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<h2 align="center">Open, Closed and Filled Polygons,<br>
Bezier Lines and<br>
Regions Creation</h2>
<p>The functions <font><strong>cdBegin</strong></font>,
<font><strong>cdVertex</strong></font> and <font>
<strong>cdEnd</strong></font> are use for many situations.
<font><strong>cdBegin</strong></font> is called once,
<font><strong>cdVertex</strong></font> can be called many
times, and <font><strong>cdEnd</strong></font> is called once
to actually do something. If you call <font><strong>cdBegin</strong></font>
again before <font><strong>cdEnd</strong></font> the process is
restarted, except for <strong><font>cdBegin(</font></strong><b>CD_REGION</b><strong><font>)</font></strong>
that can contains one or more polygons inside. </p>
<hr>
<pre class="function"><span class="mainFunction">void <a name="cdBegin">cdCanvasBegin</a>(cdCanvas* canvas, int mode); [in C]</span>
canvas:Begin(mode: number) [in Lua]</pre>
<p>Starts defining a polygon to be drawn (or filled) according to the mode:
<b>CD_CLOSED_LINES</b>, <b>CD_OPEN_LINES</b>, <b>CD_FILL</b><strong><b>,
</b></strong><b>CD_CLIP, CD_REGION</b> or <strong><b>CD_BEZIER</b></strong>.
Do not create embedded polygons, that is, do not call function
<font><strong>cdBegin</strong></font> twice without a call to
<font><strong>cdEnd</strong></font> in between.</p>
<ul>
<li><strong>CD_OPEN_LINES</strong><b>:</b> connects all the points at cdEnd. Depends
on line width and line style attributes. </li>
<li><b><b>CD_CLOSED_LINES:</b> </b>connects all the points at cdEnd and
connects the last point to the first. Depends on line width and line
style attributes. </li>
<li><b>CD_FILL:</b> connects the last point to the first and fills
the resulting polygon according to the current interior style. When the
interior style <strong><b>CD_HOLLOW</b></strong> is defined the it behaves
as if the mode were <b>CD_CLOSED_LINES</b><strong>.</strong></li>
<li><b>CD_CLIP: i</b>nstead of creating a polygon to be drawn,
creates a polygon to define a polygonal clipping region. </li>
<li><strong><b>CD_BEZIER:</b></strong><b> </b>defines the points of a bezier
curve. There must be at least 4 points: <i>start</i>, <i>control</i>, <i>
control</i> and <i>end</i>. To specify a sequence of curves use 3 more points
for each curve: <i>control</i>, <i>control</i>, <i>end</i>, <i>control</i>, <i>
control</i>, <i>end</i>, ... The end point is used as start point for the next
curve.</li>
<li><strong><b>CD_REGION</b></strong>: starts the creation of a complex
region for clipping. All calls to <font><strong>cdBox</strong></font>,
<font><strong>cdSector</strong></font>, <font>
<strong>cdChord, Filled</strong></font> <font><strong>Polygons</strong></font>
and <font><strong>cdText</strong></font> will be composed in a
region for clipping. See <a href="region.html">Regions</a> documentation.</li>
<li><strong>CD_PATH</strong>: creates a path composed of several primitives
that can be line draw, filled or used as clipping. Must call <strong>
cdCanvasPathSet</strong> to configure the action between sequences of
<strong>cdCanvasVertex</strong>.</li>
</ul>
<p align="center"><font size="4">Open, Closed and Filled Polygons<br>
</font><img src="../../img/polygon.gif" border="2" width="249" height="116"></p>
<p align="center"><font size="4">Bezier Lines<br>
</font><img src="../../img/bezier.gif" border="2" width="241" height="220"></p>
<pre class="function"><span class="mainFunction">void <a name="cdVertex">cdCanvasVertex</a>(cdCanvas* canvas, int x, int y); [in C]</span>
void cdfCanvasVertex(cdCanvas* canvas, double x, double y); [in C]
void wdCanvasVertex(cdCanvas* canvas, double x, double y); (WC) [in C]
canvas:Vertex(x, y: number) [in Lua]
canvas:wVertex(x, y: number) (WC) [in Lua]</pre>
<p>Adds a vertex to the polygon definition.</p>
<pre class="function"><span class="mainFunction">void <a name="cdEnd">cdCanvasEnd</a>(cdCanvas* canvas); [in C]</span>
canvas:End() [in Lua]</pre>
<p>Ends the polygon's definition and draws it.</p>
<pre class="function"><span class="mainFunction">void <a name="cdPathSet">cdCanvasPathSet</a>(cdCanvas* canvas, int action); [in C]</span>
canvas:PathSet(action: number) [in Lua]</pre>
<p>Configures the action between sequences of <strong>cdCanvasVertex</strong>.
