path: root/widget/gtk/WidgetStyleCache.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include <dlfcn.h>
#include <gtk/gtk.h>
#include "WidgetStyleCache.h"
#include "gtkdrawing.h"
#include "mozilla/Assertions.h"
#include "mozilla/PodOperations.h"
#include "mozilla/ScopeExit.h"
#include "nsDebug.h"
#include "nsPrintfCString.h"
#include "nsString.h"

#define STATE_FLAG_DIR_LTR (1U << 7)
#define STATE_FLAG_DIR_RTL (1U << 8)
static_assert(GTK_STATE_FLAG_DIR_LTR == STATE_FLAG_DIR_LTR &&
                  GTK_STATE_FLAG_DIR_RTL == STATE_FLAG_DIR_RTL,
              "incorrect direction state flags");

enum class CSDStyle {
  Unknown,
  Solid,
  Normal,
};

static bool gHeaderBarShouldDrawContainer = false;
static bool gMaximizedHeaderBarShouldDrawContainer = false;
static CSDStyle gCSDStyle = CSDStyle::Unknown;
static GtkWidget* sWidgetStorage[MOZ_GTK_WIDGET_NODE_COUNT];
static GtkStyleContext* sStyleStorage[MOZ_GTK_WIDGET_NODE_COUNT];

static GtkStyleContext* GetWidgetRootStyle(WidgetNodeType aNodeType);
static GtkStyleContext* GetCssNodeStyleInternal(WidgetNodeType aNodeType);

static GtkWidget* CreateWindowWidget() {
  GtkWidget* widget = gtk_window_new(GTK_WINDOW_POPUP);
  MOZ_RELEASE_ASSERT(widget, "We're missing GtkWindow widget!");
  gtk_widget_set_name(widget, "MozillaGtkWidget");
  return widget;
}

static GtkWidget* CreateWindowContainerWidget() {
  GtkWidget* widget = gtk_fixed_new();
  gtk_container_add(GTK_CONTAINER(GetWidget(MOZ_GTK_WINDOW)), widget);
  return widget;
}

static void AddToWindowContainer(GtkWidget* widget) {
  gtk_container_add(GTK_CONTAINER(GetWidget(MOZ_GTK_WINDOW_CONTAINER)), widget);
}

static GtkWidget* CreateScrollbarWidget(WidgetNodeType aAppearance,
                                        GtkOrientation aOrientation) {
  GtkWidget* widget = gtk_scrollbar_new(aOrientation, nullptr);
  AddToWindowContainer(widget);
  return widget;
}

static GtkWidget* CreateCheckboxWidget() {
  GtkWidget* widget = gtk_check_button_new_with_label("M");
  AddToWindowContainer(widget);
  return widget;
}

static GtkWidget* CreateRadiobuttonWidget() {
  GtkWidget* widget = gtk_radio_button_new_with_label(nullptr, "M");
  AddToWindowContainer(widget);
  return widget;
}

static GtkWidget* CreateMenuPopupWidget() {
  GtkWidget* widget = gtk_menu_new();
  GtkStyleContext* style = gtk_widget_get_style_context(widget);
  gtk_style_context_add_class(style, GTK_STYLE_CLASS_POPUP);
  gtk_menu_attach_to_widget(GTK_MENU(widget), GetWidget(MOZ_GTK_WINDOW),
                            nullptr);
  return widget;
}

static GtkWidget* CreateProgressWidget() {
  GtkWidget* widget = gtk_progress_bar_new();
  AddToWindowContainer(widget);
  return widget;
}

static GtkWidget* CreateTooltipWidget() {
  MOZ_ASSERT(gtk_check_version(3, 20, 0) != nullptr,
             "CreateTooltipWidget should be used for Gtk < 3.20 only.");
  GtkWidget* widget = CreateWindowWidget();
  GtkStyleContext* style = gtk_widget_get_style_context(widget);
  gtk_style_context_add_class(style, GTK_STYLE_CLASS_TOOLTIP);
  return widget;
}

static GtkWidget* CreateExpanderWidget() {
  GtkWidget* widget = gtk_expander_new("M");
  AddToWindowContainer(widget);
  return widget;
}

static GtkWidget* CreateFrameWidget() {
  GtkWidget* widget = gtk_frame_new(nullptr);
  AddToWindowContainer(widget);
  return widget;
}

static GtkWidget* CreateGripperWidget() {
  GtkWidget* widget = gtk_handle_box_new();
  AddToWindowContainer(widget);
  return widget;
}

static GtkWidget* CreateToolbarWidget() {
  GtkWidget* widget = gtk_toolbar_new();
  gtk_container_add(GTK_CONTAINER(GetWidget(MOZ_GTK_GRIPPER)), widget);
  return widget;
}

static GtkWidget* CreateToolbarSeparatorWidget() {
  GtkWidget* widget = GTK_WIDGET(gtk_separator_tool_item_new());
  AddToWindowContainer(widget);
  return widget;
}

static GtkWidget* CreateButtonWidget() {
  GtkWidget* widget = gtk_button_new_with_label("M");
  AddToWindowContainer(widget);
  return widget;
}

static GtkWidget* CreateToggleButtonWidget() {
  GtkWidget* widget = gtk_toggle_button_new();
  AddToWindowContainer(widget);
  return widget;
}

static GtkWidget* CreateButtonArrowWidget() {
  GtkWidget* widget = gtk_arrow_new(GTK_ARROW_DOWN, GTK_SHADOW_OUT);
  gtk_container_add(GTK_CONTAINER(GetWidget(MOZ_GTK_TOGGLE_BUTTON)), widget);
  gtk_widget_show(widget);
  return widget;
}

static GtkWidget* CreateSpinWidget() {
  GtkWidget* widget = gtk_spin_button_new(nullptr, 1, 0);
  AddToWindowContainer(widget);
  return widget;
}

static GtkWidget* CreateEntryWidget() {
  GtkWidget* widget = gtk_entry_new();
  AddToWindowContainer(widget);
  return widget;
}

static GtkWidget* CreateComboBoxWidget() {
  GtkWidget* widget = gtk_combo_box_new();
  AddToWindowContainer(widget);
  return widget;
}

typedef struct {
  GType type;
  GtkWidget** widget;
} GtkInnerWidgetInfo;

static void GetInnerWidget(GtkWidget* widget, gpointer client_data) {
  auto info = static_cast<GtkInnerWidgetInfo*>(client_data);

  if (G_TYPE_CHECK_INSTANCE_TYPE(widget, info->type)) {
    *info->widget = widget;
  }
}

static GtkWidget* CreateComboBoxButtonWidget() {
  GtkWidget* comboBox = GetWidget(MOZ_GTK_COMBOBOX);
  GtkWidget* comboBoxButton = nullptr;

  /* Get its inner Button */
  GtkInnerWidgetInfo info = {GTK_TYPE_TOGGLE_BUTTON, &comboBoxButton};
  gtk_container_forall(GTK_CONTAINER(comboBox), GetInnerWidget, &info);

  if (!comboBoxButton) {
    /* Shouldn't be reached with current internal gtk implementation; we
     * use a generic toggle button as last resort fallback to avoid
     * crashing. */
    comboBoxButton = GetWidget(MOZ_GTK_TOGGLE_BUTTON);
  } else {
    /* We need to have pointers to the inner widgets (button, separator, arrow)
     * of the ComboBox to get the correct rendering from theme engines which
     * special cases their look. Since the inner layout can change, we ask GTK
     * to NULL our pointers when they are about to become invalid because the
     * corresponding widgets don't exist anymore. It's the role of
     * g_object_add_weak_pointer().
     * Note that if we don't find the inner widgets (which shouldn't happen), we
     * fallback to use generic "non-inner" widgets, and they don't need that
     * kind of weak pointer since they are explicit children of gProtoLayout and
     * as such GTK holds a strong reference to them. */
    g_object_add_weak_pointer(
        G_OBJECT(comboBoxButton),
        reinterpret_cast<gpointer*>(sWidgetStorage) + MOZ_GTK_COMBOBOX_BUTTON);
  }

  return comboBoxButton;
}

static GtkWidget* CreateComboBoxArrowWidget() {
  GtkWidget* comboBoxButton = GetWidget(MOZ_GTK_COMBOBOX_BUTTON);
  GtkWidget* comboBoxArrow = nullptr;

