~ubuntu-branches/ubuntu/breezy/libgnomecanvas/breezy

<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>GnomeCanvas</title><meta name="generator" content="DocBook XSL Stylesheets V1.65.1"><link rel="home" href="index.html" title="GNOME Canvas Library Reference Manual"><link rel="up" href="ch02.html" title="GNOME Canvas Library (libgnomecanvas)"><link rel="previous" href="ch02.html" title="GNOME Canvas Library (libgnomecanvas)"><link rel="next" href="GnomeCanvasBpath.html" title="GnomeCanvasBpath"><link rel="chapter" href="ch01.html" title="Object Hierarchy"><link rel="chapter" href="ch02.html" title="GNOME Canvas Library (libgnomecanvas)"><link rel="refentry" href="GnomeCanvas.html" title="GnomeCanvas"><link rel="refentry" href="GnomeCanvasBpath.html" title="GnomeCanvasBpath"><link rel="refentry" href="GnomeCanvasClipgroup.html" title="GnomeCanvasClipgroup"><link rel="refentry" href="GnomeCanvasEllipse.html" title="GnomeCanvasEllipse"><link rel="refentry" href="GnomeCanvasGroup.html" title="GnomeCanvasGroup"><link rel="refentry" href="GnomeCanvasItem.html" title="GnomeCanvasItem"><link rel="refentry" href="GnomeCanvasLine.html" title="GnomeCanvasLine"><link rel="refentry" href="GnomeCanvasPixbuf.html" title="GnomeCanvasPixbuf"><link rel="refentry" href="GnomeCanvasPolygon.html" title="GnomeCanvasPolygon"><link rel="refentry" href="GnomeCanvasRE.html" title="GnomeCanvasRE"><link rel="refentry" href="GnomeCanvasRect.html" title="GnomeCanvasRect"><link rel="refentry" href="GnomeCanvasRichText.html" title="GnomeCanvasRichText"><link rel="refentry" href="GnomeCanvasShape.html" title="GnomeCanvasShape"><link rel="refentry" href="GnomeCanvasText.html" title="GnomeCanvasText"><link rel="refentry" href="GnomeCanvasWidget.html" title="GnomeCanvasWidget"><link rel="refentry" href="libgnomecanvas-gnome-canvas-path-def.html" title="gnome-canvas-path-def"><link rel="refentry" href="libgnomecanvas-gnome-canvas-util.html" title="gnome-canvas-util"><link rel="section" href="GnomeCanvas.html#id2971479" title="Object Hierarchy"><link rel="section" href="GnomeCanvas.html#id2971528" title="Implemented Interfaces"><link rel="section" href="GnomeCanvas.html#id2971547" title="Properties"><link rel="section" href="GnomeCanvas.html#id2971576" title="Signal Prototypes"><link rel="section" href="GnomeCanvas.html#id2971700" title="Description"><link rel="section" href="GnomeCanvas.html#id2972047" title="Details"><link rel="section" href="GnomeCanvas.html#id2975089" title="Properties"><link rel="section" href="GnomeCanvas.html#id2975161" title="Signals"><meta name="generator" content="GTK-Doc V1.2 (XML mode)"><link rel="stylesheet" href="style.css" type="text/css"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><table class="navigation" width="100%" summary="Navigation header" cellpadding="2" cellspacing="2"><tr valign="middle"><td><a accesskey="p" href="ch02.html"><img src="left.png" width="24" height="24" border="0" alt="Prev"></a></td><td><a accesskey="u" href="ch02.html"><img src="up.png" width="24" height="24" border="0" alt="Up"></a></td><td><a accesskey="h" href="index.html"><img src="home.png" width="24" height="24" border="0" alt="Home"></a></td><th width="100%" align="center">GNOME Canvas Library Reference Manual</th><td><a accesskey="n" href="GnomeCanvasBpath.html"><img src="right.png" width="24" height="24" border="0" alt="Next"></a></td></tr></table><div class="refentry" lang="en"><a name="GnomeCanvas"></a><div class="titlepage"><div></div><div></div></div><div class="refnamediv"><h2><span class="refentrytitle">GnomeCanvas</span></h2><p>GnomeCanvas — Main canvas widget</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><pre class="synopsis">

#include <libgnomecanvas/libgnomecanvas.h>

struct <a href="GnomeCanvas.html#GnomeCanvas-struct">GnomeCanvas</a>;

#define <a href="GnomeCanvas.html#GNOME-CANVAS-EPSILON-CAPS">GNOME_CANVAS_EPSILON</a>

#define <a href="GnomeCanvas.html#GNOME-CANVAS-COLOR-CAPS">GNOME_CANVAS_COLOR</a> (r, g, b)

#define <a href="GnomeCanvas.html#GNOME-CANVAS-COLOR-A-CAPS">GNOME_CANVAS_COLOR_A</a> (r, g, b, a)

struct <a href="GnomeCanvas.html#GnomeCanvasBuf">GnomeCanvasBuf</a>;

GtkWidget* <a href="GnomeCanvas.html#gnome-canvas-new">gnome_canvas_new</a> (void);

GtkWidget* <a href="GnomeCanvas.html#gnome-canvas-new-aa">gnome_canvas_new_aa</a> (void);

<a href="GnomeCanvasGroup.html" title="GnomeCanvasGroup">GnomeCanvasGroup</a>* <a href="GnomeCanvas.html#gnome-canvas-root">gnome_canvas_root</a> (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas);

void <a href="GnomeCanvas.html#gnome-canvas-set-scroll-region">gnome_canvas_set_scroll_region</a> (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

double x1,

double y1,

double x2,

double y2);

void <a href="GnomeCanvas.html#gnome-canvas-get-scroll-region">gnome_canvas_get_scroll_region</a> (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

double *x1,

double *y1,

double *x2,

double *y2);

void <a href="GnomeCanvas.html#gnome-canvas-set-center-scroll-region">gnome_canvas_set_center_scroll_region</a>

