chrome/browser/ui/libgtkui/nav_button_provider_gtk3.cc

// Copyright 2017 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/nav_button_provider_gtk3.h"

#include <gtk/gtk.h>

#include "chrome/browser/ui/libgtkui/gtk_util.h"
#include "ui/base/glib/scoped_gobject.h"
#include "ui/gfx/image/image_skia.h"
#include "ui/gfx/image/image_skia_source.h"
#include "ui/views/resources/grit/views_resources.h"

namespace libgtkui {

namespace {

// gtkheaderbar.c uses GTK_ICON_SIZE_MENU, which is 16px.
const int kIconSize = 16;

// Specified in GtkHeaderBar spec.
const int kHeaderSpacing = 6;

const char* ButtonStyleClassFromButtonType(
    chrome::FrameButtonDisplayType type) {
  switch (type) {
    case chrome::FrameButtonDisplayType::kMinimize:
      return "minimize";
    case chrome::FrameButtonDisplayType::kMaximize:
      return "maximize";
    case chrome::FrameButtonDisplayType::kRestore:
      return "restore";
    case chrome::FrameButtonDisplayType::kClose:
      return "close";
    default:
      NOTREACHED();
      return "";
  }
}

GtkStateFlags GtkStateFlagsFromButtonState(views::Button::ButtonState state) {
  switch (state) {
    case views::Button::STATE_NORMAL:
      return GTK_STATE_FLAG_NORMAL;
    case views::Button::STATE_HOVERED:
      return GTK_STATE_FLAG_PRELIGHT;
    case views::Button::STATE_PRESSED:
      return static_cast<GtkStateFlags>(GTK_STATE_FLAG_PRELIGHT |
                                        GTK_STATE_FLAG_ACTIVE);
    case views::Button::STATE_DISABLED:
      return GTK_STATE_FLAG_INSENSITIVE;
    default:
      NOTREACHED();
      return GTK_STATE_FLAG_NORMAL;
  }
}

const char* IconNameFromButtonType(chrome::FrameButtonDisplayType type) {
  switch (type) {
    case chrome::FrameButtonDisplayType::kMinimize:
      return "window-minimize-symbolic";
    case chrome::FrameButtonDisplayType::kMaximize:
      return "window-maximize-symbolic";
    case chrome::FrameButtonDisplayType::kRestore:
      return "window-restore-symbolic";
    case chrome::FrameButtonDisplayType::kClose:
      return "window-close-symbolic";
    default:
      NOTREACHED();
      return "";
  }
}

gfx::Insets InsetsFromGtkBorder(const GtkBorder& border) {
  return gfx::Insets(border.top, border.left, border.bottom, border.right);
}

gfx::Insets PaddingFromStyleContext(GtkStyleContext* context,
                                    GtkStateFlags state) {
  GtkBorder padding;
  gtk_style_context_get_padding(context, state, &padding);
  return InsetsFromGtkBorder(padding);
}

gfx::Insets BorderFromStyleContext(GtkStyleContext* context,
                                   GtkStateFlags state) {
  GtkBorder border;
  gtk_style_context_get_border(context, state, &border);
  return InsetsFromGtkBorder(border);
}

gfx::Insets MarginFromStyleContext(GtkStyleContext* context,
                                   GtkStateFlags state) {
  GtkBorder margin;
  gtk_style_context_get_margin(context, state, &margin);
  return InsetsFromGtkBorder(margin);
}

int DefaultMonitorScaleFactor() {
  GdkScreen* screen = gdk_screen_get_default();
  return gdk_screen_get_monitor_scale_factor(
      screen, gdk_screen_get_primary_monitor(screen));
}

ScopedGObject<GdkPixbuf> LoadNavButtonIcon(chrome::FrameButtonDisplayType type,
                                           GtkStyleContext* button_context,
                                           int scale) {
  const char* icon_name = IconNameFromButtonType(type);
  ScopedGObject<GtkIconInfo> icon_info(gtk_icon_theme_lookup_icon_for_scale(
      gtk_icon_theme_get_default(), icon_name, kIconSize, scale,
      static_cast<GtkIconLookupFlags>(GTK_ICON_LOOKUP_USE_BUILTIN |
                                      GTK_ICON_LOOKUP_GENERIC_FALLBACK)));
  return ScopedGObject<GdkPixbuf>(gtk_icon_info_load_symbolic_for_context(
      icon_info, button_context, nullptr, nullptr));
}

void CalculateUnscaledButtonSize(chrome::FrameButtonDisplayType type,
                                 gfx::Size* button_size,
                                 gfx::Insets* button_margin) {
  // views::ImageButton expects the images for each state to be of the
  // same size, but GTK can, in general, use a differnetly-sized
  // button for each state.  For this reason, render buttons for all
  // states at the size of a GTK_STATE_FLAG_NORMAL button.
  auto button_context = GetStyleContextFromCss(
      "GtkHeaderBar#headerbar.header-bar.titlebar "
      "GtkButton#button.titlebutton");
  gtk_style_context_add_class(button_context,
                              ButtonStyleClassFromButtonType(type));

