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<div class="refentry" lang="en">
<a name="GnomeCanvas"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2><span class="refentrytitle">GnomeCanvas</span></h2>
<p>GnomeCanvas — Main canvas widget</p>
</td>
<td valign="top" align="right"></td>
</tr></table></div>
<div class="refsynopsisdiv">
<h2>Synopsis</h2>
<pre class="synopsis">
#include <libgnomecanvas/libgnomecanvas.h>
<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)
<a href="GnomeCanvas.html#GnomeCanvasBuf">GnomeCanvasBuf</a>;
<a
href="/usr/share/gtk-doc/html/gtk/GtkWidget.html"
>GtkWidget</a>* <a href="GnomeCanvas.html#gnome-canvas-new">gnome_canvas_new</a> (void);
<a
href="/usr/share/gtk-doc/html/gtk/GtkWidget.html"
>GtkWidget</a>* <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,
<a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gboolean"
>gboolean</a> center_scroll_region);
<a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gboolean"
>gboolean</a> <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,
<a
href="/usr/share/gtk-doc/html/gdk/gdk-Colormaps-and-Colors.html#GdkColor"
>GdkColor</a> *color);
<a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gulong"
>gulong</a> <a href="GnomeCanvas.html#gnome-canvas-get-color-pixel">gnome_canvas_get_color_pixel</a> (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,
<a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#guint"
>guint</a> 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,
<a
href="/usr/share/gtk-doc/html/gdk/gdk-Graphics-Contexts.html#GdkGC"
>GdkGC</a> *gc);
void <a href="GnomeCanvas.html#gnome-canvas-set-dither">gnome_canvas_set_dither</a> (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,
<a
href="/usr/share/gtk-doc/html/gdk/gdk-GdkRGB.html#GdkRgbDither"
>GdkRgbDither</a> dither);
<a
href="/usr/share/gtk-doc/html/gdk/gdk-GdkRGB.html#GdkRgbDither"
>GdkRgbDither</a> <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="id2656181"></a><h2>Object Hierarchy</h2>
<pre class="synopsis">
<a
href="/usr/share/gtk-doc/html/gobject/gobject-The-Base-Object-Type.html#GObject"
>GObject</a>
+----<a
href="/usr/share/gtk-doc/html/gtk/GtkObject.html"
>GtkObject</a>
+----<a
href="/usr/share/gtk-doc/html/gtk/GtkWidget.html"
>GtkWidget</a>
+----<a
href="/usr/share/gtk-doc/html/gtk/GtkContainer.html"
>GtkContainer</a>
+----<a
href="/usr/share/gtk-doc/html/gtk/GtkLayout.html"
>GtkLayout</a>
+----GnomeCanvas
</pre>
</div>
<div class="refsect1" lang="en">
<a name="id2656230"></a><h2>Implemented Interfaces</h2>
<p>
GnomeCanvas implements
AtkImplementorIface.</p>
</div>
<div class="refsect1" lang="en">
<a name="id2656248"></a><h2>Properties</h2>
<pre class="synopsis">
"<a href="GnomeCanvas.html#GnomeCanvas--aa">aa</a>" <a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gboolean"
>gboolean</a> : Read / Write / Construct Only
</pre>
</div>
<div class="refsect1" lang="en">
<a name="id2656276"></a><h2>Signal Prototypes</h2>
<pre class="synopsis">
"<a href="GnomeCanvas.html#GnomeCanvas-draw-background">draw-background</a>"
void user_function (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,
<a
href="/usr/share/gtk-doc/html/gdk/gdk-Drawing-Primitives.html#GdkDrawable"
>GdkDrawable</a> *arg1,
<a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gint"
>gint</a> arg2,
<a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gint"
>gint</a> arg3,
<a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gint"
>gint</a> arg4,
<a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gint"
>gint</a> arg5,
<a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gpointer"
>gpointer</a> user_data);
"<a href="GnomeCanvas.html#GnomeCanvas-render-background">render-background</a>"
void user_function (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,
<a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gpointer"
>gpointer</a> arg1,
<a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gpointer"
>gpointer</a> user_data);
</pre>
</div>
<div class="refsect1" lang="en">
<a name="id2656400"></a><h2>Description</h2>
<p>
The <a href="GnomeCanvas.html" title="GnomeCanvas"><span class="type">GnomeCanvas</span></a> is an engine for structured graphics that offers a
rich imaging model, high performance rendering, and a powerful,
high level API. It offers a choice of two rendering back-ends,
one based on Xlib for extremely fast display, and another based on
Libart, a sophisticated, antialiased, alpha-compositing engine.
