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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><html> <head> <title> GtkStyle and Themes </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="GDK Basics" href="cha-gdk.html"> <link rel="PREVIOUS" title="GDK Resource Management" href= "sec-gdkresourcemgmt.html"> <link rel="NEXT" title="Writing a GtkWidget" href= "cha-widget.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="sec-gdkresourcemgmt.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="cha-widget.html"><font color="#0000ff" size= "2"><b>Next >>></b></font></a> </td> </tr> </table> </div> <div class="SECT1"> <h1 class="SECT1"> <a name="SEC-STYLE"><span class="STRUCTNAME"> GtkStyle</span> and Themes</a> </h1> <p> <span class="STRUCTNAME">GtkStyle</span> is not part of GDK, but it is an important abstraction layer between GTK+ and GDK that allows users to customize how widgets are rendered. Instead of drawing with GDK directly, widgets should prefer GDK resources from a <span class= "STRUCTNAME">GtkStyle</span>, and special drawing functions provided in <tt class="FILENAME">gtk/gtkstyle.h</tt>. Often there is no appropriate function, but when there is it should be used. </p> <p> A <span class="STRUCTNAME">GtkStyle</span> stores GDK resources to be used when drawing widgets. Styles allow widgets to share these resources, reducing overhead; they also permit users to customize GTK+'s appearance. Here is the <span class="STRUCTNAME">GtkStyle</span> struct: </p> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="PROGRAMLISTING"> typedef struct _GtkStyle GtkStyle;struct _GtkStyle{ GtkStyleClass *klass; GdkColor fg[5]; GdkColor bg[5]; GdkColor light[5]; GdkColor dark[5]; GdkColor mid[5]; GdkColor text[5]; GdkColor base[5]; GdkColor black; GdkColor white; GdkFont *font; GdkGC *fg_gc[5]; GdkGC *bg_gc[5]; GdkGC *light_gc[5]; GdkGC *dark_gc[5]; GdkGC *mid_gc[5]; GdkGC *text_gc[5]; GdkGC *base_gc[5]; GdkGC *black_gc; GdkGC *white_gc; GdkPixmap *bg_pixmap[5]; /* private */ gint ref_count; gint attach_count; gint depth; GdkColormap *colormap; GtkThemeEngine *engine; gpointer engine_data; GtkRcStyle *rc_style; GSList *styles;}; </pre> </td> </tr> </table> <p> The private fields should be ignored. The public fields contain GDK resources for widget rendering. The first group of fields contains arrays of colors; these arrays are indexed by the widget state enumeration (<span class= "STRUCTNAME">GTK_STATE_ACTIVE</span>, etc.). A widget might use <span class="STRUCTNAME"> widget->style->fg[GTK_STATE_NORMAL]</span> to render text, for example. Each widget has an associated style, stored in the <span class="STRUCTNAME">style</span> field of <tt class="CLASSNAME">GtkWidget</tt>. </p> <p> Widgets should use the font stored in their associated <span class="STRUCTNAME">GtkStyle</span>; they should use the style's graphics contexts when drawing in the style's colors. </p> <p> <span class="STRUCTNAME">GtkStyle</span> also contains a virtual table, <span class="STRUCTNAME"> GtkStyleClass</span>, which can be implemented by a dynamically-loaded theme engine. The virtual table is quite large, so it isn't reproduced here. Have a look at <tt class="FILENAME">gtk/gtkstyle.h</tt>. </p> <p> <tt class="FILENAME">gtk/gtkstyle.h</tt> contains drawing functions that use a style's virtual table to draw various GUI elements. There are two variants of each drawing function. One variant, prefixed with <span class= "STRUCTNAME">gtk_draw_</span>, renders to any drawable; the other variant, prefixed with <span class="STRUCTNAME"> gtk_paint_</span>, renders part of a widget. For example, <tt class="FUNCTION">gtk_draw_shadow()</tt> looks like this: </p> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="PROGRAMLISTING"> void gtk_draw_shadow (GtkStyle *style, GdkWindow *window, GtkStateType state_type, GtkShadowType shadow_type, gint x, gint y, gint width, gint height); </pre> </td> </tr> </table> <p> While <tt class="FUNCTION">gtk_paint_shadow()</tt> adds <span class="STRUCTNAME">area</span>, <span class= "STRUCTNAME">widget</span>, and <span class="STRUCTNAME"> detail</span> arguments: </p> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="PROGRAMLISTING"> void gtk_paint_shadow (GtkStyle *style, GdkWindow *window, GtkStateType state_type, GtkShadowType shadow_type, GdkRectangle *area, GtkWidget *widget, gchar *detail, gint x, gint y, gint width, gint height); </pre> </td> </tr> </table> <p> Each of these corresponds to the <span class="STRUCTNAME"> draw_shadow</span> member in <span class="STRUCTNAME"> GtkStyleClass</span>. </p> <p> All <span class="STRUCTNAME">gtk_paint_</span> functions add the same three arguments to their <span class= "STRUCTNAME">gtk_draw_</span> counterparts; the <span class="STRUCTNAME">area</span> argument is a clipping rectangle, the <span class="STRUCTNAME">widget</span> argument is the widget being drawn to, and the <span class= "STRUCTNAME">detail</span> argument is a hint used by theme engines. Here's a call to <tt class="FUNCTION"> gtk_paint_shadow()</tt> from the <tt class="CLASSNAME"> GtkEntry</tt> source code, for example: </p> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="PROGRAMLISTING"> gtk_paint_shadow (widget->style, widget->window, GTK_STATE_NORMAL, GTK_SHADOW_IN, NULL, widget, "entry", x, y, width, height); </pre> </td> </tr> </table> <p> Here the <span class="STRUCTNAME">area</span> argument is <span class="STRUCTNAME">NULL</span>, specifying that no clipping should be used. </p> <p> Because there are a couple dozen functions in <span class= "STRUCTNAME">GtkStyleClass</span>, and there are numerous examples in the GTK+ source code, this book won't describe them in detail. When writing your own widgets, simply locate a GTK+ widget that draws a similar graphical element, and use the same <span class="STRUCTNAME"> gtk_paint_</span> function it uses. </p> </div> <div class="NAVFOOTER"> <br> <br> <table width="100%" border="0" bgcolor="#ffffff" cellpadding= "1" cellspacing="0"> <tr> <td width="25%" bgcolor="#ffffff" align="left"> <a href="sec-gdkresourcemgmt.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="cha-widget.html"><font color="#0000ff" size= "2"><b>Next >>></b></font></a> </td> </tr> <tr> <td colspan="2" align="left"> <font color="#000000" size="2"><b>GDK Resource Management</b></font> </td> <td colspan="2" align="right"> <font color="#000000" size="2"><b>Writing a <tt class= "CLASSNAME">GtkWidget</tt></b></font> </td> </tr> </table> </div> </body></html>⌨️ 快捷键说明
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