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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><html> <head> <title> GdkWindow </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 Basics" href="cha-gdk.html"> <link rel="NEXT" title="Visuals and Colormaps" href= "sec-gdkvisual.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-gdk.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="sec-gdkvisual.html"><font color="#0000ff" size="2"><b>Next >>></b></font></a> </td> </tr> </table> </div> <div class="SECT1"> <h1 class="SECT1"> <a name="SEC-GDKWINDOW"><span class="STRUCTNAME"> GdkWindow</span></a> </h1> <p> <span class="STRUCTNAME">GdkWindow</span> is a wrapper around Xlib's <span class="STRUCTNAME">Window</span> object. (It was discussed briefly in <a href= "z57.html#SEC-REALIZINGSHOWING">the section called <i> Realizing, Mapping, and Showing</i> in the chapter called <i>GTK+ Basics</i></a>.) A <span class="STRUCTNAME"> GdkWindow</span> represents a region on the screen. It can be shown or hidden (called <i class="FIRSTTERM">mapping</i> and <i class="FIRSTTERM">unmapping</i> the window in Xlib). You can capture events received by a <span class= "STRUCTNAME">GdkWindow</span>, draw graphics inside it, and move or resize it. <span class="STRUCTNAME"> GdkWindow</span>s are arranged in a tree structure; that is, each window can have child windows. Child windows are positioned relative to their parent window, and move when the parent moves. Child windows don't draw outside of their parent's bounds (i.e. they are clipped by the parent window). </p> <p> The tree of <span class="STRUCTNAME">GdkWindow</span>s is not specific to each application; there is a global tree of windows controlled by the X server and the window manager. The <i class="FIRSTTERM">root window</i> has no parent; all windows derive from it. All or part of it is visible as your desktop background. Each window can be owned by a different UNIX process; some windows will be created by the window manager, some will come from user applications. </p> <p> <span class="STRUCTNAME">GdkWindow</span> and <tt class= "CLASSNAME">GtkWindow</tt> are very different things; <tt class="CLASSNAME">GtkWindow</tt> is a GTK+ widget used to represent toplevel windows (toplevel windows are the highest application-controlled windows in the window hierarchy). Window managers typically create <i class= "FIRSTTERM">decorations</i> for toplevel windows; decorations include title bars, close buttons, and the like. </p> <p> It's important to understand that an X window is primarily an object on the X server. X clients receive a unique integer ID for each window, and refer to windows by ID. Thus, all window operations take place on the server; all functions that deal with X windows go across the network. </p> <p> <span class="STRUCTNAME">GdkWindow</span> is a wrapper around the integer ID returned by X. It does keep local copies of some information (such as the window's dimensions), so some GDK operations are more efficient than the corresponding Xlib operations. Still, <span class= "STRUCTNAME">GdkWindow</span> is essentially a handle for a server-side object. Many GDK objects are similar; fonts, pixmaps, cursors, and so on are also handles for server-side objects. </p> <div class="SECT2"> <h2 class="SECT2"> <a name="Z113"><span class="STRUCTNAME">GdkWindow</span> and <span class="STRUCTNAME">GtkWidget</span></a> </h2> <p> Many <span class="STRUCTNAME">GtkWidget</span> subclasses have an associated <span class="STRUCTNAME"> GdkWindow</span>. In theory, GTK+ applications could create only toplevel windows, and have all widgets draw into them. However, it would make little sense to do so; <span class="STRUCTNAME">GdkWindow</span> allows the X Window System to automatically handle many details. For example, events received from GDK are marked with the window they occurred in; GTK+ can rapidly determine which widget each event corresponds to. </p> <p> There are some widgets with no associated <span class= "STRUCTNAME">GdkWindow</span>; these are called "no window" widgets, an allusion to the <span class= "STRUCTNAME">GTK_NO_WINDOW</span> flag that marks them. (You can test this flag with the macro <tt class= "FUNCTION">GTK_WIDGET_NO_WINDOW()</tt>.) Widgets without a window render themselves into their parent container's <span class="STRUCTNAME">GdkWindow</span>. Windowless widgets are relatively small and lightweight; <tt class= "CLASSNAME">GtkLabel</tt> is the most common example. Because events are always received on a <span class= "STRUCTNAME">GdkWindow</span>, windowless widgets do not receive events. (The <tt class="CLASSNAME"> GtkEventBox</tt> container can be used if you need to capture events on a windowless widget.) </p> </div> <div class="SECT2"> <h2 class="SECT2"> <a name="SEC-GDKWINATTR"><span class="STRUCTNAME"> GdkWindow</span> Attributes</a> </h2> <p> <tt class="FUNCTION">gdk_window_new()</tt> (shown in <a href="sec-gdkwindow.html#FL-GDKWINNEW">Figure 1</a>) allows you to specify all of a window's attributes when you create it; many of them can be changed later as well. To specify a block of attributes, you pass in a <span class="STRUCTNAME">GdkWindowAttr</span> object; its contents will give you an idea what attributes a <span class="STRUCTNAME">GdkWindow</span> can have: </p> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="PROGRAMLISTING"> typedef struct _GdkWindowAttr GdkWindowAttr;struct _GdkWindowAttr{ gchar *title; gint event_mask; gint16 x, y; gint16 width; gint16 height; GdkWindowClass wclass; GdkVisual *visual; GdkColormap *colormap; GdkWindowType window_type; GdkCursor *cursor; gchar *wmclass_name; gchar *wmclass_class; gboolean override_redirect;}; </pre> </td> </tr> </table> <p> Because some of the fields