Add a11y support for selected text (#4584)

lib/ui/semantics.dart

@@ -293,6 +293,9 @@ class SemanticsUpdateBuilder extends NativeFieldWrapperClass2 {
   /// string describes what result an action performed on this node has. The
   /// reading direction of all these strings is given by `textDirection`.
   ///
+  /// The fields 'textSelectionStart' and 'textSelectionEnd' describe the
+  /// currently selected text within `value`.
+  ///
   /// The `rect` is the region occupied by this node in its own coordinate
   /// system.
   ///
@@ -302,6 +305,8 @@ class SemanticsUpdateBuilder extends NativeFieldWrapperClass2 {
     int id,
     int flags,
     int actions,
+    int textSelectionStart,
+    int textSelectionEnd,
     Rect rect,
     String label,
     String hint,
@@ -318,6 +323,8 @@ class SemanticsUpdateBuilder extends NativeFieldWrapperClass2 {
       id,
       flags,
       actions,
+      textSelectionStart,
+      textSelectionEnd,
       rect.left,
       rect.top,
       rect.right,
@@ -336,6 +343,8 @@ class SemanticsUpdateBuilder extends NativeFieldWrapperClass2 {
     int id,
     int flags,
     int actions,
+    int textSelectionStart,
+    int textSelectionEnd,
     double left,
     double top,
     double right,

lib/ui/semantics/semantics_node.h

@@ -55,6 +55,8 @@ struct SemanticsNode {
   int32_t id = 0;
   int32_t flags = 0;
   int32_t actions = 0;
+  int32_t textSelectionStart = -1;
+  int32_t textSelectionEnd = -1;
   std::string label;
   std::string hint;
   std::string value;

lib/ui/semantics/semantics_update_builder.cc

@@ -37,6 +37,8 @@ SemanticsUpdateBuilder::~SemanticsUpdateBuilder() = default;
 void SemanticsUpdateBuilder::updateNode(int id,
                                         int flags,
                                         int actions,
+                                        int textSelectionStart,
+                                        int textSelectionEnd,
                                         double left,
                                         double top,
                                         double right,
@@ -53,6 +55,8 @@ void SemanticsUpdateBuilder::updateNode(int id,
   node.id = id;
   node.flags = flags;
   node.actions = actions;
+  node.textSelectionStart = textSelectionStart;
+  node.textSelectionEnd = textSelectionEnd;
   node.rect = SkRect::MakeLTRB(left, top, right, bottom);
   node.label = label;
   node.hint = hint;

lib/ui/semantics/semantics_update_builder.h

@@ -28,6 +28,8 @@ class SemanticsUpdateBuilder
   void updateNode(int id,
                   int flags,
                   int actions,
+                  int textSelectionStart,
+                  int textSelectionEnd,
                   double left,
                   double top,
                   double right,

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

@@ -123,8 +123,12 @@ class AccessibilityBridge extends AccessibilityNodeProvider implements BasicMess
 
         if (object.hasFlag(Flag.IS_TEXT_FIELD)) {
             result.setClassName("android.widget.EditText");
-            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR2)
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR2) {
                 result.setEditable(true);
+                if (object.textSelectionStart != -1 && object.textSelectionEnd != -1) {
+                    result.setTextSelection(object.textSelectionStart, object.textSelectionEnd);
+                }
+            }
 
             // Cursor movements
             int granularities = 0;
@@ -599,6 +603,8 @@ class AccessibilityBridge extends AccessibilityNodeProvider implements BasicMess
 
         int flags;
         int actions;
+        int textSelectionStart;
+        int textSelectionEnd;
         String label;
         String value;
         String increasedValue;
@@ -658,6 +664,8 @@ class AccessibilityBridge extends AccessibilityNodeProvider implements BasicMess
 
             flags = buffer.getInt();
             actions = buffer.getInt();
+            textSelectionStart = buffer.getInt();
+            textSelectionEnd = buffer.getInt();
 
             int stringIndex = buffer.getInt();
             label = stringIndex == -1 ? null : strings[stringIndex];

shell/platform/android/platform_view_android.cc

@@ -461,7 +461,7 @@ bool PlatformViewAndroid::ResourceContextMakeCurrent() {
 
 void PlatformViewAndroid::UpdateSemantics(
     std::vector<blink::SemanticsNode> update) {
-  constexpr size_t kBytesPerNode = 30 * sizeof(int32_t);
+  constexpr size_t kBytesPerNode = 32 * sizeof(int32_t);
   constexpr size_t kBytesPerChild = sizeof(int32_t);
 
   JNIEnv* env = fml::jni::AttachCurrentThread();
@@ -488,6 +488,8 @@ void PlatformViewAndroid::UpdateSemantics(
       buffer_int32[position++] = node.id;
       buffer_int32[position++] = node.flags;
       buffer_int32[position++] = node.actions;
+      buffer_int32[position++] = node.textSelectionStart;
+      buffer_int32[position++] = node.textSelectionEnd;
       if (node.label.empty()) {
         buffer_int32[position++] = -1;
       } else {