From 1546beac329d017b86331d0acd2dd0dd86101506 Mon Sep 17 00:00:00 2001
From: rodri <rgl@antares-labs.eu>
Date: Fri, 12 Mar 2021 11:37:09 +0000
Subject: implemented fixed-time dynamics stepper, animated sprites and cleaned
 things up.

---
 sprite.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 72 insertions(+)
 create mode 100644 sprite.c

(limited to 'sprite.c')

diff --git a/sprite.c b/sprite.c
new file mode 100644
index 0000000..a2bf290
--- /dev/null
+++ b/sprite.c
@@ -0,0 +1,72 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include "dat.h"
+#include "fns.h"
+
+static void
+sprite_step(Sprite *spr, ulong Δt)
+{
+	if(spr->nframes < 2)
+		return;
+
+	spr->elapsed += Δt;
+
+	if(spr->elapsed >= spr->period){
+		spr->elapsed -= spr->period;
+		spr->curframe = ++spr->curframe % spr->nframes;
+	}
+}
+
+static void
+sprite_draw(Sprite *spr, Image *dst, Point dp)
+{
+	Point sp = (Point){
+		spr->curframe * Dx(spr->r),
+		0
+	};
+	sp = addpt(spr->sp, sp);
+
+	draw(dst, rectaddpt(spr->r, dp), spr->sheet, nil, sp);
+}
+
+Sprite *
+newsprite(Image *sheet, Point sp, Rectangle r, int nframes, ulong period)
+{
+	Sprite *spr;
+
+	spr = emalloc(sizeof(Sprite));
+	spr->sheet = sheet;
+	spr->sp = sp;
+	spr->r = r;
+	spr->nframes = nframes;
+	spr->curframe = 0;
+	spr->period = period;
+	spr->elapsed = 0;
+	spr->step = sprite_step;
+	spr->draw = sprite_draw;
+
+	return spr;
+}
+
+Sprite *
+readsprite(char *sheetfile, Point sp, Rectangle r, int nframes, ulong period)
+{
+	Image *sheet;
+	int fd;
+
+	fd = open(sheetfile, OREAD);
+	if(fd < 0)
+		sysfatal("readsprite: %r");
+	sheet = readimage(display, fd, 1);
+	close(fd);
+
+	return newsprite(sheet, sp, r, nframes, period);
+}
+
+void
+delsprite(Sprite *spr)
+{
+	freeimage(spr->sheet);
+	free(spr);
+}
-- 
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