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

chrome/browser/ui/libgtkui/native_theme_gtk3.cc

 // Copyright 2016 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 "chrome/browser/ui/libgtkui/native_theme_gtk3.h"
 
 #include <gtk/gtk.h>
 
 #include "chrome/browser/ui/libgtkui/chrome_gtk_frame.h"
 #include "chrome/browser/ui/libgtkui/chrome_gtk_menu_subclasses.h"
 #include "chrome/browser/ui/libgtkui/gtk_util.h"
 #include "chrome/browser/ui/libgtkui/skia_utils_gtk.h"
 #include "ui/gfx/color_palette.h"
 #include "ui/gfx/color_utils.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/native_theme/native_theme_dark_aura.h"
 
 namespace libgtkui {
 
 namespace {
 
 void PaintWidget(SkCanvas* canvas,
                  const gfx::Rect& rect,
-                 const char* css_selector,
-                 GtkStateFlags state) {
+                 GtkStyleContext* context) {
   SkBitmap bitmap;
   bitmap.allocN32Pixels(rect.width(), rect.height());
   bitmap.eraseColor(0);
 
   cairo_surface_t* surface = cairo_image_surface_create_for_data(
       static_cast<unsigned char*>(bitmap.getAddr(0, 0)), CAIRO_FORMAT_ARGB32,
       rect.width(), rect.height(),
       cairo_format_stride_for_width(CAIRO_FORMAT_ARGB32, rect.width()));
   cairo_t* cr = cairo_create(surface);
 
-  auto context = GetStyleContextFromCss(css_selector);
-  gtk_style_context_set_state(context, state);
-
   gtk_render_background(context, cr, 0, 0, rect.width(), rect.height());
   gtk_render_frame(context, cr, 0, 0, rect.width(), rect.height());
   cairo_destroy(cr);
   cairo_surface_destroy(surface);
   canvas->drawBitmap(bitmap, rect.x(), rect.y());
 }
 
 GtkStateFlags StateToStateFlags(NativeThemeGtk3::State state) {
   switch (state) {
     case NativeThemeGtk3::kDisabled:
@@ skipping 282 matching lines @@
 
   SkColor color = SkColorFromColorId(color_id);
   color_cache_[color_id] = color;
   return color;
 }
 
 void NativeThemeGtk3::PaintMenuPopupBackground(
     SkCanvas* canvas,
     const gfx::Size& size,
     const MenuBackgroundExtraParams& menu_background) const {
-  PaintWidget(canvas, gfx::Rect(size), "GtkMenu#menu", GTK_STATE_FLAG_NORMAL);
+  PaintWidget(canvas, gfx::Rect(size), GetStyleContextFromCss("GtkMenu#menu"));
 }
 
 void NativeThemeGtk3::PaintMenuItemBackground(
     SkCanvas* canvas,
     State state,
     const gfx::Rect& rect,
     const MenuItemExtraParams& menu_item) const {
-  PaintWidget(canvas, rect, "GtkMenu#menu GtkMenuItem#menuitem",
-              StateToStateFlags(state));
+  auto context = GetStyleContextFromCss("GtkMenu#menu GtkMenuItem#menuitem");
+  gtk_style_context_set_state(context, StateToStateFlags(state));
+  PaintWidget(canvas, rect, context);
+}
+
+void NativeThemeGtk3::PaintFrameTopArea(
+    SkCanvas* canvas,
+    State state,
+    const gfx::Rect& rect,
+    const FrameTopAreaExtraParams& frame_top_area) const {
+  auto context = GetStyleContextFromCss("#headerbar.header-bar.titlebar");
+  RemoveBorders(context);
+  gtk_style_context_set_state(context,
+                              frame_top_area.is_active
+                                  ? GTK_STATE_FLAG_NORMAL
+                                  : GTK_STATE_FLAG_BACKDROP);
+  PaintWidget(canvas, rect, context);
 }
 
 }  // namespace libgtkui