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<!doctype HTML PUBLIC "-//IETF//DTD HTML//EN">
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<title>Clipping</title>
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<h2 align="center">Clipping</h2>
<p>The clipping area is an area that limits the available drawing area inside the
canvas. Any primitive is drawn only inside the clipping area. It affects all
primitives.</p>
<p>You can set the clipping area by using the function <b>cdClipArea</b>, and
retrieve it using <b>cdGetClipArea</b>. The clipping area is a rectangle by
default, but it can has other shapes. In some drivers a polygon area can be
defined, and in display based drivers a complex region can be defined. The
complex region can be a combination of boxes, polygons, sectors, chords and
texts.</p>
<p>The <b>Clip</b> function activates and deactivaes the clipping.</p>
<hr>
<pre class="function"><span class="mainFunction">int cdCanvasClip(cdCanvas* canvas, int mode); [in C]</span>
canvas:Clip(mode: number) -> (old_mode: number) [in Lua]</pre>
<p>Activates or deactivates clipping. Returns the previous status. Values: <b>CD_CLIPAREA,
CD_CLIPPOLYGON, CD_CLIPREGION</b> or <b>CD_CLIPOFF</b>. The value <b>CD_QUERY</b>
simply returns the current status. Default value: <b>CD_CLIPOFF</b>.</p>
<p>The value <b>CD_CLIPAREA</b> activates a rectangular area as the clipping
region.
</p>
<p>The value <b>CD_CLIPPOLYGON</b> activates a polygon as a clipping region, but
works only in some drivers (please refer to the notes of each driver). The
clipping polygon must be defined before activating the polygon clipping; if it
is not defined, the current clipping state remains unchanged. See the
documentation of <a href="polygon.html">cdBegin/cdVertex/cdEnd</a> to create a
polygon.</p>
<p>The value <b>CD_CLIPREGION</b> activates a complex clipping region. See the
documentation of <a href="region.html">Regions</a>.</p>
<p>The defined clipping area, polygon and complex regions are stored
internally, so you may define them independently and switch between area,
polygon and complex region without having to define them again. Also if the
active clipping region is re-defined it immediately becomes the current
clipping region.</p>
<pre class="function"><span class="mainFunction">void cdCanvasClipArea(cdCanvas* canvas, int xmin, int xmax, int ymin, int ymax); [in C]</span>
void cdfCanvasClipArea(cdCanvas* canvas, double xmin, double xmax, double ymin, double ymax); [in C]
void wdCanvasClipArea(cdCanvas* canvas, double xmin, double xmax, double ymin, double ymax); (WC) [in C]
canvas:ClipArea(xmin, xmax, ymin, ymax: number) [in Lua]
canvas:wClipArea(xmin, xmax, ymin, ymax: number) (WC) [in Lua]</pre>
<p>Defines the current rectangle for clipping. Only the points in the interval <i><b>xmin<=
x <= xmax</b></i> and<b> </b><i><b>ymin <= y <= ymax</b></i> will
be printed. Default region: (0, w-1, 0, h-1).
</p>
<pre class="function"><span class="mainFunction">int cdCanvasGetClipArea(cdCanvas* canvas, int *xmin, int *xmax, int *ymin, int *ymax); [in C]</span>
int cdfCanvasGetClipArea(cdCanvas* canvas, double *xmin, double *xmax, double *ymin, double *ymax); [in C]
int wdCanvasGetClipArea(cdCanvas* canvas, double *xmin, double *xmax, double *ymin, double *ymax); (WC) [in C]
canvas:GetClipArea() -> (xmin, xmax, ymin, ymax, status: number) [in Lua]
canvas:wGetClipArea() -> (xmin, xmax, ymin, ymax, status: number) (WC) [in Lua]</pre>
<p>Returns the rectangle and the clipping status. It is not necessary to provide
all return pointers, you can provide only the desired values and <i><b>NULL</b></i>
for the others.</p>
<h4><a name="Polygons">Polygons</a></h4>
<p>A polygon for clipping can be created using <font face="Courier"><strong>cdBegin(</strong>CD_CLIP<strong>)/cdVertex(x,y)/.../cdEnd()</strong></font>.</p>
<p>See the documentation of <a href="polygon.html">cdBegin/cdVertex/cdEnd</a>.</p>
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