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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><html> <head> <title> Standard Canvas Item Reference </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="GnomeCanvas" href="cha-canvas.html"> <link rel="PREVIOUS" title="Using the Canvas" href="z177.html"> <link rel="NEXT" title="Writing a GnomeCanvasItem" href= "cha-canvasitem.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="z177.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-canvasitem.html"><font color="#0000ff" size="2"><b>Next >>></b></font></a> </td> </tr> </table> </div> <div class="SECT1"> <h1 class="SECT1"> <a name="SEC-ITEMREFERENCE">Standard Canvas Item Reference</a> </h1> <p> This section describes each of the canvas items that come with Gnome, giving a table of arguments and describing any non-obvious arguments. </p> <div class="SECT2"> <h2 class="SECT2"> <a name="SEC-CANVASRE">Rectangle and Ellipse Items</a> </h2> <p> The <span class="STRUCTNAME">GnomeCanvasRect</span> and <span class="STRUCTNAME">GnomeCanvasEllipse</span> canvas items share exactly the same interface, via a <span class="STRUCTNAME">GnomeCanvasRE</span> base class. Their shape is given as a bounding box: a top left coordinate (x1, y1) and a bottom right coordinate (x2, y2). The rectangle item matches the shape of the bounding box; the ellipse is inscribed in the bounding box, touching the center of each side. Rectangles and ellipses can be filled or simply an outline. If they are only an outline, they are considered to be "hollow"; that is, the transparent area inside the shape is not part of the canvas item and events that occur in that area will not be relayed to the item. </p> <p> <span class="STRUCTNAME">GnomeCanvasRE</span> does not behave gracefully if you give the coordinates in the wrong order. That is, x2 must be greater than x1, and y2 must be greater than y1; otherwise <span class= "STRUCTNAME">GnomeCanvasRE</span> gets confused. </p> <div class="TABLE"> <a name="TAB-GNOME-CANVAS-RE"></a> <p> <b>Table 1. <span class="STRUCTNAME"> GnomeCanvasRE</span> Arguments</b> </p> <table border="1" bgcolor="#E0E0E0" cellspacing="0" cellpadding="4" class="CALSTABLE"> <tr> <th align="LEFT" valign="TOP"> Name </th> <th align="LEFT" valign="TOP"> Type </th> <th align="LEFT" valign="TOP"> Read/Write </th> <th align="LEFT" valign="TOP"> Description </th> </tr> <tr> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">x1</span> </td> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">double</span> </td> <td align="LEFT" valign="TOP"> Both </td> <td align="LEFT" valign="TOP"> Leftmost coordinate </td> </tr> <tr> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">y1</span> </td> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">double</span> </td> <td align="LEFT" valign="TOP"> Both </td> <td align="LEFT" valign="TOP"> Topmost coordinate </td> </tr> <tr> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">x2</span> </td> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">double</span> </td> <td align="LEFT" valign="TOP"> Both </td> <td align="LEFT" valign="TOP"> Rightmost coordinate </td> </tr> <tr> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">y2</span> </td> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">double</span> </td> <td align="LEFT" valign="TOP"> Both </td> <td align="LEFT" valign="TOP"> Bottommost coordinate </td> </tr> <tr> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">fill_color</span> </td> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">gchar*</span> </td> <td align="LEFT" valign="TOP"> Write-only </td> <td align="LEFT" valign="TOP"> Fill color; string for <tt class="FUNCTION"> gdk_color_parse()</tt>, or <span class= "STRUCTNAME">NULL</span> for transparent </td> </tr> <tr> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">fill_color_gdk</span> </td> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">GdkColor*</span> </td> <td align="LEFT" valign="TOP"> Both </td> <td align="LEFT" valign="TOP"> Fill color; specified as already-allocated <span class="STRUCTNAME">GdkColor</span> </td> </tr> <tr> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">fill_color_rgba</span> </td> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">guint32</span> </td> <td align="LEFT" valign="TOP"> Both </td> <td align="LEFT" valign="TOP"> Fill color; specified as 32-bit value packing red, green, blue, and alpha into bytes 1, 2, 3, and 