  /* Get the widgets inside the Button */
  GtkWidget* buttonChild = gtk_bin_get_child(GTK_BIN(comboBoxButton));
  if (GTK_IS_BOX(buttonChild)) {
    /* appears-as-list = FALSE, cell-view = TRUE; the button
     * contains an hbox. This hbox is there because the ComboBox
     * needs to place a cell renderer, a separator, and an arrow in
     * the button when appears-as-list is FALSE. */
    GtkInnerWidgetInfo info = {GTK_TYPE_ARROW, &comboBoxArrow};
    gtk_container_forall(GTK_CONTAINER(buttonChild), GetInnerWidget, &info);
  } else if (GTK_IS_ARROW(buttonChild)) {
    /* appears-as-list = TRUE, or cell-view = FALSE;
     * the button only contains an arrow */
    comboBoxArrow = buttonChild;
  }

  if (!comboBoxArrow) {
    /* Shouldn't be reached with current internal gtk implementation;
     * we gButtonArrowWidget as last resort fallback to avoid
     * crashing. */
    comboBoxArrow = GetWidget(MOZ_GTK_BUTTON_ARROW);
  } else {
    g_object_add_weak_pointer(
        G_OBJECT(comboBoxArrow),
        reinterpret_cast<gpointer*>(sWidgetStorage) + MOZ_GTK_COMBOBOX_ARROW);
  }

  return comboBoxArrow;
}

static GtkWidget* CreateComboBoxSeparatorWidget() {
  // Ensure to search for separator only once as it can fail
  // TODO - it won't initialize after ResetWidgetCache() call
  static bool isMissingSeparator = false;
  if (isMissingSeparator) return nullptr;

  /* Get the widgets inside the Button */
  GtkWidget* comboBoxSeparator = nullptr;
  GtkWidget* buttonChild =
      gtk_bin_get_child(GTK_BIN(GetWidget(MOZ_GTK_COMBOBOX_BUTTON)));
  if (GTK_IS_BOX(buttonChild)) {
    /* appears-as-list = FALSE, cell-view = TRUE; the button
     * contains an hbox. This hbox is there because the ComboBox
     * needs to place a cell renderer, a separator, and an arrow in
     * the button when appears-as-list is FALSE. */
    GtkInnerWidgetInfo info = {GTK_TYPE_SEPARATOR, &comboBoxSeparator};
    gtk_container_forall(GTK_CONTAINER(buttonChild), GetInnerWidget, &info);
  }

  if (comboBoxSeparator) {
    g_object_add_weak_pointer(G_OBJECT(comboBoxSeparator),
                              reinterpret_cast<gpointer*>(sWidgetStorage) +
                                  MOZ_GTK_COMBOBOX_SEPARATOR);
  } else {
    /* comboBoxSeparator may be NULL
     * when "appears-as-list" = TRUE or "cell-view" = FALSE;
     * if there is no separator, then we just won't paint it. */
    isMissingSeparator = true;
  }

  return comboBoxSeparator;
}

static GtkWidget* CreateComboBoxEntryWidget() {
  GtkWidget* widget = gtk_combo_box_new_with_entry();
  AddToWindowContainer(widget);
  return widget;
}

static GtkWidget* CreateComboBoxEntryTextareaWidget() {
  GtkWidget* comboBoxTextarea = nullptr;

  /* Get its inner Entry and Button */
  GtkInnerWidgetInfo info = {GTK_TYPE_ENTRY, &comboBoxTextarea};
  gtk_container_forall(GTK_CONTAINER(GetWidget(MOZ_GTK_COMBOBOX_ENTRY)),
                       GetInnerWidget, &info);

  if (!comboBoxTextarea) {
    comboBoxTextarea = GetWidget(MOZ_GTK_ENTRY);
  } else {
    g_object_add_weak_pointer(
        G_OBJECT(comboBoxTextarea),
        reinterpret_cast<gpointer*>(sWidgetStorage) + MOZ_GTK_COMBOBOX_ENTRY);
  }

  return comboBoxTextarea;
}

static GtkWidget* CreateComboBoxEntryButtonWidget() {
  GtkWidget* comboBoxButton = nullptr;

  /* Get its inner Entry and Button */
  GtkInnerWidgetInfo info = {GTK_TYPE_TOGGLE_BUTTON, &comboBoxButton};
  gtk_container_forall(GTK_CONTAINER(GetWidget(MOZ_GTK_COMBOBOX_ENTRY)),
                       GetInnerWidget, &info);

  if (!comboBoxButton) {
    comboBoxButton = GetWidget(MOZ_GTK_TOGGLE_BUTTON);
  } else {
    g_object_add_weak_pointer(G_OBJECT(comboBoxButton),
                              reinterpret_cast<gpointer*>(sWidgetStorage) +
                                  MOZ_GTK_COMBOBOX_ENTRY_BUTTON);
  }

  return comboBoxButton;
}

static GtkWidget* CreateComboBoxEntryArrowWidget() {
  GtkWidget* comboBoxArrow = nullptr;

  /* Get the Arrow inside the Button */
  GtkWidget* buttonChild =
      gtk_bin_get_child(GTK_BIN(GetWidget(MOZ_GTK_COMBOBOX_ENTRY_BUTTON)));

  if (GTK_IS_BOX(buttonChild)) {
    /* appears-as-list = FALSE, cell-view = TRUE; the button
     * contains an hbox. This hbox is there because the ComboBox
     * needs to place a cell renderer, a separator, and an arrow in
     * the button when appears-as-list is FALSE. */
    GtkInnerWidgetInfo info = {GTK_TYPE_ARROW, &comboBoxArrow};
    gtk_container_forall(GTK_CONTAINER(buttonChild), GetInnerWidget, &info);
  } else if (GTK_IS_ARROW(buttonChild)) {
    /* appears-as-list = TRUE, or cell-view = FALSE;
     * the button only contains an arrow */
    comboBoxArrow = buttonChild;
  }

  if (!comboBoxArrow) {
    /* Shouldn't be reached with current internal gtk implementation;
     * we gButtonArrowWidget as last resort fallback to avoid
     * crashing. */
    comboBoxArrow = GetWidget(MOZ_GTK_BUTTON_ARROW);
  } else {
    g_object_add_weak_pointer(G_OBJECT(comboBoxArrow),
                              reinterpret_cast<gpointer*>(sWidgetStorage) +
                                  MOZ_GTK_COMBOBOX_ENTRY_ARROW);
  }

  return comboBoxArrow;
}

static GtkWidget* CreateScrolledWindowWidget() {
  GtkWidget* widget = gtk_scrolled_window_new(nullptr, nullptr);
  AddToWindowContainer(widget);
  return widget;
}

static GtkWidget* CreateTreeViewWidget() {
  GtkWidget* widget = gtk_tree_view_new();
  AddToWindowContainer(widget);
  return widget;
}

static GtkWidget* CreateTreeHeaderCellWidget() {
  /*
   * Some GTK engines paint the first and last cell
   * of a TreeView header with a highlight.
   * Since we do not know where our widget will be relative
   * to the other buttons in the TreeView header, we must
   * paint it as a button that is between two others,
   * thus ensuring it is neither the first or last button
   * in the header.
   * GTK doesn't give us a way to do this explicitly,
   * so we must paint with a button that is between two
   * others.
   */
  GtkTreeViewColumn* firstTreeViewColumn;
  GtkTreeViewColumn* middleTreeViewColumn;
  GtkTreeViewColumn* lastTreeViewColumn;

  GtkWidget* treeView = GetWidget(MOZ_GTK_TREEVIEW);

  /* Create and append our three columns */
  firstTreeViewColumn = gtk_tree_view_column_new();
  gtk_tree_view_column_set_title(firstTreeViewColumn, "M");
  gtk_tree_view_append_column(GTK_TREE_VIEW(treeView), firstTreeViewColumn);

  middleTreeViewColumn = gtk_tree_view_column_new();
  gtk_tree_view_column_set_title(middleTreeViewColumn, "M");
  gtk_tree_view_append_column(GTK_TREE_VIEW(treeView), middleTreeViewColumn);

  lastTreeViewColumn = gtk_tree_view_column_new();
  gtk_tree_view_column_set_title(lastTreeViewColumn, "M");
  gtk_tree_view_append_column(GTK_TREE_VIEW(treeView), lastTreeViewColumn);

