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<li><a class="reference internal" href="#">Sprites</a><ul>
<li><a class="reference internal" href="#sprite-classes">Sprite Classes</a></li>
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  <div class="section" id="sprites">
<span id="id1"></span><h1>Sprites<a class="headerlink" href="#sprites" title="Permalink to this headline"> link</a></h1>
<p>To support the display of a large number of images at once, Ren'Py supports
a sprite system. This system allows one to create sprites, where each sprite
contains a displayable. The sprites can then have their location on the
screen and vertical ordering changed.</p>
<p>If one ignores performance, the sprite system is conceptually similar
to a <a class="reference internal" href="displayables.html#Fixed" title="Fixed"><code class="xref py py-func docutils literal notranslate"><span class="pre">Fixed()</span></code></a> wrapping <a class="reference internal" href="trans_trans_python.html#Transform" title="Transform"><code class="xref py py-func docutils literal notranslate"><span class="pre">Transform()</span></code></a>s. Sprites are much
faster than transforms, but also less flexible. The big performance
improvement of sprites is that each Displayable is rendered only once
per frame, even if that Displayable is used by many sprites. The limitation
is that Sprites only allow one to change their xoffset and yoffset, rather
than the many properties that a Transform has.</p>
<p>To use the sprite system, create a SpriteManager object, and then call
its create method to create new particles. As necessary, update the
xoffset, yoffset, and zorder fields of each sprite to move it around
the screen. By supplying <cite>update</cite> and <cite>event</cite> arguments to
SpriteManager, you can have the sprites change over time, and react to
user input.</p>
<div class="section" id="sprite-classes">
<h2>Sprite Classes<a class="headerlink" href="#sprite-classes" title="Permalink to this headline"> link</a></h2>
<dl class="class">
<dt id="Sprite">
<em class="property">class </em><code class="descname">Sprite</code><a class="headerlink" href="#Sprite" title="Permalink to this definition"> link</a></dt>
<dd><p>This represents a sprite that is managed by the SpriteManager. It contains
fields that control the placement of the sprite on the screen. Sprites
should not be created directly. Instead, they should be created by
calling <a class="reference internal" href="#SpriteManager.create" title="SpriteManager.create"><code class="xref py py-meth docutils literal notranslate"><span class="pre">SpriteManager.create()</span></code></a>.</p>
<p>The fields of a sprite object are:</p>
<dl class="docutils">
<dt><cite>x</cite>, <cite>y</cite></dt>
<dd>The x and y coordinates of the upper-left corner of the sprite,
relative to the SpriteManager.</dd>
<dt><cite>zorder</cite></dt>
<dd>An integer that's used to control the order of this sprite in the
relative to the other sprites in the SpriteManager. The larger the
number is, the closer to the viewer the sprite is.</dd>
<dt><cite>events</cite></dt>
<dd>If True, then events are passed to child. If False, the default,
the children ignore events (and hence don't spend time processing
them).</dd>
</dl>
<p>The methods of a Sprite object are:</p>
<dl class="method">
<dt id="Sprite.destroy">
<code class="descname">destroy</code><span class="sig-paren">(</span><em>self</em><span class="sig-paren">)</span><a class="headerlink" href="#Sprite.destroy" title="Permalink to this definition"> link</a></dt>
<dd><p>Destroys this sprite, preventing it from being displayed and
removing it from the SpriteManager.</p>
</dd></dl>

<dl class="method">
<dt id="Sprite.set_child">
<code class="descname">set_child</code><span class="sig-paren">(</span><em>d</em><span class="sig-paren">)</span><a class="headerlink" href="#Sprite.set_child" title="Permalink to this definition"> link</a></dt>
<dd><p>Changes the Displayable associated with this sprite to <cite>d</cite>.</p>
</dd></dl>

