add day 20 of devlog

docs/index.html

···
     <tr>
         <td class=table-post>
             <div class="date">
-                08/04 — 2021
+                11/04 — 2021
             </div>
             <a href="/posts/SDL2_devlog" class="post-link">
                 <span class="post-link">SDL2 Devlog</span>
···
         </td>
         <td class=table-stats>
             <span class="stats-number">
-                9.6
+                10.0
             </span>
             <span class=stats-unit>min</span>
         </td>

docs/index.xml

···
       <item>
 <title>SDL2 Devlog</title>
 <description>&lt;p&gt;I have been working on an editor for the &lt;a href="https://git.peppe.rs/graphics/obi/about"&gt;One Bit Image&lt;/a&gt; file format in Rust and SDL2. This entry in my blog follows my progress on the editor. The days are listed in reverse chronological order, begin from the bottom, if this is your first time on this page.&lt;/p&gt;
+&lt;h3 id="day-20"&gt;Day 20&lt;/h3&gt;
+&lt;p&gt;More &lt;code&gt;lisp&lt;/code&gt; stuff! I added a new brush, for rectangular selections. While selection doesn’t do much on its own, the selected area can be passed onto a &lt;code&gt;lisp&lt;/code&gt; procedure, for example, a procedure to draw horizontal black and white lines:&lt;/p&gt;
+&lt;figure&gt;
+&lt;video src="https://u.peppe.rs/frU.mp4" controls=""&gt;&lt;a href="https://u.peppe.rs/frU.mp4"&gt;Day 20&lt;/a&gt;&lt;/video&gt;&lt;figcaption aria-hidden="true"&gt;Day 20&lt;/figcaption&gt;
+&lt;/figure&gt;
 &lt;h3 id="day-19"&gt;Day 19&lt;/h3&gt;
 &lt;p&gt;Attempted &lt;a href="https://peppe.rs/art/conduit.png"&gt;some isometric art&lt;/a&gt; within the editor. The angles displayed alongside the line brush are handly, however, having only a rectangular grid did not help. I implemented an isometric grid today. Isometric grids in pixel art differ in that the tangent of the isometric angle is exactly 0.5! For every pixel down, you go exactly two pixels sideways. The math works out really well in the drawing procedures too, dealing with floating points is a pain.&lt;/p&gt;
 &lt;figure&gt;
···
 &lt;img src="https://u.peppe.rs/Ma.png" alt="Day 1" /&gt;&lt;figcaption aria-hidden="true"&gt;Day 1&lt;/figcaption&gt;
 &lt;/figure&gt;</description>
 <link>https://peppe.rs/posts/SDL2_devlog/</link>
-<pubDate>Thu, 08 Apr 2021 12:09:00 +0000</pubDate>
+<pubDate>Sun, 11 Apr 2021 10:46:00 +0000</pubDate>
 <guid>https://peppe.rs/posts/SDL2_devlog/</guid>
 </item>
 <item>

docs/posts/SDL2_devlog/index.html

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 ">View Raw</a>
           <div class="separator"></div>
           <div class="date">
-            08/04 — 2021
+            11/04 — 2021
             <div class="stats">
               <span class="stats-number">
-                120.28
+                124.28
               </span>
               <span class="stats-unit">cm</span>
               &nbsp
               <span class="stats-number">
-                9.6
+                10.0
               </span>
               <span class="stats-unit">min</span>
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···
           </h1>
           <div class="post-text">
             <p>I have been working on an editor for the <a href="https://git.peppe.rs/graphics/obi/about">One Bit Image</a> file format in Rust and SDL2. This entry in my blog follows my progress on the editor. The days are listed in reverse chronological order, begin from the bottom, if this is your first time on this page.</p>
+<h3 id="day-20">Day 20</h3>
+<p>More <code>lisp</code> stuff! I added a new brush, for rectangular selections. While selection doesn’t do much on its own, the selected area can be passed onto a <code>lisp</code> procedure, for example, a procedure to draw horizontal black and white lines:</p>
+<figure>
+<video src="https://u.peppe.rs/frU.mp4" controls=""><a href="https://u.peppe.rs/frU.mp4">Day 20</a></video><figcaption aria-hidden="true">Day 20</figcaption>
+</figure>
 <h3 id="day-19">Day 19</h3>
 <p>Attempted <a href="https://peppe.rs/art/conduit.png">some isometric art</a> within the editor. The angles displayed alongside the line brush are handly, however, having only a rectangular grid did not help. I implemented an isometric grid today. Isometric grids in pixel art differ in that the tangent of the isometric angle is exactly 0.5! For every pixel down, you go exactly two pixels sideways. The math works out really well in the drawing procedures too, dealing with floating points is a pain.</p>
 <figure>

docs/posts/index.html

···
     <tr>
         <td class=table-post>
             <div class="date">
-                08/04 — 2021
+                11/04 — 2021
             </div>
             <a href="/posts/SDL2_devlog" class="post-link">
                 <span class="post-link">SDL2 Devlog</span>
···
         </td>
         <td class=table-stats>
             <span class="stats-number">
-                9.6
+                10.0
             </span>
             <span class=stats-unit>min</span>
         </td>

posts/SDL2_devlog.md

···
 order, begin from the bottom, if this is your first time on
 this page.
 
+### Day 20
+
+More `lisp` stuff! I added a new brush, for rectangular
+selections. While selection doesn't do much on its own, the
+selected area can be passed onto a `lisp` procedure, for
+example, a procedure to draw horizontal black and white
+lines:
+
+![Day 20](https://u.peppe.rs/frU.mp4)
+
 ### Day 19
 
 Attempted [some isometric