<div class="blog">
<h1 id="NAME">
-Updates on Plan for v2.4
+SDL RC 2.5 decides to play with PDL
</h1>
<div class="CONTENT">
-<div style="text-align: right;"><i>A fierce storm came,<br />With a crash,<br />Old oaks went lame.</i></div><p>After some hunting for memory leaks, it became obvious that some rewrite of XS will be necessary. Since this will be a big undertaking I asked for some help from <a href="http://modernperlbooks.com/mt/index.html">chromatic</a> and <a href="http://onionstand.blogspot.com/">garu</a>. We came up with the following plan for v2.4.</p><br /><p>Currently all XS is mapped to the SDL_perl module. This does not reflect the modular nature of the sdl libs. So the plan is to gradually move SDL structs and their respective functions to their correct namespaces. We will start with SDL::Rect as garu has <a href="http://github.com/garu/SDL_perl/commit/68210590cb457b273ba0f1f891d378b876dc6cd7">added many tests</a> for it. This way the build system will be a lot easier to hack since Module::Build was made for one XS per module. Moreover we will move the Build utilities to Alien::SDL, making it even simpler. The main idea is to adhere to single responsibility principle and encapsulation. </p><br /><p>Obviously this will take some time and effort, but it will pay off in the long run. Any help will be greatly appreciated. <br /></p><i>--yapgh</i><div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/3102167581424744259-5293501082670630307?l=yapgh.blogspot.com' alt='' /></div></div></div>
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+<i>PDL provides great number crunching capabilities to Perl and SDL provides game-developer quality real-time bitmapping and sound.<br />
+You can use PDL and SDL together to create real-time,<br />
+responsive animations and simulations.<br />
+In this section we will go through the pleasures and pitfalls of working with both powerhouse libraries.</i> <b>-- David Mertnes</b><br />
+<br />
+<br />
+<h1>Creating a SDL Surface piddle</h1><br />
+PDL's core type is a piddle.<br />
+Once a piddle is provided to PDL it can go do a numerous amounts of things.<br />
+Please see the example in '<a href="http://github.com/kthakore/SDL_perl/blob/master/examples/cookbook/pdl.pl">examples/cookbook/pdl.pl</a>' in github.<br />
+<br />
+<h3>Creating a simple piddle</h3><br />
+First lets get the right modules.<br />
+<br />
+<pre style='color:#d1d1d1;background:#000000;'> <span style='color:#e66170; font-weight:bold; '>use</span> <span style='color:#b060b0; '>PDL;</span>
+ <span style='color:#e66170; font-weight:bold; '>use</span> <span style='color:#904050; '>SDL</span><span style='color:#d2cd86; '>::</span><span style='color:#904050; '>Rect</span><span style='color:#b060b0; '>;</span>
+ <span style='color:#e66170; font-weight:bold; '>use</span> <span style='color:#904050; '>SDL</span><span style='color:#d2cd86; '>::</span><span style='color:#904050; '>Video</span><span style='color:#b060b0; '>;</span>
+ <span style='color:#e66170; font-weight:bold; '>use</span> <span style='color:#904050; '>SDL</span><span style='color:#d2cd86; '>::</span><span style='color:#904050; '>Surface</span><span style='color:#b060b0; '>;</span>
+ <span style='color:#e66170; font-weight:bold; '>use</span> <span style='color:#904050; '>SDL</span><span style='color:#d2cd86; '>::</span><span style='color:#904050; '>PixelFormat</span><span style='color:#b060b0; '>;</span>
+</pre><br />
+Suppose you want a surface of size (200,400) and 32 bit (RGBA).<br />
+<br />
+<pre style='color:#d1d1d1;background:#000000;'><span style='color:#e66170; font-weight:bold; '>my</span> <span style='color:#d2cd86; '>(</span> $bytes_per_pixel<span style='color:#d2cd86; '>,</span> $width<span style='color:#d2cd86; '>,</span> $height <span style='color:#d2cd86; '>)</span> <span style='color:#d2cd86; '>=</span> <span style='color:#d2cd86; '>(</span> <span style='color:#00a800; '>4</span><span style='color:#d2cd86; '>,</span> <span style='color:#00a800; '>200</span><span style='color:#d2cd86; '>,</span> <span style='color:#00a800; '>400</span> <span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span>
+</pre><br />
+Define the <b>$width</b>, <b>$height</b> and <b>$bytes_per_pixel</b>. Your <b>$bytes_per_pixel</b> is the number of bits (in this case 32) divided by 8 bits per byte. Therefore for our 32 bpp we have 4 Bpp;<br />
+<br />