(<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

gboolean center_scroll_region);

gboolean <a href="GnomeCanvas.html#gnome-canvas-get-center-scroll-region">gnome_canvas_get_center_scroll_region</a>

(<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas);

void <a href="GnomeCanvas.html#gnome-canvas-set-pixels-per-unit">gnome_canvas_set_pixels_per_unit</a>

(<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

double n);

void <a href="GnomeCanvas.html#gnome-canvas-scroll-to">gnome_canvas_scroll_to</a> (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

int cx,

int cy);

void <a href="GnomeCanvas.html#gnome-canvas-get-scroll-offsets">gnome_canvas_get_scroll_offsets</a> (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

int *cx,

int *cy);

void <a href="GnomeCanvas.html#gnome-canvas-update-now">gnome_canvas_update_now</a> (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas);

<a href="GnomeCanvasItem.html" title="GnomeCanvasItem">GnomeCanvasItem</a>* <a href="GnomeCanvas.html#gnome-canvas-get-item-at">gnome_canvas_get_item_at</a> (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

double x,

double y);

void <a href="GnomeCanvas.html#gnome-canvas-request-redraw-uta">gnome_canvas_request_redraw_uta</a> (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

ArtUta *uta);

void <a href="GnomeCanvas.html#gnome-canvas-request-redraw">gnome_canvas_request_redraw</a> (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

int x1,

int y1,

int x2,

int y2);

void <a href="GnomeCanvas.html#gnome-canvas-w2c-affine">gnome_canvas_w2c_affine</a> (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

double affine[6]);

void <a href="GnomeCanvas.html#gnome-canvas-w2c">gnome_canvas_w2c</a> (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

double wx,

double wy,

int *cx,

int *cy);

void <a href="GnomeCanvas.html#gnome-canvas-w2c-d">gnome_canvas_w2c_d</a> (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

double wx,

double wy,

double *cx,

double *cy);

void <a href="GnomeCanvas.html#gnome-canvas-c2w">gnome_canvas_c2w</a> (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

int cx,

int cy,

double *wx,

double *wy);

void <a href="GnomeCanvas.html#gnome-canvas-window-to-world">gnome_canvas_window_to_world</a> (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

double winx,

double winy,

double *worldx,

double *worldy);

void <a href="GnomeCanvas.html#gnome-canvas-world-to-window">gnome_canvas_world_to_window</a> (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

double worldx,

double worldy,

double *winx,

double *winy);

int <a href="GnomeCanvas.html#gnome-canvas-get-color">gnome_canvas_get_color</a> (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

const char *spec,

GdkColor *color);

gulong <a href="GnomeCanvas.html#gnome-canvas-get-color-pixel">gnome_canvas_get_color_pixel</a> (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

guint rgba);

void <a href="GnomeCanvas.html#gnome-canvas-set-stipple-origin">gnome_canvas_set_stipple_origin</a> (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

GdkGC *gc);

void <a href="GnomeCanvas.html#gnome-canvas-set-dither">gnome_canvas_set_dither</a> (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

GdkRgbDither dither);

GdkRgbDither <a href="GnomeCanvas.html#gnome-canvas-get-dither">gnome_canvas_get_dither</a> (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas);

</pre></div><div class="refsect1" lang="en"><a name="id2971479"></a><h2>Object Hierarchy</h2><pre class="synopsis">

GObject

+----GtkObject

+----GtkWidget

+----GtkContainer

+----GtkLayout

+----GnomeCanvas

</pre></div><div class="refsect1" lang="en"><a name="id2971528"></a><h2>Implemented Interfaces</h2><p>

GnomeCanvas implements

AtkImplementorIface.</p></div><div class="refsect1" lang="en"><a name="id2971547"></a><h2>Properties</h2><pre class="synopsis">

"<a href="GnomeCanvas.html#GnomeCanvas--aa">aa</a>" gboolean : Read / Write / Construct Only

100

</pre></div><div class="refsect1" lang="en"><a name="id2971576"></a><h2>Signal Prototypes</h2><pre class="synopsis">

101

102

"<a href="GnomeCanvas.html#GnomeCanvas-draw-background">draw-background</a>"

103

void user_function (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

104

GdkDrawable *arg1,

105

gint arg2,

106

gint arg3,

107

gint arg4,

108

gint arg5,

109

gpointer user_data);

110

"<a href="GnomeCanvas.html#GnomeCanvas-render-background">render-background</a>"

111

void user_function (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

112

gpointer arg1,

113

gpointer user_data);

114

</pre></div><div class="refsect1" lang="en"><a name="id2971700"></a><h2>Description</h2><p>

115

The <a href="GnomeCanvas.html" title="GnomeCanvas"><span class="type">GnomeCanvas</span></a> is an engine for structured graphics that offers a

116

rich imaging model, high performance rendering, and a powerful,

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high level API. It offers a choice of two rendering back-ends,

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one based on Xlib for extremely fast display, and another based on

119

Libart, a sophisticated, antialiased, alpha-compositing engine.

120

This widget can be used for flexible display of graphics and for

121

creating interactive user interface elements.

122

</p><p>

123

To create a new <a href="GnomeCanvas.html" title="GnomeCanvas"><span class="type">GnomeCanvas</span></a> widget call <a href="GnomeCanvas.html#gnome-canvas-new"><tt class="function">gnome_canvas_new()</tt></a> or

124

<a href="GnomeCanvas.html#gnome-canvas-new-aa"><tt class="function">gnome_canvas_new_aa()</tt></a> for an anti-aliased mode canvas.

