qcanvas.html

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</h3>
Changes the size of the canvas to have a width of <em>w</em> and a height of <em>h</em>.
This is a slow operation.

<p>Examples: <a href="canvas-example.html#x2686">canvas/canvas.cpp</a> and <a href="canvas-chart-example.html#x2593">chart/chartform.cpp</a>.
<h3 class=fn>void <a name="resized"></a>QCanvas::resized ()<tt> [signal]</tt>
</h3>

<p> This signal is emitted whenever the canvas is resized. Each <a href="qcanvasview.html">QCanvasView</a>
connects to this signal to keep the scrollview size correct.

<h3 class=fn>void <a name="retune"></a>QCanvas::retune ( int&nbsp;chunksze, int&nbsp;mxclusters = 100 )<tt> [virtual]</tt>
</h3>
<p> Change the efficiency tuning parameters to <em>mxclusters</em> clusters,
each of size <em>chunksze</em>. This is a slow operation if there are many
objects on the canvas.
<p> The canvas is divided into chunks which are rectangular areas of the canvas
<em>chunksze</em> wide by <em>chunksze</em> high. Use a chunk size which is about
the average size of the canvas items. If you choose a chunk size which
is too small it will increase the amount of calculation required when
drawing since each change will affect many chunks. If you choose a chunk
size which is too large the amount of drawing required will increase
because for each change, a lot of drawing will be required since there
will be many (unchanged) canvas items which are in the same chunk as the
changed canvas items.
<p> Internally, a canvas uses a low-resolution "chunk matrix" to keep
track of all the items in the canvas. A 64x64 chunk matrix is the
default for a 1024x1024 pixel canvas, where each chunk collects canvas
items in a 16x16 pixel square. This default is also affected by
<a href="#setTiles">setTiles</a>(). You can tune this default with this function. For example
if you have a very large canvas and want to trade off speed for memory
then you might set the chunk size to 32 or 64.
<p> The <em>mxclusters</em> argument is the number of rectangular groups of chunks
that will be separately drawn. If the canvas has a large number of
small, dispersed items, this should be about that number. Our testing
suggests that a large number of clusters is almost always best.
<p> 
<h3 class=fn>void <a name="setAdvancePeriod"></a>QCanvas::setAdvancePeriod ( int&nbsp;ms )<tt> [virtual]</tt>
</h3>
Sets the canvas to call <a href="#advance">advance</a>() every <em>ms</em> milliseconds. Any
previous setting by <a href="#setAdvancePeriod">setAdvancePeriod</a>() or <a href="#setUpdatePeriod">setUpdatePeriod</a>() is
overridden.
<p> If <em>ms</em> is less than 0 advancing will be stopped.

<p>Example: <a href="canvas-example.html#x2739">canvas/main.cpp</a>.
<h3 class=fn>void <a name="setAllChanged"></a>QCanvas::setAllChanged ()<tt> [virtual]</tt>
</h3>
Marks the whole canvas as changed.
All views of the canvas will be entirely redrawn when
<a href="#update">update</a>() is called next.

<h3 class=fn>void <a name="setBackgroundColor"></a>QCanvas::setBackgroundColor ( const&nbsp;<a href="qcolor.html">QColor</a>&nbsp;&amp;&nbsp;c )<tt> [virtual]</tt>
</h3>
Sets the solid background to be the color <em>c</em>.
<p> <p>See also <a href="#backgroundColor">backgroundColor</a>(), <a href="#setBackgroundPixmap">setBackgroundPixmap</a>() and <a href="#setTiles">setTiles</a>().

<h3 class=fn>void <a name="setBackgroundPixmap"></a>QCanvas::setBackgroundPixmap ( const&nbsp;<a href="qpixmap.html">QPixmap</a>&nbsp;&amp;&nbsp;p )<tt> [virtual]</tt>
</h3>
Sets the solid background to be the pixmap <em>p</em> repeated as
necessary to cover the entire canvas.
<p> <p>See also <a href="#backgroundPixmap">backgroundPixmap</a>(), <a href="#setBackgroundColor">setBackgroundColor</a>() and <a href="#setTiles">setTiles</a>().

<h3 class=fn>void <a name="setChanged"></a>QCanvas::setChanged ( const&nbsp;<a href="qrect.html">QRect</a>&nbsp;&amp;&nbsp;area )<tt> [virtual]</tt>
</h3>
Marks <em>area</em> as changed. This area will be redrawn in all views
that are showing it when <a href="#update">update</a>() is called next.

<h3 class=fn>void <a name="setDoubleBuffering"></a>QCanvas::setDoubleBuffering ( bool&nbsp;y )<tt> [virtual]</tt>
</h3>
If <em>y</em> is TRUE (the default) double-buffering is switched on;
otherwise double-buffering is switched off.
<p> Turning off double-buffering causes the redrawn areas to flicker a
bit and also gives a (usually small) performance improvement.

<p>Example: <a href="canvas-example.html#x2687">canvas/canvas.cpp</a>.
<h3 class=fn>void <a name="setTile"></a>QCanvas::setTile ( int&nbsp;x, int&nbsp;y, int&nbsp;tilenum )<tt> [virtual]</tt>
</h3>  Sets the tile at (<em>x</em>, <em>y</em>) to use tile number <em>tilenum</em>,
which is an index into the tile pixmaps. The canvas will update
appropriately when <a href="#update">update</a>() is next called.
<p> The images are taken from the pixmap set by <a href="#setTiles">setTiles</a>() and are
arranged left to right, (and in the case of pixmaps that have multiple
rows of tiles, top to bottom), with tile 0 in the top-left corner,
tile 1 next to the right, and so on, e.g.
<p> <center><table cellpadding="4" cellspacing="2" border="0">
<tr bgcolor="#f0f0f0"> <td valign="top">0 <td valign="top">1 <td valign="top">2 <td valign="top">3
<tr bgcolor="#d0d0d0"> <td valign="top">4 <td valign="top">5 <td valign="top">6 <td valign="top">7
</table></center>
<p> <p>See also <a href="#tile">tile</a>() and <a href="#setTiles">setTiles</a>().

