一个偏好对话框

一个典型的应用程序应该有一些偏好设置，在每次打开时都能被记住。即使是为这个小范例程序，我们也将想改变正文的字体。

我们将用GSettings 来保存偏好设置，GSettings 需要一个描述我们设置的模式。

  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <schemalist>
  3.   <schema path="/org/gtk/exampleapp/" id="org.gtk.exampleapp">
  4.     <key name="font" type="s">
  5.       <default>'Monospace 12'</default>
  6.       <summary>Font</summary>
  7.       <description>The font to be used for content.</description>
  8.     </key>
  9.     <key name="transition" type="s">
  10.       <choices>
  11.         <choice value='none'/>
  12.         <choice value='crossfade'/>
  13.         <choice value='slide-left-right'/>
  14.       </choices>
  15.       <default>'none'</default>
  16.       <summary>Transition</summary>
  17.       <description>The transition to use when switching tabs.</description>
  18.     </key>
  19.   </schema>
  20. </schemalist>

当我们在应用程序中使用这个模式之前，我们需要从GSettings 中将这编译进二进制文件。GIO 提供macros来在工程中做这件事。

接着，我们需要连接settings 和我们的目标部件。一个简便的方法是用GSettings bind 函数绑定设定关键词和目标属性，就像我们这里为转换设置做的。

  1. ...
  3. static void
  4. example_app_window_init (ExampleAppWindow *win)
  5. {
  6.   ExampleAppWindowPrivate *priv;
  8.   priv = example_app_window_get_instance_private (win);
  9.   gtk_widget_init_template (GTK_WIDGET (win));
  10.   priv->settings = g_settings_new ("org.gtk.exampleapp");
  12.   g_settings_bind (priv->settings, "transition",
  13.                    priv->stack, "transition-type",
  14.                    G_SETTINGS_BIND_DEFAULT);
  15. }
  17. ...

(full source)

这个连接字体设置的代码有点儿复杂，因为我们没有对应的简单的目标属性，我们本没打算这么做。

至此，如果我们改变一个设置，程序将会有反应，比如用gsettings 命令行工具。当然，我们希望应用程序提供一个偏好对话框。所以干吧，我们的偏好对话框是GtkDialog 的子类，我们将使用我们已经用过的技术：templates,private structs, settingbindings。

让我们从模板开始。

  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <interface>
  3.   <!-- interface-requires gtk+ 3.8 -->
  4.   <template class="ExampleAppPrefs" parent="GtkDialog">
  5.     <property name="title" translatable="yes">Preferences</property>
  6.     <property name="resizable">False</property>
  7.     <property name="modal">True</property>
  8.     <child internal-child="vbox">
  9.       <object class="GtkBox" id="vbox">
  10.         <child>
  11.           <object class="GtkGrid" id="grid">
  12.             <property name="visible">True</property>
  13.             <property name="margin">6</property>
  14.             <property name="row-spacing">12</property>
  15.             <property name="column-spacing">6</property>
  16.             <child>
  17.               <object class="GtkLabel" id="fontlabel">
  18.                 <property name="visible">True</property>
  19.                 <property name="label">_Font:</property>
  20.                 <property name="use-underline">True</property>
  21.                 <property name="mnemonic-widget">font</property>
  22.                 <property name="xalign">1</property>
  23.               </object>
  24.               <packing>
  25.                 <property name="left-attach">0</property>
  26.                 <property name="top-attach">0</property>
  27.               </packing>
  28.             </child>
  29.             <child>
  30.               <object class="GtkFontButton" id="font">
  31.                 <property name="visible">True</property>
  32.               </object>
  33.               <packing>
  34.                 <property name="left-attach">1</property>
  35.                 <property name="top-attach">0</property>
  36.               </packing>
  37.             </child>
  38.             <child>
  39.               <object class="GtkLabel" id="transitionlabel">
  40.                 <property name="visible">True</property>
  41.                 <property name="label">_Transition:</property>
  42.                 <property name="use-underline">True</property>
  43.                 <property name="mnemonic-widget">transition</property>
  44.                 <property name="xalign">1</property>
  45.               </object>
  46.               <packing>
  47.                 <property name="left-attach">0</property>
  48.                 <property name="top-attach">1</property>
  49.               </packing>
  50.             </child>
  51.             <child>
  52.               <object class="GtkComboBoxText" id="transition">
  53.                 <property name="visible">True</property>
  54.                 <items>
  55.                   <item translatable="yes" id="none">None</item>
  56.                   <item translatable="yes" id="crossfade">Fade</item>
  57.                   <item translatable="yes" id="slide-left-right">Slide</item>
  58.                 </items>
  59.               </object>
  60.               <packing>
  61.                 <property name="left-attach">1</property>
  62.                 <property name="top-attach">1</property>
  63.               </packing>
  64.             </child>
  65.           </object>
  66.         </child>
  67.       </object>
  68.     </child>
  69.   </template>
  70. </interface>