  ScopedGObject<GdkPixbuf> icon_pixbuf =
      LoadNavButtonIcon(type, button_context, 1);

  const int monitor_scale = DefaultMonitorScaleFactor();

  gfx::Size icon_size(gdk_pixbuf_get_width(icon_pixbuf) / monitor_scale,
                      gdk_pixbuf_get_height(icon_pixbuf) / monitor_scale);
  gfx::Rect button_rect(icon_size);
  if (GtkVersionCheck(3, 20)) {
    int min_width, min_height;
    gtk_style_context_get(button_context, GTK_STATE_FLAG_NORMAL, "min-width",
                          &min_width, "min-height", &min_height, NULL);
    button_rect.set_width(std::max(button_rect.width(), min_width));
    button_rect.set_height(std::max(button_rect.height(), min_height));
  }

  // TODO(thomasanderson): Factor in the GtkImage size, border, padding, and
  // margin
  button_rect.Inset(
      -PaddingFromStyleContext(button_context, GTK_STATE_FLAG_NORMAL));
  button_rect.Inset(
      -BorderFromStyleContext(button_context, GTK_STATE_FLAG_NORMAL));

  *button_size = button_rect.size();
  *button_margin =
      MarginFromStyleContext(button_context, GTK_STATE_FLAG_NORMAL);
}

class NavButtonImageSource : public gfx::ImageSkiaSource {
 public:
  NavButtonImageSource(chrome::FrameButtonDisplayType type,
                       views::Button::ButtonState state,
                       bool active,
                       gfx::Size button_size)
      : type_(type),
        state_(state),
        active_(active),
        button_size_(button_size) {}

  ~NavButtonImageSource() override {}

  gfx::ImageSkiaRep GetImageForScale(float scale) override {
    // gfx::ImageSkia kindly caches the result of this function, so
    // RenderNavButton() is called at most once for each needed scale
    // factor.  Additionally, buttons in the HOVERED or PRESSED states
    // are not actually rendered until they are needed.
    auto button_context = GetStyleContextFromCss(
        "GtkHeaderBar#headerbar.header-bar.titlebar "
        "GtkButton#button.titlebutton");
    gtk_style_context_add_class(button_context,
                                ButtonStyleClassFromButtonType(type_));
    GtkStateFlags button_state = GtkStateFlagsFromButtonState(state_);
    if (!active_) {
      button_state =
          static_cast<GtkStateFlags>(button_state | GTK_STATE_FLAG_BACKDROP);
    }
    gtk_style_context_set_state(button_context, button_state);

    // Gtk doesn't support fractional scale factors, but chrome does.
    // Rendering the button background and border at a fractional
    // scale factor is easy, since we can adjust the cairo context
    // transform.  But the icon is loaded from a pixbuf, so we pick
    // the next-highest integer scale and manually downsize.
    int pixbuf_scale = scale == static_cast<int>(scale) ? scale : scale + 1;
    ScopedGObject<GdkPixbuf> icon_pixbuf =
        LoadNavButtonIcon(type_, button_context, pixbuf_scale);

    gfx::Size icon_size(gdk_pixbuf_get_width(icon_pixbuf),
                        gdk_pixbuf_get_height(icon_pixbuf));

    SkBitmap bitmap;
    bitmap.allocN32Pixels(scale * button_size_.width(),
                          scale * button_size_.height());
    bitmap.eraseColor(0);

    CairoSurface surface(bitmap);
    cairo_t* cr = surface.cairo();

    cairo_save(cr);
    cairo_scale(cr, scale, scale);
    if (GtkVersionCheck(3, 11, 3) ||
        (button_state & (GTK_STATE_FLAG_PRELIGHT | GTK_STATE_FLAG_ACTIVE))) {
      gtk_render_background(button_context, cr, 0, 0, button_size_.width(),
                            button_size_.height());
      gtk_render_frame(button_context, cr, 0, 0, button_size_.width(),
                       button_size_.height());
    }
    cairo_restore(cr);
    cairo_save(cr);
    float pixbuf_extra_scale = scale / pixbuf_scale;
    cairo_scale(cr, pixbuf_extra_scale, pixbuf_extra_scale);
    gtk_render_icon(
        button_context, cr, icon_pixbuf,
        ((pixbuf_scale * button_size_.width() - icon_size.width()) / 2),
        ((pixbuf_scale * button_size_.height() - icon_size.height()) / 2));
    cairo_restore(cr);

    return gfx::ImageSkiaRep(bitmap, scale);
  }

  bool HasRepresentationAtAllScales() const override { return true; }

 private:
  chrome::FrameButtonDisplayType type_;
  views::Button::ButtonState state_;
  bool active_;
  gfx::Size button_size_;
};