This widget can be used for flexible display of graphics and for
creating interactive user interface elements.
</p>
<p>
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"><code class="function">gnome_canvas_new()</code></a> or
<a href="GnomeCanvas.html#gnome-canvas-new-aa"><code class="function">gnome_canvas_new_aa()</code></a> for an anti-aliased mode canvas.
</p>
<p>
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>
objects. Items consist of graphing elements like lines, ellipses,
polygons, images, text, and curves. These items are organized using
<a href="GnomeCanvasGroup.html" title="GnomeCanvasGroup"><span class="type">GnomeCanvasGroup</span></a> objects, which are themselves derived from
<a href="GnomeCanvasItem.html" title="GnomeCanvasItem"><span class="type">GnomeCanvasItem</span></a>. Since a group is an item it can be contained within
other groups, forming a tree of canvas items. Certain operations, like
translating and scaling, can be performed on all items in a group.
</p>
<p>
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
level group under which all items in a canvas are contained. To get the root
group from a canvas call <a href="GnomeCanvas.html#gnome-canvas-root"><code class="function">gnome_canvas_root()</code></a>.
</p>
<p>
There are several different coordinate systems used by <a href="GnomeCanvas.html" title="GnomeCanvas"><span class="type">GnomeCanvas</span></a>
widgets. The primary system is a logical, abstract coordinate space
called world coordinates. World coordinates are expressed as unbounded
double floating point numbers. When it comes to rendering to a screen
the canvas pixel coordinate system (also referred to as just canvas
coordinates) is used. This system uses integers to specify screen
pixel positions. A user defined scaling factor and offset are used to
convert between world coordinates and canvas coordinates. Each item in
a canvas has its own coordinate system called item coordinates. This
system is specified in world coordinates but they are relative to an
item (0.0, 0.0 would be the top left corner of the item). The final
coordinate system of interest is window coordinates. These are like
canvas coordinates but are offsets from within a window a canvas is
displayed in. This last system is rarely used, but is useful when
manually handling GDK events (such as drag and drop) which are
specified in window coordinates (the events processed by the canvas
are already converted for you).
</p>
<p>
Along with different coordinate systems comes functions to convert
between them. <a href="GnomeCanvas.html#gnome-canvas-w2c"><code class="function">gnome_canvas_w2c()</code></a> converts world to canvas pixel
coordinates and <a href="GnomeCanvas.html#gnome-canvas-c2w"><code class="function">gnome_canvas_c2w()</code></a> converts from canvas to
world. <a href="GnomeCanvas.html#gnome-canvas-w2c-d"><code class="function">gnome_canvas_w2c_d()</code></a> is like <a href="GnomeCanvas.html#gnome-canvas-w2c"><code class="function">gnome_canvas_w2c()</code></a> but returns the
pixel coordinates as doubles which is useful to avoid precision loss
from integer rounding. To get the affine transform matrix for converting
from world coordinates to canvas coordinates call <a href="GnomeCanvas.html#gnome-canvas-w2c-affine"><code class="function">gnome_canvas_w2c_affine()</code></a>.
<a href="GnomeCanvas.html#gnome-canvas-window-to-world"><code class="function">gnome_canvas_window_to_world()</code></a> converts from window to world
coordinates and <a href="GnomeCanvas.html#gnome-canvas-world-to-window"><code class="function">gnome_canvas_world_to_window()</code></a> converts in the other
direction. There are no functions for converting between canvas and
window coordinates, since this is just a matter of subtracting the
canvas scrolling offset. To convert to/from item coordinates use the
functions defined for <a href="GnomeCanvasItem.html" title="GnomeCanvasItem"><span class="type">GnomeCanvasItem</span></a> objects.
