ class _CodeEditorControlState extends State<CodeEditorControl> {
TextSelection? _selection;
String _value = "";
String? _languageName;
String? _lastControlValue;
TextSelection? _lastControlSelection;

@override
void initState() {
Expand All @@ -31,6 +33,12 @@ class _CodeEditorControlState extends State<CodeEditorControl> {
_controller = _createController();
_value = _readValue();
_selection = _controller.selection;
_lastControlValue = widget.control.getString("value");
_lastControlSelection = widget.control.getTextSelection(
"selection",
minOffset: 0,
maxOffset: _controller.text.length,
);
_controller.addListener(_handleControllerChange);
widget.control.addInvokeMethodListener(_invokeMethod);
}
Expand Down Expand Up @@ -97,6 +105,20 @@ class _CodeEditorControlState extends State<CodeEditorControl> {
_controller.fullText = value;
}

bool get _isComposing {
final composing = _controller.value.composing;
return composing.isValid && !composing.isCollapsed;
}

bool _shouldApplyExternalState({
required bool incomingChanged,
}) {
if (!_focusNode.hasFocus) {
return true;
}
return incomingChanged && !_isComposing;
}

void _handleControllerChange() {
final value = _readValue();
final selection = _controller.selection;
Expand Down Expand Up @@ -160,7 +182,11 @@ class _CodeEditorControlState extends State<CodeEditorControl> {

final value = widget.control.getString("value");
final controllerValue = _readValue();
if (value != null && value != controllerValue) {
final valueChangedInControl = value != _lastControlValue;
_lastControlValue = value;
if (value != null &&
value != controllerValue &&
_shouldApplyExternalState(incomingChanged: valueChangedInControl)) {
_setValue(value);
_value = value;
}
Comment on lines +185 to 192
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Copilot AI Mar 1, 2026

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_lastControlValue is updated before the external value is applied. If a control-side value change arrives while the editor is focused and composing, _shouldApplyExternalState blocks applying it, but _lastControlValue still advances—so on subsequent builds valueChangedInControl becomes false and the external update can be dropped permanently (e.g., a programmatic value update during IME composition will never apply even after composition ends/blur). Consider tracking the last applied control value (or keeping a pending external value) and only advancing _lastControlValue after the update is actually applied / when not composing, so suppressed updates can be applied later when it’s safe.

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Expand All @@ -170,7 +196,11 @@ class _CodeEditorControlState extends State<CodeEditorControl> {
minOffset: 0,
maxOffset: _controller.text.length,
);
if (explicitSelection != null && explicitSelection != _controller.selection) {
final selectionChangedInControl = explicitSelection != _lastControlSelection;
_lastControlSelection = explicitSelection;
if (explicitSelection != null &&
explicitSelection != _controller.selection &&
_shouldApplyExternalState(incomingChanged: selectionChangedInControl)) {
_controller.selection = explicitSelection;
Comment on lines +200 to 204
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Copilot AI Mar 1, 2026

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Same pattern for selection: _lastControlSelection is updated even when an incoming selection change is suppressed due to focus/composition. That can prevent a queued control-side selection update from ever being applied later (after composition ends or focus is lost). Consider only updating the "last seen/applied" selection marker when the selection is actually applied, or store a pending selection to apply once _isComposing becomes false.

Suggested change
_lastControlSelection = explicitSelection;
if (explicitSelection != null &&
explicitSelection != _controller.selection &&
_shouldApplyExternalState(incomingChanged: selectionChangedInControl)) {
_controller.selection = explicitSelection;
if (explicitSelection == null) {
// Control explicitly cleared selection; record this immediately.
_lastControlSelection = null;
} else if (explicitSelection != _controller.selection &&
_shouldApplyExternalState(incomingChanged: selectionChangedInControl)) {
_controller.selection = explicitSelection;
_lastControlSelection = explicitSelection;

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}

Expand Down
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