Add support for panning the magnifier viewport with Ctrl+Alt+Arrow keys

AX-Relnotes: Add support for panning the fullscreen magnifier viewport with Ctrl+Alt+Arrow keys
Change-Id: I263be6236f7060cd12d2037e82f070a6f0863cf4
Bug: 1140624
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2510911
Commit-Queue: Josiah Krutz <josiahk@google.com>
Reviewed-by: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#822900}

ash/events/accessibility_event_rewriter.cc

@@ -6,6 +6,8 @@
 
 #include "ash/accessibility/accessibility_controller_impl.h"
 #include "ash/accessibility/point_scan_controller.h"
+#include "ash/keyboard/keyboard_util.h"
+#include "ash/magnifier/magnification_controller.h"
 #include "ash/public/cpp/accessibility_event_rewriter_delegate.h"
 #include "ash/shell.h"
 #include "ui/chromeos/events/event_rewriter_chromeos.h"
@@ -199,6 +201,65 @@ bool AccessibilityEventRewriter::RewriteEventForSwitchAccess(
   return capture;
 }
 
+bool AccessibilityEventRewriter::RewriteEventForMagnifier(
+    const ui::Event& event,
+    const Continuation continuation) {
+  if (!event.IsKeyEvent())
+    return false;
+
+  const ui::KeyEvent* key_event = event.AsKeyEvent();
+
+  if (!keyboard_util::IsArrowKeyCode(key_event->key_code()) ||
+      !key_event->IsControlDown() || !key_event->IsAltDown()) {
+    return false;
+  }
+
+  if (key_event->type() == ui::ET_KEY_PRESSED) {
+    // If first time key is pressed (e.g. not repeat), start scrolling.
+    if (!(key_event->flags() & ui::EF_IS_REPEAT))
+      OnMagnifierKeyPressed(key_event);
+
+    // Either way (first or repeat), capture key press.
+    return true;
+  }
+
+  if (key_event->type() == ui::ET_KEY_RELEASED) {
+    OnMagnifierKeyReleased(key_event);
+    return true;
+  }
+
+  return false;
+}
+
+void AccessibilityEventRewriter::OnMagnifierKeyPressed(
+    const ui::KeyEvent* event) {
+  MagnificationController* controller =
+      Shell::Get()->magnification_controller();
+  switch (event->key_code()) {
+    case ui::VKEY_UP:
+      controller->SetScrollDirection(MagnificationController::SCROLL_UP);
+      break;
+    case ui::VKEY_DOWN:
+      controller->SetScrollDirection(MagnificationController::SCROLL_DOWN);
+      break;
+    case ui::VKEY_LEFT:
+      controller->SetScrollDirection(MagnificationController::SCROLL_LEFT);
+      break;
+    case ui::VKEY_RIGHT:
+      controller->SetScrollDirection(MagnificationController::SCROLL_RIGHT);
+      break;
+    default:
+      NOTREACHED() << "Unexpected keyboard_code:" << event->key_code();
+  }
+}
+
+void AccessibilityEventRewriter::OnMagnifierKeyReleased(
+    const ui::KeyEvent* event) {
+  MagnificationController* controller =
+      Shell::Get()->magnification_controller();
+  controller->SetScrollDirection(MagnificationController::SCROLL_NONE);
+}
+
 void AccessibilityEventRewriter::UpdateKeyboardDeviceIds() {
   keyboard_device_ids_.clear();
   for (auto& keyboard :
@@ -224,6 +285,10 @@ ui::EventDispatchDetails AccessibilityEventRewriter::RewriteEvent(
     captured = RewriteEventForSwitchAccess(event, continuation);
   }
 
+  if (!captured && Shell::Get()->magnification_controller()->IsEnabled()) {
+    captured = RewriteEventForMagnifier(event, continuation);
+  }
+
   if (!captured) {
     captured = RewriteEventForChromeVox(event, continuation);
   }

ash/events/accessibility_event_rewriter.h

@@ -24,6 +24,7 @@ namespace ash {
 
 class AccessibilityEventRewriterDelegate;
 enum class SwitchAccessCommand;
+enum class MagnifierCommand;
 
 // AccessibilityEventRewriter sends key events to Accessibility extensions (such
 // as ChromeVox and Switch Access) via the delegate when the corresponding
@@ -79,6 +80,10 @@ class ASH_EXPORT AccessibilityEventRewriter
                                 const Continuation continuation);
   bool RewriteEventForSwitchAccess(const ui::Event& event,
                                    const Continuation continuation);
+  bool RewriteEventForMagnifier(const ui::Event& event,
+                                const Continuation continuation);
+  void OnMagnifierKeyPressed(const ui::KeyEvent* event);
+  void OnMagnifierKeyReleased(const ui::KeyEvent* event);
 
   // Updates the list of allowed keyboard device ids based on the current set of
   // keyboard input types.