</p>
<p>
To set the canvas zoom factor (canvas pixels per world unit, the
scaling factor) call <a href="GnomeCanvas.html#gnome-canvas-set-pixels-per-unit"><code class="function">gnome_canvas_set_pixels_per_unit()</code></a>, setting this
to 1.0 will cause the two coordinate systems to correspond (e.g., [5, 6]
in pixel units would be [5.0, 6.0] in world units).
</p>
<p>
Defining the scrollable area of a canvas widget is done by calling
<a href="GnomeCanvas.html#gnome-canvas-set-scroll-region"><code class="function">gnome_canvas_set_scroll_region()</code></a> and to get the current region
<a href="GnomeCanvas.html#gnome-canvas-get-scroll-region"><code class="function">gnome_canvas_get_scroll_region()</code></a> can be used. If the window is
larger than the canvas scrolling region it can optionally be centered
in the window. Use <a href="GnomeCanvas.html#gnome-canvas-set-center-scroll-region"><code class="function">gnome_canvas_set_center_scroll_region()</code></a> to enable or
disable this behavior. To scroll to a particular canvas pixel coordinate
use <a href="GnomeCanvas.html#gnome-canvas-scroll-to"><code class="function">gnome_canvas_scroll_to()</code></a> (typically not used since scrollbars are
usually set up to handle the scrolling), and to get the current canvas pixel
scroll offset call <a href="GnomeCanvas.html#gnome-canvas-get-scroll-offsets"><code class="function">gnome_canvas_get_scroll_offsets()</code></a>.
</p>
</div>
<div class="refsect1" lang="en">
<a name="id2656746"></a><h2>Details</h2>
<div class="refsect2" lang="en">
<a name="id2656752"></a><h3>
<a name="GnomeCanvas-struct"></a>GnomeCanvas</h3>
<a class="indexterm" name="id2656762"></a><pre class="programlisting">typedef struct _GnomeCanvas GnomeCanvas;</pre>
<p>
This should not be accessed directly. Use the accessor functions as described
below.
</p>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2656779"></a><h3>
<a name="GNOME-CANVAS-EPSILON:CAPS"></a>GNOME_CANVAS_EPSILON</h3>
<a class="indexterm" name="id2656790"></a><pre class="programlisting">#define GNOME_CANVAS_EPSILON 1e-10
</pre>
<p>
A tiny value used by internal canvas operations.
</p>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2656806"></a><h3>
<a name="GNOME-CANVAS-COLOR:CAPS"></a>GNOME_CANVAS_COLOR()</h3>
<a class="indexterm" name="id2656816"></a><pre class="programlisting">#define GNOME_CANVAS_COLOR(r, g, b)</pre>
<p>
Macro for creating a canvas 32 bit RGBA color from red, green and blue
components.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>r</code></em> :</span></td>
<td>Red value (0-255)
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>g</code></em> :</span></td>
<td>Green value (0-255)
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>b</code></em> :</span></td>
<td>Blue value (0-255)
</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"
component set to 0xFF (fully visible, no transparency) and the other bytes
set to the input parameters.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2656899"></a><h3>
<a name="GNOME-CANVAS-COLOR-A:CAPS"></a>GNOME_CANVAS_COLOR_A()</h3>
<a class="indexterm" name="id2656909"></a><pre class="programlisting">#define GNOME_CANVAS_COLOR_A(r, g, b, a)</pre>
<p>
Macro for creating a canvas 32 bit RGBA color from red, green, blue and
alpha components.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>r</code></em> :</span></td>
<td>Red value (0-255)
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>g</code></em> :</span></td>
<td>Green value (0-255)
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>b</code></em> :</span></td>
<td>Blue value (0-255)
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>a</code></em> :</span></td>
<td>Alpha value (0-255, 0=completely transparent, 255=opaque)
</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
parameters.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2656998"></a><h3>
<a name="GnomeCanvasBuf"></a>GnomeCanvasBuf</h3>
<a class="indexterm" name="id2657008"></a><pre class="programlisting">typedef struct {
/* 24-bit RGB buffer for rendering */
guchar *buf;
/* Rectangle describing the rendering area */
ArtIRect rect;
/* Rowstride for the buffer */
int buf_rowstride;
/* Background color, given as 0xrrggbb */
guint32 bg_color;
/* Invariant: at least one of the following flags is true. */
/* Set when the render rectangle area is the solid color bg_color */
unsigned int is_bg : 1;
/* Set when the render rectangle area is represented by the buf */
unsigned int is_buf : 1;
} GnomeCanvasBuf;
</pre>
<p>
A buffer used for rendering for antialiased mode canvas widgets.
