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<title>Complex Clipping Regions</title>
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<h2 align="center">Complex Clipping Regions</h2>
<p>A complex region can composed of boxes, sectors, chords, polygons and
texts. It is implemented only in the Windows GDI, GDI+ and X-Windows base drivers.</p>
<p>Complex clipping regions can be created using <font><strong>
cdBegin(</strong></font><b><tt>CD_REGION</tt></b><font><strong>)/(filled
primtives)/.../cdEnd()</strong></font>. For more about cdBegin and cdEnd see
<a href="polygon.html">Polygons</a>.</p>
<p>Between a <strong><font>cdBegin(</font></strong><b><tt>CD_REGION</tt></b><strong><font>)</font></strong>
and a <strong><font>cdEnd()</font></strong>, all calls to
<font><strong>cdBox</strong></font>, <font>
<strong>cdSector</strong></font>, <font><strong>cdChord,
cdBegin(CD_FILL)/cdVertex(x,y)/.../cdEnd()</strong></font> and
<font><strong>cdText</strong></font> will be composed in a
region for clipping. This is the only exception when you can call a
<font><strong>cdBegin</strong></font> after another
<font><strong>cdBegin</strong></font>.</p>
<p>When you call <font><strong>cdBegin(</strong></font><b><tt>CD_REGION</tt></b><strong><font>)</font></strong>
a new empty region will be created. So for the first operation you should use
<b><tt>CD_UNION</tt></b> or <b><tt>CD_NOTINTERSECT</tt></b> combine modes.
When you finished to compose the region call <font><strong>
cdEnd()</strong></font>.</p>
<p>To make the region active you must call <strong><font>
cdClip(</font></strong><b><tt>CD_CLIPREGION</tt></b><strong><font>)</font></strong>.
For other clipping regions see <a href="clipping.html">Clipping</a>.</p>
<p>Complex clipping regions are not saved by <strong>cdSaveState</strong>.</p>
<hr>
<pre class="function"><span class="mainFunction">int cdCanvasRegionCombineMode(cdCanvas* canvas, int mode); [in C]</span>
canvas:RegionCombineMode(mode: number) -> (old_mode: number) [in Lua]</pre>
<p>Changes the way regions are combined when created. Returns the previous
status. Values: <b><tt>CD_UNION, CD_INTERSECT, CD_DIFFERENCE or
CD_NOTINTERSECT</tt></b>. The value <b><tt>CD_QUERY</tt></b> simply returns
the current status. Default value: <b><tt>CD_UNION</tt></b>.</p>
<p align="center"><font size="4">Combine Modes<br>
</font><img src="../../img/regions.gif" border="2" width="297" height="361"></p>
<pre class="function"><span class="mainFunction">int cdCanvasIsPointInRegion(cdCanvas* canvas, int x, int y); [in C]</span>
int wdCanvasIsPointInRegion(cdCanvas* canvas, double x, double y); (WC) [in C]
canvas:IsPointInRegion(x, y: number) -> (status: boolean) [in Lua]
canvas:wIsPointInRegion(x, y: number) -> (status: boolean) [in Lua]</pre>
<p>Returns a non zero value if the point is contained inside the current
region.</p>
<pre class="function"><span class="mainFunction">void cdCanvasOffsetRegion(cdCanvas* canvas, int dx, int dy); [in C]</span>
void wdCanvasOffsetRegion(cdCanvas* canvas, double dx, double dy); (WC) [in C]
canvas:OffsetRegion(dx, dy: number) [in Lua]
canvas:wOffsetRegion(dx, dy: number) (WC) [in Lua]</pre>
<p>Moves the current region by the given offset. In X-Windows, if the region
moves to outside the canvas border, the part moved outside will be lost, the
region will need to be reconstructed.</p>
<pre class="function"><span class="mainFunction">void cdCanvasGetRegionBox(cdCanvas* canvas, int *xmin, int *xmax, int *ymin, int *ymax); [in C]</span>
void wdCanvasGetRegionBox(cdCanvas* canvas, double *xmin, double *xmax, double *ymin, double *ymax); (WC) [in C]
canvas:GetRegionBox() -> (xmin, xmax, ymin, ymax, status: number) [in Lua]
canvas:wGetRegionBox() -> (xmin, xmax, ymin, ymax, status: number) (WC) [in Lua]</pre>
<p>Returns the rectangle of the bounding box of the current region. It is not
necessary to provide all return pointers, you can provide only the desired
values and <i><tt>NULL</tt></i> for the others.</p>
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