update for SDL::Event

[sdlgit/SDL-Site.git] / pages / blog-0011.html-inc

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@@ -1,17 +1,81 @@
 <div class="blog">
 <h1 id="NAME">
-SDL Perl Documentation: Reviewers need
+Providing direct memory access to SDL_Surface's pixels
 </h1>
 <div class="CONTENT">
-<div style="text-align: right;"><i><br />
-The written word, <br />
-survives; <br />
-the tests of Time,<br />
-the fires of Hades,<br />
-and wrath of Pluto.<br />
-</i><br />
-</div><br />
-<h1>Documentation </h1><p>In an effort to learn from past versions of SDL Perl and improve. We have been writing lots of documentation for our users. Of course since this is the first time we have been providing documentation we need your help. Please review our docs, at <a href="http://sdl.perl.org/documentation.html">sdl.perl.org</a> and give us some feed back. Send us the feeback at sdl-devel@mail.org or join us at #sdl irc.perl.org</p><br />
-<i>--yapgh</i><div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/3102167581424744259-1574568821593098925?l=yapgh.blogspot.com' alt='' /></div>
-<p><a href="http://feedads.g.doubleclick.net/~a/VvEuEQbih1n042j8cAGxEVAiawg/0/da"><img src="http://feedads.g.doubleclick.net/~a/VvEuEQbih1n042j8cAGxEVAiawg/0/di" border="0" ismap="true"></img></a><br/>
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+<p>In an attempt to make pixel access easier on SDL_Surface pixels. I have started work on <a href="http://github.com/kthakore/SDL_perl/commit/7ee1a1a7f162080a6fa5274e95b80961486e21e5">SDLx::Surface</a>. So far I have only start on the 32 bpp surfaces.</p><br />
+<p>The general idea is to make Pointer Values (PV) of each pixel in the surface and place them into a 2D matrix. First I make pointer values like this: </p><br />
+<pre style='color:#d1d1d1;background:#000000;'>SV <span style='color:#d2cd86; '>*</span> get_pixel32 <span style='color:#d2cd86; '>(</span>SDL_Surface <span style='color:#d2cd86; '>*</span>surface<span style='color:#d2cd86; '>,</span> <span style='color:#e66170; font-weight:bold; '>int</span> x<span style='color:#d2cd86; '>,</span> <span style='color:#e66170; font-weight:bold; '>int</span> y<span style='color:#d2cd86; '>)</span>
+<span style='color:#b060b0; '>{</span>
+ <span style='color:#9999a9; '>//Convert the pixels to 32 bit </span>
+ Uint32 <span style='color:#d2cd86; '>*</span>pixels <span style='color:#d2cd86; '>=</span> <span style='color:#d2cd86; '>(</span>Uint32 <span style='color:#d2cd86; '>*</span><span style='color:#d2cd86; '>)</span>surface<span style='color:#d2cd86; '>-</span><span style='color:#d2cd86; '>></span>pixels<span style='color:#b060b0; '>;</span> 
+
+ <span style='color:#9999a9; '>//Get the requested pixel  </span>
+ Uint32<span style='color:#d2cd86; '>*</span> u_ptr <span style='color:#d2cd86; '>=</span>  pixels <span style='color:#d2cd86; '>+</span> <span style='color:#d2cd86; '>(</span> y <span style='color:#d2cd86; '>*</span> surface<span style='color:#d2cd86; '>-</span><span style='color:#d2cd86; '>></span>w <span style='color:#d2cd86; '>)</span> <span style='color:#d2cd86; '>+</span> x <span style='color:#b060b0; '>;</span> 
+
+        SV<span style='color:#d2cd86; '>*</span> sv <span style='color:#d2cd86; '>=</span> newSVpv<span style='color:#d2cd86; '>(</span><span style='color:#02d045; '>"</span><span style='color:#00c4c4; '>a</span><span style='color:#02d045; '>"</span><span style='color:#d2cd86; '>,</span><span style='color:#008c00; '>1</span><span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span> <span style='color:#9999a9; '>//Make a temp SV* value on the go</span>