125

</p><p>

126

A <a href="GnomeCanvas.html" title="GnomeCanvas"><span class="type">GnomeCanvas</span></a> widget contains one or more <a href="GnomeCanvasItem.html" title="GnomeCanvasItem"><span class="type">GnomeCanvasItem</span></a>

127

objects. Items consist of graphing elements like lines, ellipses,

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polygons, images, text, and curves. These items are organized using

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<a href="GnomeCanvasGroup.html" title="GnomeCanvasGroup"><span class="type">GnomeCanvasGroup</span></a> objects, which are themselves derived from

130

<a href="GnomeCanvasItem.html" title="GnomeCanvasItem"><span class="type">GnomeCanvasItem</span></a>. Since a group is an item it can be contained within

131

other groups, forming a tree of canvas items. Certain operations, like

132

translating and scaling, can be performed on all items in a group.

133

</p><p>

134

There is a special root group created by a <a href="GnomeCanvas.html" title="GnomeCanvas"><span class="type">GnomeCanvas</span></a>. This is the top

135

level group under which all items in a canvas are contained. To get the root

136

group from a canvas call <a href="GnomeCanvas.html#gnome-canvas-root"><tt class="function">gnome_canvas_root()</tt></a>.

137

</p><p>

138

There are several different coordinate systems used by <a href="GnomeCanvas.html" title="GnomeCanvas"><span class="type">GnomeCanvas</span></a>

139

widgets. The primary system is a logical, abstract coordinate space

140

called world coordinates. World coordinates are expressed as unbounded

141

double floating point numbers. When it comes to rendering to a screen

142

the canvas pixel coordinate system (also referred to as just canvas

143

coordinates) is used. This system uses integers to specify screen

144

pixel positions. A user defined scaling factor and offset are used to

145

convert between world coordinates and canvas coordinates. Each item in

146

a canvas has its own coordinate system called item coordinates. This

147

system is specified in world coordinates but they are relative to an

148

item (0.0, 0.0 would be the top left corner of the item). The final

149

coordinate system of interest is window coordinates. These are like

150

canvas coordinates but are offsets from within a window a canvas is

151

displayed in. This last system is rarely used, but is useful when

152

manually handling GDK events (such as drag and drop) which are

153

specified in window coordinates (the events processed by the canvas

154

are already converted for you).

155

</p><p>

156

Along with different coordinate systems comes functions to convert

157

between them. <a href="GnomeCanvas.html#gnome-canvas-w2c"><tt class="function">gnome_canvas_w2c()</tt></a> converts world to canvas pixel

158

coordinates and <a href="GnomeCanvas.html#gnome-canvas-c2w"><tt class="function">gnome_canvas_c2w()</tt></a> converts from canvas to

159

world. <a href="GnomeCanvas.html#gnome-canvas-w2c-d"><tt class="function">gnome_canvas_w2c_d()</tt></a> is like <a href="GnomeCanvas.html#gnome-canvas-w2c"><tt class="function">gnome_canvas_w2c()</tt></a> but returns the

160

pixel coordinates as doubles which is useful to avoid precision loss

161

from integer rounding. To get the affine transform matrix for converting

162

from world coordinates to canvas coordinates call <a href="GnomeCanvas.html#gnome-canvas-w2c-affine"><tt class="function">gnome_canvas_w2c_affine()</tt></a>.

163

<a href="GnomeCanvas.html#gnome-canvas-window-to-world"><tt class="function">gnome_canvas_window_to_world()</tt></a> converts from window to world

164

coordinates and <a href="GnomeCanvas.html#gnome-canvas-world-to-window"><tt class="function">gnome_canvas_world_to_window()</tt></a> converts in the other

165

direction. There are no functions for converting between canvas and

166

window coordinates, since this is just a matter of subtracting the

167

canvas scrolling offset. To convert to/from item coordinates use the

168

functions defined for <a href="GnomeCanvasItem.html" title="GnomeCanvasItem"><span class="type">GnomeCanvasItem</span></a> objects.

169

</p><p>

170

To set the canvas zoom factor (canvas pixels per world unit, the

171

scaling factor) call <a href="GnomeCanvas.html#gnome-canvas-set-pixels-per-unit"><tt class="function">gnome_canvas_set_pixels_per_unit()</tt></a>, setting this

172

to 1.0 will cause the two coordinate systems to correspond (e.g., [5, 6]

173

in pixel units would be [5.0, 6.0] in world units).

174

</p><p>

175

Defining the scrollable area of a canvas widget is done by calling

176

<a href="GnomeCanvas.html#gnome-canvas-set-scroll-region"><tt class="function">gnome_canvas_set_scroll_region()</tt></a> and to get the current region

177

<a href="GnomeCanvas.html#gnome-canvas-get-scroll-region"><tt class="function">gnome_canvas_get_scroll_region()</tt></a> can be used. If the window is

178

larger than the canvas scrolling region it can optionally be centered

179

in the window. Use <a href="GnomeCanvas.html#gnome-canvas-set-center-scroll-region"><tt class="function">gnome_canvas_set_center_scroll_region()</tt></a> to enable or

180

disable this behavior. To scroll to a particular canvas pixel coordinate

181

use <a href="GnomeCanvas.html#gnome-canvas-scroll-to"><tt class="function">gnome_canvas_scroll_to()</tt></a> (typically not used since scrollbars are

182

usually set up to handle the scrolling), and to get the current canvas pixel

183

scroll offset call <a href="GnomeCanvas.html#gnome-canvas-get-scroll-offsets"><tt class="function">gnome_canvas_get_scroll_offsets()</tt></a>.