  /* Use the middle column's header for our button */
  return gtk_tree_view_column_get_button(middleTreeViewColumn);
}

static GtkWidget* CreateTreeHeaderSortArrowWidget() {
  /* TODO, but it can't be NULL */
  GtkWidget* widget = gtk_button_new();
  AddToWindowContainer(widget);
  return widget;
}

static GtkWidget* CreateHPanedWidget() {
  GtkWidget* widget = gtk_paned_new(GTK_ORIENTATION_HORIZONTAL);
  AddToWindowContainer(widget);
  return widget;
}

static GtkWidget* CreateVPanedWidget() {
  GtkWidget* widget = gtk_paned_new(GTK_ORIENTATION_VERTICAL);
  AddToWindowContainer(widget);
  return widget;
}

static GtkWidget* CreateScaleWidget(GtkOrientation aOrientation) {
  GtkWidget* widget = gtk_scale_new(aOrientation, nullptr);
  AddToWindowContainer(widget);
  return widget;
}

static GtkWidget* CreateNotebookWidget() {
  GtkWidget* widget = gtk_notebook_new();
  AddToWindowContainer(widget);
  return widget;
}

static bool HasBackground(GtkStyleContext* aStyle) {
  GdkRGBA gdkColor;
  gtk_style_context_get_background_color(aStyle, GTK_STATE_FLAG_NORMAL,
                                         &gdkColor);
  if (gdkColor.alpha != 0.0) {
    return true;
  }

  GValue value = G_VALUE_INIT;
  gtk_style_context_get_property(aStyle, "background-image",
                                 GTK_STATE_FLAG_NORMAL, &value);
  auto cleanup = mozilla::MakeScopeExit([&] { g_value_unset(&value); });
  return g_value_get_boxed(&value);
}

static void CreateHeaderBarWidget(WidgetNodeType aAppearance) {
  GtkWidget* window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
  GtkStyleContext* windowStyle = gtk_widget_get_style_context(window);

  // Headerbar has to be placed to window with csd or solid-csd style
  // to properly draw the decorated.
  gtk_style_context_add_class(windowStyle,
                              IsSolidCSDStyleUsed() ? "solid-csd" : "csd");

  GtkWidget* fixed = gtk_fixed_new();
  GtkStyleContext* fixedStyle = gtk_widget_get_style_context(fixed);
  gtk_style_context_add_class(fixedStyle, "titlebar");

  GtkWidget* headerBar = gtk_header_bar_new();

  // Emulate what create_titlebar() at gtkwindow.c does.
  GtkStyleContext* headerBarStyle = gtk_widget_get_style_context(headerBar);
  gtk_style_context_add_class(headerBarStyle, "titlebar");

  // TODO: Define default-decoration titlebar style as workaround
  // to ensure the titlebar buttons does not overflow outside.
  // Recently the titlebar size is calculated as
  // tab size + titlebar border/padding (default-decoration has 6px padding
  // at default Adwaita theme).
  // We need to fix titlebar size calculation to also include
  // titlebar button sizes. (Bug 1419442)
  gtk_style_context_add_class(headerBarStyle, "default-decoration");

  sWidgetStorage[aAppearance] = headerBar;
  if (aAppearance == MOZ_GTK_HEADER_BAR_MAXIMIZED) {
    MOZ_ASSERT(!sWidgetStorage[MOZ_GTK_HEADERBAR_WINDOW_MAXIMIZED],
               "Window widget is already created!");
    MOZ_ASSERT(!sWidgetStorage[MOZ_GTK_HEADERBAR_FIXED_MAXIMIZED],
               "Fixed widget is already created!");

    gtk_style_context_add_class(windowStyle, "maximized");

    sWidgetStorage[MOZ_GTK_HEADERBAR_WINDOW_MAXIMIZED] = window;
    sWidgetStorage[MOZ_GTK_HEADERBAR_FIXED_MAXIMIZED] = fixed;
  } else {
    MOZ_ASSERT(!sWidgetStorage[MOZ_GTK_HEADERBAR_WINDOW],
               "Window widget is already created!");
    MOZ_ASSERT(!sWidgetStorage[MOZ_GTK_HEADERBAR_FIXED],
               "Fixed widget is already created!");
    sWidgetStorage[MOZ_GTK_HEADERBAR_WINDOW] = window;
    sWidgetStorage[MOZ_GTK_HEADERBAR_FIXED] = fixed;
  }

  gtk_container_add(GTK_CONTAINER(window), fixed);
  gtk_container_add(GTK_CONTAINER(fixed), headerBar);

  gtk_style_context_invalidate(headerBarStyle);
  gtk_style_context_invalidate(fixedStyle);

  // Some themes like Elementary's style the container of the headerbar rather
  // than the header bar itself.
  bool& shouldDrawContainer = aAppearance == MOZ_GTK_HEADER_BAR
                                  ? gHeaderBarShouldDrawContainer
                                  : gMaximizedHeaderBarShouldDrawContainer;
  shouldDrawContainer = [&] {
    const bool headerBarHasBackground = HasBackground(headerBarStyle);
    if (headerBarHasBackground && GetBorderRadius(headerBarStyle)) {
      return false;
    }
    if (HasBackground(fixedStyle) &&
        (GetBorderRadius(fixedStyle) || !headerBarHasBackground)) {
      return true;
    }
    return false;
  }();
}

#define ICON_SCALE_VARIANTS 2

static void LoadWidgetIconPixbuf(GtkWidget* aWidgetIcon) {
  GtkStyleContext* style = gtk_widget_get_style_context(aWidgetIcon);

  const gchar* iconName;
  GtkIconSize gtkIconSize;
  gtk_image_get_icon_name(GTK_IMAGE(aWidgetIcon), &iconName, &gtkIconSize);

  gint iconWidth, iconHeight;
  gtk_icon_size_lookup(gtkIconSize, &iconWidth, &iconHeight);

  /* Those are available since Gtk+ 3.10 as well as GtkHeaderBar */
  for (int scale = 1; scale < ICON_SCALE_VARIANTS + 1; scale++) {
    GtkIconInfo* gtkIconInfo = gtk_icon_theme_lookup_icon_for_scale(
        gtk_icon_theme_get_default(), iconName, iconWidth, scale,
        (GtkIconLookupFlags)0);

    if (!gtkIconInfo) {
      // We miss the icon, nothing to do here.
      return;
    }

    gboolean unused;
    GdkPixbuf* iconPixbuf = gtk_icon_info_load_symbolic_for_context(
        gtkIconInfo, style, &unused, nullptr);
    g_object_unref(G_OBJECT(gtkIconInfo));

    cairo_surface_t* iconSurface =
        gdk_cairo_surface_create_from_pixbuf(iconPixbuf, scale, nullptr);
    g_object_unref(iconPixbuf);

    nsPrintfCString surfaceName("MozillaIconSurface%d", scale);
    g_object_set_data_full(G_OBJECT(aWidgetIcon), surfaceName.get(),
                           iconSurface, (GDestroyNotify)cairo_surface_destroy);
  }
}

cairo_surface_t* GetWidgetIconSurface(GtkWidget* aWidgetIcon, int aScale) {
  if (aScale > ICON_SCALE_VARIANTS) {
    aScale = ICON_SCALE_VARIANTS;
  }

  nsPrintfCString surfaceName("MozillaIconSurface%d", aScale);
  return (cairo_surface_t*)g_object_get_data(G_OBJECT(aWidgetIcon),
                                             surfaceName.get());
}

static void CreateHeaderBarButton(GtkWidget* aParentWidget,
                                  WidgetNodeType aAppearance) {
  GtkWidget* widget = gtk_button_new();

  // We have to add button to widget hierarchy now to pick
  // right icon style at LoadWidgetIconPixbuf().
  if (GTK_IS_BOX(aParentWidget)) {
    gtk_box_pack_start(GTK_BOX(aParentWidget), widget, FALSE, FALSE, 0);
  } else {
    gtk_container_add(GTK_CONTAINER(aParentWidget), widget);
  }

  // We bypass GetWidget() here because we create all titlebar
  // buttons at once when a first one is requested.
  NS_ASSERTION(!sWidgetStorage[aAppearance],
               "Titlebar button is already created!");
  sWidgetStorage[aAppearance] = widget;

  // We need to show the button widget now as GtkBox does not
  // place invisible widgets and we'll miss first-child/last-child
  // css selectors at the buttons otherwise.
  gtk_widget_show(widget);

  GtkStyleContext* style = gtk_widget_get_style_context(widget);
  gtk_style_context_add_class(style, "titlebutton");