+        SvCUR_set<span style='color:#d2cd86; '>(</span>sv<span style='color:#d2cd86; '>,</span> <span style='color:#e66170; font-weight:bold; '>sizeof</span><span style='color:#d2cd86; '>(</span>Uint32<span style='color:#d2cd86; '>)</span><span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span> <span style='color:#9999a9; '>//Specify the new CUR length</span>
+ SvLEN_set<span style='color:#d2cd86; '>(</span>sv<span style='color:#d2cd86; '>,</span> <span style='color:#e66170; font-weight:bold; '>sizeof</span><span style='color:#d2cd86; '>(</span>Uint32<span style='color:#d2cd86; '>)</span><span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span> <span style='color:#9999a9; '>//Specify the LEN length</span>
+        SvPV_set<span style='color:#d2cd86; '>(</span>sv<span style='color:#d2cd86; '>,</span><span style='color:#d2cd86; '>(</span><span style='color:#e66170; font-weight:bold; '>char</span><span style='color:#d2cd86; '>*</span><span style='color:#d2cd86; '>)</span>u_ptr<span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span> <span style='color:#9999a9; '>// set the actual pixel's pointer as the memory space to use</span>
+
+ <span style='color:#e66170; font-weight:bold; '>return</span> sv<span style='color:#b060b0; '>;</span> <span style='color:#9999a9; '>//make a modifiable reference using u_ptr's place as the memory :)</span>
+
+<span style='color:#b060b0; '>}</span>
+</pre><br />
+<p>Next I loop through all the pixels and put them in a 2D array format, shown below: </p><pre style='color:#d1d1d1;background:#000000;'>AV <span style='color:#d2cd86; '>*</span> construct_p_matrix <span style='color:#d2cd86; '>(</span> SDL_Surface <span style='color:#d2cd86; '>*</span>surface <span style='color:#d2cd86; '>)</span>
+<span style='color:#b060b0; '>{</span>
+    AV <span style='color:#d2cd86; '>*</span> matrix <span style='color:#d2cd86; '>=</span> newAV<span style='color:#d2cd86; '>(</span><span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span>
+     <span style='color:#e66170; font-weight:bold; '>int</span> i<span style='color:#d2cd86; '>,</span> j<span style='color:#b060b0; '>;</span>
+     <span style='color:#e66170; font-weight:bold; '>for</span><span style='color:#d2cd86; '>(</span>  i <span style='color:#d2cd86; '>=</span><span style='color:#008c00; '>0</span> <span style='color:#b060b0; '>;</span> i <span style='color:#d2cd86; '>&lt;</span> surface<span style='color:#d2cd86; '>-</span><span style='color:#d2cd86; '>></span>w<span style='color:#b060b0; '>;</span> i<span style='color:#d2cd86; '>+</span><span style='color:#d2cd86; '>+</span><span style='color:#d2cd86; '>)</span>
+      <span style='color:#b060b0; '>{</span>
+        AV <span style='color:#d2cd86; '>*</span> matrix_row <span style='color:#d2cd86; '>=</span> newAV<span style='color:#d2cd86; '>(</span><span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span>
+        <span style='color:#e66170; font-weight:bold; '>for</span><span style='color:#d2cd86; '>(</span> j <span style='color:#d2cd86; '>=</span><span style='color:#008c00; '>0</span> <span style='color:#b060b0; '>;</span> j <span style='color:#d2cd86; '>&lt;</span> surface<span style='color:#d2cd86; '>-</span><span style='color:#d2cd86; '>></span>h<span style='color:#b060b0; '>;</span> j<span style='color:#d2cd86; '>+</span><span style='color:#d2cd86; '>+</span><span style='color:#d2cd86; '>)</span>
+        <span style='color:#b060b0; '>{</span>
+           av_push<span style='color:#d2cd86; '>(</span>matrix_row<span style='color:#d2cd86; '>,</span> get_pixel32<span style='color:#d2cd86; '>(</span>surface<span style='color:#d2cd86; '>,</span> i<span style='color:#d2cd86; '>,</span>j<span style='color:#d2cd86; '>)</span> <span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span>
