From 4abcce013c9ee3053badf2abda77190233066676 Mon Sep 17 00:00:00 2001
From: Mitja Felicijan <mitja.felicijan@gmail.com>
Date: Fri, 23 Feb 2024 10:35:22 +0100
Subject: Testing thoughts page

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+---
+title: "Drawing Pixels in Plan9"
+permalink: /drawing-pixels-in-plan9.html
+date: 2023-05-27T17:41:33+02:00
+layout: post
+type: note
+draft: false
+tags: [plan9, graphics]
+---
+
+I have started exploring Plan9's graphics capabilities. This is a hello world
+alternative for drawing that draws a yellow square on a blue background.
+
+More information:
+
+- [draw.h header file](https://github.com/0intro/plan9/blob/main/sys/include/draw.h)
+  contains all the drawing functions
+- [draw man page](https://9fans.github.io/plan9port/man/man3/draw.html)
+  has a bit more digestable descriptions of the draw functions
+- [graphics man page](https://9fans.github.io/plan9port/man/man3/graphics.html)
+  has a bit more digestable descriptions of the graphics functions
+- [all man pages](https://9fans.github.io/plan9port/man/man3/)
+  can be a valuable resource for learning about the system
+
+![Plan9 Howdy World!](/assets/notes/plan9-pixels.png){:loading="lazy"}
+
+```c
+// main.c
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <cursor.h>
+
+void
+main()
+{
+  ulong co;
+  Image *im, *bg;
+  co = 0x0000FFFF;
+
+  if (initdraw(nil, nil, argv0) < 0)
+  {
+    sysfatal("%s: %r", argv0);
+  }
+
+  im = allocimage(display, Rect(0, 0, 300, 300), RGB24, 0, DYellow);
+  bg = allocimage(display, Rect(0, 0, 1, 1), RGB24, 1, co);
+
+  if (im == nil || bg == nil)
+  {
+    sysfatal("not enough memory");
+  }
+
+  draw(screen, screen->r, bg, nil, ZP);
+  draw(screen, screen->r, im, nil, Pt(-40, -40));
+
+  flushimage(display, Refnone);
+
+  // Wait 10 seconds before exiting.
+  sleep(10000);
+
+  exits(nil);
+}
+```
+
+And then compile with `mk` (mkfile below):
+
+```makefile
+# mkfile
+</$objtype/mkfile
+
+RC=/rc/bin
+BIN=/$objtype/bin
+MAN=/sys/man
+
+main:
+	$CC $CFLAGS main.c
+	$LD $LDFLAGS -o main main.$O
+```
+
+And run with `./main`. To exit the program, press `Delete key` (strange but this
+is the alternative for Ctrl+C).
+
+*This is **very cool** indeed!*
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