in <span class="STRUCTNAME"> GdkWindowAttr</span> are optional, <tt class="FUNCTION"> gdk_window_new()</tt> is used with an <span class= "STRUCTNAME">attributes_mask</span> to specify which optional fields contain valid information (bit flags are available representing each optional field). GDK will only examine the optional fields given in the mask, so you can let the default values remain for fields you aren't interested in. <a href= "sec-gdkwindow.html#TAB-GDKWINDOWATTR">Table 1</a> summarizes them briefly; fields with no <span class= "STRUCTNAME">attributes_mask</span> flag are required and have no default value. </p> <p> <tt class="FUNCTION">gdk_window_new()</tt> is typically used in widget implementations to create the widget's <span class="STRUCTNAME">GdkWindow</span>; you will rarely use it in any other context. <tt class="FUNCTION"> gdk_window_destroy()</tt> destroys a window when you are done with it. Windows are also reference counted; be sure to read <a href="sec-gdkresourcemgmt.html">the section called <i>GDK Resource Management</i></a> for more details on this. </p> <div class="FIGURE"> <a name="FL-GDKWINNEW"></a> <div class="FUNCSYNOPSIS"> <a name="FL-GDKWINNEW.SYNOPSIS"></a> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="FUNCSYNOPSISINFO">#include <gdk/gdk.h></pre> </td> </tr> </table> <p> <code><code class="FUNCDEF">GdkWindow* <tt class= "FUNCTION">gdk_window_new</tt></code>(GdkWindow* <tt class="PARAMETER"><i>parent</i></tt>, GdkWindowAttr* <tt class="PARAMETER"><i>attributes</i></tt>, gint <tt class="PARAMETER"><i> attributes_mask</i></tt>);</code> </p> <p> <code><code class="FUNCDEF">void <tt class= "FUNCTION">gdk_window_destroy</tt></code>(GdkWindow* <tt class="PARAMETER"><i>window</i></tt>);</code> </p> </div> <p> <b>Figure 1. <span class="STRUCTNAME"> GdkWindow</span></b> </p> </div> <p> A <span class="STRUCTNAME">GdkWindow</span>'s title is only really important for toplevel windows; most window managers will place it in the titlebar. Usually you should not specify it when creating a <span class= "STRUCTNAME">GdkWindow</span>, however; instead, let your widget's users call <tt class="FUNCTION"> gtk_window_set_title()</tt>. </p> <p> The window's event mask determines which events will be received on this window; <a href="sec-gdkevent.html">the section called <i>Events</i></a> goes into more detail about events. </p> <p> The X and Y coordinates for a window are specified in pixels, relative to the parent window's origin. The origin of each window is its top left ("northwest") corner. Notice that a 16-bit signed integer is used; X windows have a maximum size of 32768 pixels. Negative values are allowed, but the window will be clipped by its parent window (only the portion inside the parent window will be visible). </p> <p> The width and height of a window are given in pixels, and are also 16-bit signed integers. </p> <p> A window's <span class="STRUCTNAME">GdkWindowClass</span> can have one of two values: </p> <ul> <li> <p> <span class="STRUCTNAME">GDK_INPUT_OUTPUT</span> is a normal window. </p> </li> <li> <p> <span class="STRUCTNAME">GDK_INPUT_ONLY</span> is a window that has a position and receives events but has no visual representation. Its children must also be input only. You can set the cursor and other attributes for an input only window, but there is no way to draw to it (it's invisible). Input-only windows are occasionally useful to capture events or change the cursor in a region that overlaps two normal windows. </p> </li> </ul> <p> A <i class="FIRSTTERM">visual</i> describes the color-handling characteristics of a display; a <i class= "FIRSTTERM">colormap</i> contains the colors you can use to draw. <a href="sec-gdkvisual.html">the section called <i>Visuals and Colormaps</i></a> gives details on visuals and colormaps. </p> <p> Windows can be one of several different types, specified by the <span class="STRUCTNAME">GdkWindowType</span> enumeration: </p> <ul> <li> <p> <span class="STRUCTNAME">GDK_WINDOW_ROOT</span> is the type of the GDK wrapper for the root window, created at initialization time. </p> </li> <li> <p> <span class="STRUCTNAME">GDK_WINDOW_TOPLEVEL</span> is a toplevel window; the <span class="STRUCTNAME"> parent</span> argument to <tt class="FUNCTION"> gdk_window_new()</tt> should be <span class= "STRUCTNAME">NULL</span> in this case. GDK automatically uses the root window as the window's parent. </p> </li> <li> <p> <span class="STRUCTNAME">GDK_WINDOW_CHILD</span> is a subwindow within a toplevel window. </p> </li> <li> <p> <span class="STRUCTNAME">GDK_WINDOW_DIALOG</span> is essentially the same as a toplevel window; its parent should be <span class="STRUCTNAME">NULL</span> and GDK will substitute the root window. A hint will be set to tell the window manager the window is a dialog; some window managers take this into account. </p> </li> <li> <p> <span class="STRUCTNAME">GDK_WINDOW_TEMP</span> is used for popup menus and the like; it's a window that will exist only briefly. It's a toplevel window, so its parent should be <span class="STRUCTNAME"> NULL</span>. These windows are always override redirect and their cursor is always the same as their parent's. So they will ignore those elements of the attributes struct. </p> </li> <li> <p> <span class="STRUCTNAME">GDK_WINDOW_PIXMAP</span> is not a window at all; <span class="STRUCTNAME"> GdkPixmap</span> and <span class="STRUCTNAME"> GdkWindow</span> are almost always treated the same way, so GDK uses the same struct to represent them. They can both be considered kinds of <span class= "STRUCTNAME">GdkDrawable</span>. See <a href= "sec-gdkdrawable.html">the section called <i> Drawables and Pixmaps</i></a>. </p> </li> <li> <p>?? 快捷鍵說明
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