接下来是对话框子类。

  1. #include <gtk/gtk.h>
  3. #include "exampleapp.h"
  4. #include "exampleappwin.h"
  5. #include "exampleappprefs.h"
  7. struct _ExampleAppPrefs
  8. {
  9.   GtkDialog parent;
  10. };
  12. struct _ExampleAppPrefsClass
  13. {
  14.   GtkDialogClass parent_class;
  15. };
  17. typedef struct _ExampleAppPrefsPrivate ExampleAppPrefsPrivate;
  19. struct _ExampleAppPrefsPrivate
  20. {
  21.   GSettings *settings;
  22.   GtkWidget *font;
  23.   GtkWidget *transition;
  24. };
  26. G_DEFINE_TYPE_WITH_PRIVATE(ExampleAppPrefs, example_app_prefs, GTK_TYPE_DIALOG)
  28. static void
  29. example_app_prefs_init (ExampleAppPrefs *prefs)
  30. {
  31.   ExampleAppPrefsPrivate *priv;
  33.   priv = example_app_prefs_get_instance_private (prefs);
  34.   gtk_widget_init_template (GTK_WIDGET (prefs));
  35.   priv->settings = g_settings_new ("org.gtk.exampleapp");
  37.   g_settings_bind (priv->settings, "font",
  38.                    priv->font, "font",
  39.                    G_SETTINGS_BIND_DEFAULT);
  40.   g_settings_bind (priv->settings, "transition",
  41.                    priv->transition, "active-id",
  42.                    G_SETTINGS_BIND_DEFAULT);
  43. }
  45. static void
  46. example_app_prefs_dispose (GObject *object)
  47. {
  48.   ExampleAppPrefsPrivate *priv;
  50.   priv = example_app_prefs_get_instance_private (EXAMPLE_APP_PREFS (object));
  51.   g_clear_object (&priv->settings);
  53.   G_OBJECT_CLASS (example_app_prefs_parent_class)->dispose (object);
  54. }
  56. static void
  57. example_app_prefs_class_init (ExampleAppPrefsClass *class)
  58. {
  59.   G_OBJECT_CLASS (class)->dispose = example_app_prefs_dispose;
  61.   gtk_widget_class_set_template_from_resource (GTK_WIDGET_CLASS (class),
  62.                                                "/org/gtk/exampleapp/prefs.ui");
  63.   gtk_widget_class_bind_template_child_private (GTK_WIDGET_CLASS (class), ExampleAppPrefs, font);
  64.   gtk_widget_class_bind_template_child_private (GTK_WIDGET_CLASS (class), ExampleAppPrefs, transition);
  65. }
  67. ExampleAppPrefs *
  68. example_app_prefs_new (ExampleAppWindow *win)
  69. {
  70.   return g_object_new (EXAMPLE_APP_PREFS_TYPE, "transient-for", win, "use-header-bar", TRUE, NULL);
  71. }

现在我们再看preferences_activated()函数，使它打开一个偏好对话框。

  1. ...
  3. static void
  4. preferences_activated (GSimpleAction *action,
  5.                        GVariant      *parameter,
  6.                        gpointer       app)
  7. {
  8.   ExampleAppPrefs *prefs;
  9.   GtkWindow *win;
  11.   win = gtk_application_get_active_window (GTK_APPLICATION (app));
  12.   prefs = example_app_prefs_new (EXAMPLE_APP_WINDOW (win));
  13.   gtk_window_present (GTK_WINDOW (prefs));
  14. }
  16. ...

(full source)

完成所有这些工作后，我们的应用程序现在可以像这样显示一个偏好对话框：

getting-started-app6.png