184

</p></div><div class="refsect1" lang="en"><a name="id2972047"></a><h2>Details</h2><div class="refsect2" lang="en"><a name="id2972052"></a><h3><a name="GnomeCanvas-struct"></a>struct GnomeCanvas</h3><a class="indexterm" name="id2972063"></a><pre class="programlisting">struct GnomeCanvas;</pre><p>

185

This should not be accessed directly. Use the accessor functions as described

186

below.

187

</p></div><hr><div class="refsect2" lang="en"><a name="id2972079"></a><h3><a name="GNOME-CANVAS-EPSILON-CAPS"></a>GNOME_CANVAS_EPSILON</h3><a class="indexterm" name="id2972090"></a><pre class="programlisting">#define GNOME_CANVAS_EPSILON 1e-10

188

</pre><p>

189

A tiny value used by internal canvas operations.

190

</p></div><hr><div class="refsect2" lang="en"><a name="id2972107"></a><h3><a name="GNOME-CANVAS-COLOR-CAPS"></a>GNOME_CANVAS_COLOR()</h3><a class="indexterm" name="id2972118"></a><pre class="programlisting">#define GNOME_CANVAS_COLOR(r, g, b)</pre><p>

191

Macro for creating a canvas 32 bit RGBA color from red, green and blue

192

components.

193

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>r</tt></i>�:</span></td><td>Red value (0-255)

194

</td></tr><tr><td><span class="term"><i class="parameter"><tt>g</tt></i>�:</span></td><td>Green value (0-255)

195

</td></tr><tr><td><span class="term"><i class="parameter"><tt>b</tt></i>�:</span></td><td>Blue value (0-255)

196

</td></tr><tr><td><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td><td>A 32 bit integer of the format 0xRRGGBBAA with the alpha "AA"

197

component set to 0xFF (fully visible, no transparency) and the other bytes

198

set to the input parameters.

199

200

201

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2972199"></a><h3><a name="GNOME-CANVAS-COLOR-A-CAPS"></a>GNOME_CANVAS_COLOR_A()</h3><a class="indexterm" name="id2972210"></a><pre class="programlisting">#define GNOME_CANVAS_COLOR_A(r, g, b, a)</pre><p>

202

Macro for creating a canvas 32 bit RGBA color from red, green, blue and

203

alpha components.

204

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>r</tt></i>�:</span></td><td>Red value (0-255)

205

</td></tr><tr><td><span class="term"><i class="parameter"><tt>g</tt></i>�:</span></td><td>Green value (0-255)

206

</td></tr><tr><td><span class="term"><i class="parameter"><tt>b</tt></i>�:</span></td><td>Blue value (0-255)

207

</td></tr><tr><td><span class="term"><i class="parameter"><tt>a</tt></i>�:</span></td><td>Alpha value (0-255, 0=completely transparent, 255=opaque)

208

</td></tr><tr><td><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td><td>A 32 bit integer of the format 0xRRGGBBAA created from the input

209

parameters.

210

211

212

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2972296"></a><h3><a name="GnomeCanvasBuf"></a>struct GnomeCanvasBuf</h3><a class="indexterm" name="id2972308"></a><pre class="programlisting">struct GnomeCanvasBuf {

213

214

/* 24-bit RGB buffer for rendering */

215

guchar *buf;

216

217

/* Rectangle describing the rendering area */

218

ArtIRect rect;

219

220

/* Rowstride for the buffer */

221

int buf_rowstride;

222

223

/* Background color, given as 0xrrggbb */

224

guint32 bg_color;

225

226

/* Invariant: at least one of the following flags is true. */

227

228

/* Set when the render rectangle area is the solid color bg_color */

229

unsigned int is_bg : 1;

230

231

/* Set when the render rectangle area is represented by the buf */

232

unsigned int is_buf : 1;

233

};

234

</pre><p>

235

A buffer used for rendering for antialiased mode canvas widgets.

236

</p></div><hr><div class="refsect2" lang="en"><a name="id2972331"></a><h3><a name="gnome-canvas-new"></a>gnome_canvas_new ()</h3><a class="indexterm" name="id2972340"></a><pre class="programlisting">GtkWidget* gnome_canvas_new (void);</pre><p>

237

Creates a new empty canvas in non-antialiased mode.</p><p>

238

239

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td><td> A newly-created canvas.

240

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2972381"></a><h3><a name="gnome-canvas-new-aa"></a>gnome_canvas_new_aa ()</h3><a class="indexterm" name="id2972392"></a><pre class="programlisting">GtkWidget* gnome_canvas_new_aa (void);</pre><p>

241

Creates a new empty canvas in antialiased mode.</p><p>

242

243

244

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2972432"></a><h3><a name="gnome-canvas-root"></a>gnome_canvas_root ()</h3><a class="indexterm" name="id2972443"></a><pre class="programlisting"><a href="GnomeCanvasGroup.html" title="GnomeCanvasGroup">GnomeCanvasGroup</a>* gnome_canvas_root (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas);</pre><p>

245

Queries the root group of a canvas.</p><p>

246

247

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

248

</td></tr><tr><td><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td><td> The root group of the specified canvas.

249

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2972503"></a><h3><a name="gnome-canvas-set-scroll-region"></a>gnome_canvas_set_scroll_region ()</h3><a class="indexterm" name="id2972515"></a><pre class="programlisting">void gnome_canvas_set_scroll_region (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

250

double x1,

251

double y1,

252

double x2,

253

double y2);</pre><p>

254

Sets the scrolling region of a canvas to the specified rectangle. The canvas

255

will then be able to scroll only within this region. The view of the canvas

256

is adjusted as appropriate to display as much of the new region as possible.</p><p>

257

258

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

259

</td></tr><tr><td><span class="term"><i class="parameter"><tt>x1</tt></i>�:</span></td><td> Leftmost limit of the scrolling region.