+<pre style='color:#d1d1d1;background:#000000;'><span style='color:#e66170; font-weight:bold; '>my</span> $piddle <span style='color:#d2cd86; '>=</span> zeros<span style='color:#d2cd86; '>(</span> byte<span style='color:#d2cd86; '>,</span> $bytes_per_pixel<span style='color:#d2cd86; '>,</span> $width<span style='color:#d2cd86; '>,</span> $height <span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span>
+</pre><br />
+Create a normal $piddle with zeros, byte format and the Bpp x width x height dimensions.<br />
+<br />
+<pre style='color:#d1d1d1;background:#000000;'><span style='color:#e66170; font-weight:bold; '>my</span> $pointer <span style='color:#d2cd86; '>=</span> $piddle<span style='color:#d2cd86; '>-></span>get_dataref<span style='color:#d2cd86; '>(</span><span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span>
+</pre><br />
+Here is where we get the acutal data the piddle is pointing to. We will have SDL create a new surface from this function.<br />
+<br />
+<pre style='color:#d1d1d1;background:#000000;'><span style='color:#e66170; font-weight:bold; '>my</span> $surface <span style='color:#d2cd86; '>=</span> <span style='color:#904050; '>SDL</span><span style='color:#d2cd86; '>::</span><span style='color:#904050; '>Surface</span><span style='color:#d2cd86; '>-></span>new_from<span style='color:#d2cd86; '>(</span> $pointer<span style='color:#d2cd86; '>,</span> $width<span style='color:#d2cd86; '>,</span> $height<span style='color:#d2cd86; '>,</span> <span style='color:#00a800; '>32</span><span style='color:#d2cd86; '>,</span>
+ $width <span style='color:#d2cd86; '>*</span> $bytes_per_pixel <span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span>
+</pre><br />
+Using the same dimensions we create the surface using <b>SDL::Surface->new_form()</b>. The <b>$width * $Bpp</b> is the scanline (pitch) of the surface in bytes.<br />
+<br />
+<pre style='color:#d1d1d1;background:#000000;'><span style='color:#e66170; font-weight:bold; '>warn</span> <span style='color:#00c4c4; '>"Made surface of </span><span style='color:#00c4c4; '>$width</span><span style='color:#00c4c4; '>, </span><span style='color:#00c4c4; '>$height</span><span style='color:#00c4c4; '> and "</span><span style='color:#d2cd86; '>.</span> $surface<span style='color:#d2cd86; '>-></span>format<span style='color:#d2cd86; '>-></span>BytesPerPixel<span style='color:#b060b0; '>;</span>
+ <span style='color:#e66170; font-weight:bold; '>return</span> <span style='color:#d2cd86; '>(</span> $piddle<span style='color:#d2cd86; '>,</span> $surface <span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span>
+</pre><br />
+Finally make sure that the surface acutally has the correct dimensions we gave.<br />
+<br />
+<b>NOTE:</b> <b>$surface->format->BytesPerPixel</b> must return 1,2,3,4. !!<br />
+<br />
+Now you can blit and use the surface as needed; and do PDL operations as required.<br />
+<br />
+<h3>Operating on the Surface safely</h3><br />
+To make sure SDL is in sync with the data. You must call SDL::Video::lock <b>before</b> doing PDL operations on the piddle.<br />
+<br />
+<pre><pre style='color:#d1d1d1;background:#000000;'><span style='color:#904050; '>SDL</span><span style='color:#d2cd86; '>::</span><span style='color:#904050; '>Video</span><span style='color:#d2cd86; '>:</span><span style='color:#d2cd86; '>:</span>lock_surface<span style='color:#d2cd86; '>(</span>$surface<span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span>
+
+ $piddle <span style='color:#d2cd86; '>(</span> <span style='color:#d2cd86; '>:</span><span style='color:#d2cd86; '>,</span> <span style='color:#00a800; '>0</span> <span style='color:#d2cd86; '>:</span> <span style='color:#e66170; font-weight:bold; '>rand</span><span style='color:#d2cd86; '>(</span><span style='color:#00a800; '>400</span><span style='color:#d2cd86; '>)</span><span style='color:#d2cd86; '>,</span> <span style='color:#00a800; '>0</span> <span style='color:#d2cd86; '>:</span> <span style='color:#e66170; font-weight:bold; '>rand</span><span style='color:#d2cd86; '>(</span><span style='color:#00a800; '>200</span><span style='color:#d2cd86; '>)</span> <span style='color:#d2cd86; '>)</span> <span style='color:#d2cd86; '>.</span><span style='color:#d2cd86; '>=</span> pdl<span style='color:#d2cd86; '>(</span> <span style='color:#e66170; font-weight:bold; '>rand</span><span style='color:#d2cd86; '>(</span><span style='color:#00a800; '>225</span><span style='color:#d2cd86; '>)</span><span style='color:#d2cd86; '>,</span> <span style='color:#e66170; font-weight:bold; '>rand</span><span style='color:#d2cd86; '>(</span><span style='color:#00a800; '>225</span><span style='color:#d2cd86; '>)</span><span style='color:#d2cd86; '>,</span> <span style='color:#e66170; font-weight:bold; '>rand</span><span style='color:#d2cd86; '>(</span><span style='color:#00a800; '>255</span><span style='color:#d2cd86; '>)</span><span style='color:#d2cd86; '>,</span> <span style='color:#00a800; '>255</span> <span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span>
