Gtk3: Render a GtkHeaderBar as the background of the tab strip

ui/views/window/frame_background.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/views/window/frame_background.h"
 
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "ui/base/theme_provider.h"
 #include "ui/gfx/canvas.h"
+#include "ui/native_theme/native_theme.h"
 #include "ui/views/view.h"
 
 namespace views {
 
 FrameBackground::FrameBackground()
     : frame_color_(0),
+      is_active_(true),
       top_area_height_(0),
       left_edge_(nullptr),
       top_edge_(nullptr),
       right_edge_(nullptr),
       bottom_edge_(nullptr),
       top_left_corner_(nullptr),
       top_right_corner_(nullptr),
       bottom_left_corner_(nullptr),
       bottom_right_corner_(nullptr),
       maximized_top_inset_(0) {}
@@ skipping 91 matching lines @@
 }
 
 void FrameBackground::PaintMaximized(gfx::Canvas* canvas,
                                      const View* view) const {
   // We will be painting from -|maximized_top_inset_| to
   // -|maximized_top_inset_| + |theme_image_|.height(). If this is less than
   // |top_area_height_|, we need to paint the frame color to fill in the area
   // beneath the image.
   int theme_frame_bottom = -maximized_top_inset_ +
                            (theme_image_.isNull() ? 0 : theme_image_.height());
-  if (top_area_height_ > theme_frame_bottom) {
-    canvas->FillRect(gfx::Rect(0, 0, view->width(), top_area_height_),
-                     frame_color_);
-  }
+  if (top_area_height_ > theme_frame_bottom)
+    PaintFrameTopArea(canvas, view);
 
   // Draw the theme frame.
   if (!theme_image_.isNull()) {
     canvas->TileImageInt(theme_image_, 0, -maximized_top_inset_, view->width(),
                          theme_image_.height());
   }
   // Draw the theme frame overlay, if available.
   if (!theme_overlay_image_.isNull())
     canvas->DrawImageInt(theme_overlay_image_, 0, -maximized_top_inset_);
 }
 
 void FrameBackground::PaintFrameColor(gfx::Canvas* canvas,
                                       const View* view) const {
-  // Fill the top area.
-  canvas->FillRect(gfx::Rect(0, 0, view->width(), top_area_height_),
-                   frame_color_);
+  PaintFrameTopArea(canvas, view);
 
   // If the window is very short, we're done.
   int remaining_height = view->height() - top_area_height_;
   if (remaining_height <= 0)
     return;
 
   // Fill down the sides.
   canvas->FillRect(gfx::Rect(0, top_area_height_, left_edge_->width(),
                              remaining_height), frame_color_);
   canvas->FillRect(gfx::Rect(view->width() - right_edge_->width(),
                              top_area_height_, right_edge_->width(),
                              remaining_height), frame_color_);
 
   // If the window is very narrow, we're done.
   int center_width =
       view->width() - left_edge_->width() - right_edge_->width();
   if (center_width <= 0)
     return;
 
   // Fill the bottom area.
   canvas->FillRect(gfx::Rect(left_edge_->width(),
                              view->height() - bottom_edge_->height(),
                              center_width, bottom_edge_->height()),
                              frame_color_);
 }
 
+void FrameBackground::PaintFrameTopArea(gfx::Canvas* canvas,
+                                        const View* view) const {
+  auto* native_theme = view->GetNativeTheme();
+  ui::NativeTheme::ExtraParams params;
+  params.frame_top_area.is_active = is_active_;
+  params.frame_top_area.default_background_color = frame_color_;
+  native_theme->Paint(canvas->sk_canvas(), ui::NativeTheme::kFrameTopArea,
+                      ui::NativeTheme::kNormal,
+                      gfx::Rect(0, 0, view->width(), top_area_height_), params);
+}
+
 }  // namespace views