  GtkWidget* image = nullptr;
  switch (aAppearance) {
    case MOZ_GTK_HEADER_BAR_BUTTON_CLOSE:
      gtk_style_context_add_class(style, "close");
      image = gtk_image_new_from_icon_name("window-close-symbolic",
                                           GTK_ICON_SIZE_MENU);
      break;
    case MOZ_GTK_HEADER_BAR_BUTTON_MINIMIZE:
      gtk_style_context_add_class(style, "minimize");
      image = gtk_image_new_from_icon_name("window-minimize-symbolic",
                                           GTK_ICON_SIZE_MENU);
      break;

    case MOZ_GTK_HEADER_BAR_BUTTON_MAXIMIZE:
      gtk_style_context_add_class(style, "maximize");
      image = gtk_image_new_from_icon_name("window-maximize-symbolic",
                                           GTK_ICON_SIZE_MENU);
      break;

    case MOZ_GTK_HEADER_BAR_BUTTON_MAXIMIZE_RESTORE:
      gtk_style_context_add_class(style, "maximize");
      image = gtk_image_new_from_icon_name("window-restore-symbolic",
                                           GTK_ICON_SIZE_MENU);
      break;
    default:
      break;
  }

  gtk_widget_set_valign(widget, GTK_ALIGN_CENTER);
  g_object_set(image, "use-fallback", TRUE, NULL);
  gtk_container_add(GTK_CONTAINER(widget), image);

  // We bypass GetWidget() here by explicit sWidgetStorage[] update so
  // invalidate the style as well as GetWidget() does.
  style = gtk_widget_get_style_context(image);
  gtk_style_context_invalidate(style);

  LoadWidgetIconPixbuf(image);
}

static bool IsToolbarButtonEnabled(ButtonLayout* aButtonLayout,
                                   size_t aButtonNums,
                                   WidgetNodeType aAppearance) {
  for (size_t i = 0; i < aButtonNums; i++) {
    if (aButtonLayout[i].mType == aAppearance) {
      return true;
    }
  }
  return false;
}

bool IsSolidCSDStyleUsed() {
  if (gCSDStyle == CSDStyle::Unknown) {
    bool solid;
    {
      GtkWidget* window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
      gtk_window_set_titlebar(GTK_WINDOW(window), gtk_header_bar_new());
      gtk_widget_realize(window);
      GtkStyleContext* windowStyle = gtk_widget_get_style_context(window);
      solid = gtk_style_context_has_class(windowStyle, "solid-csd");
      gtk_widget_destroy(window);
    }
    gCSDStyle = solid ? CSDStyle::Solid : CSDStyle::Normal;
  }
  return gCSDStyle == CSDStyle::Solid;
}

static void CreateHeaderBarButtons() {
  GtkWidget* headerBar = sWidgetStorage[MOZ_GTK_HEADER_BAR];
  MOZ_ASSERT(headerBar, "We're missing header bar widget!");

  gint buttonSpacing = 6;
  g_object_get(headerBar, "spacing", &buttonSpacing, nullptr);

  GtkWidget* buttonBox = gtk_box_new(GTK_ORIENTATION_HORIZONTAL, buttonSpacing);
  gtk_container_add(GTK_CONTAINER(headerBar), buttonBox);
  // We support only LTR headerbar layout for now.
  gtk_style_context_add_class(gtk_widget_get_style_context(buttonBox),
                              GTK_STYLE_CLASS_LEFT);

  ButtonLayout buttonLayout[TOOLBAR_BUTTONS];

  size_t activeButtons =
      GetGtkHeaderBarButtonLayout(mozilla::Span(buttonLayout), nullptr);

  if (IsToolbarButtonEnabled(buttonLayout, activeButtons,
                             MOZ_GTK_HEADER_BAR_BUTTON_MINIMIZE)) {
    CreateHeaderBarButton(buttonBox, MOZ_GTK_HEADER_BAR_BUTTON_MINIMIZE);
  }
  if (IsToolbarButtonEnabled(buttonLayout, activeButtons,
                             MOZ_GTK_HEADER_BAR_BUTTON_MAXIMIZE)) {
    CreateHeaderBarButton(buttonBox, MOZ_GTK_HEADER_BAR_BUTTON_MAXIMIZE);
    // We don't pack "restore" headerbar button to box as it's an icon
    // placeholder. Pack it only to header bar to get correct style.
    CreateHeaderBarButton(GetWidget(MOZ_GTK_HEADER_BAR_MAXIMIZED),
                          MOZ_GTK_HEADER_BAR_BUTTON_MAXIMIZE_RESTORE);
  }
  if (IsToolbarButtonEnabled(buttonLayout, activeButtons,
                             MOZ_GTK_HEADER_BAR_BUTTON_CLOSE)) {
    CreateHeaderBarButton(buttonBox, MOZ_GTK_HEADER_BAR_BUTTON_CLOSE);
  }
}

static void CreateHeaderBar() {
  CreateHeaderBarWidget(MOZ_GTK_HEADER_BAR);
  CreateHeaderBarWidget(MOZ_GTK_HEADER_BAR_MAXIMIZED);
  CreateHeaderBarButtons();
}

static GtkWidget* CreateWidget(WidgetNodeType aAppearance) {
  switch (aAppearance) {
    case MOZ_GTK_WINDOW:
      return CreateWindowWidget();
    case MOZ_GTK_WINDOW_CONTAINER:
      return CreateWindowContainerWidget();
    case MOZ_GTK_CHECKBUTTON_CONTAINER:
      return CreateCheckboxWidget();
    case MOZ_GTK_PROGRESSBAR:
      return CreateProgressWidget();
    case MOZ_GTK_RADIOBUTTON_CONTAINER:
      return CreateRadiobuttonWidget();
    case MOZ_GTK_SCROLLBAR_VERTICAL:
      return CreateScrollbarWidget(aAppearance, GTK_ORIENTATION_VERTICAL);
    case MOZ_GTK_MENUPOPUP:
      return CreateMenuPopupWidget();
    case MOZ_GTK_EXPANDER:
      return CreateExpanderWidget();
    case MOZ_GTK_FRAME:
      return CreateFrameWidget();
    case MOZ_GTK_GRIPPER:
      return CreateGripperWidget();
    case MOZ_GTK_TOOLBAR:
      return CreateToolbarWidget();
    case MOZ_GTK_TOOLBAR_SEPARATOR:
      return CreateToolbarSeparatorWidget();
    case MOZ_GTK_SPINBUTTON:
      return CreateSpinWidget();
    case MOZ_GTK_BUTTON:
      return CreateButtonWidget();
    case MOZ_GTK_TOGGLE_BUTTON:
      return CreateToggleButtonWidget();
    case MOZ_GTK_BUTTON_ARROW:
      return CreateButtonArrowWidget();
    case MOZ_GTK_ENTRY:
    case MOZ_GTK_DROPDOWN_ENTRY:
      return CreateEntryWidget();
    case MOZ_GTK_SCROLLED_WINDOW:
      return CreateScrolledWindowWidget();
    case MOZ_GTK_TREEVIEW:
      return CreateTreeViewWidget();
    case MOZ_GTK_TREE_HEADER_CELL:
      return CreateTreeHeaderCellWidget();
    case MOZ_GTK_TREE_HEADER_SORTARROW:
      return CreateTreeHeaderSortArrowWidget();
    case MOZ_GTK_SPLITTER_HORIZONTAL:
      return CreateHPanedWidget();
    case MOZ_GTK_SPLITTER_VERTICAL:
      return CreateVPanedWidget();
    case MOZ_GTK_SCALE_HORIZONTAL:
      return CreateScaleWidget(GTK_ORIENTATION_HORIZONTAL);
    case MOZ_GTK_SCALE_VERTICAL:
      return CreateScaleWidget(GTK_ORIENTATION_VERTICAL);
    case MOZ_GTK_NOTEBOOK:
      return CreateNotebookWidget();
    case MOZ_GTK_COMBOBOX:
      return CreateComboBoxWidget();
    case MOZ_GTK_COMBOBOX_BUTTON:
      return CreateComboBoxButtonWidget();
    case MOZ_GTK_COMBOBOX_ARROW:
      return CreateComboBoxArrowWidget();
    case MOZ_GTK_COMBOBOX_SEPARATOR:
      return CreateComboBoxSeparatorWidget();
    case MOZ_GTK_COMBOBOX_ENTRY:
      return CreateComboBoxEntryWidget();
    case MOZ_GTK_COMBOBOX_ENTRY_TEXTAREA:
      return CreateComboBoxEntryTextareaWidget();
    case MOZ_GTK_COMBOBOX_ENTRY_BUTTON:
      return CreateComboBoxEntryButtonWidget();
    case MOZ_GTK_COMBOBOX_ENTRY_ARROW:
      return CreateComboBoxEntryArrowWidget();
    case MOZ_GTK_HEADERBAR_WINDOW:
    case MOZ_GTK_HEADERBAR_WINDOW_MAXIMIZED:
    case MOZ_GTK_HEADERBAR_FIXED:
    case MOZ_GTK_HEADERBAR_FIXED_MAXIMIZED:
    case MOZ_GTK_HEADER_BAR:
    case MOZ_GTK_HEADER_BAR_MAXIMIZED:
    case MOZ_GTK_HEADER_BAR_BUTTON_CLOSE:
    case MOZ_GTK_HEADER_BAR_BUTTON_MINIMIZE:
    case MOZ_GTK_HEADER_BAR_BUTTON_MAXIMIZE:
    case MOZ_GTK_HEADER_BAR_BUTTON_MAXIMIZE_RESTORE:
      /* Create header bar widgets once and fill with child elements as we need
         the header bar fully configured to get a correct style */
      CreateHeaderBar();
      return sWidgetStorage[aAppearance];
    default:
      /* Not implemented */
      return nullptr;
  }
}