</dd></dl>

<dl class="class">
<dt id="SpriteManager">
<em class="property">class </em><code class="descname">SpriteManager</code><span class="sig-paren">(</span><em>update=None</em>, <em>event=None</em>, <em>predict=None</em>, <em>ignore_time=False</em>, <em>**properties</em><span class="sig-paren">)</span><a class="headerlink" href="#SpriteManager" title="Permalink to this definition"> link</a></dt>
<dd><p>This displayable manages a collection of sprites, and displays
them at the fastest speed possible.</p>
<dl class="docutils">
<dt><cite>update</cite></dt>
<dd>If not None, a function that is called each time a sprite
is rendered by this sprite manager. It is called with one
argument, the time in seconds since this sprite manager
was first displayed.  It is expected to return the number
of seconds until the function is called again, and the
SpriteManager is rendered again.</dd>
<dt><cite>event</cite></dt>
<dd>If not None, a function that is called when an event occurs.
It takes as arguments:
* A pygame event object.
* The x coordinate of the event.
* The y coordinate of the event.
* The time since the sprite manager was first shown.
If it returns a non-None value, the interaction ends, and
that value is returned.</dd>
<dt><cite>predict</cite></dt>
<dd>If not None, a function that returns a list of
displayables. These displayables are predicted when the
sprite manager is.</dd>
<dt><cite>ignore_time</cite></dt>
<dd>If True, then time is ignored when rendering displayables. This
should be used when the sprite manager is used with a relatively
small pool of images, and those images do not change over time.
This should only be used with a small number of displayables, as
it will keep all displayables used in memory for the life of the
SpriteManager.</dd>
</dl>
<p>After being rendered once (before the <cite>update</cite> function is called),
SpriteManagers have the following fields:</p>
<dl class="docutils">
<dt><cite>width</cite>, <cite>height</cite></dt>
<dd>The width and height of this SpriteManager, in pixels.</dd>
</dl>
<p>SpriteManagers have the following methods:</p>
<dl class="method">
<dt id="SpriteManager.create">
<code class="descname">create</code><span class="sig-paren">(</span><em>d</em><span class="sig-paren">)</span><a class="headerlink" href="#SpriteManager.create" title="Permalink to this definition"> link</a></dt>
<dd><p>Creates a new Sprite for the displayable <cite>d</cite>, and adds it to this
SpriteManager.</p>
</dd></dl>

<dl class="method">
<dt id="SpriteManager.redraw">
<code class="descname">redraw</code><span class="sig-paren">(</span><em>delay=0</em><span class="sig-paren">)</span><a class="headerlink" href="#SpriteManager.redraw" title="Permalink to this definition"> link</a></dt>
<dd><p>Causes this SpriteManager to be redrawn in <cite>delay</cite> seconds.</p>
</dd></dl>

</dd></dl>

<dl class="function">
<dt id="SnowBlossom">
<code class="descname">SnowBlossom</code><span class="sig-paren">(</span><em>d</em>, <em>count=10</em>, <em>border=50</em>, <em>xspeed=(20</em>, <em>50)</em>, <em>yspeed=(100</em>, <em>200)</em>, <em>start=0</em>, <em>fast=False</em>, <em>horizontal=False</em><span class="sig-paren">)</span><a class="headerlink" href="#SnowBlossom" title="Permalink to this definition"> link</a></dt>
<dd><p>The snowblossom effect moves multiple instances of a sprite up,
down, left or right on the screen. When a sprite leaves the screen, it
is returned to the start.</p>
<dl class="docutils">
<dt><cite>d</cite></dt>
<dd>The displayable to use for the sprites.</dd>
<dt><cite>border</cite></dt>
<dd>The size of the border of the screen. The sprite is considered to be
on the screen until it clears the border, ensuring that sprites do
not disappear abruptly.</dd>
<dt><cite>xspeed</cite>, <cite>yspeed</cite></dt>
<dd>The speed at which the sprites move, in the horizontal and vertical
directions, respectively. These can be a single number or a tuple of
two numbers. In the latter case, each particle is assigned a random
speed between the two numbers. The speeds can be positive or negative,
as long as the second number in a tuple is larger than the first.</dd>
<dt><cite>start</cite></dt>
<dd>The delay, in seconds, before each particle is added. This can be
allows the particles to start at the top of the screen, while not
looking like a &quot;wave&quot; effect.</dd>
<dt><cite>fast</cite></dt>
<dd>If true, particles start in the center of the screen, rather than
only at the edges.</dd>
<dt><cite>horizontal</cite></dt>
<dd>If true, particles appear on the left or right side of the screen,
rather than the top or bottom.</dd>
</dl>
</dd></dl>