+</pre></pre><br />
+After that you can unlock the surface to blit.<br />
+<br />
+<pre style='color:#d1d1d1;background:#000000;'><span style='color:#904050; '>SDL</span><span style='color:#d2cd86; '>::</span><span style='color:#904050; '>Video</span><span style='color:#d2cd86; '>:</span><span style='color:#d2cd86; '>:</span>unlock_surface<span style='color:#d2cd86; '>(</span>$surface<span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span>
+</pre><br />
+<h3>Errors due to BPP at blitting</h3><br />
+When blitting the new surface check for the return value to see if there has been a problem.<br />
+<br />
+<pre style='color:#d1d1d1;background:#000000;'><span style='color:#e66170; font-weight:bold; '>my</span> $b <span style='color:#d2cd86; '>=</span> <span style='color:#904050; '>SDL</span><span style='color:#d2cd86; '>::</span><span style='color:#904050; '>Video</span><span style='color:#d2cd86; '>:</span><span style='color:#d2cd86; '>:</span>blit_surface<span style='color:#d2cd86; '>(</span>
+ $surface<span style='color:#d2cd86; '>,</span> <span style='color:#904050; '>SDL</span><span style='color:#d2cd86; '>::</span><span style='color:#904050; '>Rect</span><span style='color:#d2cd86; '>-></span>new<span style='color:#d2cd86; '>(</span> <span style='color:#00a800; '>0</span><span style='color:#d2cd86; '>,</span> <span style='color:#00a800; '>0</span><span style='color:#d2cd86; '>,</span> $surface<span style='color:#d2cd86; '>-></span>w<span style='color:#d2cd86; '>,</span> $surface<span style='color:#d2cd86; '>-></span>h <span style='color:#d2cd86; '>)</span><span style='color:#d2cd86; '>,</span>
+ $app<span style='color:#d2cd86; '>,</span> <span style='color:#904050; '>SDL</span><span style='color:#d2cd86; '>::</span><span style='color:#904050; '>Rect</span><span style='color:#d2cd86; '>-></span>new<span style='color:#d2cd86; '>(</span> <span style='color:#d2cd86; '>(</span> $app<span style='color:#d2cd86; '>-></span>w <span style='color:#d2cd86; '>-</span> $surface<span style='color:#d2cd86; '>-></span>w <span style='color:#d2cd86; '>)</span> <span style='color:#d2cd86; '>/</span> <span style='color:#00a800; '>2</span><span style='color:#d2cd86; '>,</span> <span style='color:#d2cd86; '>(</span> $app<span style='color:#d2cd86; '>-></span>h <span style='color:#d2cd86; '>-</span> $surface<span style='color:#d2cd86; '>-></span>h <span style='color:#d2cd86; '>)</span> <span style='color:#d2cd86; '>/</span> <span style='color:#00a800; '>2</span><span style='color:#d2cd86; '>,</span> $app<span style='color:#d2cd86; '>-></span>w<span style='color:#d2cd86; '>,</span> $app<span style='color:#d2cd86; '>-></span>h <span style='color:#d2cd86; '>)</span>
+ <span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span>
+
+ <span style='color:#e66170; font-weight:bold; '>die</span> <span style='color:#00c4c4; '>"Could not blit: "</span> <span style='color:#d2cd86; '>.</span> <span style='color:#904050; '>SDL</span><span style='color:#d2cd86; '>::</span><span style='color:#904050; '>get_error</span><span style='color:#d2cd86; '>(</span><span style='color:#d2cd86; '>)</span> <span style='color:#e66170; font-weight:bold; '>if</span> <span style='color:#d2cd86; '>(</span> $b <span style='color:#d2cd86; '>=</span><span style='color:#d2cd86; '>=</span> <span style='color:#d2cd86; '>-</span><span style='color:#00a800; '>1</span> <span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span>
+</pre><br />
+If the error message is 'Blit combination not supported' that means that the BPP is incorrect or incosistent with the dimensions. After that a simple update_rect will so your new surface on the screen.<div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/3102167581424744259-3580429408870545769?l=yapgh.blogspot.com' alt='' /></div>
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