}  // namespace

NavButtonProviderGtk3::NavButtonProviderGtk3() {}

NavButtonProviderGtk3::~NavButtonProviderGtk3() {}

void NavButtonProviderGtk3::RedrawImages(int top_area_height,
                                         bool maximized,
                                         bool active) {
  auto header_context =
      GetStyleContextFromCss("GtkHeaderBar#headerbar.header-bar.titlebar");

  GtkBorder header_padding;
  gtk_style_context_get_padding(header_context, GTK_STATE_FLAG_NORMAL,
                                &header_padding);
  GtkBorder header_border;
  gtk_style_context_get_border(header_context, GTK_STATE_FLAG_NORMAL,
                               &header_border);

  double scale = 1.0f;
  std::map<chrome::FrameButtonDisplayType, gfx::Size> button_sizes;
  std::map<chrome::FrameButtonDisplayType, gfx::Insets> button_margins;
  std::vector<chrome::FrameButtonDisplayType> display_types{
      chrome::FrameButtonDisplayType::kMinimize,
      maximized ? chrome::FrameButtonDisplayType::kRestore
                : chrome::FrameButtonDisplayType::kMaximize,
      chrome::FrameButtonDisplayType::kClose,
  };
  for (auto type : display_types) {
    CalculateUnscaledButtonSize(type, &button_sizes[type],
                                &button_margins[type]);
    int button_unconstrained_height = button_sizes[type].height() +
                                      button_margins[type].top() +
                                      button_margins[type].bottom();

    int needed_height = header_border.top + header_padding.top +
                        button_unconstrained_height + header_padding.bottom +
                        header_border.bottom;

    if (needed_height > top_area_height)
      scale =
          std::min(scale, static_cast<double>(top_area_height) / needed_height);
  }

  top_area_spacing_ =
      InsetsFromGtkBorder(header_padding) + InsetsFromGtkBorder(header_border);
  top_area_spacing_ = gfx::Insets(scale * top_area_spacing_.top() + 0.5f,
                                  scale * top_area_spacing_.left() + 0.5f,
                                  scale * top_area_spacing_.bottom() + 0.5f,
                                  scale * top_area_spacing_.right() + 0.5f);

  inter_button_spacing_ = scale * kHeaderSpacing + 0.5f;

  for (auto type : display_types) {
    double button_height =
        scale * (button_sizes[type].height() + button_margins[type].top() +
                 button_margins[type].bottom());
    double available_height =
        top_area_height - scale * ((header_padding.top + header_padding.bottom +
                                    header_border.top + header_border.bottom));
    double scaled_button_offset = (available_height - button_height) / 2;

    gfx::Size size = button_sizes[type];
    size = gfx::Size(scale * size.width() + 0.5f, scale * size.height() + 0.5f);
    gfx::Insets margin = button_margins[type];
    margin = gfx::Insets(
        scale * (header_border.top + header_padding.top + margin.top()) +
            scaled_button_offset + 0.5f,
        0, scale * margin.left() + 0.5f, scale * margin.right() + 0.5f);

    button_margins_[type] = margin;

    for (size_t state = 0; state < views::Button::STATE_COUNT; state++) {
      button_images_[type][state] = gfx::ImageSkia(
          std::make_unique<NavButtonImageSource>(
              type, static_cast<views::Button::ButtonState>(state), active,
              size),
          size);
    }
  }
}

gfx::ImageSkia NavButtonProviderGtk3::GetImage(
    chrome::FrameButtonDisplayType type,
    views::Button::ButtonState state) const {
  auto it = button_images_.find(type);
  DCHECK(it != button_images_.end());
  return it->second[state];
}

gfx::Insets NavButtonProviderGtk3::GetNavButtonMargin(
    chrome::FrameButtonDisplayType type) const {
  auto it = button_margins_.find(type);
  DCHECK(it != button_margins_.end());
  return it->second;
}

gfx::Insets NavButtonProviderGtk3::GetTopAreaSpacing() const {
  return top_area_spacing_;
}

int NavButtonProviderGtk3::GetInterNavButtonSpacing() const {
  return inter_button_spacing_;
}

}  // namespace libgtkui