From e3e16e2fb021b61e45b01113cb1654cd7e4911c6 Mon Sep 17 00:00:00 2001
From: rodri <rgl@antares-labs.eu>
Date: Sat, 13 Jun 2020 21:35:02 +0000
Subject: added basic canvas and layer management.

---
 canvas.c | 30 ++++++++++++++++++++++++++++++
 dat.h    | 13 +++++++++++--
 layer.c  | 26 ++++++++++++++++++++++++++
 main.c   | 44 +++++++++++++++++++++++++++++++++++++++-----
 4 files changed, 106 insertions(+), 7 deletions(-)
 create mode 100644 canvas.c

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;
+}
diff --git a/dat.h b/dat.h
index 5426da9..b913602 100644
--- a/dat.h
+++ b/dat.h
@@ -1,7 +1,16 @@
 typedef struct Layer Layer;
+typedef struct Canvas Canvas;
 
 struct Layer
 {
-	RFrame rf;
-	Image *canvas;
+	RFrame;
+	Image *image;
+	Layer *prev, *next;
+};
+
+struct Canvas
+{
+	RFrame;
+	Image *image;
+	Layer layers;
 };
diff --git a/layer.c b/layer.c
index 5673183..d238b99 100644
--- a/layer.c
+++ b/layer.c
@@ -2,4 +2,30 @@
 #include <libc.h>
 #include <draw.h>
 #include <geometry.h>
+#include "dat.h"
+#include "fns.h"
 
+Layer*
+newlayer(Canvas *c)
+{
+	Layer *l;
+
+	l = emalloc(sizeof(Layer));
+	l->p = Pt2(0,0,1);
+	l->bx = c->bx;
+	l->by = c->by;
+	l->image = eallocimage(display, c->image->r, c->image->chan, 0, DNofill);
+	l->prev = c->layers.prev;
+	l->next = &c->layers;
+	c->layers.prev->next = l;
+	c->layers.prev = l;
+}
+
+void
+rmlayer(Layer *l)
+{
+	l->prev->next = l->next;
+	l->next->prev = l->prev;
+	freeimage(l->image);
+	free(l);
+}
diff --git a/main.c b/main.c
index 67b2832..ad42fbb 100644
--- a/main.c
+++ b/main.c
@@ -8,14 +8,17 @@
 #include "dat.h"
 #include "fns.h"
 
+/* palette colors */
 enum {
-	CBlack,
-	CWhite,
+	PCBlack,
+	PCWhite,
 	NCOLOR
 };
 
 RFrame worldrf;
 Image *pal[NCOLOR];
+Image *background;
+Canvas *curcanvas;
 
 Point
 toscreen(Point2 p)
@@ -33,15 +36,46 @@ fromscreen(Point p)
 void
 initpalette(void)
 {
-	pal[CBlack] = eallocimage(display, Rect(0,0,1,1), screen->chan, 1, DBlack);
-	pal[CWhite] = eallocimage(display, Rect(0,0,1,1), screen->chan, 1, DWhite);
+	pal[PCBlack] = eallocimage(display, Rect(0,0,1,1), screen->chan, 1, DBlack);
+	pal[PCWhite] = eallocimage(display, Rect(0,0,1,1), screen->chan, 1, DWhite);
+}
+
+Image*
+gencheckerboard(int w, int h)
+{
+	Image *i, *dark, *light;
+	int x, y;
+
+	i = eallocimage(display, Rect(0,0,2*w,2*h), screen->chan, 1, DNofill);
+	dark = eallocimage(display, Rect(0,0,w,h), screen->chan, 0, DBlack&~0x7f);
+	light = eallocimage(display, Rect(0,0,w,h), screen->chan, 0, DBlack&~0xdf);
+
+	for(y = 0; y < h; y += h)
+		for(x = 0; x < w; x += w)
+			draw(i, Rect(x,y,x+w,y+h), (x+y) % 2? light: dark, ZP);
+
+	freeimage(dark);
+	freeimage(light);
+	return i;
+}
+
+void
+drawlayer(Canvas *c, Layer *l)
+{
+	draw(c->image, c->image->r, l->image, nil, ZP);
+}
+
+void
+drawcanvas(Canvas *c)
+{
+
 }
 
 void
 redraw(void)
 {
 	lockdisplay(display);
-	draw(screen, screen->r, pal[CBlack], nil, ZP);
+	draw(screen, screen->r, pal[PCBlack], nil, ZP);
 	flushimage(display, 1);
 	unlockdisplay(display);
 }
-- 
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