add dedicated backend (WIP)

luigi/backend/ffisdl/image.lua

@@ -0,0 +1,46 @@
+local REL = (...):gsub('[^.]*$', '')
+
+local ffi = require 'ffi'
+local sdl = require(REL .. 'sdl')
+
+local SDL2_image = ffi.load 'SDL2_image'
+
+ffi.cdef [[ SDL_Surface *IMG_Load(const char *file); ]]
+
+local Image = setmetatable({}, { __call = function (self, ...)
+    local object = setmetatable({}, { __index = self })
+    return object, self.constructor(object, ...)
+end })
+
+function Image:constructor (renderer, path)
+    self.sdlRenderer = renderer
+    self.sdlSurface = SDL2_image.IMG_Load(path)
+    ffi.gc(self.sdlSurface, sdl.freeSurface)
+    self.sdlTexture = sdl.createTextureFromSurface(renderer, self.sdlSurface)
+    ffi.gc(self.sdlTexture, sdl.destroyTexture)
+    self.width = self.sdlSurface.w
+    self.height = self.sdlSurface.h
+end
+
+function Image:getWidth ()
+    return self.width
+end
+
+function Image:getHeight ()
+    return self.height
+end
+
+function Image:draw (x, y, sx, sy)
+    local w = self.width * (sx or 1)
+    local h = self.height * (sy or 1)
+
+    -- HACK. Somehow drawing something first prevents renderCopy from
+    -- incorrectly scaling up in some cases (after rendering slices).
+    -- For example http://stackoverflow.com/questions/28218906
+    sdl.renderDrawPoint(self.sdlRenderer, -1, -1)
+
+    -- Draw the image.
+    sdl.renderCopy(self.sdlRenderer, self.sdlTexture, nil, sdl.Rect(x, y, w, h))
+end
+
+return Image