Fire synthesised keydown/keyup events for AT increment/decrement.

This is a proof of concept at this stage.

Written cooperatively with meredithl@ and chrishall@

Bug: 1099069
Change-Id: Ib2c7cf94145bf7080973f7f619cc60dc89124931
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2264176
Commit-Queue: Alice Boxhall <aboxhall@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#784271}

third_party/blink/renderer/modules/accessibility/ax_node_object.cc

@@ -32,6 +32,7 @@
 
 #include <algorithm>
 
+#include "third_party/blink/public/common/input/web_keyboard_event.h"
 #include "third_party/blink/public/strings/grit/blink_strings.h"
 #include "third_party/blink/renderer/bindings/core/v8/v8_image_bitmap_options.h"
 #include "third_party/blink/renderer/core/aom/accessible_node.h"
@@ -47,6 +48,7 @@
 #include "third_party/blink/renderer/core/editing/editing_utilities.h"
 #include "third_party/blink/renderer/core/editing/markers/document_marker_controller.h"
 #include "third_party/blink/renderer/core/editing/position.h"
+#include "third_party/blink/renderer/core/events/keyboard_event.h"
 #include "third_party/blink/renderer/core/frame/local_frame_view.h"
 #include "third_party/blink/renderer/core/frame/settings.h"
 #include "third_party/blink/renderer/core/html/canvas/html_canvas_element.h"
@@ -100,9 +102,12 @@
 #include "third_party/blink/renderer/modules/accessibility/ax_svg_root.h"
 #include "third_party/blink/renderer/modules/media_controls/elements/media_control_elements_helper.h"
 #include "third_party/blink/renderer/platform/graphics/image_data_buffer.h"
+#include "third_party/blink/renderer/platform/keyboard_codes.h"
 #include "third_party/blink/renderer/platform/text/platform_locale.h"
 #include "third_party/blink/renderer/platform/weborigin/kurl.h"
 #include "third_party/blink/renderer/platform/wtf/text/string_builder.h"
+#include "ui/events/keycodes/dom/dom_code.h"
+#include "ui/events/keycodes/dom/keycode_converter.h"
 
 namespace {
 bool IsNeutralWithinTable(blink::AXObject* obj) {
@@ -114,6 +119,38 @@ bool IsNeutralWithinTable(blink::AXObject* obj) {
          role == ax::mojom::blink::Role::kIgnored ||
          role == ax::mojom::blink::Role::kRowGroup;
 }
+
+enum class AXAction {
+  kActionIncrement = 0,
+  kActionDecrement,
+};
+
+blink::KeyboardEvent* CreateKeyboardEvent(
+    blink::LocalDOMWindow* local_dom_window,
+    blink::WebInputEvent::Type type,
+    AXAction action) {
+  blink::WebKeyboardEvent key(type,
+                              blink::WebInputEvent::Modifiers::kNoModifiers,
+                              base::TimeTicks::Now());
+
+  // TODO(crbug.com/1099069): Fire different arrow events depending on
+  // orientation and dir (RTL/LTR)
+  switch (action) {
+    case AXAction::kActionIncrement:
+      key.dom_key = ui::DomKey::ARROW_UP;
+      key.dom_code = static_cast<int>(ui::DomCode::ARROW_UP);
+      key.native_key_code = key.windows_key_code = blink::VKEY_UP;
+      break;
+    case AXAction::kActionDecrement:
+      key.dom_key = ui::DomKey::ARROW_DOWN;
+      key.dom_code = static_cast<int>(ui::DomCode::ARROW_DOWN);
+      key.native_key_code = key.windows_key_code = blink::VKEY_DOWN;
+      break;
+  }
+
+  return blink::KeyboardEvent::Create(key, local_dom_window, true);
+}
+
 }  // namespace
 
 namespace blink {
@@ -137,6 +174,8 @@ AXNodeObject::~AXNodeObject() {
 }
 
 void AXNodeObject::AlterSliderOrSpinButtonValue(bool increase) {
+  if (!GetNode())
+    return;
   if (!IsSlider() && !IsSpinButton())
     return;
 
@@ -150,15 +189,39 @@ void AXNodeObject::AlterSliderOrSpinButtonValue(bool increase) {
 
   value += increase ? step : -step;
 
-  OnNativeSetValueAction(String::Number(value));
+  // If this is a native element, set the value directly.
+  if (native_role_ == ax::mojom::blink::Role::kSlider ||
+      native_role_ == ax::mojom::blink::Role::kSpinButton) {
+    OnNativeSetValueAction(String::Number(value));
+    // Dispatching an event could result in changes to the document, like
+    // this AXObject becoming detached.
+    if (IsDetached())
+      return;
 
