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首选项对话框

经典的应用程序会有一些首选项，它们应该被记住而不需要在下次运行时在进行设置。即使对于我们这个简单的应用程序示例，我们可能也想改变用于文本内容的字体。

我们将使用Gio::Settings来储存我们的首选项。Gio::Settings需要一个用于描述我们的设置的模式，在本例中为org.gtkmm.exampleapp.gschema.xml文件。

在我们应用程序使用模式之前，我们需要将其编译为Gio::Settings能期望的二进制格式。GUI为此提供了基于autotools项目的宏来执行此操作。具体信息请参阅GSettings。而Meson在GNOME模块中提供了compile_schemas()执行此操作。

接下来，我们需要将设置连接到应该被控制的部件上。一种很方便的方法是使用Gio::Settings::bind()将对象的属性和设置键相互绑定，就像我们在ExampleAppWindow的构造函数中做的过渡设置一样。

m_settings = Gio::Settings::create("org.gtkmm.exampleapp");
m_settings->bind("transition", m_stack->property_transition_type());

字体设置的连接要麻烦的多，因为我们需要先创建对应的对象属性的Gtk::TextTag。以下代码在ExampleAppWindow::open_file_view()函数中。

auto tag = buffer->create_tag();
m_settings->bind("font", tag->property_font());
buffer->apply_tag(tag, buffer->begin(), buffer->end());

此时，如果你更改其中一项设置（例如：使用gsettings命令行工具。），则应用程序会做出反应。当然，我们会希望应用程序为这些首选项提供一个对话框。所以我们现在就如此做。我们的首选项对话框将是Gtk::Dialog的子类，并且使用我们之前已经在ExampleAppWindow中看到的技术：Gtk::Builder UI文件和设置绑定。

我们创建prefs.ui文件和ExampleAppPrefs子类之后，我们重访ExampleApplication::on_action_preferences()成员函数，并使其打开一个新的首选项对话框。

auto prefs_dialog = ExampleAppPrefs::create(*get_active_window());
prefs_dialog->present();

完成所有工作后，我们的应用程序现在可以显示如下所示的首选项对话框：

Figure 29-5 首选项对话框

源代码

File: exampleapplication.h (For use with gtkmm 4)

#include "../step4/exampleapplication.h"
// Equal to the corresponding file in step4

File: exampleappprefs.h (For use with gtkmm 4)

#ifndef GTKMM_EXAMPLEAPPPREFS_H_
#define GTKMM_EXAMPLEAPPPREFS_H_

#include <gtkmm.h>

class ExampleAppPrefs : public Gtk::Dialog
{
public:
  ExampleAppPrefs(BaseObjectType* cobject,
    const Glib::RefPtr<Gtk::Builder>& refBuilder);

  static ExampleAppPrefs* create(Gtk::Window& parent);

protected:
  Glib::RefPtr<Gtk::Builder> m_refBuilder;
  Glib::RefPtr<Gio::Settings> m_settings;
  Gtk::FontButton* m_font;
  Gtk::ComboBoxText* m_transition;
};

#endif /* GTKMM_EXAMPLEAPPPREFS_H_ */

File: exampleappwindow.h (For use with gtkmm 4)

#ifndef GTKMM_EXAMPLEAPPWINDOW_H_
#define GTKMM_EXAMPLEAPPWINDOW_H_

#include <gtkmm.h>

class ExampleAppWindow : public Gtk::ApplicationWindow
{
public:
  ExampleAppWindow(BaseObjectType* cobject,
    const Glib::RefPtr<Gtk::Builder>& refBuilder);

  static ExampleAppWindow* create();

  void open_file_view(const Glib::RefPtr<Gio::File>& file);

protected:
  Glib::RefPtr<Gtk::Builder> m_refBuilder;
  Glib::RefPtr<Gio::Settings> m_settings;
  Gtk::Stack* m_stack;
  Gtk::MenuButton* m_gears;
};

#endif /* GTKMM_EXAMPLEAPPWINDOW_H */

File: main.cc (For use with gtkmm 4)

#include "exampleapplication.h"

int main(int argc, char* argv[])
{
  // Since this example is running uninstalled, we have to help it find its
  // schema. This is *not* necessary in a properly installed application.
  Glib::setenv ("GSETTINGS_SCHEMA_DIR", ".", false);

  auto application = ExampleApplication::create();