GtkWidget* GetWidget(WidgetNodeType aAppearance) {
  GtkWidget* widget = sWidgetStorage[aAppearance];
  if (!widget) {
    widget = CreateWidget(aAppearance);
    // Some widgets (MOZ_GTK_COMBOBOX_SEPARATOR for instance) may not be
    // available or implemented.
    if (!widget) {
      return nullptr;
    }
    // In GTK versions prior to 3.18, automatic invalidation of style contexts
    // for widgets was delayed until the next resize event.  Gecko however,
    // typically uses the style context before the resize event runs and so an
    // explicit invalidation may be required.  This is necessary if a style
    // property was retrieved before all changes were made to the style
    // context.  One such situation is where gtk_button_construct_child()
    // retrieves the style property "image-spacing" during construction of the
    // GtkButton, before its parent is set to provide inheritance of ancestor
    // properties.  More recent GTK versions do not need this, but do not
    // re-resolve until required and so invalidation does not trigger
    // unnecessary resolution in general.
    GtkStyleContext* style = gtk_widget_get_style_context(widget);
    gtk_style_context_invalidate(style);

    sWidgetStorage[aAppearance] = widget;
  }
  return widget;
}

static void AddStyleClassesFromStyle(GtkStyleContext* aDest,
                                     GtkStyleContext* aSrc) {
  GList* classes = gtk_style_context_list_classes(aSrc);
  for (GList* link = classes; link; link = link->next) {
    gtk_style_context_add_class(aDest, static_cast<gchar*>(link->data));
  }
  g_list_free(classes);
}

GtkStyleContext* CreateStyleForWidget(GtkWidget* aWidget,
                                      GtkStyleContext* aParentStyle) {
  static auto sGtkWidgetClassGetCSSName =
      reinterpret_cast<const char* (*)(GtkWidgetClass*)>(
          dlsym(RTLD_DEFAULT, "gtk_widget_class_get_css_name"));

  GtkWidgetClass* widgetClass = GTK_WIDGET_GET_CLASS(aWidget);
  const gchar* name = sGtkWidgetClassGetCSSName
                          ? sGtkWidgetClassGetCSSName(widgetClass)
                          : nullptr;

  GtkStyleContext* context =
      CreateCSSNode(name, aParentStyle, G_TYPE_FROM_CLASS(widgetClass));

  // Classes are stored on the style context instead of the path so that any
  // future gtk_style_context_save() will inherit classes on the head CSS
  // node, in the same way as happens when called on a style context owned by
  // a widget.
  //
  // Classes can be stored on a GtkCssNodeDeclaration and/or the path.
  // gtk_style_context_save() reuses the GtkCssNodeDeclaration, and appends a
  // new object to the path, without copying the classes from the old path
  // head.  The new head picks up classes from the GtkCssNodeDeclaration, but
  // not the path.  GtkWidgets store their classes on the
  // GtkCssNodeDeclaration, so make sure to add classes there.
  //
  // Picking up classes from the style context also means that
  // https://bugzilla.gnome.org/show_bug.cgi?id=767312, which can stop
  // gtk_widget_path_append_for_widget() from finding classes in GTK 3.20,
  // is not a problem.
  GtkStyleContext* widgetStyle = gtk_widget_get_style_context(aWidget);
  AddStyleClassesFromStyle(context, widgetStyle);

  // Release any floating reference on aWidget.
  g_object_ref_sink(aWidget);
  g_object_unref(aWidget);

  return context;
}

static GtkStyleContext* CreateStyleForWidget(GtkWidget* aWidget,
                                             WidgetNodeType aParentType) {
  return CreateStyleForWidget(aWidget, GetWidgetRootStyle(aParentType));
}

GtkStyleContext* CreateCSSNode(const char* aName, GtkStyleContext* aParentStyle,
                               GType aType) {
  static auto sGtkWidgetPathIterSetObjectName =
      reinterpret_cast<void (*)(GtkWidgetPath*, gint, const char*)>(
          dlsym(RTLD_DEFAULT, "gtk_widget_path_iter_set_object_name"));

  GtkWidgetPath* path;
  if (aParentStyle) {
    path = gtk_widget_path_copy(gtk_style_context_get_path(aParentStyle));
    // Copy classes from the parent style context to its corresponding node in
    // the path, because GTK will only match against ancestor classes if they
    // are on the path.
    GList* classes = gtk_style_context_list_classes(aParentStyle);
    for (GList* link = classes; link; link = link->next) {
      gtk_widget_path_iter_add_class(path, -1, static_cast<gchar*>(link->data));
    }
    g_list_free(classes);
  } else {
    path = gtk_widget_path_new();
  }

  gtk_widget_path_append_type(path, aType);

  if (sGtkWidgetPathIterSetObjectName) {
    (*sGtkWidgetPathIterSetObjectName)(path, -1, aName);
  }

  GtkStyleContext* context = gtk_style_context_new();
  gtk_style_context_set_path(context, path);
  gtk_style_context_set_parent(context, aParentStyle);
  gtk_widget_path_unref(path);

  // In GTK 3.4, gtk_render_* functions use |theming_engine| on the style
  // context without ensuring any style resolution sets it appropriately
  // in style_data_lookup(). e.g.
  // https://git.gnome.org/browse/gtk+/tree/gtk/gtkstylecontext.c?h=3.4.4#n3847
  //
  // That can result in incorrect drawing on first draw.  To work around this,
  // force a style look-up to set |theming_engine|.  It is sufficient to do
  // this only on context creation, instead of after every modification to the
  // context, because themes typically (Ambiance and oxygen-gtk, at least) set
  // the "engine" property with the '*' selector.
  if (GTK_MAJOR_VERSION == 3 && gtk_get_minor_version() < 6) {
    GdkRGBA unused;
    gtk_style_context_get_color(context, GTK_STATE_FLAG_NORMAL, &unused);
  }

  return context;
}

// Return a style context matching that of the root CSS node of a widget.
// This is used by all GTK versions.
static GtkStyleContext* GetWidgetRootStyle(WidgetNodeType aNodeType) {
  GtkStyleContext* style = sStyleStorage[aNodeType];
  if (style) return style;

  switch (aNodeType) {
    case MOZ_GTK_MENUITEM:
      style = CreateStyleForWidget(gtk_menu_item_new(), MOZ_GTK_MENUPOPUP);
      break;
    case MOZ_GTK_TEXT_VIEW:
      style =
          CreateStyleForWidget(gtk_text_view_new(), MOZ_GTK_SCROLLED_WINDOW);
      break;
    case MOZ_GTK_TOOLTIP:
      if (gtk_check_version(3, 20, 0) != nullptr) {
        // The tooltip style class is added first in CreateTooltipWidget()
        // and transfered to style in CreateStyleForWidget().
        GtkWidget* tooltipWindow = CreateTooltipWidget();
        style = CreateStyleForWidget(tooltipWindow, nullptr);
        gtk_widget_destroy(tooltipWindow);  // Release GtkWindow self-reference.
      } else {
        // We create this from the path because GtkTooltipWindow is not public.
        style = CreateCSSNode("tooltip", nullptr, GTK_TYPE_TOOLTIP);
        gtk_style_context_add_class(style, GTK_STYLE_CLASS_BACKGROUND);
      }
      break;
    case MOZ_GTK_TOOLTIP_BOX:
      style = CreateStyleForWidget(gtk_box_new(GTK_ORIENTATION_HORIZONTAL, 0),
                                   MOZ_GTK_TOOLTIP);
      break;
    case MOZ_GTK_TOOLTIP_BOX_LABEL:
      style = CreateStyleForWidget(gtk_label_new(nullptr), MOZ_GTK_TOOLTIP_BOX);
      break;
    default:
      GtkWidget* widget = GetWidget(aNodeType);
      MOZ_ASSERT(widget);
      return gtk_widget_get_style_context(widget);
  }

