[SuperEditor][iOS] Fix caret blinking while dragging (Resolves #2104) (#2185)

Author: angelosilvestre

super_editor/lib/src/infrastructure/platforms/ios/ios_document_controls.dart

@@ -643,7 +643,7 @@ class IosControlsDocumentLayerState extends DocumentLayoutLayerState<IosHandlesD
 
   void _startOrStopBlinking() {
     // TODO: allow a configurable policy as to whether to show the caret at all when the selection is expanded: https://github.com/superlistapp/super_editor/issues/234
-    final wantsToBlink = widget.selection.value != null;
+    final wantsToBlink = widget.selection.value != null && widget.shouldCaretBlink.value;
     if (wantsToBlink && _caretBlinkController.isBlinking) {
       return;
     }

super_editor/test/super_editor/mobile/super_editor_ios_overlay_controls_test.dart

@@ -60,6 +60,46 @@ void main() {
       await tester.pump(const Duration(milliseconds: 100));
     });
 
+    testWidgetsOnIos("does not blink caret while dragging it", (tester) async {
+      BlinkController.indeterminateAnimationsEnabled = true;
+      addTearDown(() => BlinkController.indeterminateAnimationsEnabled = false);
+
+      await _pumpSingleParagraphApp(tester);
+
+      // Place the caret.
+      await tester.tapInParagraph("1", 200);
+
+      // Press and drag the caret somewhere else in the paragraph.
+      final gesture = await tester.tapDownInParagraph("1", 200);
+      for (int i = 0; i < 5; i += 1) {
+        await gesture.moveBy(const Offset(24, 0));
+        await tester.pump();
+      }
+
+      // Duration for the caret to switch between visible and invisible.
+      final flashPeriod = SuperEditorInspector.caretFlashPeriod();
+
+      // Ensure caret is visible.
+      expect(SuperEditorInspector.isCaretVisible(), isTrue);
+
+      // Trigger a frame with an ellapsed time equal to the flashPeriod,
+      // so if the caret is blinking it will change from visible to invisible.
+      await tester.pump(flashPeriod);
+
+      // Ensure caret is still visible after the flash period, which means it isn't blinking.
+      expect(SuperEditorInspector.isCaretVisible(), isTrue);
+
+      // Trigger another frame.
+      await tester.pump(flashPeriod);
+
+      // Ensure caret is still visible.
+      expect(SuperEditorInspector.isCaretVisible(), isTrue);
+
+      // Resolve the gesture so that we don't have pending gesture timers.
+      await gesture.up();
+      await tester.pump(const Duration(milliseconds: 100));
+    });
+
     testWidgetsOnIos("shows toolbar when selection is expanded", (tester) async {
       await _pumpSingleParagraphApp(tester);