</p>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2657031"></a><h3>
<a name="gnome-canvas-new"></a>gnome_canvas_new ()</h3>
<a class="indexterm" name="id2657039"></a><pre class="programlisting"><a
href="/usr/share/gtk-doc/html/gtk/GtkWidget.html"
>GtkWidget</a>* gnome_canvas_new (void);</pre>
<p>
Creates a new empty canvas in non-antialiased mode.</p>
<p>
</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.
</td>
</tr></tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2657079"></a><h3>
<a name="gnome-canvas-new-aa"></a>gnome_canvas_new_aa ()</h3>
<a class="indexterm" name="id2657089"></a><pre class="programlisting"><a
href="/usr/share/gtk-doc/html/gtk/GtkWidget.html"
>GtkWidget</a>* gnome_canvas_new_aa (void);</pre>
<p>
Creates a new empty canvas in antialiased mode.</p>
<p>
</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 antialiased canvas.
</td>
</tr></tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2657129"></a><h3>
<a name="gnome-canvas-root"></a>gnome_canvas_root ()</h3>
<a class="indexterm" name="id2657140"></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>
Queries the root group of a canvas.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</td>
</tr>
<tr>
<td>
<span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td>
<td> The root group of the specified canvas.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2657201"></a><h3>
<a name="gnome-canvas-set-scroll-region"></a>gnome_canvas_set_scroll_region ()</h3>
<a class="indexterm" name="id2657212"></a><pre class="programlisting">void gnome_canvas_set_scroll_region (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,
double x1,
double y1,
double x2,
double y2);</pre>
<p>
Sets the scrolling region of a canvas to the specified rectangle. The canvas
will then be able to scroll only within this region. The view of the canvas
is adjusted as appropriate to display as much of the new region as possible.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>x1</code></em> :</span></td>
<td> Leftmost limit of the scrolling region.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>y1</code></em> :</span></td>
<td> Upper limit of the scrolling region.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>x2</code></em> :</span></td>
<td> Rightmost limit of the scrolling region.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>y2</code></em> :</span></td>
<td> Lower limit of the scrolling region.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2657353"></a><h3>
<a name="gnome-canvas-get-scroll-region"></a>gnome_canvas_get_scroll_region ()</h3>
<a class="indexterm" name="id2657364"></a><pre class="programlisting">void gnome_canvas_get_scroll_region (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,
double *x1,
double *y1,
double *x2,
double *y2);</pre>
<p>
Queries the scrolling region of a canvas.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>x1</code></em> :</span></td>
<td> Leftmost limit of the scrolling region (return value).
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>y1</code></em> :</span></td>
<td> Upper limit of the scrolling region (return value).
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>x2</code></em> :</span></td>
<td> Rightmost limit of the scrolling region (return value).
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>y2</code></em> :</span></td>
<td> Lower limit of the scrolling region (return value).