4; alpha of 255 is opaque, 0 is invisible </td> </tr> <tr> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">outline_color</span> </td> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">gchar*</span> </td> <td align="LEFT" valign="TOP"> Write-only </td> <td align="LEFT" valign="TOP"> Outline color; string for <tt class="FUNCTION"> gdk_color_parse</tt>, or <span class="STRUCTNAME"> NULL</span> for transparent </td> </tr> <tr> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">outline_color_gdk</span> </td> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">GdkColor*</span> </td> <td align="LEFT" valign="TOP"> Both </td> <td align="LEFT" valign="TOP"> Outline color; specified as already-allocated <span class="STRUCTNAME">GdkColor</span> </td> </tr> <tr> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">outline_color_rgba</span> </td> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">guint32</span> </td> <td align="LEFT" valign="TOP"> Both </td> <td align="LEFT" valign="TOP"> Outline color; specified as 32-bit value packing red, green, blue, and alpha into bytes 1, 2, 3, and 4; alpha of 255 is opaque, 0 is invisible </td> </tr> <tr> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">fill_stipple</span> </td> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">GdkBitmap*</span> </td> <td align="LEFT" valign="TOP"> Both </td> <td align="LEFT" valign="TOP"> Stipple to use when drawing fill; GDK mode only </td> </tr> <tr> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">outline_stipple</span> </td> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">GdkBitmap*</span> </td> <td align="LEFT" valign="TOP"> Both </td> <td align="LEFT" valign="TOP"> Stipple to use when drawing outline; GDK mode only </td> </tr> <tr> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">width_pixels</span> </td> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">guint</span> </td> <td align="LEFT" valign="TOP"> Write-only </td> <td align="LEFT" valign="TOP"> Width of the outline, in pixels (independent of zoom) </td> </tr> <tr> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">width_units</span> </td> <td align="LEFT" valign="TOP"> <span class="STRUCTNAME">double</span> </td> <td align="LEFT" valign="TOP"> Write-only </td> <td align="LEFT" valign="TOP"> Width of the outline, in canvas units; pixel width changes with zoom factor (pixels per unit) </td> </tr> </table> </div> </div> <div class="SECT2"> <h2 class="SECT2"> <a name="SEC-CANVASLINE">Line Item</a> </h2> <p> <span class="STRUCTNAME">GnomeCanvasLine</span> represents one or more line segments joined at their endpoints. You can use it to represent an unfilled polygon as well. <span class="STRUCTNAME"> GnomeCanvasPolygon</span> is used for filled polygons. </p> <p> A line is specified using a <span class="STRUCTNAME"> GnomeCanvasPoints</span> structure, which looks like this: </p> <table border="0" bgcolor="#E0E0E0" width="100%"> <tr> <td><pre class="PROGRAMLISTING"> typedef struct { int num_points; double *coords; int ref_count;} GnomeCanvasPoints; </pre> </td> </tr> </table> <p> The <span class="STRUCTNAME">coords</span> field contains an array of points, alternating X and Y coordinates. You fill the <span class="STRUCTNAME">coords</span> array directly, after creating a <span class="STRUCTNAME"> GnomeCanvasPoints</span> with <tt class="FUNCTION"> gnome_canvas_points_new()</tt>; the structure should be destroyed with <tt class="FUNCTION"> gnome_canvas_points_unref()</tt>. </p> <p> Lines can have arrowheads on either end; the arrowhead shape is specified via three parameters, arbitrarily named A, B, and C. Parameter A (specified with the <span class="STRUCTNAME">arrow_shape_a</span> argument) specifies the distance from the base of the arrowhead to the tip. B specifies the distance from the tip of the arrowhead to one of the trailing points; C specifies the distance of a trailing point from the outer edge of the line. </p> <div class="TABLE"> <a name="TAB-GNOME-CANVAS-LINE"></a> <p> <b>Table 2. <span class="STRUCTNAME"> GnomeCanvasLine</span> Arguments</b> </p> <table border="1" bgcolor="#E0E0E0" cellspacing="0" cellpadding="4" class="CALSTABLE"> <tr> <th align="LEFT" valign="TOP"> Name </th> <th align="LEFT" valign="TOP"> Type </th> <th align="LEFT" valign="TOP"> Read/Write </th> <th align="LEFT" valign="TOP"> Description </th> </tr> <tr>?? 快捷鍵說(shuō)明
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