demo for djvu support

wait for code clean up

frontend/document/djvudocument.lua

@@ -0,0 +1,153 @@
+require "cache"
+require "ui/geometry"
+
+DjvuDocument = Document:new{
+	_document = false,
+	-- libdjvulibre manages its own additional cache, default value is hard written in c module.
+	djvulibre_cache_size = nil,
+	dc_null = DrawContext.new()
+}
+
+function DjvuDocument:init()
+	local ok
+	ok, self._document = pcall(djvu.openDocument, self.file, self.djvulibre_cache_size)
+	if not ok then
+		self.error_message = self.doc -- will contain error message
+		return
+	end
+	self.is_open = true
+	self.info.has_pages = true
+	self:_readMetadata()
+end
+
+function DjvuDocument:_readMetadata()
+	self.info.number_of_pages = self._document:getPages()
+	return true
+end
+
+function DjvuDocument:close()
+	if self.is_open then
+		self.is_open = false
+		self._document:close()
+	end
+end
+
+function DjvuDocument:getNativePageDimensions(pageno)
+	local hash = "pgdim|"..self.file.."|"..pageno
+	local cached = Cache:check(hash)
+	if cached then
+		return cached[1]
+	end
+	local page = self._document:openPage(pageno)
+	local page_size_w, page_size_h = page:getSize(self.dc_null)
+	local page_size = Geom:new{ w = page_size_w, h = page_size_h }
+	Cache:insert(hash, CacheItem:new{ page_size })
+	page:close()
+	return page_size
+end
+
+function DjvuDocument:getUsedBBox(pageno)
+	--local hash = "pgubbox|"..self.file.."|"..pageno
+	--local cached = Cache:check(hash)
+	--if cached then
+		--return cached.data
+	--end
+	--local page = self._document:openPage(pageno)
+	local used = {}
+	used.x, used.y, used.w, used.h = 0.01, 0.01, -0.01, -0.01
+	--Cache:insert(hash, CacheItem:new{ used })
+	--page:close()
+	return used
+end
+
+function DjvuDocument:getPageText(pageno)
+	-- is this worth caching? not done yet.
+	local page = self._document:openPage(pageno)
+	local text = page:getPageText()
+	page:close()
+	return text
+end
+
+function DjvuDocument:renderPage(pageno, rect, zoom, rotation)
+	local hash = "renderpg|"..self.file.."|"..pageno.."|"..zoom.."|"..rotation
+	local page_size = self:getPageDimensions(pageno, zoom, rotation)
+	-- this will be the size we actually render
+	local size = page_size
+	-- we prefer to render the full page, if it fits into cache
+	if not Cache:willAccept(size.w * size.h / 2) then
+		-- whole page won't fit into cache
+		DEBUG("rendering only part of the page")
+		-- TODO: figure out how to better segment the page
+		if not rect then
+			DEBUG("aborting, since we do not have a specification for that part")
+			-- required part not given, so abort
+			return
+		end
+		-- only render required part
+		hash = "renderpg|"..self.file.."|"..pageno.."|"..zoom.."|"..rotation.."|"..tostring(rect)
+		size = rect
+	end
+
+	-- prepare cache item with contained blitbuffer	
+	local tile = CacheItem:new{
+		size = size.w * size.h / 2 + 64, -- estimation
+		excerpt = size,
+		pageno = pageno,
+		bb = Blitbuffer.new(size.w, size.h)
+	}
+
+	-- create a draw context
+	local dc = DrawContext.new()
+
+	dc:setRotate(rotation)
+	-- correction of rotation
+	if rotation == 90 then
+		dc:setOffset(page_size.w, 0)
+	elseif rotation == 180 then
+		dc:setOffset(page_size.w, page_size.h)
+	elseif rotation == 270 then
+		dc:setOffset(0, page_size.h)
+	end
+	dc:setZoom(zoom)
+
+	-- render
+	local page = self._document:openPage(pageno)
+	page:draw(dc, tile.bb, size.x, size.y)
+	page:close()
+	Cache:insert(hash, tile)
+
+	return tile
+end
+
+-- a hint for the cache engine to paint a full page to the cache
+-- TODO: this should trigger a background operation
+function DjvuDocument:hintPage(pageno, zoom, rotation)
+	self:renderPage(pageno, nil, zoom, rotation)
+end
+
+function DjvuDocument:drawPage(target, x, y, rect, pageno, zoom, rotation)
+	local hash_full_page = "renderpg|"..self.file.."|"..pageno.."|"..zoom.."|"..rotation
+	local hash_excerpt = "renderpg|"..self.file.."|"..pageno.."|"..zoom.."|"..rotation.."|"..tostring(rect)
+	local tile = Cache:check(hash_full_page)
+	if not tile then
+		tile = Cache:check(hash_excerpt)
+		if not tile then
+			DEBUG("rendering")
+			tile = self:renderPage(pageno, rect, zoom, rotation)
+		end
+	end
+	DEBUG("now painting", tile)
+	target:blitFrom(tile.bb, x, y, rect.x - tile.excerpt.x, rect.y - tile.excerpt.y, rect.w, rect.h)
+end
+
+function DjvuDocument:invertTextYAxel(pageno, text_table)
+	local _, height = self.doc:getOriginalPageSize(pageno)
+	for _,text in pairs(text_table) do
+		for _,line in ipairs(text) do
+			line.y0, line.y1 = (height - line.y1), (height - line.y0)
+		end
+	end
+	return text_table
+end
+
+DocumentRegistry:addProvider("djvu", "application/djvu", DjvuDocument)

frontend/document/document.lua

@@ -99,3 +99,4 @@ end
 -- load implementations:
 
 require "document/pdfdocument"
+require "document/djvudocument"