260

</td></tr><tr><td><span class="term"><i class="parameter"><tt>y1</tt></i>�:</span></td><td> Upper limit of the scrolling region.

261

</td></tr><tr><td><span class="term"><i class="parameter"><tt>x2</tt></i>�:</span></td><td> Rightmost limit of the scrolling region.

262

</td></tr><tr><td><span class="term"><i class="parameter"><tt>y2</tt></i>�:</span></td><td> Lower limit of the scrolling region.

263

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2972656"></a><h3><a name="gnome-canvas-get-scroll-region"></a>gnome_canvas_get_scroll_region ()</h3><a class="indexterm" name="id2972668"></a><pre class="programlisting">void gnome_canvas_get_scroll_region (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

264

double *x1,

265

double *y1,

266

double *x2,

267

double *y2);</pre><p>

268

Queries the scrolling region of a canvas.</p><p>

269

270

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

271

</td></tr><tr><td><span class="term"><i class="parameter"><tt>x1</tt></i>�:</span></td><td> Leftmost limit of the scrolling region (return value).

272

</td></tr><tr><td><span class="term"><i class="parameter"><tt>y1</tt></i>�:</span></td><td> Upper limit of the scrolling region (return value).

273

</td></tr><tr><td><span class="term"><i class="parameter"><tt>x2</tt></i>�:</span></td><td> Rightmost limit of the scrolling region (return value).

274

</td></tr><tr><td><span class="term"><i class="parameter"><tt>y2</tt></i>�:</span></td><td> Lower limit of the scrolling region (return value).

275

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2972806"></a><h3><a name="gnome-canvas-set-center-scroll-region"></a>gnome_canvas_set_center_scroll_region ()</h3><a class="indexterm" name="id2972818"></a><pre class="programlisting">void gnome_canvas_set_center_scroll_region

276

(<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

277

gboolean center_scroll_region);</pre><p>

278

When the scrolling region of the canvas is smaller than the canvas window,

279

e.g. the allocation of the canvas, it can be either centered on the window

280

or simply made to be on the upper-left corner on the window. This function

281

lets you configure this property.</p><p>

282

283

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

284

</td></tr><tr><td><span class="term"><i class="parameter"><tt>center_scroll_region</tt></i>�:</span></td><td> Whether to center the scrolling region in the canvas

285

window when it is smaller than the canvas' allocation.

286

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2972897"></a><h3><a name="gnome-canvas-get-center-scroll-region"></a>gnome_canvas_get_center_scroll_region ()</h3><a class="indexterm" name="id2972909"></a><pre class="programlisting">gboolean gnome_canvas_get_center_scroll_region

287

(<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas);</pre><p>

288

Returns whether the canvas is set to center the scrolling region in the window

289

if the former is smaller than the canvas' allocation.</p><p>

290

291

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

292

</td></tr><tr><td><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td><td> Whether the scroll region is being centered in the canvas window.

293

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2972973"></a><h3><a name="gnome-canvas-set-pixels-per-unit"></a>gnome_canvas_set_pixels_per_unit ()</h3><a class="indexterm" name="id2972984"></a><pre class="programlisting">void gnome_canvas_set_pixels_per_unit

294

(<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

295

double n);</pre><p>

296

Sets the zooming factor of a canvas by specifying the number of pixels that

297

correspond to one canvas unit.

298

</p><p>

299

The anchor point for zooming, i.e. the point that stays fixed and all others

300

zoom inwards or outwards from it, depends on whether the canvas is set to

301

center the scrolling region or not. You can control this using the

302

<a href="GnomeCanvas.html#gnome-canvas-set-center-scroll-region"><tt class="function">gnome_canvas_set_center_scroll_region()</tt></a> function. If the canvas is set to

303

center the scroll region, then the center of the canvas window is used as the

304

anchor point for zooming. Otherwise, the upper-left corner of the canvas

305

window is used as the anchor point.</p><p>

306

307

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

308

</td></tr><tr><td><span class="term"><i class="parameter"><tt>n</tt></i>�:</span></td><td> The number of pixels that correspond to one canvas unit.

309

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2973081"></a><h3><a name="gnome-canvas-scroll-to"></a>gnome_canvas_scroll_to ()</h3><a class="indexterm" name="id2973092"></a><pre class="programlisting">void gnome_canvas_scroll_to (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

310

int cx,

311

int cy);</pre><p>

312

Makes a canvas scroll to the specified offsets, given in canvas pixel units.

313

The canvas will adjust the view so that it is not outside the scrolling

314

region. This function is typically not used, as it is better to hook

315

scrollbars to the canvas layout's scrolling adjusments.</p><p>

316

317

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

318

</td></tr><tr><td><span class="term"><i class="parameter"><tt>cx</tt></i>�:</span></td><td> Horizontal scrolling offset in canvas pixel units.

319

</td></tr><tr><td><span class="term"><i class="parameter"><tt>cy</tt></i>�:</span></td><td> Vertical scrolling offset in canvas pixel units.

320

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2973189"></a><h3><a name="gnome-canvas-get-scroll-offsets"></a>gnome_canvas_get_scroll_offsets ()</h3><a class="indexterm" name="id2973201"></a><pre class="programlisting">void gnome_canvas_get_scroll_offsets (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

321

int *cx,

322

int *cy);</pre><p>

323

Queries the scrolling offsets of a canvas. The values are returned in canvas

324

pixel units.</p><p>

325

326

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

327

</td></tr><tr><td><span class="term"><i class="parameter"><tt>cx</tt></i>�:</span></td><td> Horizontal scrolling offset (return value).

328

</td></tr><tr><td><span class="term"><i class="parameter"><tt>cy</tt></i>�:</span></td><td> Vertical scrolling offset (return value).

