Support child-based node offsets when setting accessible selections

https://docs.google.com/document/d/1IZ7HtM0BZlMgNyYo6AUHGL84k RTnH4qt3fd-hXqfjvs/edit# Review-Url: https://codereview.chromium.org/2339093003 Cr-Commit-Position: refs/heads/master@{#419325}

Support child-based node offsets when setting accessible selections
https://docs.google.com/document/d/1IZ7HtM0BZlMgNyYo6AUHGL84k RTnH4qt3fd-hXqfjvs/edit# Review-Url: https://codereview.chromium.org/2339093003 Cr-Commit-Position: refs/heads/master@{#419325}
f1dfcce8 · dtseng · Commit bot · 3a408779 · f1dfcce8 · f1dfcce8
Commit f1dfcce8 authored Sep 16, 2016 by dtseng Committed by Commit bot Sep 16, 2016
2 changed files
--- a/third_party/WebKit/LayoutTests/accessibility/set-selection-child-offset.html
+++ b/third_party/WebKit/LayoutTests/accessibility/set-selection-child-offset.html
+<!DOCTYPE html>
+<script src="../resources/testharness.js"></script>
+<script src="../resources/testharnessreport.js"></script>
+
+<div role="region">
+    <span role="presentation" id="span1">this is a<a id="link" href="#1">test</a></span>
+    <span role="presentation" id="span2">of selection</span>
+</div>
+
+<script>
+    var sel = null;
+    function updateSelectedRangeFromPage() {
+        sel = window.getSelection().getRangeAt(0);
+    }
+
+    // The accessibility tree contains a region with 3 children, select each.
+    test(function()
+    {
+        assert_not_equals(window.accessibilityController, undefined, 'This test requires accessibilityController');
+
+        var axRegion = accessibilityController.accessibleElementById("link").parentElement();
+        assert_equals(axRegion.role, "AXRole: AXRegion");
+
+        // An insertion point before the first child.
+        axRegion.setSelection(axRegion, 0, axRegion, 0);
+        updateSelectedRangeFromPage();
+        assert_equals(sel.toString(), "");
+        assert_true(sel.collapsed);
+        assert_equals(sel.startContainer.constructor, Text);
+        assert_equals(sel.startOffset, 0);
+        assert_equals(sel.startContainer.textContent, "this is a");
+
+        // A straight-forward selection of the first child.
+        axRegion.setSelection(axRegion, 0, axRegion, 1);
+        updateSelectedRangeFromPage();
+        assert_equals(sel.toString(), "this is a");
+        assert_false(sel.collapsed);
+        assert_equals(sel.startContainer.constructor, Text);
+        assert_equals(sel.endContainer.constructor, Text);
+        assert_equals(sel.startOffset, 0);
+        assert_equals(sel.startContainer.textContent, "this is a");
+        assert_equals(sel.endOffset, 9);
+        assert_equals(sel.endContainer.textContent, "this is a");
+
+        // Another insertion point after the first child, before the second.
+        axRegion.setSelection(axRegion, 1, axRegion, 1);
+        updateSelectedRangeFromPage();
+        assert_equals(sel.toString(), "");
+        assert_true(sel.collapsed);
+        assert_equals(sel.startContainer.constructor, Text);
+        assert_equals(sel.startOffset, 9);
+        assert_equals(sel.startContainer.textContent, "this is a");
+
+        // Select the second child.
+        axRegion.setSelection(axRegion, 1, axRegion, 2);
+        updateSelectedRangeFromPage();
+        assert_equals(sel.toString(), "test\n");
+        assert_false(sel.collapsed);
+        assert_equals(sel.startContainer.constructor, Text);
+        assert_equals(sel.endContainer.constructor, Text);
+        assert_equals(sel.startOffset, 0);
+        assert_equals(sel.startContainer.textContent, "test");
+        assert_equals(sel.startContainer.compareDocumentPosition(sel.endContainer), 4 /* before */);
+        assert_equals(sel.endOffset, 1);
+        assert_equals(sel.endContainer.textContent, "\n    ");
+
+        // Next, another insertion point between second and third child.
+        axRegion.setSelection(axRegion, 2, axRegion, 2);
+        updateSelectedRangeFromPage();
+        assert_equals(sel.toString(), "");
+        assert_true(sel.collapsed);
+        assert_equals(sel.startContainer.constructor, Text);
+        assert_equals(sel.startOffset, 1);
+        assert_equals(sel.startContainer.textContent, "\n    ");
+
+        // Select the third child.
+        axRegion.setSelection(axRegion, 2, axRegion, 3);
+        updateSelectedRangeFromPage();
+        assert_equals(sel.toString(), "of selection");
+        assert_false(sel.collapsed);
+        assert_equals(sel.startContainer.constructor, Text);
+        assert_equals(sel.endContainer.constructor, Text);
+        assert_equals(sel.startOffset, 0);
+        assert_equals(sel.startContainer.textContent, "of selection");
+        assert_equals(sel.endOffset, 12);
+        assert_equals(sel.endContainer.textContent, "of selection");
+
+        // Select the first and second children.
+        axRegion.setSelection(axRegion, 0, axRegion, 2);
+        updateSelectedRangeFromPage();
+        assert_equals(sel.toString(), "this is atest\n");
+        assert_false(sel.collapsed);
+        assert_equals(sel.startContainer.constructor, Text);
+        assert_equals(sel.endContainer.constructor, Text);
+        assert_equals(sel.startOffset, 0);
+        assert_equals(sel.startContainer.textContent, "this is a");
+        assert_equals(sel.endOffset, 1);
+        assert_equals(sel.endContainer.textContent, "\n    ");
+
+        // Select the second and third children.
+        axRegion.setSelection(axRegion, 1, axRegion, 3);
+        updateSelectedRangeFromPage();
+        assert_equals(sel.toString(), "test\n    of selection");
+        assert_false(sel.collapsed);
+        assert_equals(sel.startContainer.constructor, Text);
+        assert_equals(sel.endContainer.constructor, Text);
+        assert_equals(sel.startOffset, 0);
+        assert_equals(sel.startContainer.textContent, "test");
+        assert_equals(sel.endOffset, 12);
+        assert_equals(sel.endContainer.textContent, "of selection");
+
+        // Select everything.
+        axRegion.setSelection(axRegion, 0, axRegion, 3);
+        updateSelectedRangeFromPage();
+        assert_equals(sel.toString(), "this is atest\n    of selection");
+        assert_false(sel.collapsed);
+        assert_equals(sel.startContainer.constructor, Text);
+        assert_equals(sel.endContainer.constructor, Text);
+        assert_equals(sel.startOffset, 0);
+        assert_equals(sel.startContainer.textContent, "this is a");
+        assert_equals(sel.endOffset, 12);
+        assert_equals(sel.endContainer.textContent, "of selection");
+
+        // Last, the insertion point after third child.
+        axRegion.setSelection(axRegion, 3, axRegion, 3);
+        updateSelectedRangeFromPage();
+        assert_equals(sel.toString(), "");
+        assert_true(sel.collapsed);
+        assert_equals(sel.startContainer.constructor, Text);
+        assert_equals(sel.startOffset, 12);
+        assert_equals(sel.startContainer.textContent, "of selection");
+    }, "Select child node at index.");
+</script>
--- a/third_party/WebKit/Source/modules/accessibility/AXLayoutObject.cpp
+++ b/third_party/WebKit/Source/modules/accessibility/AXLayoutObject.cpp
@@ -1817,21 +1817,43 @@ AXLayoutObject* AXLayoutObject::getUnignoredObjectFromNode(Node& node) const
 // Convert from an accessible object and offset to a VisiblePosition.
 static VisiblePosition toVisiblePosition(AXObject* obj, int offset)
 {
-    // First walk up until we find an accessible object with an associated node.
-    AXObject* runner = obj;
-    Node* node = nullptr;
-    while (runner && !node) {
-        node = runner->getNode();
-        runner = runner->parentObject();
+    if (!obj->getNode())
+        return VisiblePosition();
+
+    Node* node = obj->getNode();
+    if (!node->isTextNode()) {
+        int childCount = obj->children().size();
+
+        // Place position immediately before the container node, if there was no children.
+        if (childCount == 0) {
+            if (!obj->parentObject())
+                return VisiblePosition();
+            return toVisiblePosition(obj->parentObject(), obj->indexInParent());
        }

