Introduce read only text field semantics (flutter/engine#9281)

engine/src/flutter/lib/ui/semantics.dart

@@ -288,6 +288,7 @@ class SemanticsFlag {
   static const int _kHasToggledStateIndex = 1 << 16;
   static const int _kIsToggledIndex = 1 << 17;
   static const int _kHasImplicitScrollingIndex = 1 << 18;
+  static const int _kIsReadOnlyIndex = 1 << 20;
 
   const SemanticsFlag._(this.index);
 
@@ -341,6 +342,11 @@ class SemanticsFlag {
   /// affordances.
   static const SemanticsFlag isTextField = SemanticsFlag._(_kIsTextFieldIndex);
 
+  /// Whether the semantic node is read only.
+  ///
+  /// Only applicable when [isTextField] is true.
+  static const SemanticsFlag isReadOnly = SemanticsFlag._(_kIsReadOnlyIndex);
+
   /// Whether the semantic node currently holds the user's focus.
   ///
   /// The focused element is usually the current receiver of keyboard inputs.
@@ -506,6 +512,7 @@ class SemanticsFlag {
     _kHasToggledStateIndex: hasToggledState,
     _kIsToggledIndex: isToggled,
     _kHasImplicitScrollingIndex: hasImplicitScrolling,
+    _kIsReadOnlyIndex: isReadOnly,
   };
 
   @override
@@ -549,6 +556,8 @@ class SemanticsFlag {
         return 'SemanticsFlag.isToggled';
       case _kHasImplicitScrollingIndex:
         return 'SemanticsFlag.hasImplicitScrolling';
+      case _kIsReadOnlyIndex:
+        return 'SemanticsFlag.isReadOnly';
     }
     return null;
   }

engine/src/flutter/lib/ui/semantics/semantics_node.h

@@ -69,6 +69,7 @@ enum class SemanticsFlags : int32_t {
   kHasToggledState = 1 << 16,
   kIsToggled = 1 << 17,
   kHasImplicitScrolling = 1 << 18,
+  kIsReadOnly = 1 << 20,
 };
 
 const int kScrollableSemanticsFlags =

engine/src/flutter/shell/platform/android/io/flutter/view/AccessibilityBridge.java

@@ -529,9 +529,11 @@ public class AccessibilityBridge extends AccessibilityNodeProvider {
 
         if (semanticsNode.hasFlag(Flag.IS_TEXT_FIELD)) {
             result.setPassword(semanticsNode.hasFlag(Flag.IS_OBSCURED));
-            result.setClassName("android.widget.EditText");
+            if (!semanticsNode.hasFlag(Flag.IS_READ_ONLY)) {
+                result.setClassName("android.widget.EditText");
+            }
             if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR2) {
-                result.setEditable(true);
+                result.setEditable(!semanticsNode.hasFlag(Flag.IS_READ_ONLY));
                 if (semanticsNode.textSelectionBase != -1 && semanticsNode.textSelectionExtent != -1) {
                     result.setTextSelection(semanticsNode.textSelectionBase, semanticsNode.textSelectionExtent);
                 }
@@ -1611,7 +1613,8 @@ public class AccessibilityBridge extends AccessibilityNodeProvider {
         IS_LIVE_REGION(1 << 15),
         HAS_TOGGLED_STATE(1 << 16),
         IS_TOGGLED(1 << 17),
-        HAS_IMPLICIT_SCROLLING(1 << 18);
+        HAS_IMPLICIT_SCROLLING(1 << 18),
+        IS_READ_ONLY(1 << 20);
 
         final int value;
 

engine/src/flutter/shell/platform/darwin/ios/framework/Source/accessibility_bridge.mm

@@ -713,7 +713,8 @@ SemanticsObject* AccessibilityBridge::GetOrCreateObject(int32_t uid,
   if (!object) {
     // New node case: simply create a new SemanticsObject.
     flutter::SemanticsNode node = updates[uid];
-    if (node.HasFlag(flutter::SemanticsFlags::kIsTextField)) {
+    if (node.HasFlag(flutter::SemanticsFlags::kIsTextField) &&
+        !node.HasFlag(flutter::SemanticsFlags::kIsReadOnly)) {
       // Text fields are backed by objects that implement UITextInput.
       object = [[[TextInputSemanticsObject alloc] initWithBridge:GetWeakPtr() uid:uid] autorelease];
     } else {
@@ -729,13 +730,16 @@ SemanticsObject* AccessibilityBridge::GetOrCreateObject(int32_t uid,
       flutter::SemanticsNode node = nodeEntry->second;
       BOOL isTextField = node.HasFlag(flutter::SemanticsFlags::kIsTextField);
       BOOL wasTextField = object.node.HasFlag(flutter::SemanticsFlags::kIsTextField);
-      if (wasTextField != isTextField) {
+      BOOL isReadOnly = node.HasFlag(flutter::SemanticsFlags::kIsReadOnly);
+      BOOL wasReadOnly = object.node.HasFlag(flutter::SemanticsFlags::kIsReadOnly);
+      if (wasTextField != isTextField || isReadOnly != wasReadOnly) {
         // The node changed its type from text field to something else, or vice versa. In this
         // case, we cannot reuse the existing SemanticsObject implementation. Instead, we replace
         // it with a new instance.
         NSUInteger positionInChildlist = [object.parent.children indexOfObject:object];
+        SemanticsObject* parent = object.parent;
         [objects_ removeObjectForKey:@(node.id)];
-        if (isTextField) {
+        if (isTextField && !isReadOnly) {
           // Text fields are backed by objects that implement UITextInput.
           object = [[[TextInputSemanticsObject alloc] initWithBridge:GetWeakPtr()
                                                                  uid:uid] autorelease];
@@ -743,6 +747,7 @@ SemanticsObject* AccessibilityBridge::GetOrCreateObject(int32_t uid,
           object = [[[FlutterSemanticsObject alloc] initWithBridge:GetWeakPtr()
                                                                uid:uid] autorelease];
         }
+        object.parent = parent;
         [object.parent.children replaceObjectAtIndex:positionInChildlist withObject:object];
         objects_.get()[@(node.id)] = object;
       }

engine/src/flutter/shell/platform/embedder/embedder.h

@@ -153,6 +153,10 @@ typedef enum {
   // |PageView| widget does not have implicit scrolling, so that users don't
   // navigate to the next page when reaching the end of the current one.
   kFlutterSemanticsFlagHasImplicitScrolling = 1 << 18,
+  // Whether the semantic node is read only.
+  //
+  // Only applicable when kFlutterSemanticsFlagIsTextField flag is on.
+  kFlutterSemanticsFlagIsReadOnly = 1 << 20,
 } FlutterSemanticsFlag;
 
 typedef enum {