UIDevTools: Don't highlight empty elements

When an empty element is hovered, do not show a tiny highlighted
square. There is no need to highlight in this case. However, for
invisible non-empty element, we still show its bound for information.

BUG=898998

Change-Id: I8d5569710c427011dac90ec5ef9bc4dbc63eadd4
Reviewed-on: https://chromium-review.googlesource.com/c/1309413
Commit-Queue: Wei Li <weili@chromium.org>
Reviewed-by: Leonard Grey <lgrey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604945}

components/ui_devtools/views/overlay_agent_aura.cc

@@ -503,16 +503,18 @@ Response OverlayAgentAura::HighlightNode(int node_id, bool show_size) {
 
   highlight_rect_config_ = HighlightRectsConfiguration::NO_DRAW;
   show_size_on_canvas_ = show_size;
-  UpdateHighlight(element->GetNodeWindowAndBounds());
-
-  if (!layer_for_highlighting_->visible())
-    layer_for_highlighting_->SetVisible(true);
-
+  layer_for_highlighting_->SetVisible(
+      UpdateHighlight(element->GetNodeWindowAndBounds()));
   return Response::OK();
 }
 
-void OverlayAgentAura::UpdateHighlight(
+bool OverlayAgentAura::UpdateHighlight(
     const std::pair<gfx::NativeWindow, gfx::Rect>& window_and_bounds) {
+  if (window_and_bounds.second.IsEmpty()) {
+    hovered_rect_.SetRect(0, 0, 0, 0);
+    return false;
+  }
+
   gfx::NativeWindow root = window_and_bounds.first->GetRootWindow();
   layer_for_highlighting_->SetBounds(root->bounds());
   layer_for_highlighting_->SchedulePaint(root->bounds());
@@ -528,6 +530,7 @@ void OverlayAgentAura::UpdateHighlight(
   gfx::Point origin = hovered_rect_.origin();
   screen_position_client->ConvertPointFromScreen(root, &origin);
   hovered_rect_.set_origin(origin);
+  return true;
 }
 
 void OverlayAgentAura::OnMouseEvent(ui::MouseEvent* event) {

components/ui_devtools/views/overlay_agent_aura.h

@@ -67,9 +67,11 @@ class OverlayAgentAura : public OverlayAgent,
   FRIEND_TEST_ALL_PREFIXES(OverlayAgentTest, HighlightWidget);
 #if defined(USE_AURA)
   FRIEND_TEST_ALL_PREFIXES(OverlayAgentTest, HighlightWindow);
+  FRIEND_TEST_ALL_PREFIXES(OverlayAgentTest, HighlightEmptyOrInvisibleWindow);
 #endif
   protocol::Response HighlightNode(int node_id, bool show_size = false);
-  void UpdateHighlight(
+  // Returns true when there is any visible element to highlight.
+  bool UpdateHighlight(
       const std::pair<gfx::NativeWindow, gfx::Rect>& window_and_bounds);
 
   // Shows the distances between the nodes identified by |pinned_id| and

components/ui_devtools/views/overlay_agent_unittest.cc

@@ -92,6 +92,16 @@ class OverlayAgentTest : public views::ViewsTestBase {
             node_id));
   }
 
+  std::unique_ptr<aura::Window> CreateWindowElement(const gfx::Rect& bounds) {
+    std::unique_ptr<aura::Window> window = std::make_unique<aura::Window>(
+        nullptr, aura::client::WINDOW_TYPE_NORMAL);
+    window->Init(ui::LAYER_NOT_DRAWN);
+    window->SetBounds(bounds);
+    GetContext()->AddChild(window.get());
+    window->Show();
+    return window;
+  }
+
   std::unique_ptr<views::Widget> CreateWidget() {
     auto widget = std::make_unique<views::Widget>();
     views::Widget::InitParams params;
@@ -333,12 +343,7 @@ TEST_F(OverlayAgentTest, HighlightWindow) {
   dom_agent()->getDocument(&root);
 
   std::unique_ptr<aura::Window> window =
-      std::make_unique<aura::Window>(nullptr, aura::client::WINDOW_TYPE_NORMAL);
-  window->Init(ui::LAYER_NOT_DRAWN);
-  window->SetBounds(gfx::Rect());
-  GetContext()->AddChild(window.get());
-  window->Show();
-
+      CreateWindowElement(gfx::Rect(0, 0, 20, 20));
   int window_id =
       dom_agent()
           ->element_root()
@@ -355,6 +360,38 @@ TEST_F(OverlayAgentTest, HighlightWindow) {
   overlay_agent()->hideHighlight();
   EXPECT_FALSE(highlightingLayer->visible());
 }
+
+TEST_F(OverlayAgentTest, HighlightEmptyOrInvisibleWindow) {
+  std::unique_ptr<protocol::DOM::Node> root;
+  dom_agent()->getDocument(&root);
+
+  std::unique_ptr<aura::Window> window = CreateWindowElement(gfx::Rect());
+  int window_id =
+      dom_agent()
+          ->element_root()
+          ->FindUIElementIdForBackendElement<aura::Window>(window.get());
+  DCHECK_NE(window_id, 0);
+
+  overlay_agent()->highlightNode(nullptr, window_id);
+  ui::Layer* highlightingLayer = overlay_agent()->layer_for_highlighting();
+  DCHECK(highlightingLayer);
+
+  // Highlight doesn't show for empty element.
+  EXPECT_FALSE(highlightingLayer->parent());
+  EXPECT_FALSE(highlightingLayer->visible());
+
+  // Make the window non-empty, the highlight shows up.
+  window->SetBounds(gfx::Rect(10, 10, 50, 50));
+  overlay_agent()->highlightNode(nullptr, window_id);
+  EXPECT_EQ(highlightingLayer->parent(), GetContext()->layer());
+  EXPECT_TRUE(highlightingLayer->visible());
+
+  // Make the window invisible, the highlight still shows.
+  window->Hide();
+  overlay_agent()->highlightNode(nullptr, window_id);
+  EXPECT_EQ(highlightingLayer->parent(), GetContext()->layer());
+  EXPECT_TRUE(highlightingLayer->visible());
+}
 #endif
 
 TEST_F(OverlayAgentTest, HighlightWidget) {