Add scrollIndex and scrollChildren to semantics, add Android implemen…

…tation (flutter#6239)
shenguangyao · Sep 13, 2018 · abd918e · abd918e
1 parent 23fcc27
commit abd918e
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Showing 6 changed files with 40 additions and 4 deletions.
diff --git a/lib/ui/semantics.dart b/lib/ui/semantics.dart
@@ -596,7 +596,9 @@ class SemanticsUpdateBuilder extends NativeFieldWrapperClass2 {
   /// describe the maximum and minimum in-rage values that `scrollPosition` can
   /// be. Both or either may be infinity to indicate unbound scrolling. The
   /// value for `scrollPosition` can (temporarily) be outside this range, for
-  /// example during an overscroll.
+  /// example during an overscroll. `scrollChildren` is the count of the
+  /// total number of child nodes that contribute semantics and `scrollIndex`
+  /// is the index of the first visible child node that contributes semantics.
   ///
   /// The `rect` is the region occupied by this node in its own coordinate
   /// system.
@@ -609,6 +611,8 @@ class SemanticsUpdateBuilder extends NativeFieldWrapperClass2 {
     int actions,
     int textSelectionBase,
     int textSelectionExtent,
+    int scrollChildren,
+    int scrollIndex,
     double scrollPosition,
     double scrollExtentMax,
     double scrollExtentMin,
@@ -634,6 +638,8 @@ class SemanticsUpdateBuilder extends NativeFieldWrapperClass2 {
       actions,
       textSelectionBase,
       textSelectionExtent,
+      scrollChildren,
+      scrollIndex,
       scrollPosition,
       scrollExtentMax,
       scrollExtentMin,
@@ -659,6 +665,8 @@ class SemanticsUpdateBuilder extends NativeFieldWrapperClass2 {
     int actions,
     int textSelectionBase,
     int textSelectionExtent,
+    int scrollChildren,
+    int scrollIndex,
     double scrollPosition,
     double scrollExtentMax,
     double scrollExtentMin,

diff --git a/lib/ui/semantics/semantics_node.h b/lib/ui/semantics/semantics_node.h
@@ -79,6 +79,8 @@ struct SemanticsNode {
   int32_t actions = 0;
   int32_t textSelectionBase = -1;
   int32_t textSelectionExtent = -1;
+  int32_t scrollChildren = 0;
+  int32_t scrollIndex = 0;
   double scrollPosition = std::nan("");
   double scrollExtentMax = std::nan("");
   double scrollExtentMin = std::nan("");

diff --git a/lib/ui/semantics/semantics_update_builder.cc b/lib/ui/semantics/semantics_update_builder.cc
@@ -41,6 +41,8 @@ void SemanticsUpdateBuilder::updateNode(
     int actions,
     int textSelectionBase,
     int textSelectionExtent,
+    int scrollChildren,
+    int scrollIndex,
     double scrollPosition,
     double scrollExtentMax,
     double scrollExtentMin,
@@ -64,6 +66,8 @@ void SemanticsUpdateBuilder::updateNode(
   node.actions = actions;
   node.textSelectionBase = textSelectionBase;
   node.textSelectionExtent = textSelectionExtent;
+  node.scrollChildren = scrollChildren;
+  node.scrollIndex = scrollIndex;
   node.scrollPosition = scrollPosition;
   node.scrollExtentMax = scrollExtentMax;
   node.scrollExtentMin = scrollExtentMin;

diff --git a/lib/ui/semantics/semantics_update_builder.h b/lib/ui/semantics/semantics_update_builder.h
@@ -29,6 +29,8 @@ class SemanticsUpdateBuilder
                   int actions,
                   int textSelectionBase,
                   int textSelectionExtent,
+                  int scrollChildren,
+                  int scrollIndex,
                   double scrollPosition,
                   double scrollExtentMax,
                   double scrollExtentMin,

diff --git a/shell/platform/android/io/flutter/view/AccessibilityBridge.java b/shell/platform/android/io/flutter/view/AccessibilityBridge.java
@@ -144,8 +144,8 @@ public AccessibilityNodeInfo createAccessibilityNodeInfo(int virtualViewId) {
         }
 