329

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2973294"></a><h3><a name="gnome-canvas-update-now"></a>gnome_canvas_update_now ()</h3><a class="indexterm" name="id2973306"></a><pre class="programlisting">void gnome_canvas_update_now (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas);</pre><p>

330

Forces an immediate update and redraw of a canvas. If the canvas does not

331

have any pending update or redraw requests, then no action is taken. This is

332

typically only used by applications that need explicit control of when the

333

display is updated, like games. It is not needed by normal applications.</p><p>

334

335

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

336

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2973361"></a><h3><a name="gnome-canvas-get-item-at"></a>gnome_canvas_get_item_at ()</h3><a class="indexterm" name="id2973372"></a><pre class="programlisting"><a href="GnomeCanvasItem.html" title="GnomeCanvasItem">GnomeCanvasItem</a>* gnome_canvas_get_item_at (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

337

double x,

338

double y);</pre><p>

339

Looks for the item that is under the specified position, which must be

340

specified in world coordinates.</p><p>

341

342

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

343

</td></tr><tr><td><span class="term"><i class="parameter"><tt>x</tt></i>�:</span></td><td> X position in world coordinates.

344

</td></tr><tr><td><span class="term"><i class="parameter"><tt>y</tt></i>�:</span></td><td> Y position in world coordinates.

345

</td></tr><tr><td><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td><td> The sought item, or NULL if no item is at the specified

346

coordinates.

347

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2973478"></a><h3><a name="gnome-canvas-request-redraw-uta"></a>gnome_canvas_request_redraw_uta ()</h3><a class="indexterm" name="id2973489"></a><pre class="programlisting">void gnome_canvas_request_redraw_uta (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

348

ArtUta *uta);</pre><p>

349

Informs a canvas that the specified area, given as a microtile array, needs

350

to be repainted. To be used only by item implementations.</p><p>

351

352

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

353

</td></tr><tr><td><span class="term"><i class="parameter"><tt>uta</tt></i>�:</span></td><td> Microtile array that specifies the area to be redrawn. It will

354

be freed by this function, so the argument you pass will be invalid

355

after you call this function.

356

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2973565"></a><h3><a name="gnome-canvas-request-redraw"></a>gnome_canvas_request_redraw ()</h3><a class="indexterm" name="id2973577"></a><pre class="programlisting">void gnome_canvas_request_redraw (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

357

int x1,

358

int y1,

359

int x2,

360

int y2);</pre><p>

361

Convenience function that informs a canvas that the specified rectangle needs

362

to be repainted. This function converts the rectangle to a microtile array

363

and feeds it to <a href="GnomeCanvas.html#gnome-canvas-request-redraw-uta"><tt class="function">gnome_canvas_request_redraw_uta()</tt></a>. The rectangle includes

364

<i class="parameter"><tt>x1</tt></i> and <i class="parameter"><tt>y1</tt></i>, but not <i class="parameter"><tt>x2</tt></i> and <i class="parameter"><tt>y2</tt></i>. To be used only by item implementations.</p><p>

365

366

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

367

</td></tr><tr><td><span class="term"><i class="parameter"><tt>x1</tt></i>�:</span></td><td> Leftmost coordinate of the rectangle to be redrawn.

368

</td></tr><tr><td><span class="term"><i class="parameter"><tt>y1</tt></i>�:</span></td><td> Upper coordinate of the rectangle to be redrawn.

369

</td></tr><tr><td><span class="term"><i class="parameter"><tt>x2</tt></i>�:</span></td><td> Rightmost coordinate of the rectangle to be redrawn, plus 1.

370

</td></tr><tr><td><span class="term"><i class="parameter"><tt>y2</tt></i>�:</span></td><td> Lower coordinate of the rectangle to be redrawn, plus 1.

371

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2973750"></a><h3><a name="gnome-canvas-w2c-affine"></a>gnome_canvas_w2c_affine ()</h3><a class="indexterm" name="id2973761"></a><pre class="programlisting">void gnome_canvas_w2c_affine (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

372

double affine[6]);</pre><p>

373

Gets the affine transform that converts from world coordinates to canvas

374

pixel coordinates.</p><p>

375

376

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

377

</td></tr><tr><td><span class="term"><i class="parameter"><tt>affine</tt></i>�:</span></td><td> An affine transformation matrix (return value).

378

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2973834"></a><h3><a name="gnome-canvas-w2c"></a>gnome_canvas_w2c ()</h3><a class="indexterm" name="id2973845"></a><pre class="programlisting">void gnome_canvas_w2c (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

379

double wx,

380

double wy,

381

int *cx,

382

int *cy);</pre><p>

383

Converts world coordinates into canvas pixel coordinates.</p><p>

384

385

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

386

</td></tr><tr><td><span class="term"><i class="parameter"><tt>wx</tt></i>�:</span></td><td> World X coordinate.

387

</td></tr><tr><td><span class="term"><i class="parameter"><tt>wy</tt></i>�:</span></td><td> World Y coordinate.

388

</td></tr><tr><td><span class="term"><i class="parameter"><tt>cx</tt></i>�:</span></td><td> X pixel coordinate (return value).

389

</td></tr><tr><td><span class="term"><i class="parameter"><tt>cy</tt></i>�:</span></td><td> Y pixel coordinate (return value).

390

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2973981"></a><h3><a name="gnome-canvas-w2c-d"></a>gnome_canvas_w2c_d ()</h3><a class="indexterm" name="id2973992"></a><pre class="programlisting">void gnome_canvas_w2c_d (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

391

double wx,

392

double wy,

393

double *cx,

394

double *cy);</pre><p>

395

Converts world coordinates into canvas pixel coordinates. This

396

version returns coordinates in floating point coordinates, for

397

greater precision.</p><p>

398

399

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

400

</td></tr><tr><td><span class="term"><i class="parameter"><tt>wx</tt></i>�:</span></td><td> World X coordinate.