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2657502"></a><h3>
<a name="gnome-canvas-set-center-scroll-region"></a>gnome_canvas_set_center_scroll_region ()</h3>
<a class="indexterm" name="id2657514"></a><pre class="programlisting">void gnome_canvas_set_center_scroll_region
(<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,
<a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gboolean"
>gboolean</a> center_scroll_region);</pre>
<p>
When the scrolling region of the canvas is smaller than the canvas window,
e.g. the allocation of the canvas, it can be either centered on the window
or simply made to be on the upper-left corner on the window. This function
lets you configure this property.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>center_scroll_region</code></em> :</span></td>
<td> Whether to center the scrolling region in the canvas
window when it is smaller than the canvas' allocation.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2657592"></a><h3>
<a name="gnome-canvas-get-center-scroll-region"></a>gnome_canvas_get_center_scroll_region ()</h3>
<a class="indexterm" name="id2657604"></a><pre class="programlisting"><a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gboolean"
>gboolean</a> gnome_canvas_get_center_scroll_region
(<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas);</pre>
<p>
Returns whether the canvas is set to center the scrolling region in the window
if the former is smaller than the canvas' allocation.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</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.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2657668"></a><h3>
<a name="gnome-canvas-set-pixels-per-unit"></a>gnome_canvas_set_pixels_per_unit ()</h3>
<a class="indexterm" name="id2657679"></a><pre class="programlisting">void gnome_canvas_set_pixels_per_unit
(<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,
double n);</pre>
<p>
Sets the zooming factor of a canvas by specifying the number of pixels that
correspond to one canvas unit.
</p>
<p>
The anchor point for zooming, i.e. the point that stays fixed and all others
zoom inwards or outwards from it, depends on whether the canvas is set to
center the scrolling region or not. You can control this using the
<a href="GnomeCanvas.html#gnome-canvas-set-center-scroll-region"><code class="function">gnome_canvas_set_center_scroll_region()</code></a> function. If the canvas is set to
center the scroll region, then the center of the canvas window is used as the
anchor point for zooming. Otherwise, the upper-left corner of the canvas
window is used as the anchor point.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>n</code></em> :</span></td>
<td> The number of pixels that correspond to one canvas unit.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2657776"></a><h3>
<a name="gnome-canvas-scroll-to"></a>gnome_canvas_scroll_to ()</h3>
<a class="indexterm" name="id2657786"></a><pre class="programlisting">void gnome_canvas_scroll_to (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,
int cx,
int cy);</pre>
<p>
Makes a canvas scroll to the specified offsets, given in canvas pixel units.
The canvas will adjust the view so that it is not outside the scrolling
region. This function is typically not used, as it is better to hook
scrollbars to the canvas layout's scrolling adjusments.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>cx</code></em> :</span></td>
<td> Horizontal scrolling offset in canvas pixel units.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>cy</code></em> :</span></td>
<td> Vertical scrolling offset in canvas pixel units.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2657884"></a><h3>
<a name="gnome-canvas-get-scroll-offsets"></a>gnome_canvas_get_scroll_offsets ()</h3>
<a class="indexterm" name="id2657894"></a><pre class="programlisting">void gnome_canvas_get_scroll_offsets (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,
int *cx,
int *cy);</pre>
<p>
Queries the scrolling offsets of a canvas. The values are returned in canvas
pixel units.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>cx</code></em> :</span></td>
<td> Horizontal scrolling offset (return value).
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>cy</code></em> :</span></td>
<td> Vertical scrolling offset (return value).
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2657988"></a><h3>
<a name="gnome-canvas-update-now"></a>gnome_canvas_update_now ()</h3>
<a class="indexterm" name="id2657999"></a><pre class="programlisting">void gnome_canvas_update_now (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas);</pre>
<p>
Forces an immediate update and redraw of a canvas. If the canvas does not
have any pending update or redraw requests, then no action is taken. This is
typically only used by applications that need explicit control of when the
display is updated, like games. It is not needed by normal applications.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody><tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</td>
</tr></tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2658054"></a><h3>
<a name="gnome-canvas-get-item-at"></a>gnome_canvas_get_item_at ()</h3>
<a class="indexterm" name="id2658064"></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,
double x,
double y);</pre>
<p>
Looks for the item that is under the specified position, which must be
specified in world coordinates.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>x</code></em> :</span></td>
<td> X position in world coordinates.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>y</code></em> :</span></td>
<td> Y position in world coordinates.