<strong>action</strong> can be:</p>
<ul>
<li> <strong>CD_PATH_NEW</strong> - creates a new empty path. Useful if more than one
path is configured. <strong>cdCanvasBegin</strong>(CD_PATH) already creates
a new path.</li>
<li><strong>CD_PATH_MOVETO</strong> - moves the current position to the given coordinates.
Must be followed by 1 call to <strong>cdCanvasVertex</strong>, <strong>
cdfCanvasVertex</strong>, or <strong>wdCanvasVertex</strong>.</li>
<li><strong>CD_PATH_LINETO</strong> - adds a line to the path from the current position to
the given coordinates. The current position is updated to the given
coordinates. If there is no current position, nothing is connected and only
the current position is updated. Must be followed by 1 call to <strong>
cdCanvasVertex</strong>, <strong>cdfCanvasVertex</strong>, or <strong>
wdCanvasVertex</strong>.</li>
<li><strong>CD_PATH_ARC</strong> - adds an arc to the path. If there is a current position
adds also a line from the current position to the start of the arc. The end
of the arc becomes the current position. Must be followed by 3 calls to
<strong>cdCanvasVertex</strong>, <strong>cdfCanvasVertex</strong>, or
<strong>wdCanvasVertex</strong>. One for the center of the arc (xc,yc), one
for the bounding rectangle size (w,h), and one for the start and end angles
(angle1,angle2). Angles are in degrees and oriented counter-clockwise, but
angle2 can be smaller than angle1 to describe a clockwise arc. When using integer coordinates
angles must be multiplied by 1000.</li>
<li><strong>CD_PATH_CURVETO</strong> - adds a bezier curve to the path. If there is no
current position, the first point will be used twice. The end point becomes
the current position. Must be followed by 3 calls to <strong>cdCanvasVertex</strong>,
<strong>cdfCanvasVertex</strong>, or <strong>wdCanvasVertex</strong>. Must
be first control point (x1,y1) + second control point (x2,y2) + end point
(x3,y3).</li>
<li><strong>CD_PATH_CLOSE</strong> - adds a line to the path that connects the last point
with the first point of the path, closing it.</li>
<li><strong>CD_PATH_FILL</strong> - fills the path with the current fill attributes,
then the path is discarded.</li>
<li><strong>CD_PATH_STROKE</strong> - strokes the path with the current line attributes, then the
path is discarded.</li>
<li><strong>CD_PATH_FILLSTROKE</strong> - fills the path with the current fill
attributes, strokes the path with the current line attributes, then the path
is discarded.</li>
<li><strong>CD_PATH_CLIP</strong> - use the path as a clipping area to be
intersected with the current clipping area, then the path is discarded.</li>
</ul>
<p>So the normal path creation to draw a line will do:</p>
<pre>cdCanvasBegin(canvas, CD_PATH);
cdCanvasPathSet(canvas, CD_PATH_MOVETO);
cdCanvasVertex(canvas, x1, y1);
cdCanvasPathSet(canvas, CD_PATH_LINETO);
cdCanvasVertex(canvas, x2, y2);
cdCanvasPathSet(canvas, CD_PATH_CURVETO);
cdCanvasVertex(canvas, x3, y3); /* control point for start point */
cdCanvasVertex(canvas, x4, y4); /* control point for end point */
cdCanvasVertex(canvas, x5, y5); /* end point */
cdCanvasPathSet(canvas, CD_PATH_ARC);
cdCanvasVertex(canvas, x6, y6); /* center */
cdCanvasVertex(canvas, x7, y7); /* width, height */
cdCanvasVertex(canvas, x8, y8); /* start angle, end angle (degrees / 1000) */
cdCanvasPathSet(canvas, CD_PATH_STROKE);
cdCanvasEnd(canvas);</pre>
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