</div>
<div class="section" id="sprite-examples">
<h2>Sprite Examples<a class="headerlink" href="#sprite-examples" title="Permalink to this headline"> link</a></h2>
<p>The SnowBlossom class is an easy-to use way of placing falling things
on the screen.</p>
<div class="highlight-renpy notranslate"><div class="highlight"><pre><span></span><span class="k">image</span> <span class="n">snow</span> <span class="o">=</span> <span class="n">SnowBlossom</span><span class="p">(</span><span class="s2">&quot;snow.png&quot;</span><span class="p">,</span> <span class="n">count</span><span class="o">=</span><span class="mi">100</span><span class="p">)</span>
</pre></div>
</div>
<p>This example shows how a SpriteManager can be used to create complex
behaviors. In this case, it shows 400 particles, and has them avoid
the mouse.</p>
<div class="highlight-renpy notranslate"><div class="highlight"><pre><span></span><span class="k">init</span> <span class="k">python</span><span class="p">:</span>
    <span class="kn">import</span> <span class="nn">math</span>

    <span class="k">def</span> <span class="nf">repulsor_update</span><span class="p">(</span><span class="n">st</span><span class="p">):</span>

        <span class="c1"># If we don&#39;t know where the mouse is, give up.</span>
        <span class="k">if</span> <span class="n">repulsor_pos</span> <span class="k">is</span> <span class="kc">None</span><span class="p">:</span>
            <span class="k">return</span> <span class="o">.</span><span class="mi">01</span>

        <span class="n">px</span><span class="p">,</span> <span class="n">py</span> <span class="o">=</span> <span class="n">repulsor_pos</span>

        <span class="c1"># For each sprite...</span>
        <span class="k">for</span> <span class="n">i</span> <span class="k">in</span> <span class="n">repulsor_sprites</span><span class="p">:</span>

            <span class="c1"># Compute the vector between it and the mouse.</span>
            <span class="n">vx</span> <span class="o">=</span> <span class="n">i</span><span class="o">.</span><span class="n">x</span> <span class="o">-</span> <span class="n">px</span>
            <span class="n">vy</span> <span class="o">=</span> <span class="n">i</span><span class="o">.</span><span class="n">y</span> <span class="o">-</span> <span class="n">py</span>

            <span class="c1"># Get the vector length, normalize the vector.</span>
            <span class="n">vl</span> <span class="o">=</span> <span class="n">math</span><span class="o">.</span><span class="n">hypot</span><span class="p">(</span><span class="n">vx</span><span class="p">,</span> <span class="n">vy</span><span class="p">)</span>
            <span class="k">if</span> <span class="n">vl</span> <span class="o">&gt;=</span> <span class="mi">150</span><span class="p">:</span>
                <span class="k">continue</span>

            <span class="c1"># Compute the distance to move.</span>
            <span class="n">distance</span> <span class="o">=</span> <span class="mf">3.0</span> <span class="o">*</span> <span class="p">(</span><span class="mi">150</span> <span class="o">-</span> <span class="n">vl</span><span class="p">)</span> <span class="o">/</span> <span class="mi">150</span>

            <span class="c1"># Move</span>
            <span class="n">i</span><span class="o">.</span><span class="n">x</span> <span class="o">+=</span> <span class="n">distance</span> <span class="o">*</span> <span class="n">vx</span> <span class="o">/</span> <span class="n">vl</span>
            <span class="n">i</span><span class="o">.</span><span class="n">y</span> <span class="o">+=</span> <span class="n">distance</span> <span class="o">*</span> <span class="n">vy</span> <span class="o">/</span> <span class="n">vl</span>

            <span class="c1"># Ensure we stay on the screen.</span>
            <span class="k">if</span> <span class="n">i</span><span class="o">.</span><span class="n">x</span> <span class="o">&lt;</span> <span class="mi">2</span><span class="p">:</span>
                <span class="n">i</span><span class="o">.</span><span class="n">x</span> <span class="o">=</span> <span class="mi">2</span>

            <span class="k">if</span> <span class="n">i</span><span class="o">.</span><span class="n">x</span> <span class="o">&gt;</span> <span class="n">repulsor</span><span class="o">.</span><span class="na">width</span> <span class="o">-</span> <span class="mi">2</span><span class="p">:</span>
                <span class="n">i</span><span class="o">.</span><span class="n">x</span> <span class="o">=</span> <span class="n">repulsor</span><span class="o">.</span><span class="na">width</span> <span class="o">-</span> <span class="mi">2</span>