</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
coordinates.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2658170"></a><h3>
<a name="gnome-canvas-request-redraw-uta"></a>gnome_canvas_request_redraw_uta ()</h3>
<a class="indexterm" name="id2658181"></a><pre class="programlisting">void gnome_canvas_request_redraw_uta (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,
ArtUta *uta);</pre>
<p>
Informs a canvas that the specified area, given as a microtile array, needs
to be repainted. To be used only by item implementations.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>uta</code></em> :</span></td>
<td> Microtile array that specifies the area to be redrawn. It will
be freed by this function, so the argument you pass will be invalid
after you call this function.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2658258"></a><h3>
<a name="gnome-canvas-request-redraw"></a>gnome_canvas_request_redraw ()</h3>
<a class="indexterm" name="id2658269"></a><pre class="programlisting">void gnome_canvas_request_redraw (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,
int x1,
int y1,
int x2,
int y2);</pre>
<p>
Convenience function that informs a canvas that the specified rectangle needs
to be repainted. This function converts the rectangle to a microtile array
and feeds it to <a href="GnomeCanvas.html#gnome-canvas-request-redraw-uta"><code class="function">gnome_canvas_request_redraw_uta()</code></a>. The rectangle includes
<em class="parameter"><code>x1</code></em> and <em class="parameter"><code>y1</code></em>, but not <em class="parameter"><code>x2</code></em> and <em class="parameter"><code>y2</code></em>. To be used only by item implementations.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>x1</code></em> :</span></td>
<td> Leftmost coordinate of the rectangle to be redrawn.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>y1</code></em> :</span></td>
<td> Upper coordinate of the rectangle to be redrawn.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>x2</code></em> :</span></td>
<td> Rightmost coordinate of the rectangle to be redrawn, plus 1.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>y2</code></em> :</span></td>
<td> Lower coordinate of the rectangle to be redrawn, plus 1.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2658441"></a><h3>
<a name="gnome-canvas-w2c-affine"></a>gnome_canvas_w2c_affine ()</h3>
<a class="indexterm" name="id2658452"></a><pre class="programlisting">void gnome_canvas_w2c_affine (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,
double affine[6]);</pre>
<p>
Gets the affine transform that converts from world coordinates to canvas
pixel coordinates.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>affine</code></em> :</span></td>
<td> An affine transformation matrix (return value).
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2658525"></a><h3>
<a name="gnome-canvas-w2c"></a>gnome_canvas_w2c ()</h3>
<a class="indexterm" name="id2658535"></a><pre class="programlisting">void gnome_canvas_w2c (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,
double wx,
double wy,
int *cx,
int *cy);</pre>
<p>
Converts world coordinates into canvas pixel coordinates.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>wx</code></em> :</span></td>
<td> World X coordinate.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>wy</code></em> :</span></td>
<td> World Y coordinate.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>cx</code></em> :</span></td>
<td> X pixel coordinate (return value).
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>cy</code></em> :</span></td>
<td> Y pixel coordinate (return value).
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2658672"></a><h3>
<a name="gnome-canvas-w2c-d"></a>gnome_canvas_w2c_d ()</h3>
<a class="indexterm" name="id2658683"></a><pre class="programlisting">void gnome_canvas_w2c_d (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,
double wx,
double wy,
double *cx,
double *cy);</pre>
<p>
Converts world coordinates into canvas pixel coordinates. This
version returns coordinates in floating point coordinates, for
greater precision.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>wx</code></em> :</span></td>
<td> World X coordinate.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>wy</code></em> :</span></td>
<td> World Y coordinate.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>cx</code></em> :</span></td>
<td> X pixel coordinate (return value).
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>cy</code></em> :</span></td>
<td> Y pixel coordinate (return value).
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2658820"></a><h3>
<a name="gnome-canvas-c2w"></a>gnome_canvas_c2w ()</h3>
<a class="indexterm" name="id2658830"></a><pre class="programlisting">void gnome_canvas_c2w (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,
int cx,
int cy,
double *wx,
double *wy);</pre>
<p>
Converts canvas pixel coordinates to world coordinates.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>cx</code></em> :</span></td>
<td> Canvas pixel X coordinate.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>cy</code></em> :</span></td>
<td> Canvas pixel Y coordinate.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>wx</code></em> :</span></td>
<td> X world coordinate (return value).
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>wy</code></em> :</span></td>
<td> Y world coordinate (return value).
