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	plot lines thanks to dcat - ploot - simple plotting tools
	git clone git://bitreich.org/ploot git://enlrupgkhuxnvlhsf6lc3fziv5h2hhfrinws65…
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	---
	commit bb9f77683b2a4c23a519b71baaea8bec6eb5be90
	parent 6e13cd89684d0129aa13995c3f0e2ba4f0a7aae1
	Author: Josuah Demangeon <[email protected]>
	Date: Mon, 30 Apr 2018 14:25:31 +0200

	plot lines thanks to dcat

	Diffstat:
	M .gitignore \| 1 +
	M font.c \| 55 ++++++++++++++++++++++-------…

	2 files changed, 41 insertions(+), 15 deletions(-)
	---
	diff --git a/.gitignore b/.gitignore
	@@ -1,2 +1,3 @@
	*.o
	+*.core
	ploot
	diff --git a/font.c b/font.c
	@@ -1,5 +1,9 @@
	/*
	* Render bitmapped font as a farbfeld image
	+ *
	+ * The convention used: y
	+ * - (0,0) is at the lower left corner of the canvas. \|
	+ * - (0,1) is above it. +--x
	*/

	#include <arpa/inet.h>
	@@ -32,6 +36,10 @@ void
	ffdraw_pixel(Canvas *can, Color c,
	int x, int y)
	{
	+/* Make it segfault early.
	+ x = MIN(can->w - 1, x);
	+ y = MIN(can->h - 1, y);
	+*/
	memcpy(can->b + x + (can->h - 1 - y) * can->w, c, sizeof(*can->b));
	}

	@@ -50,20 +58,37 @@ ffdraw_rectangle(Canvas *can, Color c,
	ffdraw_pixel(can, c, x, y);
	}

	-void
	+/*
	+ * Adapted from Bresenham's line algorithm and dcat's tplot.
	+ */
	+static void
	ffdraw_line(Canvas *can, Color c,
	- int x1, int y1,
	- int x2, int y2)
	+ int x0, int y0,
	+ int x1, int y1)
	{
	- int x, y;
	-
	- (void)c;
	- (void)can;
	-
	- x = x1;
	- y = y1;
	- while (x < x2 && y < y2) {
	- x++; y++;
	+ int dx, dy, sx, sy, err, e;
	+
	+ sx = x0 < x1 ? 1 : -1;
	+ sy = y0 < y1 ? 1 : -1;
	+ dx = abs(x1 - x0);
	+ dy = abs(y1 - y0);
	+ err = (dx > dy ? dx : -dy) / 2;
	+
	+ for (;;) {
	+ ffdraw_pixel(can, c, x0, y0);
	+
	+ if (x0 == x1 && y0 == y1)
	+ break;
	+
	+ e = err;
	+ if (e > -dx) {
	+ x0 += sx;
	+ err -= dy;
	+ }
	+ if (e < dy) {
	+ y0 += sy;
	+ err += dx;
	+ }
	}
	}

	@@ -80,9 +105,9 @@ ffdraw(Canvas *can)
	Color c2 = { 0x3333, 0xffff, 0x8888, 0xffff };

	ffdraw_fill(can, c1);
	- ffdraw_rectangle(can, c2,
	- 0, 20,
	- can->w - 10, 4);
	+ ffdraw_line(can, c2,
	+ 0, 0,
	+ 50 - 1, 80 - 1);
	}

	void