added basic canvas and layer management.

1 files changed, 30 insertions, 0 deletions

diff --git a/canvas.c b/canvas.c
new file mode 100644
index 0000000..a017fb0
--- /dev/null
+++ b/canvas.c
@@ -0,0 +1,30 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include <geometry.h>
+#include "dat.h"
+#include "fns.h"
+
+static int
+alphachan(ulong chan)
+{
+	for(; chan; chan >>= 8)
+		if(TYPE(chan) == CAlpha)
+			return 1;
+	return 0;
+}
+
+Canvas*
+newcanvas(Point2 p, Rectangle r, ulong chan)
+{
+	Canvas *c;
+
+	c = emalloc(sizeof(Canvas));
+	c->p = p;
+	c->bx = Vec2(1,0);
+	c->by = Vec2(0,1);
+	c->image = eallocimage(display, r, chan, 0, alphachan(chan)? DTransparent: DNofill);
+	memset(&c->layers, 0, sizeof(Layer));
+	c->layers.next = &c->layers;
+	c->layers.prev = &c->layers;
+}