Gtk3: Refactor NativeThemeGtk3 to use foreign drawing only

chrome/browser/ui/libgtkui/gtk_util.cc

Index: chrome/browser/ui/libgtkui/gtk_util.cc
diff --git a/chrome/browser/ui/libgtkui/gtk_util.cc b/chrome/browser/ui/libgtkui/gtk_util.cc
index aab971785907c7b330a0fd56d43f49e7cde63823..caed0237fab0b4900d9c69d4db49dfc7998aadcd 100644
--- a/chrome/browser/ui/libgtkui/gtk_util.cc
+++ b/chrome/browser/ui/libgtkui/gtk_util.cc
@@ -14,6 +14,9 @@
 #include "base/command_line.h"
 #include "base/debug/leak_annotations.h"
 #include "base/environment.h"
+#include "base/strings/string_split.h"
+#include "base/strings/string_tokenizer.h"
+#include "base/strings/string_util.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_tree_host.h"
 #include "ui/base/accelerators/accelerator.h"
@@ -188,4 +191,218 @@ void ClearAuraTransientParent(GtkWidget* dialog) {
   g_object_set_data(G_OBJECT(dialog), kAuraTransientParent, NULL);
 }
 
+#if GTK_MAJOR_VERSION > 2
+ScopedStyleContext AppendNode(GtkStyleContext* context,
+                              const std::string& css_node) {
+  GtkWidgetPath* path =
+      context ? gtk_widget_path_copy(gtk_style_context_get_path(context))
+              : gtk_widget_path_new();
+
+  enum {
+    // TODO(thomasanderson): Add CSS_NAME here to handle the Gtk3.20 case.
+    CSS_TYPE,
+    CSS_CLASS,
+    CSS_PSEUDOCLASS,
+  } part_type = CSS_TYPE;
+  static const struct {
+    const char* name;
+    GtkStateFlags state_flag;
+  } pseudo_classes[] = {
+      {"active", GTK_STATE_FLAG_ACTIVE},
+      {"hover", GTK_STATE_FLAG_PRELIGHT},
+      {"selected", GTK_STATE_FLAG_SELECTED},
+      {"disabled", GTK_STATE_FLAG_INSENSITIVE},
+      {"indeterminate", GTK_STATE_FLAG_INCONSISTENT},
+      {"focus", GTK_STATE_FLAG_FOCUSED},
+      {"backdrop", GTK_STATE_FLAG_BACKDROP},
+      // TODO(thomasanderson): These state flags are only available in
+      // GTK 3.10 or later, which is unavailable in the wheezy
+      // sysroot.  Add them once the sysroot is updated to jessie.
+      // { "link",          GTK_STATE_FLAG_LINK },
+      // { "visited",       GTK_STATE_FLAG_VISITED },
+      // { "checked",       GTK_STATE_FLAG_CHECKED },
+  };
+  GtkStateFlags state =
+      context ? gtk_style_context_get_state(context) : GTK_STATE_FLAG_NORMAL;
+  base::StringTokenizer t(css_node, ".:");
+  t.set_options(base::StringTokenizer::RETURN_DELIMS);
+  while (t.GetNext()) {
+    if (t.token_is_delim()) {
+      if (t.token_begin() == css_node.begin()) {
+        // Special case for the first token.
+        gtk_widget_path_append_type(path, G_TYPE_NONE);
+      }
+      switch (*t.token_begin()) {
+        case '.':
+          part_type = CSS_CLASS;
+          break;
+        case ':':
+          part_type = CSS_PSEUDOCLASS;
+          break;
+        default:
+          NOTREACHED();
+      }
+    } else {
+      switch (part_type) {
+        case CSS_TYPE: {
+          GType type = g_type_from_name(t.token().c_str());
+          DCHECK(type);
+          gtk_widget_path_append_type(path, type);
+          break;
+        }
+        case CSS_CLASS: {
+          gtk_widget_path_iter_add_class(path, -1, t.token().c_str());
+          break;
+        }
+        case CSS_PSEUDOCLASS: {
+          GtkStateFlags state_flag = GTK_STATE_FLAG_NORMAL;
+          for (const auto& pseudo_class_entry : pseudo_classes) {
+            if (strcmp(pseudo_class_entry.name, t.token().c_str()) == 0) {
+              state_flag = pseudo_class_entry.state_flag;
+              break;
+            }
+          }
+          state = static_cast<GtkStateFlags>(state | state_flag);
+          break;
+        }
+      }
+    }
+  }
+  auto child_context = ScopedStyleContext(gtk_style_context_new());
+  gtk_style_context_set_path(child_context, path);
+  gtk_style_context_set_state(child_context, state);
+  gtk_style_context_set_parent(child_context, context);
+  gtk_widget_path_unref(path);
+  return child_context;
+}
+
+ScopedStyleContext GetStyleContextFromCss(const char* css_selector) {
+  // Prepend "GtkWindow.background" to the selector since all widgets must live
+  // in a window, but we don't want to specify that every time.