  MOZ_ASSERT(style);
  sStyleStorage[aNodeType] = style;
  return style;
}

static GtkStyleContext* CreateChildCSSNode(const char* aName,
                                           WidgetNodeType aParentNodeType) {
  return CreateCSSNode(aName, GetCssNodeStyleInternal(aParentNodeType));
}

// Create a style context equivalent to a saved root style context of
// |aAppearance| with |aStyleClass| as an additional class.  This is used to
// produce a context equivalent to what GTK versions < 3.20 use for many
// internal parts of widgets.
static GtkStyleContext* CreateSubStyleWithClass(WidgetNodeType aAppearance,
                                                const gchar* aStyleClass) {
  static auto sGtkWidgetPathIterGetObjectName =
      reinterpret_cast<const char* (*)(const GtkWidgetPath*, gint)>(
          dlsym(RTLD_DEFAULT, "gtk_widget_path_iter_get_object_name"));

  GtkStyleContext* parentStyle = GetWidgetRootStyle(aAppearance);

  // Create a new context that behaves like |parentStyle| would after
  // gtk_style_context_save(parentStyle).
  //
  // Avoiding gtk_style_context_save() avoids the need to manage the
  // restore, and a new context permits caching style resolution.
  //
  // gtk_style_context_save(context) changes the node hierarchy of |context|
  // to add a new GtkCssNodeDeclaration that is a copy of its original node.
  // The new node is a child of the original node, and so the new heirarchy is
  // one level deeper.  The new node receives the same classes as the
  // original, but any changes to the classes on |context| will change only
  // the new node.  The new node inherits properties from the original node
  // (which retains the original heirarchy and classes) and matches CSS rules
  // with the new heirarchy and any changes to the classes.
  //
  // The change in hierarchy can produce some surprises in matching theme CSS
  // rules (e.g. https://bugzilla.gnome.org/show_bug.cgi?id=761870#c2), but it
  // is important here to produce the same behavior so that rules match the
  // same widget parts in Gecko as they do in GTK.
  //
  // When using public GTK API to construct style contexts, a widget path is
  // required.  CSS rules are not matched against the style context heirarchy
  // but according to the heirarchy in the widget path.  The path that matches
  // the same CSS rules as a saved context is like the path of |parentStyle|
  // but with an extra copy of the head (last) object appended.  Setting
  // |parentStyle| as the parent context provides the same inheritance of
  // properties from the widget root node.
  const GtkWidgetPath* parentPath = gtk_style_context_get_path(parentStyle);
  const gchar* name = sGtkWidgetPathIterGetObjectName
                          ? sGtkWidgetPathIterGetObjectName(parentPath, -1)
                          : nullptr;
  GType objectType = gtk_widget_path_get_object_type(parentPath);

  GtkStyleContext* style = CreateCSSNode(name, parentStyle, objectType);

  // Start with the same classes on the new node as were on |parentStyle|.
  // GTK puts no regions or junction_sides on widget root nodes, and so there
  // is no need to copy these.
  AddStyleClassesFromStyle(style, parentStyle);

  gtk_style_context_add_class(style, aStyleClass);
  return style;
}

/* GetCssNodeStyleInternal is used by Gtk >= 3.20 */
static GtkStyleContext* GetCssNodeStyleInternal(WidgetNodeType aNodeType) {
  GtkStyleContext* style = sStyleStorage[aNodeType];
  if (style) return style;

  switch (aNodeType) {
    case MOZ_GTK_SCROLLBAR_CONTENTS_VERTICAL:
      style = CreateChildCSSNode("contents", MOZ_GTK_SCROLLBAR_VERTICAL);
      break;
    case MOZ_GTK_SCROLLBAR_TROUGH_VERTICAL:
      style = CreateChildCSSNode(GTK_STYLE_CLASS_TROUGH,
                                 MOZ_GTK_SCROLLBAR_CONTENTS_VERTICAL);
      break;
    case MOZ_GTK_SCROLLBAR_THUMB_VERTICAL:
      style = CreateChildCSSNode(GTK_STYLE_CLASS_SLIDER,
                                 MOZ_GTK_SCROLLBAR_TROUGH_VERTICAL);
      break;
    case MOZ_GTK_RADIOBUTTON:
      style = CreateChildCSSNode(GTK_STYLE_CLASS_RADIO,
                                 MOZ_GTK_RADIOBUTTON_CONTAINER);
      break;
    case MOZ_GTK_CHECKBUTTON:
      style = CreateChildCSSNode(GTK_STYLE_CLASS_CHECK,
                                 MOZ_GTK_CHECKBUTTON_CONTAINER);
      break;
    case MOZ_GTK_PROGRESS_TROUGH:
      /* Progress bar background (trough) */
      style = CreateChildCSSNode(GTK_STYLE_CLASS_TROUGH, MOZ_GTK_PROGRESSBAR);
      break;
    case MOZ_GTK_PROGRESS_CHUNK:
      style = CreateChildCSSNode("progress", MOZ_GTK_PROGRESS_TROUGH);
      break;
    case MOZ_GTK_GRIPPER:
      // TODO - create from CSS node
      style = CreateSubStyleWithClass(MOZ_GTK_GRIPPER, GTK_STYLE_CLASS_GRIP);
      break;
    case MOZ_GTK_SPINBUTTON_ENTRY:
      // TODO - create from CSS node
      style =
          CreateSubStyleWithClass(MOZ_GTK_SPINBUTTON, GTK_STYLE_CLASS_ENTRY);
      break;
    case MOZ_GTK_SCROLLED_WINDOW:
      // TODO - create from CSS node
      style = CreateSubStyleWithClass(MOZ_GTK_SCROLLED_WINDOW,
                                      GTK_STYLE_CLASS_FRAME);
      break;
    case MOZ_GTK_TEXT_VIEW_TEXT_SELECTION:
      style = CreateChildCSSNode("selection", MOZ_GTK_TEXT_VIEW_TEXT);
      break;
    case MOZ_GTK_TEXT_VIEW_TEXT:
    case MOZ_GTK_RESIZER:
      style = CreateChildCSSNode("text", MOZ_GTK_TEXT_VIEW);
      if (aNodeType == MOZ_GTK_RESIZER) {
        // The "grip" class provides the correct builtin icon from
        // gtk_render_handle().  The icon is drawn with shaded variants of
        // the background color, and so a transparent background would lead to
        // a transparent resizer.  gtk_render_handle() also uses the
        // background color to draw a background, and so this style otherwise
        // matches what is used in GtkTextView to match the background with
        // textarea elements.
        GdkRGBA color;
        gtk_style_context_get_background_color(style, GTK_STATE_FLAG_NORMAL,
                                               &color);
        if (color.alpha == 0.0) {
          g_object_unref(style);
          style = CreateStyleForWidget(gtk_text_view_new(),
                                       MOZ_GTK_SCROLLED_WINDOW);
        }
        gtk_style_context_add_class(style, GTK_STYLE_CLASS_GRIP);
      }
      break;
    case MOZ_GTK_FRAME_BORDER:
      style = CreateChildCSSNode("border", MOZ_GTK_FRAME);
      break;
    case MOZ_GTK_TREEVIEW_VIEW:
      // TODO - create from CSS node
      style = CreateSubStyleWithClass(MOZ_GTK_TREEVIEW, GTK_STYLE_CLASS_VIEW);
      break;
    case MOZ_GTK_TREEVIEW_EXPANDER:
      // TODO - create from CSS node
      style =
          CreateSubStyleWithClass(MOZ_GTK_TREEVIEW, GTK_STYLE_CLASS_EXPANDER);
      break;
    case MOZ_GTK_SPLITTER_SEPARATOR_HORIZONTAL:
      style = CreateChildCSSNode("separator", MOZ_GTK_SPLITTER_HORIZONTAL);
      break;
    case MOZ_GTK_SPLITTER_SEPARATOR_VERTICAL:
      style = CreateChildCSSNode("separator", MOZ_GTK_SPLITTER_VERTICAL);
      break;
    case MOZ_GTK_SCALE_CONTENTS_HORIZONTAL:
      style = CreateChildCSSNode("contents", MOZ_GTK_SCALE_HORIZONTAL);
      break;
    case MOZ_GTK_SCALE_CONTENTS_VERTICAL:
      style = CreateChildCSSNode("contents", MOZ_GTK_SCALE_VERTICAL);
      break;
    case MOZ_GTK_SCALE_TROUGH_HORIZONTAL:
      style = CreateChildCSSNode(GTK_STYLE_CLASS_TROUGH,
                                 MOZ_GTK_SCALE_CONTENTS_HORIZONTAL);
      break;
    case MOZ_GTK_SCALE_TROUGH_VERTICAL:
      style = CreateChildCSSNode(GTK_STYLE_CLASS_TROUGH,
                                 MOZ_GTK_SCALE_CONTENTS_VERTICAL);
      break;
    case MOZ_GTK_SCALE_THUMB_HORIZONTAL:
      style = CreateChildCSSNode(GTK_STYLE_CLASS_SLIDER,
                                 MOZ_GTK_SCALE_TROUGH_HORIZONTAL);
      break;
    case MOZ_GTK_SCALE_THUMB_VERTICAL:
      style = CreateChildCSSNode(GTK_STYLE_CLASS_SLIDER,
                                 MOZ_GTK_SCALE_TROUGH_VERTICAL);
      break;
    case MOZ_GTK_TAB_TOP: {
      // TODO - create from CSS node
      style = CreateSubStyleWithClass(MOZ_GTK_NOTEBOOK, GTK_STYLE_CLASS_TOP);
      gtk_style_context_add_region(style, GTK_STYLE_REGION_TAB,
                                   static_cast<GtkRegionFlags>(0));
      break;
    }
    case MOZ_GTK_TAB_BOTTOM: {
      // TODO - create from CSS node
      style = CreateSubStyleWithClass(MOZ_GTK_NOTEBOOK, GTK_STYLE_CLASS_BOTTOM);
      gtk_style_context_add_region(style, GTK_STYLE_REGION_TAB,
                                   static_cast<GtkRegionFlags>(0));
      break;
    }
    case MOZ_GTK_NOTEBOOK:
    case MOZ_GTK_NOTEBOOK_HEADER:
    case MOZ_GTK_TABPANELS:
    case MOZ_GTK_TAB_SCROLLARROW: {
      // TODO - create from CSS node
      GtkWidget* widget = GetWidget(MOZ_GTK_NOTEBOOK);
      return gtk_widget_get_style_context(widget);
    }
    case MOZ_GTK_WINDOW_DECORATION: {
      GtkStyleContext* parentStyle =
          CreateSubStyleWithClass(MOZ_GTK_WINDOW, "csd");
      style = CreateCSSNode("decoration", parentStyle);
      g_object_unref(parentStyle);
      break;
    }
    case MOZ_GTK_WINDOW_DECORATION_SOLID: {
      GtkStyleContext* parentStyle =
          CreateSubStyleWithClass(MOZ_GTK_WINDOW, "solid-csd");
      style = CreateCSSNode("decoration", parentStyle);
      g_object_unref(parentStyle);
      break;
    }
    default:
      return GetWidgetRootStyle(aNodeType);
  }