  // Start the application, showing the initial window,
  // and opening extra views for any files that it is asked to open,
  // for instance as a command-line parameter.
  // run() will return when the last window has been closed.
  return application->run(argc, argv);
}

File: exampleappwindow.cc (For use with gtkmm 4)

#include "exampleappwindow.h"
#include <iostream>
#include <stdexcept>

ExampleAppWindow::ExampleAppWindow(BaseObjectType* cobject,
  const Glib::RefPtr<Gtk::Builder>& refBuilder)
: Gtk::ApplicationWindow(cobject),
  m_refBuilder(refBuilder),
  m_settings(),
  m_stack(nullptr),
  m_gears(nullptr)
{
  // Get widgets from the Gtk::Builder file.
  m_stack = m_refBuilder->get_widget<Gtk::Stack>("stack");
  if (!m_stack)
    throw std::runtime_error("No \"stack\" object in window.ui");

  m_gears = m_refBuilder->get_widget<Gtk::MenuButton>("gears");
  if (!m_gears)
    throw std::runtime_error("No \"gears\" object in window.ui");

  // Bind settings.
  m_settings = Gio::Settings::create("org.gtkmm.exampleapp");
  m_settings->bind("transition", m_stack->property_transition_type());

  // Connect the menu to the MenuButton m_gears.
  // (The connection between action and menu item is specified in gears_menu.ui.)
  auto menu_builder = Gtk::Builder::create_from_resource("/org/gtkmm/exampleapp/gears_menu.ui");
  auto menu = menu_builder->get_object<Gio::MenuModel>("menu");
  if (!menu)
    throw std::runtime_error("No \"menu\" object in gears_menu.ui");

  m_gears->set_menu_model(menu);
}

//static
ExampleAppWindow* ExampleAppWindow::create()
{
  // Load the Builder file and instantiate its widgets.
  auto refBuilder = Gtk::Builder::create_from_resource("/org/gtkmm/exampleapp/window.ui");

  auto window = Gtk::Builder::get_widget_derived<ExampleAppWindow>(refBuilder, "app_window");
  if (!window)
    throw std::runtime_error("No \"app_window\" object in window.ui");

  return window;
}

void ExampleAppWindow::open_file_view(const Glib::RefPtr<Gio::File>& file)
{
  const Glib::ustring basename = file->get_basename();

  auto scrolled = Gtk::make_managed<Gtk::ScrolledWindow>();
  scrolled->set_expand(true);
  auto view = Gtk::make_managed<Gtk::TextView>();
  view->set_editable(false);
  view->set_cursor_visible(false);
  scrolled->set_child(*view);
  m_stack->add(*scrolled, basename, basename);

  auto buffer = view->get_buffer();
  try
  {
    char* contents = nullptr;
    gsize length = 0;
    
    file->load_contents(contents, length);
    buffer->set_text(contents, contents+length);
    g_free(contents);
  }
  catch (const Glib::Error& ex)
  {
    std::cout << "ExampleAppWindow::open_file_view(\"" << file->get_parse_name()
      << "\"):\n  " << ex.what() << std::endl;
  }

  auto tag = buffer->create_tag();
  m_settings->bind("font", tag->property_font());
  buffer->apply_tag(tag, buffer->begin(), buffer->end());
}

File: exampleappprefs.cc (For use with gtkmm 4)

#include "exampleappprefs.h"
#include "exampleappwindow.h"
#include <stdexcept>

ExampleAppPrefs::ExampleAppPrefs(BaseObjectType* cobject,
  const Glib::RefPtr<Gtk::Builder>& refBuilder)
: Gtk::Dialog(cobject),
  m_refBuilder(refBuilder),
  m_settings(),
  m_font(nullptr),
  m_transition(nullptr)
{
  m_font = m_refBuilder->get_widget<Gtk::FontButton>("font");
  if (!m_font)
    throw std::runtime_error("No \"font\" object in prefs.ui");

  m_transition = m_refBuilder->get_widget<Gtk::ComboBoxText>("transition");
  if (!m_transition)
    throw std::runtime_error("No \"transition\" object in prefs.ui");

  m_settings = Gio::Settings::create("org.gtkmm.exampleapp");
  m_settings->bind("font", m_font->property_font());
  m_settings->bind("transition", m_transition->property_active_id());
}