            <span class="k">if</span> <span class="n">i</span><span class="o">.</span><span class="n">y</span> <span class="o">&lt;</span> <span class="mi">2</span><span class="p">:</span>
                <span class="n">i</span><span class="o">.</span><span class="n">y</span> <span class="o">=</span> <span class="mi">2</span>

            <span class="k">if</span> <span class="n">i</span><span class="o">.</span><span class="n">y</span> <span class="o">&gt;</span> <span class="n">repulsor</span><span class="o">.</span><span class="na">height</span> <span class="o">-</span> <span class="mi">2</span><span class="p">:</span>
                <span class="n">i</span><span class="o">.</span><span class="n">y</span> <span class="o">=</span> <span class="n">repulsor</span><span class="o">.</span><span class="na">height</span> <span class="o">-</span> <span class="mi">2</span>

        <span class="k">return</span> <span class="o">.</span><span class="mi">01</span>

    <span class="c1"># On an event, record the mouse position.</span>
    <span class="k">def</span> <span class="nf">repulsor_event</span><span class="p">(</span><span class="n">ev</span><span class="p">,</span> <span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">,</span> <span class="n">st</span><span class="p">):</span>
        <span class="n">store</span><span class="o">.</span><span class="n">repulsor_pos</span> <span class="o">=</span> <span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">)</span>


<span class="k">label</span> <span class="n">repulsor_demo</span><span class="p">:</span>

    <span class="k">python</span><span class="p">:</span>
        <span class="c1"># Create a sprite manager.</span>
        <span class="n">repulsor</span> <span class="o">=</span> <span class="n">SpriteManager</span><span class="p">(</span><span class="n">update</span><span class="o">=</span><span class="n">repulsor_update</span><span class="p">,</span> <span class="k">event</span><span class="o">=</span><span class="n">repulsor_event</span><span class="p">)</span>
        <span class="n">repulsor_sprites</span> <span class="o">=</span> <span class="p">[</span> <span class="p">]</span>
        <span class="n">repulsor_pos</span> <span class="o">=</span> <span class="kc">None</span>

        <span class="c1"># Ensure we only have one smile displayable.</span>
        <span class="n">smile</span> <span class="o">=</span> <span class="n">Image</span><span class="p">(</span><span class="s2">&quot;smile.png&quot;</span><span class="p">)</span>

        <span class="c1"># Add 400 sprites.</span>
        <span class="k">for</span> <span class="n">i</span> <span class="k">in</span> <span class="na">range</span><span class="p">(</span><span class="mi">400</span><span class="p">):</span>
            <span class="n">repulsor_sprites</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">repulsor</span><span class="o">.</span><span class="n">create</span><span class="p">(</span><span class="n">smile</span><span class="p">))</span>

        <span class="c1"># Position the 400 sprites.</span>
        <span class="k">for</span> <span class="n">i</span> <span class="k">in</span> <span class="n">repulsor_sprites</span><span class="p">:</span>
            <span class="n">i</span><span class="o">.</span><span class="n">x</span> <span class="o">=</span> <span class="n">renpy</span><span class="o">.</span><span class="n">random</span><span class="o">.</span><span class="n">randint</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="mi">798</span><span class="p">)</span>
            <span class="n">i</span><span class="o">.</span><span class="n">y</span> <span class="o">=</span> <span class="n">renpy</span><span class="o">.</span><span class="n">random</span><span class="o">.</span><span class="n">randint</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="mi">598</span><span class="p">)</span>

        <span class="k">del</span> <span class="n">smile</span>
        <span class="k">del</span> <span class="n">i</span>

    <span class="c1"># Add the repulsor to the screen.</span>
    <span class="k">show</span> <span class="k">expression</span> <span class="n">repulsor</span> <span class="k">as</span> <span class="n">repulsor</span>

    <span class="s2">&quot;...&quot;</span>

    <span class="k">hide</span> <span class="n">repulsor</span>

    <span class="c1"># Clean up.</span>
    <span class="k">python</span><span class="p">:</span>
        <span class="k">del</span> <span class="n">repulsor</span>
        <span class="k">del</span> <span class="n">repulsor_sprites</span>
        <span class="k">del</span> <span class="n">repulsor_pos</span>
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