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2658966"></a><h3>
<a name="gnome-canvas-window-to-world"></a>gnome_canvas_window_to_world ()</h3>
<a class="indexterm" name="id2658977"></a><pre class="programlisting">void gnome_canvas_window_to_world (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,
double winx,
double winy,
double *worldx,
double *worldy);</pre>
<p>
Converts window-relative coordinates into world coordinates. You can use
this when you need to convert mouse coordinates into world coordinates, for
example.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>winx</code></em> :</span></td>
<td> Window-relative X coordinate.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>winy</code></em> :</span></td>
<td> Window-relative Y coordinate.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>worldx</code></em> :</span></td>
<td> X world coordinate (return value).
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>worldy</code></em> :</span></td>
<td> Y world coordinate (return value).
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2659117"></a><h3>
<a name="gnome-canvas-world-to-window"></a>gnome_canvas_world_to_window ()</h3>
<a class="indexterm" name="id2659128"></a><pre class="programlisting">void gnome_canvas_world_to_window (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,
double worldx,
double worldy,
double *winx,
double *winy);</pre>
<p>
Converts world coordinates into window-relative coordinates.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>worldx</code></em> :</span></td>
<td> World X coordinate.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>worldy</code></em> :</span></td>
<td> World Y coordinate.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>winx</code></em> :</span></td>
<td> X window-relative coordinate.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>winy</code></em> :</span></td>
<td> Y window-relative coordinate.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2659266"></a><h3>
<a name="gnome-canvas-get-color"></a>gnome_canvas_get_color ()</h3>
<a class="indexterm" name="id2659276"></a><pre class="programlisting">int gnome_canvas_get_color (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,
const char *spec,
<a
href="/usr/share/gtk-doc/html/gdk/gdk-Colormaps-and-Colors.html#GdkColor"
>GdkColor</a> *color);</pre>
<p>
Allocates a color based on the specified X color specification. As a
convenience to item implementations, it returns TRUE if the color was
allocated, or FALSE if the specification was NULL. A NULL color
specification is considered as "transparent" by the canvas.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>spec</code></em> :</span></td>
<td> X color specification, or NULL for "transparent".
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>color</code></em> :</span></td>
<td> Returns the allocated color.
</td>
</tr>
<tr>
<td>
<span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td>
<td> TRUE if <em class="parameter"><code>spec</code></em> is non-NULL and the color is allocated. If <em class="parameter"><code>spec</code></em>
is NULL, then returns FALSE.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2659398"></a><h3>
<a name="gnome-canvas-get-color-pixel"></a>gnome_canvas_get_color_pixel ()</h3>
<a class="indexterm" name="id2659408"></a><pre class="programlisting"><a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gulong"
>gulong</a> gnome_canvas_get_color_pixel (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,
<a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#guint"
>guint</a> rgba);</pre>
<p>
Allocates a color from the RGBA value passed into this function. The alpha
opacity value is discarded, since normal X colors do not support it.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>rgba</code></em> :</span></td>
<td> RGBA color specification.
</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.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2659494"></a><h3>
<a name="gnome-canvas-set-stipple-origin"></a>gnome_canvas_set_stipple_origin ()</h3>
<a class="indexterm" name="id2659505"></a><pre class="programlisting">void gnome_canvas_set_stipple_origin (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,
<a
href="/usr/share/gtk-doc/html/gdk/gdk-Graphics-Contexts.html#GdkGC"
>GdkGC</a> *gc);</pre>
<p>
Sets the stipple origin of the specified GC as is appropriate for the canvas,
so that it will be aligned with other stipple patterns used by canvas items.