-    if (!node)
+        // The offsets are child offsets over the AX tree. Note that we allow
+        // for the offset to equal the number of children as |Range| does.
+        if (offset < 0 || offset > childCount)
            return VisiblePosition();

-    // If it's not a text node, no conversion is necessary, just create a VisiblePosition
-    // with this node and offset.
-    if (!node->isTextNode())
-        return createVisiblePosition(Position(node, offset));
+        // Clamp to between 0 and child count - 1.
+        int clampedOffset =
+            static_cast<unsigned>(offset) > (obj->children().size() - 1) ? offset - 1 : offset;
+        AXObject* childObj = obj->children()[clampedOffset];
+        Node* childNode = childObj->getNode();
+        if (!childNode || !childNode->parentNode())
+            return VisiblePosition();
+
+        // The index in parent.
+        int adjustedOffset = childNode->nodeIndex();
+
+        // If we had to clamp the offset above, the client wants to select the
+        // end of the node.
+        if (clampedOffset != offset)
+            adjustedOffset++;
+
+        return createVisiblePosition(Position::editingPositionOf(childNode->parentNode(), adjustedOffset));
+    }

    // If it is a text node, we need to call some utility functions that use a TextIterator
    // to walk the characters of the node and figure out the position corresponding to the
@@ -1860,6 +1882,7 @@ void AXLayoutObject::setSelection(const AXRange& selection)
        return;
    }

+    // The selection offsets are offsets into the accessible value.
    if (anchorObject == focusObject
        && anchorObject->getLayoutObject()->isTextControl()) {
        HTMLTextFormControlElement* textControl = toLayoutTextControl(