add image cache

frontend/ui/widget/imagewidget.lua

@@ -1,6 +1,26 @@
 local Widget = require("ui/widget/widget")
+local CacheItem = require("cacheitem")
 local Image = require("ffi/mupdfimg")
 local Geom = require("ui/geometry")
+local Cache = require("cache")
+local DEBUG = require("dbg")
+
+local ImageCache = Cache:new{
+    max_memsize = 2*1024*1024, -- 2M of image cache
+    current_memsize = 0,
+    cache = {},
+    -- this will hold the LRU order of the cache
+    cache_order = {}
+}
+
+local ImageCacheItem = CacheItem:new{}
+
+function ImageCacheItem:onFree()
+    if self.bb.free then
+        DEBUG("free image blitbuffer", self.bb)
+        self.bb:free()
+    end
+end
 
 --[[
 ImageWidget shows an image from a file
@@ -20,7 +40,21 @@ function ImageWidget:_render()
     local itype = string.lower(string.match(self.file, ".+%.([^.]+)") or "")
     if itype == "png" or itype == "jpg" or itype == "jpeg"
             or itype == "tiff" then
-        self._bb = Image:fromFile(self.file, self.width, self.height)
+        local hash = "image|"..self.file.."|"..(self.width or "").."|"..(self.height or "")
+        local cache = ImageCache:check(hash)
+        if cache then
+            -- hit cache
+            self._bb = cache.bb
+        else
+            -- cache this image
+            DEBUG("cache", hash)
+            local cache = ImageCacheItem:new{
+                bb = Image:fromFile(self.file, self.width, self.height),
+            }
+            cache.size = cache.bb.pitch * cache.bb.h
+            ImageCache:insert(hash, cache)
+            self._bb = cache.bb
+        end
     else
         error("Image file type not supported.")
     end
@@ -31,27 +65,24 @@ function ImageWidget:_render()
 end
 
 function ImageWidget:getSize()
-    if not self._bb then
-        self:_render()
-    end
+    self:_render()
     return Geom:new{ w = self._bb:getWidth(), h = self._bb:getHeight() }
 end
 
 function ImageWidget:rotate(degree)
-    if not self._bb then
-        self:_render()
-    end
+    self:_render()
     self._bb:rotate(degree)
 end
 
 function ImageWidget:paintTo(bb, x, y)
+    if self.hide then return end
+    -- self:_reader is called in getSize method
     local size = self:getSize()
     self.dimen = Geom:new{
         x = x, y = y,
         w = size.w,
         h = size.h
     }
-    if self.hide then return end
     bb:blitFrom(self._bb, x, y, 0, 0, size.w, size.h)
     if self.invert then
         bb:invertRect(x, y, size.w, size.h)
@@ -61,11 +92,4 @@ function ImageWidget:paintTo(bb, x, y)
     end
 end
 
-function ImageWidget:free()
-    if self._bb then
-        self._bb:free()
-        self._bb = nil
-    end
-end
-
 return ImageWidget