implement marching ants

Also removes abandoned bg prototype in favor of a cursor corner prototype.

panel_extreme.p8

@@ -131,6 +131,13 @@ end
 function init_title()
 
  pal({[0]=0x82,0x82,0x84,0x84,4,4,0x89,0x89,0x8e,0x8e,0x8f,0x8f,15,15,0x87,0x87},2)
+	local antbar = ants.new{
+  progress=-0.5,
+  bgcolor=8,
+  fgcolor=10,
+  trcolor=9,
+  speed=1/15,
+  w=128,h=2}
 
  return view.of{
   bg.new{c=15},
@@ -141,6 +148,18 @@ function init_title()
 	   self.x=32+6*cos(time()/3.7)
    end,
   },
+  {update = function()
+   local p = antbar.progress + 0.003
+   if p > 1.5 then
+   	p = -0.5
+   	antbar.speed += 1/30
+   end
+   antbar.progress = p
+  end},
+  view.new{
+   views=antbar,
+   y=50,h=2,
+  },
  }
 end
 
@@ -350,24 +369,73 @@ function printz(str)
 	 print(str, 0, 0)
 	end}
 end
+
+-- horizontal marching ants
+ants = {
+ w=60, h=1,
+ stride=10,
+ 
+ -- bgcolor=0,  --nil: transparent
+ ldcolor=7,
+ fgcolor=6,
+ trcolor=5,
+ 
+ speed=2/60,
+ offset=0,
+ 
+ progress=0.0,
+}
+mknew(ants)
+
+function ants:update()
+ local stride = self.stride
+	local off = self.offset + self.speed * stride
+	if (off > stride) off -= stride
+	self.offset = off
+end
+
+function ants:draw()
+ local w,h,s,p,bg=self.w, self.h, self.stride,self.progress,self.bgcolor
+	if (bg) rectfill(0,0,w,h,bg)
+	if (p<=0) return
+	local x0 = (self.offset-s)&-1
+	local bw = (p*s)&-1
+	if bw > 1 then
+	 local bwm2,c = bw-2,self.fgcolor
+	 for x=x0,w,s do
+		 rectfill(x,0,x+bwm2,h,c)
+	 end
+	end
+	if bw > 0 then
+		local c = self.ldcolor
+		for x=x0+bw-1,w,s do
+			rectfill(x,0,x,h,c)
+		end
+	end
+	if p < 1 then
+		local c = self.trcolor
+		for x = x0-1+s,w,s do
+			rectfill(x,0,x,h,c)
+		end
+	end
+end
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