[web & desktop] Hide all characters in a TextField, when obscureText is true...

[web & desktop] Hide all characters in a TextField, when obscureText is true on web & desktop (#56794)

packages/flutter/lib/src/widgets/editable_text.dart

@@ -2129,10 +2129,16 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
     if (widget.obscureText) {
       String text = _value.text;
       text = widget.obscuringCharacter * text.length;
-      final int o =
-        _obscureShowCharTicksPending > 0 ? _obscureLatestCharIndex : null;
-      if (o != null && o >= 0 && o < text.length)
-        text = text.replaceRange(o, o + 1, _value.text.substring(o, o + 1));
+      // Reveal the latest character in an obscured field only on mobile.
+      if ((defaultTargetPlatform == TargetPlatform.android ||
+              defaultTargetPlatform == TargetPlatform.iOS ||
+              defaultTargetPlatform == TargetPlatform.fuchsia) &&
+          !kIsWeb) {
+        final int o =
+            _obscureShowCharTicksPending > 0 ? _obscureLatestCharIndex : null;
+        if (o != null && o >= 0 && o < text.length)
+          text = text.replaceRange(o, o + 1, _value.text.substring(o, o + 1));
+      }
       return TextSpan(style: widget.style, text: text);
     }
     // Read only mode should not paint text composing.

packages/flutter/test/material/text_field_test.dart

@@ -758,7 +758,7 @@ void main() {
     expect(cursorOffsetSpaces.dx, inputWidth - _kCaretGap);
   });
 
-  testWidgets('obscureText control test', (WidgetTester tester) async {
+  testWidgets('mobile obscureText control test', (WidgetTester tester) async {
     await tester.pumpWidget(
       overlay(
         child: const TextField(
@@ -796,7 +796,46 @@ void main() {
 
     editText = findRenderEditable(tester).text.text;
     expect(editText.substring(editText.length - 1), '\u2022');
-  });
+  }, variant: const TargetPlatformVariant(<TargetPlatform>{ TargetPlatform.iOS, TargetPlatform.android }));
+
+  testWidgets('desktop obscureText control test', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      overlay(
+        child: const TextField(
+          obscureText: true,
+          decoration: InputDecoration(
+            hintText: 'Placeholder',
+          ),
+        ),
+      ),
+    );
+    await tester.showKeyboard(find.byType(TextField));
+
+    const String testValue = 'ABC';
+    tester.testTextInput.updateEditingValue(const TextEditingValue(
+      text: testValue,
+      selection: TextSelection.collapsed(offset: testValue.length),
+    ));
+
+    await tester.pump();
+
+    // Enter a character into the obscured field and verify that the character
+    // isn't shown to the user.
+    const String newChar = 'X';
+    tester.testTextInput.updateEditingValue(const TextEditingValue(
+      text: testValue + newChar,
+      selection: TextSelection.collapsed(offset: testValue.length + 1),
+    ));
+
+    await tester.pump();
+
+    final String editText = findRenderEditable(tester).text.text;
+    expect(editText.substring(editText.length - 1), '\u2022');
+  }, variant: const TargetPlatformVariant(<TargetPlatform>{
+      TargetPlatform.macOS,
+      TargetPlatform.linux,
+      TargetPlatform.windows,
+  }));
 
   testWidgets('Caret position is updated on tap', (WidgetTester tester) async {
     final TextEditingController controller = TextEditingController();