  MOZ_ASSERT(style, "missing style context for node type");
  sStyleStorage[aNodeType] = style;
  return style;
}

/* GetWidgetStyleInternal is used by Gtk < 3.20 */
static GtkStyleContext* GetWidgetStyleInternal(WidgetNodeType aNodeType) {
  GtkStyleContext* style = sStyleStorage[aNodeType];
  if (style) return style;

  switch (aNodeType) {
    case MOZ_GTK_SCROLLBAR_TROUGH_VERTICAL:
      style = CreateSubStyleWithClass(MOZ_GTK_SCROLLBAR_VERTICAL,
                                      GTK_STYLE_CLASS_TROUGH);
      break;
    case MOZ_GTK_SCROLLBAR_THUMB_VERTICAL:
      style = CreateSubStyleWithClass(MOZ_GTK_SCROLLBAR_VERTICAL,
                                      GTK_STYLE_CLASS_SLIDER);
      break;
    case MOZ_GTK_RADIOBUTTON:
      style = CreateSubStyleWithClass(MOZ_GTK_RADIOBUTTON_CONTAINER,
                                      GTK_STYLE_CLASS_RADIO);
      break;
    case MOZ_GTK_CHECKBUTTON:
      style = CreateSubStyleWithClass(MOZ_GTK_CHECKBUTTON_CONTAINER,
                                      GTK_STYLE_CLASS_CHECK);
      break;
    case MOZ_GTK_PROGRESS_TROUGH:
      style =
          CreateSubStyleWithClass(MOZ_GTK_PROGRESSBAR, GTK_STYLE_CLASS_TROUGH);
      break;
    case MOZ_GTK_PROGRESS_CHUNK:
      style = CreateSubStyleWithClass(MOZ_GTK_PROGRESSBAR,
                                      GTK_STYLE_CLASS_PROGRESSBAR);
      gtk_style_context_remove_class(style, GTK_STYLE_CLASS_TROUGH);
      break;
    case MOZ_GTK_GRIPPER:
      style = CreateSubStyleWithClass(MOZ_GTK_GRIPPER, GTK_STYLE_CLASS_GRIP);
      break;
    case MOZ_GTK_SPINBUTTON_ENTRY:
      style =
          CreateSubStyleWithClass(MOZ_GTK_SPINBUTTON, GTK_STYLE_CLASS_ENTRY);
      break;
    case MOZ_GTK_SCROLLED_WINDOW:
      style = CreateSubStyleWithClass(MOZ_GTK_SCROLLED_WINDOW,
                                      GTK_STYLE_CLASS_FRAME);
      break;
    case MOZ_GTK_TEXT_VIEW_TEXT:
    case MOZ_GTK_RESIZER:
      // GTK versions prior to 3.20 do not have the view class on the root
      // node, but add this to determine the background for the text window.
      style = CreateSubStyleWithClass(MOZ_GTK_TEXT_VIEW, GTK_STYLE_CLASS_VIEW);
      if (aNodeType == MOZ_GTK_RESIZER) {
        // The "grip" class provides the correct builtin icon from
        // gtk_render_handle().  The icon is drawn with shaded variants of
        // the background color, and so a transparent background would lead to
        // a transparent resizer.  gtk_render_handle() also uses the
        // background color to draw a background, and so this style otherwise
        // matches MOZ_GTK_TEXT_VIEW_TEXT to match the background with
        // textarea elements.  GtkTextView creates a separate text window and
        // so the background should not be transparent.
        gtk_style_context_add_class(style, GTK_STYLE_CLASS_GRIP);
      }
      break;
    case MOZ_GTK_FRAME_BORDER:
      return GetWidgetRootStyle(MOZ_GTK_FRAME);
    case MOZ_GTK_TREEVIEW_VIEW:
      style = CreateSubStyleWithClass(MOZ_GTK_TREEVIEW, GTK_STYLE_CLASS_VIEW);
      break;
    case MOZ_GTK_TREEVIEW_EXPANDER:
      style =
          CreateSubStyleWithClass(MOZ_GTK_TREEVIEW, GTK_STYLE_CLASS_EXPANDER);
      break;
    case MOZ_GTK_SPLITTER_SEPARATOR_HORIZONTAL:
      style = CreateSubStyleWithClass(MOZ_GTK_SPLITTER_HORIZONTAL,
                                      GTK_STYLE_CLASS_PANE_SEPARATOR);
      break;
    case MOZ_GTK_SPLITTER_SEPARATOR_VERTICAL:
      style = CreateSubStyleWithClass(MOZ_GTK_SPLITTER_VERTICAL,
                                      GTK_STYLE_CLASS_PANE_SEPARATOR);
      break;
    case MOZ_GTK_SCALE_TROUGH_HORIZONTAL:
      style = CreateSubStyleWithClass(MOZ_GTK_SCALE_HORIZONTAL,
                                      GTK_STYLE_CLASS_TROUGH);
      break;
    case MOZ_GTK_SCALE_TROUGH_VERTICAL:
      style = CreateSubStyleWithClass(MOZ_GTK_SCALE_VERTICAL,
                                      GTK_STYLE_CLASS_TROUGH);
      break;
    case MOZ_GTK_SCALE_THUMB_HORIZONTAL:
      style = CreateSubStyleWithClass(MOZ_GTK_SCALE_HORIZONTAL,
                                      GTK_STYLE_CLASS_SLIDER);
      break;
    case MOZ_GTK_SCALE_THUMB_VERTICAL:
      style = CreateSubStyleWithClass(MOZ_GTK_SCALE_VERTICAL,
                                      GTK_STYLE_CLASS_SLIDER);
      break;
    case MOZ_GTK_TAB_TOP:
      style = CreateSubStyleWithClass(MOZ_GTK_NOTEBOOK, GTK_STYLE_CLASS_TOP);
      gtk_style_context_add_region(style, GTK_STYLE_REGION_TAB,
                                   static_cast<GtkRegionFlags>(0));
      break;
    case MOZ_GTK_TAB_BOTTOM:
      style = CreateSubStyleWithClass(MOZ_GTK_NOTEBOOK, GTK_STYLE_CLASS_BOTTOM);
      gtk_style_context_add_region(style, GTK_STYLE_REGION_TAB,
                                   static_cast<GtkRegionFlags>(0));
      break;
    case MOZ_GTK_NOTEBOOK:
    case MOZ_GTK_NOTEBOOK_HEADER:
    case MOZ_GTK_TABPANELS:
    case MOZ_GTK_TAB_SCROLLARROW: {
      GtkWidget* widget = GetWidget(MOZ_GTK_NOTEBOOK);
      return gtk_widget_get_style_context(widget);
    }
    default:
      return GetWidgetRootStyle(aNodeType);
  }