This is typically only needed by item implementations.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>gc</code></em> :</span></td>
<td> GC on which to set the stipple origin.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2659580"></a><h3>
<a name="gnome-canvas-set-dither"></a>gnome_canvas_set_dither ()</h3>
<a class="indexterm" name="id2659590"></a><pre class="programlisting">void gnome_canvas_set_dither (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas,
<a
href="/usr/share/gtk-doc/html/gdk/gdk-GdkRGB.html#GdkRgbDither"
>GdkRgbDither</a> dither);</pre>
<p>
Controls dithered rendering for antialiased canvases. The value of
dither should be <span class="type">GDK_RGB_DITHER_NONE</span>, <span class="type">GDK_RGB_DITHER_NORMAL</span>, or
<span class="type">GDK_RGB_DITHER_MAX</span>. The default canvas setting is
<span class="type">GDK_RGB_DITHER_NORMAL</span>.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>dither</code></em> :</span></td>
<td> Type of dithering used to render an antialiased canvas.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2659702"></a><h3>
<a name="gnome-canvas-get-dither"></a>gnome_canvas_get_dither ()</h3>
<a class="indexterm" name="id2659712"></a><pre class="programlisting"><a
href="/usr/share/gtk-doc/html/gdk/gdk-GdkRGB.html#GdkRgbDither"
>GdkRgbDither</a> gnome_canvas_get_dither (<a href="GnomeCanvas.html" title="GnomeCanvas">GnomeCanvas</a> *canvas);</pre>
<p>
Returns the type of dithering used to render an antialiased canvas.</p>
<p>
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td> A canvas.
</td>
</tr>
<tr>
<td>
<span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td>
<td> The dither setting.
</td>
</tr>
</tbody>
</table></div>
</div>
</div>
<div class="refsect1" lang="en">
<a name="id2659775"></a><h2>Properties</h2>
<div class="refsect2" lang="en">
<a name="id2659781"></a><h3>
<a name="GnomeCanvas--aa"></a>The "<code class="literal">aa</code>" property</h3>
<pre class="programlisting"> "aa" <a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gboolean"
>gboolean</a> : Read / Write / Construct Only</pre>
<p>
Enable anti-aliasing mode?
</p>
<p>
Note that this parameter can only be set at the time of object
construction. The same effect can be achieved by calling
<a href="GnomeCanvas.html#gnome-canvas-new"><code class="function">gnome_canvas_new()</code></a> to create new non-aa canvas or
<a href="GnomeCanvas.html#gnome-canvas-new-aa"><code class="function">gnome_canvas_new_aa()</code></a> for an anti-aliased canvas.
</p>
<p>Default value: FALSE</p>
</div>
</div>
<div class="refsect1" lang="en">
<a name="id2659847"></a><h2>Signals</h2>
<div class="refsect2" lang="en">
<a name="id2659852"></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,
<a
href="/usr/share/gtk-doc/html/gdk/gdk-Drawing-Primitives.html#GdkDrawable"
>GdkDrawable</a> *arg1,
<a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gint"
>gint</a> arg2,
<a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gint"
>gint</a> arg3,
<a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gint"
>gint</a> arg4,
<a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gint"
>gint</a> arg5,
<a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gpointer"
>gpointer</a> user_data);</pre>
<p>
This signal is emitted to draw the background for non-antialiased mode
canvas widgets. The default method uses the canvas widget's style to
draw the background.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td>the object which received the signal.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>arg1</code></em> :</span></td>
<td>GdkDrawable to draw to
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>arg2</code></em> :</span></td>
<td>Leftmost X coordinate of area to draw to
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>arg3</code></em> :</span></td>
<td>Top Y coordinate of area to draw to
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>arg4</code></em> :</span></td>
<td>Width of area
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>arg5</code></em> :</span></td>
<td>Height of area
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>user_data</code></em> :</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="id2660035"></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,
<a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gpointer"
>gpointer</a> arg1,
<a
href="/usr/share/gtk-doc/html/glib/glib-Basic-Types.html#gpointer"
>gpointer</a> user_data);</pre>
<p>
This signal is emitted for antialiased mode canvas widgets to render
the background. The buf data structure contains both a pointer to a
packed 24-bit RGB array and the coordinates.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>canvas</code></em> :</span></td>
<td>the object which received the signal.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>arg1</code></em> :</span></td>
<td>
<a href="GnomeCanvas.html#GnomeCanvasBuf"><span class="type">GnomeCanvasBuf</span></a> to render to
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>user_data</code></em> :</span></td>
<td>user data set when the signal handler was connected.</td>
</tr>
</tbody>
</table></div>
</div>
</div>
</div>
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