//static
ExampleAppPrefs* ExampleAppPrefs::create(Gtk::Window& parent)
{
  // Load the Builder file and instantiate its widgets.
  auto refBuilder = Gtk::Builder::create_from_resource("/org/gtkmm/exampleapp/prefs.ui");

  auto dialog = Gtk::Builder::get_widget_derived<ExampleAppPrefs>(refBuilder, "prefs_dialog");
  if (!dialog)
    throw std::runtime_error("No \"prefs_dialog\" object in prefs.ui");

  dialog->set_transient_for(parent);

  return dialog;
}

File: exampleapplication.cc (For use with gtkmm 4)

#include "exampleapplication.h"
#include "exampleappwindow.h"
#include "exampleappprefs.h"
#include <iostream>
#include <exception>

ExampleApplication::ExampleApplication()
: Gtk::Application("org.gtkmm.examples.application", Gio::Application::Flags::HANDLES_OPEN)
{
}

Glib::RefPtr<ExampleApplication> ExampleApplication::create()
{
  return Glib::make_refptr_for_instance<ExampleApplication>(new ExampleApplication());
}

ExampleAppWindow* ExampleApplication::create_appwindow()
{
  auto appwindow = ExampleAppWindow::create();

  // Make sure that the application runs for as long this window is still open.
  add_window(*appwindow);

  // A window can be added to an application with Gtk::Application::add_window()
  // or Gtk::Window::set_application(). When all added windows have been hidden
  // or removed, the application stops running (Gtk::Application::run() returns()),
  // unless Gio::Application::hold() has been called.

  // Delete the window when it is hidden.
  appwindow->signal_hide().connect(sigc::bind(sigc::mem_fun(*this,
    &ExampleApplication::on_hide_window), appwindow));

  return appwindow;
}

void ExampleApplication::on_startup()
{
  // Call the base class's implementation.
  Gtk::Application::on_startup();

  // Add actions and keyboard accelerators for the menu.
  add_action("preferences", sigc::mem_fun(*this, &ExampleApplication::on_action_preferences));
  add_action("quit", sigc::mem_fun(*this, &ExampleApplication::on_action_quit));
  set_accel_for_action("app.quit", "<Ctrl>Q");
}

void ExampleApplication::on_activate()
{
  try
  {
    // The application has been started, so let's show a window.
    auto appwindow = create_appwindow();
    appwindow->present();
  }
  // If create_appwindow() throws an exception (perhaps from Gtk::Builder),
  // no window has been created, no window has been added to the application,
  // and therefore the application will stop running.
  catch (const Glib::Error& ex)
  {
    std::cerr << "ExampleApplication::on_activate(): " << ex.what() << std::endl;
  }
  catch (const std::exception& ex)
  {
    std::cerr << "ExampleApplication::on_activate(): " << ex.what() << std::endl;
  }
}

void ExampleApplication::on_open(const Gio::Application::type_vec_files& files,
  const Glib::ustring& /* hint */)
{
  // The application has been asked to open some files,
  // so let's open a new view for each one.
  ExampleAppWindow* appwindow = nullptr;
  auto windows = get_windows();
  if (windows.size() > 0)
    appwindow = dynamic_cast<ExampleAppWindow*>(windows[0]);

  try
  {
    if (!appwindow)
      appwindow = create_appwindow();

    for (const auto& file : files)
      appwindow->open_file_view(file);

    appwindow->present();
  }
  catch (const Glib::Error& ex)
  {
    std::cerr << "ExampleApplication::on_open(): " << ex.what() << std::endl;
  }
  catch (const std::exception& ex)
  {
    std::cerr << "ExampleApplication::on_open(): " << ex.what() << std::endl;
  }
}

void ExampleApplication::on_hide_window(Gtk::Window* window)
{
  delete window;
}

void ExampleApplication::on_action_preferences()
{
  try
  {
    auto prefs_dialog = ExampleAppPrefs::create(*get_active_window());
    prefs_dialog->present();