<h3 class=fn>void <a name="setTiles"></a>QCanvas::setTiles ( <a href="qpixmap.html">QPixmap</a>&nbsp;p, int&nbsp;h, int&nbsp;v, int&nbsp;tilewidth, int&nbsp;tileheight )<tt> [virtual]</tt>
</h3>  Sets the QCanvas to be composed of <em>h</em> tiles horizontally and <em>v</em> tiles vertically. Each tile will be an image <em>tilewidth</em> by <em>tileheight</em> pixels from pixmap <em>p</em>.
<p> The pixmap <em>p</em> is a list of tiles, arranged left to right, (and in
the case of pixmaps that have multiple rows of tiles, top to bottom),
with tile 0 in the top-left corner, tile 1 next to the right, and so
on, e.g.
<p> <center><table cellpadding="4" cellspacing="2" border="0">
<tr bgcolor="#f0f0f0"> <td valign="top">0 <td valign="top">1 <td valign="top">2 <td valign="top">3
<tr bgcolor="#d0d0d0"> <td valign="top">4 <td valign="top">5 <td valign="top">6 <td valign="top">7
</table></center>
<p> If the canvas is larger than the matrix of tiles, the entire matrix
is repeated as necessary to cover the whole canvas. If it is smaller,
tiles to the right and bottom are not visible.
<p> The width and height of <em>p</em> must be a multiple of <em>tilewidth</em> and
<em>tileheight</em>. If they are not the function will do nothing.

<h3 class=fn>void <a name="setUnchanged"></a>QCanvas::setUnchanged ( const&nbsp;<a href="qrect.html">QRect</a>&nbsp;&amp;&nbsp;area )<tt> [virtual]</tt>
</h3>
Marks <em>area</em> as <em>unchanged</em>. The area will <em>not</em> be redrawn in the
views for the next <a href="#update">update</a>(), unless it is marked or changed again
before the next call to update().

<h3 class=fn>void <a name="setUpdatePeriod"></a>QCanvas::setUpdatePeriod ( int&nbsp;ms )<tt> [virtual]</tt>
</h3>
Sets the canvas to call <a href="#update">update</a>() every <em>ms</em> milliseconds. Any
previous setting by <a href="#setAdvancePeriod">setAdvancePeriod</a>() or <a href="#setUpdatePeriod">setUpdatePeriod</a>() is
overridden.
<p> If <em>ms</em> is less than 0 automatic updating will be stopped.

<h3 class=fn><a href="qsize.html">QSize</a> <a name="size"></a>QCanvas::size () const
</h3>

<p> Returns the size of the canvas, in pixels.

<h3 class=fn>int <a name="tile"></a>QCanvas::tile ( int&nbsp;x, int&nbsp;y ) const
</h3>

<p> Returns the tile at position (<em>x</em>, <em>y</em>). Initially, all tiles are 0.
<p> The parameters must be within range, i.e.
0 &lt; <em>x</em> &lt; <a href="#tilesHorizontally">tilesHorizontally</a>() and
0 &lt; <em>y</em> &lt; <a href="#tilesVertically">tilesVertically</a>().
<p> <p>See also <a href="#setTile">setTile</a>().

<h3 class=fn>int <a name="tileHeight"></a>QCanvas::tileHeight () const
</h3>

<p> Returns the height of each tile.

<h3 class=fn>int <a name="tileWidth"></a>QCanvas::tileWidth () const
</h3>

<p> Returns the width of each tile.

<h3 class=fn>int <a name="tilesHorizontally"></a>QCanvas::tilesHorizontally () const
</h3>

<p> Returns the number of tiles horizontally.

<h3 class=fn>int <a name="tilesVertically"></a>QCanvas::tilesVertically () const
</h3>

<p> Returns the number of tiles vertically.

<h3 class=fn>void <a name="update"></a>QCanvas::update ()<tt> [virtual slot]</tt>
</h3>
Repaints changed areas in all views of the canvas.
<p> <p>See also <a href="#advance">advance</a>().

<h3 class=fn>bool <a name="validChunk"></a>QCanvas::validChunk ( int&nbsp;x, int&nbsp;y ) const
</h3>

<p> Returns TRUE if the chunk position (<em>x</em>, <em>y</em>) is on the canvas;
otherwise returns FALSE.
<p> <p>See also <a href="#onCanvas">onCanvas</a>().

<h3 class=fn>bool <a name="validChunk-2"></a>QCanvas::validChunk ( const&nbsp;<a href="qpoint.html">QPoint</a>&nbsp;&amp;&nbsp;p ) const
</h3>
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
<p> Returns TRUE if the chunk position <em>p</em> is on the canvas; otherwise
returns FALSE.
<p> <p>See also <a href="#onCanvas">onCanvas</a>().

<h3 class=fn>int <a name="width"></a>QCanvas::width () const
</h3>

<p> Returns the width of the canvas, in pixels.

<p>Example: <a href="canvas-example.html#x2688">canvas/canvas.cpp</a>.
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