+  auto context = AppendNode(nullptr, "GtkWindow.background");
+
+  for (const auto& widget_type :
+       base::SplitString(css_selector, base::kWhitespaceASCII,
+                         base::TRIM_WHITESPACE, base::SPLIT_WANT_NONEMPTY)) {
+    context = AppendNode(context, widget_type);
+  }
+  return context;
+}
+
+SkColor GdkRgbaToSkColor(const GdkRGBA& color) {
+  return SkColorSetARGB(color.alpha * 255, color.red * 255, color.green * 255,
+                        color.blue * 255);
+}
+
+SkColor GetFGColor(const char* css_selector) {
+  auto context = GetStyleContextFromCss(css_selector);
+  GdkRGBA color;
+  gtk_style_context_get_color(context, gtk_style_context_get_state(context),
+                              &color);
+  return GdkRgbaToSkColor(color);
+}
+
+GtkCssProvider* GetCssProvider(const char* css) {
+  GtkCssProvider* provider = gtk_css_provider_new();
+  GError* error = nullptr;
+  gtk_css_provider_load_from_data(provider, css, -1, &error);
+  DCHECK(!error);
+  return provider;
+}
+
+void ApplyCssToContext(GtkStyleContext* context, GtkCssProvider* provider) {
+  while (context) {
+    gtk_style_context_add_provider(context, GTK_STYLE_PROVIDER(provider),
+                                   G_MAXUINT);
+    context = gtk_style_context_get_parent(context);
+  }
+}
+
+void RemoveBorders(GtkStyleContext* context) {
+  static GtkCssProvider* provider = GetCssProvider(
+      "* {"
+      "border-style: none;"
+      "border-radius: 0px;"
+      "border-width: 0px;"
+      "border-image-width: 0px;"
+      "padding: 0px;"
+      "margin: 0px;"
+      "}");
+  ApplyCssToContext(context, provider);
+}
+
+void AddBorders(GtkStyleContext* context) {
+  static GtkCssProvider* provider = GetCssProvider(
+      "* {"
+      "border-style: solid;"
+      "border-radius: 0px;"
+      "border-width: 1px;"
+      "padding: 0px;"
+      "margin: 0px;"
+      "}");
+  ApplyCssToContext(context, provider);
+}
+
+// A 1x1 cairo surface that GTK can render into.
+class PixelSurface {
+ public:
+  PixelSurface()
+      : surface_(cairo_image_surface_create(CAIRO_FORMAT_ARGB32, 1, 1)),
+        cairo_(cairo_create(surface_)) {}
+
+  ~PixelSurface() {
+    cairo_destroy(cairo_);
+    cairo_surface_destroy(surface_);
+  }
+
+  // Get the drawing context for GTK to use.
+  cairo_t* cairo() { return cairo_; }
+
+  // Get the color value of the single pixel.
+  SkColor GetPixelValue() {
+    return *reinterpret_cast<SkColor*>(cairo_image_surface_get_data(surface_));
+  }
+
+ private:
+  cairo_surface_t* surface_;
+  cairo_t* cairo_;
+};
+
+SkColor GetBGColor(const char* css_selector) {
+  // Backgrounds are more general than solid colors (eg. gradients),
+  // but chromium requires us to boil this down to one color.  We
+  // cannot use the background-color here because some themes leave it
+  // set to a garbage color because a background-image will cover it
+  // anyway.  So we instead render the background into a single pixel,
+  // removing any borders, and hope that we get a good color.
+  auto context = GetStyleContextFromCss(css_selector);
+  RemoveBorders(context);
+  PixelSurface surface;
+  gtk_render_background(context, surface.cairo(), 0, 0, 1, 1);
+  return surface.GetPixelValue();
+}
+
+SkColor GetBorderColor(const char* css_selector) {
+  // Borders have the same issue as backgrounds, due to the
+  // border-image property.
+  auto context = GetStyleContextFromCss(css_selector);
+  GtkStateFlags state = gtk_style_context_get_state(context);
+  GtkBorderStyle border_style = GTK_BORDER_STYLE_NONE;
+  gtk_style_context_get(context, state, GTK_STYLE_PROPERTY_BORDER_STYLE,
+                        &border_style, nullptr);
+  GtkBorder border;
+  gtk_style_context_get_border(context, state, &border);
+  if ((border_style == GTK_BORDER_STYLE_NONE ||
+       border_style == GTK_BORDER_STYLE_HIDDEN) ||
+      (!border.left && !border.right && !border.top && !border.bottom)) {
+    return SK_ColorTRANSPARENT;
+  }
+
+  AddBorders(context);
+  PixelSurface surface;
+  gtk_render_frame(context, surface.cairo(), 0, 0, 1, 1);
+  return surface.GetPixelValue();
+}
+#endif
+
 }  // namespace libgtkui