+        <span style='color:#b060b0; '>}</span>
+        av_push<span style='color:#d2cd86; '>(</span>matrix<span style='color:#d2cd86; '>,</span> newRV_noinc<span style='color:#d2cd86; '>(</span><span style='color:#d2cd86; '>(</span>SV<span style='color:#d2cd86; '>*</span><span style='color:#d2cd86; '>)</span> matrix_row<span style='color:#d2cd86; '>)</span> <span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span>
+      <span style='color:#b060b0; '>}</span>
+
+ <span style='color:#e66170; font-weight:bold; '>return</span> matrix<span style='color:#b060b0; '>;</span>
+<span style='color:#b060b0; '>}</span>
+</pre><br />
+<p>You can see the complete <a href="http://github.com/kthakore/SDL_perl/blob/7ee1a1a7f162080a6fa5274e95b80961486e21e5/src/SDLx/Surface.xs">here</a>.</p><br />
+<p>In Perl I can do a get access on this pixel using: </p><br />
+<br />
+<pre style='color:#d1d1d1;background:#000000;'><span style='color:#e66170; font-weight:bold; '>my</span> $surf32_matrix <span style='color:#d2cd86; '>=</span> <span style='color:#904050; '>SDLx</span><span style='color:#d2cd86; '>::</span><span style='color:#904050; '>Surface</span><span style='color:#d2cd86; '>:</span><span style='color:#d2cd86; '>:</span>pixel_array<span style='color:#d2cd86; '>(</span>$screen_surface<span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span>
+   <span style='color:#e66170; font-weight:bold; '>print</span> <span style='color:#e66170; font-weight:bold; '>unpack</span> <span style='color:#00c4c4; '>'b*'</span><span style='color:#d2cd86; '>,</span> $surf32_matrix<span style='color:#d2cd86; '>-></span><span style='color:#d2cd86; '>[</span><span style='color:#00a800; '>0</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:#b060b0; '>;</span> <span style='color:#9999a9; '># pixel value at x = 0 and y =0</span>
+<span style='color:#9999a9; '>#OUTPUT:</span>
+<span style='color:#9999a9; '># 11111111000000000000000000000000</span>
+</pre><br />
+<p>The structure of the PV is using Devel::Peek is : </p><br />
+<pre style='color:#d1d1d1;background:#000000;'><span style='color:#e66170; font-weight:bold; '>print</span> Dump $surf32_matrix<span style='color:#d2cd86; '>-></span><span style='color:#d2cd86; '>[</span><span style='color:#00a800; '>0</span><span style='color:#d2cd86; '>]</span><span style='color:#d2cd86; '>[</span><span style='color:#00a800; '>0</span><span style='color:#d2cd86; '>]</span><span style='color:#b060b0; '>;</span>
+<span style='color:#9999a9; '>#OUTPUT:</span>
+<span style='color:#9999a9; '>#SV = PV(0xed0dbc) at 0xeb5344</span>
+<span style='color:#9999a9; '>#  REFCNT = 1</span>
+<span style='color:#9999a9; '>#  FLAGS = (POK,pPOK)</span>
+<span style='color:#9999a9; '>#  PV = 0x9e04ac "\0\0\377\0"</span>
+<span style='color:#9999a9; '>#  CUR = 4</span>
+<span style='color:#9999a9; '>#  LEN = 4</span>
+</pre><br />
+<p>The problem is in setting the value of this pointer value. I have tried the following things with no success:</p><br />
+<pre style='color:#d1d1d1;background:#000000;'><span style='color:#e66170; font-weight:bold; '>if</span> <span style='color:#d2cd86; '>(</span> <span style='color:#904050; '>SDL</span><span style='color:#d2cd86; '>::</span><span style='color:#904050; '>Video</span><span style='color:#d2cd86; '>:</span><span style='color:#d2cd86; '>:</span>MUSTLOCK<span style='color:#d2cd86; '>(</span>$screen_surface<span style='color:#d2cd86; '>)</span> <span style='color:#d2cd86; '>)</span> <span style='color:#b060b0; '>{</span>