         AccessibilityNodeInfo result = AccessibilityNodeInfo.obtain(mOwner, virtualViewId);
-        // Work around for https://github.com/flutter/flutter/issues/2101 
-        result.setViewIdResourceName(""); 
+        // Work around for https://github.com/flutter/flutter/issues/2101
+        result.setViewIdResourceName("");
         result.setPackageName(mOwner.getContext().getPackageName());
         result.setClassName("android.view.View");
         result.setSource(mOwner, virtualViewId);
@@ -717,6 +717,20 @@ void updateSemantics(ByteBuffer buffer, String[] strings) {
                     event.setScrollX((int) position);
                     event.setMaxScrollX((int) max);
                 }
+                if (object.scrollChildren > 0) {
+                    event.setItemCount(object.scrollChildren);
+                    event.setFromIndex(object.scrollIndex);
+                    int visibleChildren = object.childrenInHitTestOrder.size() - 1;
+                    // We assume that only children at the end of the list can be hidden.
+                    assert(!object.childrenInHitTestOrder.get(object.scrollIndex).hasFlag(Flag.IS_HIDDEN));
+                    for (; visibleChildren >= 0; visibleChildren--) {
+                        SemanticsObject child = object.childrenInHitTestOrder.get(visibleChildren);
+                        if (!child.hasFlag(Flag.IS_HIDDEN)) {
+                            break;
+                        }
+                    }
+                    event.setToIndex(object.scrollIndex + visibleChildren);
+                }
                 sendAccessibilityEvent(event);
             }
             if (object.hasFlag(Flag.IS_LIVE_REGION) && !object.hadFlag(Flag.IS_LIVE_REGION)) {
@@ -947,6 +961,8 @@ private class SemanticsObject {
         int actions;
         int textSelectionBase;
         int textSelectionExtent;
+        int scrollChildren;
+        int scrollIndex;
         float scrollPosition;
         float scrollExtentMax;
         float scrollExtentMin;
@@ -1048,6 +1064,8 @@ void updateWith(ByteBuffer buffer, String[] strings) {
             actions = buffer.getInt();
             textSelectionBase = buffer.getInt();
             textSelectionExtent = buffer.getInt();
+            scrollChildren = buffer.getInt();
+            scrollIndex = buffer.getInt();
             scrollPosition = buffer.getFloat();
             scrollExtentMax = buffer.getFloat();
             scrollExtentMin = buffer.getFloat();

diff --git a/shell/platform/android/platform_view_android.cc b/shell/platform/android/platform_view_android.cc
@@ -207,7 +207,7 @@ void PlatformViewAndroid::DispatchSemanticsAction(JNIEnv* env,
 void PlatformViewAndroid::UpdateSemantics(
     blink::SemanticsNodeUpdates update,
     blink::CustomAccessibilityActionUpdates actions) {
-  constexpr size_t kBytesPerNode = 36 * sizeof(int32_t);
+  constexpr size_t kBytesPerNode = 38 * sizeof(int32_t);
   constexpr size_t kBytesPerChild = sizeof(int32_t);
   constexpr size_t kBytesPerAction = 4 * sizeof(int32_t);
 
@@ -243,6 +243,8 @@ void PlatformViewAndroid::UpdateSemantics(
       buffer_int32[position++] = node.actions;
       buffer_int32[position++] = node.textSelectionBase;
       buffer_int32[position++] = node.textSelectionExtent;
+      buffer_int32[position++] = node.scrollChildren;
+      buffer_int32[position++] = node.scrollIndex;
       buffer_float32[position++] = (float)node.scrollPosition;
       buffer_float32[position++] = (float)node.scrollExtentMax;
       buffer_float32[position++] = (float)node.scrollExtentMin;