-  // Dispatching an event could result in changes to the document, like
-  // this AXObject becoming detached.
-  if (IsDetached())
+    AXObjectCache().PostNotification(GetNode(),
+                                     ax::mojom::blink::Event::kValueChanged);
     return;
+  }
+
+  // TODO(crbug.com/1099069): add a separate flag for keyboard event synthesis
+  if (!RuntimeEnabledFeatures::AccessibilityObjectModelEnabled())
+    return;
+
+  // Otherwise, fire a keyboard event instead.
+  AXAction action =
+      increase ? AXAction::kActionIncrement : AXAction::kActionDecrement;
+  LocalDOMWindow* local_dom_window = GetDocument()->domWindow();
+
+  KeyboardEvent* keydown = CreateKeyboardEvent(
+      local_dom_window, WebInputEvent::Type::kRawKeyDown, action);
+  GetNode()->DispatchEvent(*keydown);
+
+  // TODO(crbug.com/1099069): add a brief pause between keydown and keyup?
+  // TODO(crbug.com/1099069): fire a "char" event depending on platform?
 
-  AXObjectCache().PostNotification(GetNode(),
-                                   ax::mojom::blink::Event::kValueChanged);
+  KeyboardEvent* keyup = CreateKeyboardEvent(
+      local_dom_window, WebInputEvent::Type::kKeyUp, action);
+  GetNode()->DispatchEvent(*keyup);
 }
 
 AXObject* AXNodeObject::ActiveDescendant() {

third_party/blink/renderer/modules/accessibility/ax_slider.cc

@@ -41,10 +41,12 @@ AXSlider::AXSlider(LayoutObject* layout_object,
     : AXLayoutObject(layout_object, ax_object_cache) {}
 
 ax::mojom::Role AXSlider::DetermineAccessibilityRole() {
+  native_role_ = ax::mojom::blink::Role::kSlider;
+
   if ((aria_role_ = DetermineAriaRoleAttribute()) != ax::mojom::Role::kUnknown)
     return aria_role_;
 
-  return ax::mojom::Role::kSlider;
+  return native_role_;
 }
 
 AccessibilityOrientation AXSlider::Orientation() const {

third_party/blink/web_tests/accessibility/aria-slider-increment-decrement.html

+<!DOCTYPE HTML>
+<html>
+<head>
+<script src="../resources/testharness.js"></script>
+<script src="../resources/testharnessreport.js"></script>
+</head>
+<body>
+  <div id="slider"
+       role="slider"
+       aria-valuemin="0"
+       aria-valuemax="10"
+       aria-valuenow="5"></div>
+
+<script>
+  function checkEvent(event, expected_key) {
+    if (expected_key == "ArrowUp") {
+      assert_equals(event.code, "ArrowUp", "event.code on " + event.type);
+      assert_equals(event.key, "ArrowUp", "event.key on " + event.type);
+      assert_equals(event.keyCode, 38, "event.keyCode on " + event.type);
+      assert_equals(event.which, 38, "event.which on " + event.type);
+    } else if (expected_key == "ArrowDown") {
+      assert_equals(event.code, "ArrowDown", "event.code on " + event.type);
+      assert_equals(event.key, "ArrowDown", "event.key on " + event.type);
+      assert_equals(event.keyCode, 40, "event.keyCode on " + event.type);
+      assert_equals(event.which, 40, "event.which on " + event.type);
+    }
+
+    assert_true(event.isTrusted, "event.isTrusted on " + event.type);
+    assert_equals(event.charCode, 0, "event.charCode on " + event.type);
+    assert_equals(event.target, slider, "event.target on " + event.type);
+    assert_equals(event.srcElement, slider, "event.srcElement on " + event.type);
+    assert_true(event.bubbles, "event.bubbles on " + event.type);
+    assert_false(event.defaultPrevented, "event.defaultPrevented on " + event.type);
+  }
+
+  async_test(function(t) {
+    var slider = document.getElementById("slider");
+    var axSlider = accessibilityController.accessibleElementById("slider");
+
+    slider.addEventListener("keydown", t.step_func((event) => {
+      checkEvent(event, "ArrowUp");
+    }), { once: true });
+
+    slider.addEventListener("keyup", t.step_func((event) => {
+      checkEvent(event, "ArrowUp");
+
+      slider.addEventListener("keydown", t.step_func((event) => {
+        checkEvent(event, "ArrowDown");
+      }), { once: true });
+
+      slider.addEventListener("keyup", t.step_func_done((event) => {
+        checkEvent(event, "ArrowDown");
+
+        t.done();
+      }), { once: true });
+
+      window.setTimeout(() => {
+        axSlider.decrement();
+      }, 0);
+    }), { once: true });
+
+    window.setTimeout(t.step_func(() => {
+      assert(false, "didn't get all key events within 1000ms");
+      t.done();
+    }), 1000);
+
+    axSlider.increment();
+  }, "check that sending an increment event to an ARIA slider generates an up arrow key event");
+</script>
+</body>
+</html>