  MOZ_ASSERT(style);
  sStyleStorage[aNodeType] = style;
  return style;
}

void ResetWidgetCache() {
  for (int i = 0; i < MOZ_GTK_WIDGET_NODE_COUNT; i++) {
    if (sStyleStorage[i]) g_object_unref(sStyleStorage[i]);
  }
  mozilla::PodArrayZero(sStyleStorage);

  gCSDStyle = CSDStyle::Unknown;

  /* This will destroy all of our widgets */
  if (sWidgetStorage[MOZ_GTK_WINDOW]) {
    gtk_widget_destroy(sWidgetStorage[MOZ_GTK_WINDOW]);
  }
  if (sWidgetStorage[MOZ_GTK_HEADERBAR_WINDOW]) {
    gtk_widget_destroy(sWidgetStorage[MOZ_GTK_HEADERBAR_WINDOW]);
  }
  if (sWidgetStorage[MOZ_GTK_HEADERBAR_WINDOW_MAXIMIZED]) {
    gtk_widget_destroy(sWidgetStorage[MOZ_GTK_HEADERBAR_WINDOW_MAXIMIZED]);
  }

  /* Clear already freed arrays */
  mozilla::PodArrayZero(sWidgetStorage);
}

GtkStyleContext* GetStyleContext(WidgetNodeType aNodeType, int aScale,
                                 GtkTextDirection aDirection,
                                 GtkStateFlags aStateFlags) {
  GtkStyleContext* style;
  if (gtk_check_version(3, 20, 0) != nullptr) {
    style = GetWidgetStyleInternal(aNodeType);
  } else {
    style = GetCssNodeStyleInternal(aNodeType);
    StyleContextSetScale(style, aScale);
  }
  bool stateChanged = false;
  bool stateHasDirection = gtk_get_minor_version() >= 8;
  GtkStateFlags oldState = gtk_style_context_get_state(style);
  MOZ_ASSERT(!(aStateFlags & (STATE_FLAG_DIR_LTR | STATE_FLAG_DIR_RTL)));
  unsigned newState = aStateFlags;
  if (stateHasDirection) {
    switch (aDirection) {
      case GTK_TEXT_DIR_LTR:
        newState |= STATE_FLAG_DIR_LTR;
        break;
      case GTK_TEXT_DIR_RTL:
        newState |= STATE_FLAG_DIR_RTL;
        break;
      default:
        MOZ_FALLTHROUGH_ASSERT("Bad GtkTextDirection");
      case GTK_TEXT_DIR_NONE:
        // GtkWidget uses a default direction if neither is explicitly
        // specified, but here DIR_NONE is interpreted as meaning the
        // direction is not important, so don't change the direction
        // unnecessarily.
        newState |= oldState & (STATE_FLAG_DIR_LTR | STATE_FLAG_DIR_RTL);
    }
  } else if (aDirection != GTK_TEXT_DIR_NONE) {
    GtkTextDirection oldDirection = gtk_style_context_get_direction(style);
    if (aDirection != oldDirection) {
      gtk_style_context_set_direction(style, aDirection);
      stateChanged = true;
    }
  }
  if (oldState != newState) {
    gtk_style_context_set_state(style, static_cast<GtkStateFlags>(newState));
    stateChanged = true;
  }
  // This invalidate is necessary for unsaved style contexts from GtkWidgets
  // in pre-3.18 GTK, because automatic invalidation of such contexts
  // was delayed until a resize event runs.
  //
  // https://bugzilla.mozilla.org/show_bug.cgi?id=1272194#c7
  //
  // Avoid calling invalidate on contexts that are not owned and constructed
  // by widgets to avoid performing build_properties() (in 3.16 stylecontext.c)
  // unnecessarily early.
  if (stateChanged && sWidgetStorage[aNodeType]) {
    gtk_style_context_invalidate(style);
  }
  return style;
}

GtkStyleContext* CreateStyleContextWithStates(WidgetNodeType aNodeType,
                                              int aScale,
                                              GtkTextDirection aDirection,
                                              GtkStateFlags aStateFlags) {
  GtkStyleContext* style =
      GetStyleContext(aNodeType, aScale, aDirection, aStateFlags);
  GtkWidgetPath* path = gtk_widget_path_copy(gtk_style_context_get_path(style));

  static auto sGtkWidgetPathIterGetState =
      (GtkStateFlags(*)(const GtkWidgetPath*, gint))dlsym(
          RTLD_DEFAULT, "gtk_widget_path_iter_get_state");
  static auto sGtkWidgetPathIterSetState =
      (void (*)(GtkWidgetPath*, gint, GtkStateFlags))dlsym(
          RTLD_DEFAULT, "gtk_widget_path_iter_set_state");

  int pathLength = gtk_widget_path_length(path);
  for (int i = 0; i < pathLength; i++) {
    unsigned state = aStateFlags | sGtkWidgetPathIterGetState(path, i);
    sGtkWidgetPathIterSetState(path, i, GtkStateFlags(state));
  }

  style = gtk_style_context_new();
  gtk_style_context_set_path(style, path);
  gtk_widget_path_unref(path);

  return style;
}

void StyleContextSetScale(GtkStyleContext* style, gint aScaleFactor) {
  // Support HiDPI styles on Gtk 3.20+
  static auto sGtkStyleContextSetScalePtr =
      (void (*)(GtkStyleContext*, gint))dlsym(RTLD_DEFAULT,
                                              "gtk_style_context_set_scale");
  if (sGtkStyleContextSetScalePtr && style) {
    sGtkStyleContextSetScalePtr(style, aScaleFactor);
  }
}

bool HeaderBarShouldDrawContainer(WidgetNodeType aNodeType) {
  MOZ_ASSERT(aNodeType == MOZ_GTK_HEADER_BAR ||
             aNodeType == MOZ_GTK_HEADER_BAR_MAXIMIZED);
  mozilla::Unused << GetWidget(aNodeType);
  return aNodeType == MOZ_GTK_HEADER_BAR
             ? gHeaderBarShouldDrawContainer
             : gMaximizedHeaderBarShouldDrawContainer;
}

gint GetBorderRadius(GtkStyleContext* aStyle) {
  GValue value = G_VALUE_INIT;
  // NOTE(emilio): In an ideal world, we'd query the two longhands
  // (border-top-left-radius and border-top-right-radius) separately. However,
  // that doesn't work (GTK rejects the query with:
  //
  //   Style property "border-top-left-radius" is not gettable
  //
  // However! Getting border-radius does work, and it does return the
  // border-top-left-radius as a gint:
  //
  //   https://docs.gtk.org/gtk3/const.STYLE_PROPERTY_BORDER_RADIUS.html
  //   https://gitlab.gnome.org/GNOME/gtk/-/blob/gtk-3-20/gtk/gtkcssshorthandpropertyimpl.c#L961-977
  //
  // So we abuse this fact, and make the assumption here that the
  // border-top-{left,right}-radius are the same, and roll with it.
  gtk_style_context_get_property(aStyle, "border-radius", GTK_STATE_FLAG_NORMAL,
                                 &value);
  gint result = 0;
  auto type = G_VALUE_TYPE(&value);
  if (type == G_TYPE_INT) {
    result = g_value_get_int(&value);
  } else {
    NS_WARNING(nsPrintfCString("Unknown value type %lu for border-radius", type)
                   .get());
  }
  g_value_unset(&value);
  return result;
}