How a game's picture (a scene's :picture) reaches a terminal that keeps images: the size it is drawn at, how each frame is encoded, and whether frames are double buffered. Options are a list, or a comma-separated string:

• native — drawn at the game's own size times the largest whole number that fits the pane, the terminal scaling it to the pane
• native:N — at the game's own size times N
• size:WxH — the game's own size is W by H pixels, over what the game declares (a scene's :native, else the look's :native)
• png — each frame is sent as a PNG, palette when it has at most 256 colours, in place of deflated raw pixels
• swap — each frame is stored before the last is let go, so the pane never blanks between frames
• gpu — a scene that describes itself for the graphics card (a scene's :gpu) is drawn by CauldronGPU at the pane's size in pixels and shown in the pane; other scenes, and every scene when no graphics card opens, are drawn as without it
• window — as gpu, but in a window of its own: keys pressed in the window reach the client as the terminal's do, and the pane is left empty while the window opens and is open
• software — never the graphics card

Without gpu, window or software the player's drawing setting decides (Cauldron2D.Drafter.Client.Settings), which by default uses the graphics card in the pane when there is one.

• none — none of these

Without native, or with it when neither the game nor size gives a size, the picture is drawn at the pane's cells times the surface's density and sent as raw pixels.

options/2 reads a client's options from its mount props (:picture), else the application env config :cauldron_2d_drafter, picture: ..., else the environment variable CAULDRON_PICTURE, else the game's look (:picture), else default/0. surface_props/3 turns them into Cauldron2D.Drafter.Surface props.

iex> Cauldron2D.Drafter.Client.Picture.parse("native:2,png,swap")
{:ok, [{:native, 2}, :png, :swap]}