    // Delete the dialog when it is hidden.
    prefs_dialog->signal_hide().connect(sigc::bind(sigc::mem_fun(*this,
      &ExampleApplication::on_hide_window), prefs_dialog));
  }
  catch (const Glib::Error& ex)
  {
    std::cerr << "ExampleApplication::on_action_preferences(): " << ex.what() << std::endl;
  }
  catch (const std::exception& ex)
  {
    std::cerr << "ExampleApplication::on_action_preferences(): " << ex.what() << std::endl;
  }
}

void ExampleApplication::on_action_quit()
{
  // Gio::Application::quit() will make Gio::Application::run() return,
  // but it's a crude way of ending the program. The window is not removed
  // from the application. Neither the window's nor the application's
  // destructors will be called, because there will be remaining reference
  // counts in both of them. If we want the destructors to be called, we
  // must remove the window from the application. One way of doing this
  // is to hide the window. See comment in create_appwindow().
  auto windows = get_windows();
  for (auto window : windows)
    window->hide();

  // Not really necessary, when Gtk::Widget::hide() is called, unless
  // Gio::Application::hold() has been called without a corresponding call
  // to Gio::Application::release().
  quit();
}

File: exampleapp.gresource.xml (For use with gtkmm 4)

<?xml version="1.0" encoding="UTF-8"?>
<gresources>
  <gresource prefix="/org/gtkmm/exampleapp">
    <file preprocess="xml-stripblanks">window.ui</file>
    <file preprocess="xml-stripblanks">gears_menu.ui</file>
    <file preprocess="xml-stripblanks">prefs.ui</file>
  </gresource>
</gresources>

File: prefs.ui (For use with gtkmm 4)

<?xml version="1.0" encoding="UTF-8"?>
<interface>
  <object class="GtkDialog" id="prefs_dialog">
    <property name="title" translatable="yes">Preferences</property>
    <property name="resizable">False</property>
    <property name="modal">True</property>
    <child internal-child="content_area">
      <object class="GtkBox" id="content_area">
        <child>
          <object class="GtkGrid" id="grid">
            <property name="margin-start">12</property>
            <property name="margin-end">12</property>
            <property name="margin-top">12</property>
            <property name="margin-bottom">12</property>
            <property name="row-spacing">12</property>
            <property name="column-spacing">12</property>
            <child>
              <object class="GtkLabel" id="fontlabel">
                <property name="label">_Font:</property>
                <property name="use-underline">True</property>
                <property name="mnemonic-widget">font</property>
                <property name="xalign">1</property>
                <layout>
                  <property name="column">0</property>
                  <property name="row">0</property>
                </layout>
              </object>
            </child>
            <child>
              <object class="GtkFontButton" id="font">
                <layout>
                  <property name="column">1</property>
                  <property name="row">0</property>
                </layout>
              </object>
            </child>
            <child>
              <object class="GtkLabel" id="transitionlabel">
                <property name="label">_Transition:</property>
                <property name="use-underline">True</property>
                <property name="mnemonic-widget">transition</property>
                <property name="xalign">1</property>
                <layout>
                  <property name="column">0</property>
                  <property name="row">1</property>
                </layout>
              </object>
            </child>
            <child>
              <object class="GtkComboBoxText" id="transition">
                <items>
                  <item translatable="yes" id="none">None</item>
                  <item translatable="yes" id="crossfade">Fade</item>
                  <item translatable="yes" id="slide-left-right">Slide</item>
                </items>
                <layout>
                  <property name="column">1</property>
                  <property name="row">1</property>
                </layout>
              </object>
            </child>
          </object>
        </child>
      </object>
    </child>
  </object>
</interface>

File: org.gtkmm.exampleapp.gschema.xml (For use with gtkmm 4)

<?xml version="1.0" encoding="UTF-8"?>
<schemalist>
  <schema path="/org/gtkmm/exampleapp/" id="org.gtkmm.exampleapp">
    <key name="font" type="s">
      <default>'Monospace 12'</default>
      <summary>Font</summary>
      <description>The font to be used for content.</description>
    </key>
    <key name="transition" type="s">
      <choices>
        <choice value='none'/>
        <choice value='crossfade'/>
        <choice value='slide-left-right'/>
      </choices>
      <default>'none'</default>
      <summary>Transition</summary>
      <description>The transition to use when switching tabs.</description>
    </key>
  </schema>
</schemalist>
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