401

</td></tr><tr><td><span class="term"><i class="parameter"><tt>wy</tt></i>�:</span></td><td> World Y coordinate.

402

</td></tr><tr><td><span class="term"><i class="parameter"><tt>cx</tt></i>�:</span></td><td> X pixel coordinate (return value).

403

</td></tr><tr><td><span class="term"><i class="parameter"><tt>cy</tt></i>�:</span></td><td> Y pixel coordinate (return value).

404

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2974130"></a><h3><a name="gnome-canvas-c2w"></a>gnome_canvas_c2w ()</h3><a class="indexterm" name="id2974140"></a><pre class="programlisting">void gnome_canvas_c2w (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

405

int cx,

406

int cy,

407

double *wx,

408

double *wy);</pre><p>

409

Converts canvas pixel coordinates to world coordinates.</p><p>

410

411

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

412

</td></tr><tr><td><span class="term"><i class="parameter"><tt>cx</tt></i>�:</span></td><td> Canvas pixel X coordinate.

413

</td></tr><tr><td><span class="term"><i class="parameter"><tt>cy</tt></i>�:</span></td><td> Canvas pixel Y coordinate.

414

</td></tr><tr><td><span class="term"><i class="parameter"><tt>wx</tt></i>�:</span></td><td> X world coordinate (return value).

415

</td></tr><tr><td><span class="term"><i class="parameter"><tt>wy</tt></i>�:</span></td><td> Y world coordinate (return value).

416

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2974276"></a><h3><a name="gnome-canvas-window-to-world"></a>gnome_canvas_window_to_world ()</h3><a class="indexterm" name="id2974288"></a><pre class="programlisting">void gnome_canvas_window_to_world (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

417

double winx,

418

double winy,

419

double *worldx,

420

double *worldy);</pre><p>

421

Converts window-relative coordinates into world coordinates. You can use

422

this when you need to convert mouse coordinates into world coordinates, for

423

example.</p><p>

424

425

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

426

</td></tr><tr><td><span class="term"><i class="parameter"><tt>winx</tt></i>�:</span></td><td> Window-relative X coordinate.

427

</td></tr><tr><td><span class="term"><i class="parameter"><tt>winy</tt></i>�:</span></td><td> Window-relative Y coordinate.

428

</td></tr><tr><td><span class="term"><i class="parameter"><tt>worldx</tt></i>�:</span></td><td> X world coordinate (return value).

429

</td></tr><tr><td><span class="term"><i class="parameter"><tt>worldy</tt></i>�:</span></td><td> Y world coordinate (return value).

430

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2974428"></a><h3><a name="gnome-canvas-world-to-window"></a>gnome_canvas_world_to_window ()</h3><a class="indexterm" name="id2974439"></a><pre class="programlisting">void gnome_canvas_world_to_window (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

431

double worldx,

432

double worldy,

433

double *winx,

434

double *winy);</pre><p>

435

Converts world coordinates into window-relative coordinates.</p><p>

436

437

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

438

</td></tr><tr><td><span class="term"><i class="parameter"><tt>worldx</tt></i>�:</span></td><td> World X coordinate.

439

</td></tr><tr><td><span class="term"><i class="parameter"><tt>worldy</tt></i>�:</span></td><td> World Y coordinate.

440

</td></tr><tr><td><span class="term"><i class="parameter"><tt>winx</tt></i>�:</span></td><td> X window-relative coordinate.

441

</td></tr><tr><td><span class="term"><i class="parameter"><tt>winy</tt></i>�:</span></td><td> Y window-relative coordinate.

442

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2974577"></a><h3><a name="gnome-canvas-get-color"></a>gnome_canvas_get_color ()</h3><a class="indexterm" name="id2974588"></a><pre class="programlisting">int gnome_canvas_get_color (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

443

const char *spec,

444

GdkColor *color);</pre><p>

445

Allocates a color based on the specified X color specification. As a

446

convenience to item implementations, it returns TRUE if the color was

447

allocated, or FALSE if the specification was NULL. A NULL color

448

specification is considered as "transparent" by the canvas.</p><p>

449

450

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

451

</td></tr><tr><td><span class="term"><i class="parameter"><tt>spec</tt></i>�:</span></td><td> X color specification, or NULL for "transparent".

452

</td></tr><tr><td><span class="term"><i class="parameter"><tt>color</tt></i>�:</span></td><td> Returns the allocated color.

453

</td></tr><tr><td><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td><td> TRUE if <i class="parameter"><tt>spec</tt></i> is non-NULL and the color is allocated. If <i class="parameter"><tt>spec</tt></i>

454

is NULL, then returns FALSE.

455

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2974709"></a><h3><a name="gnome-canvas-get-color-pixel"></a>gnome_canvas_get_color_pixel ()</h3><a class="indexterm" name="id2974721"></a><pre class="programlisting">gulong gnome_canvas_get_color_pixel (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

456

guint rgba);</pre><p>

457

Allocates a color from the RGBA value passed into this function. The alpha

458

opacity value is discarded, since normal X colors do not support it.</p><p>

459

460

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

461

</td></tr><tr><td><span class="term"><i class="parameter"><tt>rgba</tt></i>�:</span></td><td> RGBA color specification.

462

</td></tr><tr><td><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td><td> Allocated pixel value corresponding to the specified color.

463

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2974806"></a><h3><a name="gnome-canvas-set-stipple-origin"></a>gnome_canvas_set_stipple_origin ()</h3><a class="indexterm" name="id2974817"></a><pre class="programlisting">void gnome_canvas_set_stipple_origin (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

464

GdkGC *gc);</pre><p>

465

Sets the stipple origin of the specified GC as is appropriate for the canvas,

466

so that it will be aligned with other stipple patterns used by canvas items.

