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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><html> <head> <title> The GtkWidget Base Class </title> <meta name="GENERATOR" content= "Modular DocBook HTML Stylesheet Version 1.45"> <link rel="HOME" title="GTK+ / Gnome Application Development" href="ggad.html"> <link rel="UP" title="Writing a GtkWidget" href= "cha-widget.html"> <link rel="PREVIOUS" title="Writing a GtkWidget" href= "cha-widget.html"> <link rel="NEXT" title="An Example: The GtkEv Widget" href= "z147.html"> </head> <body bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink= "#840084" alink="#0000FF"> <div class="NAVHEADER"> <table width="100%" border="0" bgcolor="#ffffff" cellpadding= "1" cellspacing="0"> <tr> <th colspan="4" align="center"> <font color="#000000" size="2">GTK+ / Gnome Application Development</font> </th> </tr> <tr> <td width="25%" bgcolor="#ffffff" align="left"> <a href="cha-widget.html"><font color="#0000ff" size= "2"><b><<< Previous</b></font></a> </td> <td width="25%" colspan="2" bgcolor="#ffffff" align= "center"> <font color="#0000ff" size="2"><b><a href="ggad.html"> <font color="#0000ff" size="2"><b> Home</b></font></a></b></font> </td> <td width="25%" bgcolor="#ffffff" align="right"> <a href="z147.html"><font color="#0000ff" size="2"><b> Next >>></b></font></a> </td> </tr> </table> </div> <div class="SECT1"> <h1 class="SECT1"> <a name="Z144">The <tt class="CLASSNAME">GtkWidget</tt> Base Class</a> </h1> <p> Obviously, to subclass <tt class="CLASSNAME"> GtkWidget</tt>, you will have to be familiar with the base class. This section offers a brief tour of the <tt class= "CLASSNAME">GtkWidget</tt> class and instance structs, and some important GTK+ routines that aren't very common in everyday programming. </p> <div class="SECT2"> <h2 class="SECT2"> <a name="Z145">The <tt class="CLASSNAME">GtkWidget</tt> Instance Struct</a> </h2> <p> A <tt class="CLASSNAME">GtkWidget</tt> instance looks like this: </p> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="PROGRAMLISTING"> typedef struct _GtkWidget GtkWidget;struct _GtkWidget{ GtkObject object; guint16 private_flags; guint8 state; guint8 saved_state; gchar *name; GtkStyle *style; GtkRequisition requisition; GtkAllocation allocation; GdkWindow *window; GtkWidget *parent;}; </pre> </td> </tr> </table> <p> The <span class="STRUCTNAME">private_flags</span>, <span class="STRUCTNAME">state</span>, and <span class= "STRUCTNAME">saved_state</span> fields should all be accessed with macros, if at all. Some of these macros will come up as we discuss widget implementations. The <span class="STRUCTNAME">state</span> field stores the widget's state as described in <a href= "z57.html#SEC-WIDGETSTATES">the section called <i>Widget States</i> in the chapter called <i>GTK+ Basics</i></a>. <span class="STRUCTNAME">saved_state</span> is used to save the widget's previous state when the current state is <span class="STRUCTNAME">GTK_STATE_INSENSITIVE</span>; when the widget is re-sensitized, its original state is restored. As <a href="z57.html#SEC-WIDGETSTATES">the section called <i>Widget States</i> in the chapter called <i>GTK+ Basics</i></a> explains, the current state can be accessed with the <tt class="FUNCTION"> GTK_WIDGET_STATE()</tt> macro. </p> <p> The <span class="STRUCTNAME">name</span> of a widget is used in a <tt class="FILENAME">gtkrc</tt> file to group widgets together for customization purposes. By default, the name of a widget is the type name registered with the object system (in GTK+, this type name is always the name of the instance struct, such as <span class="STRUCTNAME"> "GtkLabel"</span>). Particular widgets can be given a different name with <tt class="FUNCTION"> gtk_widget_set_name()</tt>; for example, if you want a particular label to appear in a different font, you can give it a name like "FunkyFontLabel" and then specify a different font for that name in a <tt class="FILENAME"> gtkrc</tt> shipped with your application. </p> <p> The <span class="STRUCTNAME">requisition</span> and <span class="STRUCTNAME">allocation</span> fields store the last requested and allocated size of the widget, respectively. <a href= "sec-widgetindetail.html#SEC-SIZENEG">the section called <i>Size Negotiation</i></a> will have more to say about this. </p> <p> The <span class="STRUCTNAME">window</span> field stores the widget's <span class="STRUCTNAME">GdkWindow</span>, or the widget's parent's <span class="STRUCTNAME"> GdkWindow</span> if the widget has none. The <span class= "STRUCTNAME">parent</span> field is a pointer to the widget's parent container; it will be <span class= "STRUCTNAME">NULL</span> if the widget is not inside a container. </p> </div> <div class="SECT2"> <h2 class="SECT2"> <a name="Z146">The <tt class="CLASSNAME">GtkWidget</tt> Class Struct</a> </h2> <p> There are a truly huge number of class functions in <span class="STRUCTNAME">GtkWidgetClass</span>. Thankfully, in most cases you only have to override a few of them. Here is the code: </p> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="PROGRAMLISTING"> typedef struct _GtkWidgetClass GtkWidgetClass;struct _GtkWidgetClass{ GtkObjectClass parent_class; guint activate_signal; guint set_scroll_adjustments_signal; /* Basics */ void (* show) (GtkWidget *widget); void (* show_all) (GtkWidget *widget); void (* hide) (GtkWidget *widget); void (* hide_all) (GtkWidget *widget); void (* map) (GtkWidget *widget); void (* unmap) (GtkWidget *widget); void (* realize) (GtkWidget *widget); void (* unrealize) (GtkWidget *widget); void (* draw) (GtkWidget *widget, GdkRectangle *area); void (* draw_focus) (GtkWidget *widget); void (* draw_default) (GtkWidget *widget); void (* size_request) (GtkWidget *widget, GtkRequisition *requisition); void (* size_allocate) (GtkWidget *widget, GtkAllocation *allocation); void (* state_changed) (GtkWidget *widget, GtkStateType previous_state); void (* parent_set) (GtkWidget *widget, GtkWidget *previous_parent); void (* style_set) (GtkWidget *widget, GtkStyle *previous_style); /* Accelerators */ gint (* add_accelerator) (GtkWidget *widget, guint accel_signal_id, GtkAccelGroup *accel_group, guint accel_key, GdkModifierType accel_mods, GtkAccelFlags accel_flags); void (* remove_accelerator) (GtkWidget *widget, GtkAccelGroup *accel_group, guint accel_key,?? 快捷鍵說明
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