+    <span style='color:#e66170; font-weight:bold; '>return</span> <span style='color:#e66170; font-weight:bold; '>if</span> <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>lock_surface<span style='color:#d2cd86; '>(</span>$screen_surface<span style='color:#d2cd86; '>)</span> <span style='color:#d2cd86; '>&lt;</span> <span style='color:#00a800; '>0</span> <span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span> <span style='color:#9999a9; '>#required for pixel operations</span>
+<span style='color:#b060b0; '>}</span>
+
+<span style='color:#9999a9; '>#USING pack</span>
+
+<span style='color:#e66170; font-weight:bold; '>my</span> $green <span style='color:#d2cd86; '>=</span> <span style='color:#e66170; font-weight:bold; '>pack</span> <span style='color:#00c4c4; '>'b*'</span><span style='color:#d2cd86; '>,</span> <span style='color:#00c4c4; '>'11111111000000000000000000000000'</span><span style='color:#b060b0; '>;</span>
+<span style='color:#e66170; font-weight:bold; '>substr</span><span style='color:#d2cd86; '>(</span> $surf32_matrix<span style='color:#d2cd86; '>-></span><span style='color:#d2cd86; '>[</span><span style='color:#00a800; '>0</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:#d2cd86; '>,</span> <span style='color:#00a800; '>0</span><span style='color:#d2cd86; '>,</span> <span style='color:#00a800; '>8</span> <span style='color:#d2cd86; '>*</span> <span style='color:#00a800; '>4</span><span style='color:#d2cd86; '>,</span> $green<span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span> <span style='color:#9999a9; '>#no change</span>
+<span style='color:#9999a9; '>#substr( $surf32_matrix->[0][0], 0, 8 * 4, 0xFF000000); segfault</span>
+<span style='color:#e66170; font-weight:bold; '>substr</span><span style='color:#d2cd86; '>(</span> ${$surf32_matrix<span style='color:#d2cd86; '>-></span><span style='color:#d2cd86; '>[</span><span style='color:#00a800; '>0</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:#d2cd86; '>,</span> <span style='color:#00a800; '>0</span><span style='color:#d2cd86; '>,</span> <span style='color:#00a800; '>8</span> <span style='color:#d2cd86; '>*</span> <span style='color:#00a800; '>4</span><span style='color:#d2cd86; '>,</span> <span style='color:#00a800; '>0xFF000000</span><span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span> <span style='color:#9999a9; '>#no change</span>
+<span style='color:#9999a9; '>#$surf32_matrix->[0][0] = $green; SEGFAULT's cannot write to memory</span>
+${$surf32_matrix<span style='color:#d2cd86; '>-></span><span style='color:#d2cd86; '>[</span><span style='color:#00a800; '>0</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:#d2cd86; '>=</span> $green<span style='color:#b060b0; '>;</span> <span style='color:#9999a9; '>#no change</span>
+
+
+<span style='color:#904050; '>SDL</span><span style='color:#d2cd86; '>::</span><span style='color:#904050; '>Video</span><span style='color:#d2cd86; '>:</span><span style='color:#d2cd86; '>:</span>unlock_surface<span style='color:#d2cd86; '>(</span>$screen_surface<span style='color:#d2cd86; '>)</span>
+  <span style='color:#e66170; font-weight:bold; '>if</span> <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>MUSTLOCK<span style='color:#d2cd86; '>(</span>$screen_surface<span style='color:#d2cd86; '>)</span> <span style='color:#d2cd86; '>)</span><span style='color:#b060b0; '>;</span>
+</pre><br />
+<p>You can see an example <a href="http://paste.scsys.co.uk/45111">here</a>.</p><br />
+<p>Any help will be greatly appreciated. </p><div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/3102167581424744259-1929043568015240773?l=yapgh.blogspot.com' alt='' /></div>
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