factored out key config and tilecache

tilecache.lua

@@ -0,0 +1,64 @@
+--[[
+a cache for rendered tiles
+]]--
+
+function init_tilecache()
+	cache = {
+		{ age = 0, no = 0, bb = blitbuffer.new(width, height), dc = pdf.newDC(), page = nil },
+		{ age = 0, no = 0, bb = blitbuffer.new(width, height), dc = pdf.newDC(), page = nil },
+		{ age = 0, no = 0, bb = blitbuffer.new(width, height), dc = pdf.newDC(), page = nil }
+	}
+end
+function freecache()
+	for i = 1, #cache do
+		if cache[i].page ~= nil then
+			print("freeing slot="..i.." oldpage="..cache[i].no)
+			cache[i].page:close()
+			cache[i].page = nil
+		end
+	end
+end
+function checkcache(no)
+	for i = 1, #cache do
+		if cache[i].no == no and cache[i].page ~= nil then
+			print("cache hit: slot="..i.." page="..no)
+			return i
+		end
+	end
+	print("cache miss")
+	return nil
+end
+function cacheslot()
+	freeslot = nil
+	while freeslot == nil do
+		for i = 1, #cache do
+			if cache[i].age > 0 then
+				print("aging slot="..i)
+				cache[i].age = cache[i].age - 1
+			else
+				if cache[i].page ~= nil then
+					print("freeing slot="..i.." oldpage="..cache[i].no)
+					cache[i].page:close()
+					cache[i].page = nil
+				end
+				freeslot = i
+			end
+		end
+	end
+	print("returning free slot="..freeslot)
+	return freeslot
+end
+
+function draworcache(no)
+	local slot = checkcache(no)
+	if slot == nil then
+		slot = cacheslot()
+		cache[slot].no = no
+		cache[slot].age = #cache
+		cache[slot].page = doc:openPage(no)
+		setzoom(slot)
+		print("drawing page="..no.." to slot="..slot)
+		cache[slot].page:draw(cache[slot].dc, cache[slot].bb, 0, 0)
+	end
+	return slot
+end