467

This is typically only needed by item implementations.</p><p>

468

469

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

470

</td></tr><tr><td><span class="term"><i class="parameter"><tt>gc</tt></i>�:</span></td><td> GC on which to set the stipple origin.

471

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2974892"></a><h3><a name="gnome-canvas-set-dither"></a>gnome_canvas_set_dither ()</h3><a class="indexterm" name="id2974903"></a><pre class="programlisting">void gnome_canvas_set_dither (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

472

GdkRgbDither dither);</pre><p>

473

Controls dithered rendering for antialiased canvases. The value of

474

dither should be <span class="type">GDK_RGB_DITHER_NONE</span>, <span class="type">GDK_RGB_DITHER_NORMAL</span>, or

475

<span class="type">GDK_RGB_DITHER_MAX</span>. The default canvas setting is

476

<span class="type">GDK_RGB_DITHER_NORMAL</span>.</p><p>

477

478

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

479

</td></tr><tr><td><span class="term"><i class="parameter"><tt>dither</tt></i>�:</span></td><td> Type of dithering used to render an antialiased canvas.

480

</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2975015"></a><h3><a name="gnome-canvas-get-dither"></a>gnome_canvas_get_dither ()</h3><a class="indexterm" name="id2975026"></a><pre class="programlisting">GdkRgbDither gnome_canvas_get_dither (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas);</pre><p>

481

Returns the type of dithering used to render an antialiased canvas.</p><p>

482

483

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td> A canvas.

484

</td></tr><tr><td><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td><td> The dither setting.

485

</td></tr></tbody></table></div></div></div><div class="refsect1" lang="en"><a name="id2975089"></a><h2>Properties</h2><div class="refsect2" lang="en"><a name="id2975094"></a><h3><a name="GnomeCanvas--aa"></a>The "<tt class="literal">aa</tt>" property</h3><pre class="programlisting"> "aa" gboolean : Read / Write / Construct Only</pre><p>

486

Enable anti-aliasing mode?

487

</p><p>

488

Note that this parameter can only be set at the time of object

489

construction. The same effect can be achieved by calling

490

<a href="GnomeCanvas.html#gnome-canvas-new"><tt class="function">gnome_canvas_new()</tt></a> to create new non-aa canvas or

491

<a href="GnomeCanvas.html#gnome-canvas-new-aa"><tt class="function">gnome_canvas_new_aa()</tt></a> for an anti-aliased canvas.

492

</p><p>Default value: FALSE</p></div></div><div class="refsect1" lang="en"><a name="id2975161"></a><h2>Signals</h2><div class="refsect2" lang="en"><a name="id2975166"></a><h3><a name="GnomeCanvas-draw-background"></a>The "draw-background" signal</h3><pre class="programlisting">void user_function (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

493

GdkDrawable *arg1,

494

gint arg2,

495

gint arg3,

496

gint arg4,

497

gint arg5,

498

gpointer user_data);</pre><p>

499

This signal is emitted to draw the background for non-antialiased mode

500

canvas widgets. The default method uses the canvas widget's style to

501

draw the background.

502

</p><div class="variablelist"><table border="0"><col align="left" valign="top"><tbody><tr><td><span class="term"><i class="parameter"><tt>canvas</tt></i>�:</span></td><td>the object which received the signal.

503

</td></tr><tr><td><span class="term"><i class="parameter"><tt>arg1</tt></i>�:</span></td><td>GdkDrawable to draw to

504

</td></tr><tr><td><span class="term"><i class="parameter"><tt>arg2</tt></i>�:</span></td><td>Leftmost X coordinate of area to draw to

505

</td></tr><tr><td><span class="term"><i class="parameter"><tt>arg3</tt></i>�:</span></td><td>Top Y coordinate of area to draw to

506

</td></tr><tr><td><span class="term"><i class="parameter"><tt>arg4</tt></i>�:</span></td><td>Width of area

507

</td></tr><tr><td><span class="term"><i class="parameter"><tt>arg5</tt></i>�:</span></td><td>Height of area

508

509

</td></tr><tr><td><span class="term"><i class="parameter"><tt>user_data</tt></i>�:</span></td><td>user data set when the signal handler was connected.</td></tr></tbody></table></div></div><hr><div class="refsect2" lang="en"><a name="id2975350"></a><h3><a name="GnomeCanvas-render-background"></a>The "render-background" signal</h3><pre class="programlisting">void user_function (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,

510

gpointer arg1,

511

gpointer user_data);</pre><p>

512

This signal is emitted for antialiased mode canvas widgets to render

513

the background. The buf data structure contains both a pointer to a

514

packed 24-bit RGB array and the coordinates.

515

516

</td></tr><tr><td><span class="term"><i class="parameter"><tt>arg1</tt></i>�:</span></td><td><a href="GnomeCanvas.html#GnomeCanvasBuf"><span class="type">GnomeCanvasBuf</span></a> to render to

517

518

</td></tr><tr><td><span class="term"><i class="parameter"><tt>user_data</tt></i>�:</span></td><td>user data set when the signal handler was connected.</td></tr></tbody></table></div></div></div></div><table class="navigation" width="100%" summary="Navigation footer" cellpadding="2" cellspacing="0"><tr valign="middle"><td align="left"><a accesskey="p" href="ch02.html"><b><<�GNOME Canvas Library (libgnomecanvas)</b></a></td><td align="right"><a accesskey="n" href="GnomeCanvasBpath.html"><b>GnomeCanvasBpath�>></b></a></td></tr></table></body></html>

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