EDIT: Actually, I'm no longer sure. Several versions later, it seems that GLFW no longer works in GHCi on OS X.
It turns out that GLFW+OpenGL fulfills all four requirements!
- You need to invoke ghci with
ghci -framework Carbon.
- You need the
EnableGUI.hs file, which you can get here. Note that you can't load it right into GHCi, you have to comiple it, first.
- OpenGL has a 2D projection mode where you can draw lines and polygons.
- Bitmaps can be loaded as textures and put on polygons.
Here is a small example that puts a bitmap onto the screen. There are some restrictions on the bitmap: its dimensions must be a power of two (here 256) and it must be a .tga file (here "Bitmap.tga"). But since transparency is supported, this is not much of a problem.
You should be able to call main multiple times without problem. The key point is that you should not call GLFW.terminate.
import Graphics.Rendering.OpenGL as GL
import qualified Graphics.UI.GLFW as GLFW
import Graphics.Rendering.OpenGL (($=))
import Control.Monad
import EnableGUI
main = do
enableGUI
GLFW.initialize
-- open window
GLFW.openWindow (GL.Size 400 400) [GLFW.DisplayAlphaBits 8] GLFW.Window
GLFW.windowTitle $= "Bitmap Test"
-- enable alpha channel
GL.blend $= GL.Enabled
GL.blendFunc $= (GL.SrcAlpha, GL.OneMinusSrcAlpha)
-- set the color to clear background
GL.clearColor $= GL.Color4 0.8 0.8 0.8 0
-- set 2D orthogonal view inside windowSizeCallback because
-- any change to the Window size should result in different
-- OpenGL Viewport.
GLFW.windowSizeCallback $= \ size@(GL.Size w h) ->
do
GL.viewport $= (GL.Position 0 0, size)
GL.matrixMode $= GL.Projection
GL.loadIdentity
GL.ortho2D 0 (realToFrac w) (realToFrac h) 0
render <- initialize
loop render
GLFW.closeWindow
loop render = do
-- draw the entire screen
render
-- swap buffer
GLFW.swapBuffers
-- check whether ESC is pressed for termination
p <- GLFW.getKey GLFW.ESC
unless (p == GLFW.Press) $ do
-- sleep for 1ms to yield CPU to other applications
GLFW.sleep 0.001
-- only continue when the window is not closed
windowOpenStatus <- GLFW.getParam GLFW.Opened
unless (windowOpenStatus == False) $
loop render
-- rendering
initialize = do
-- load texture from file
GL.texture GL.Texture2D $= Enabled
[textureName] <- GL.genObjectNames 1
GL.textureBinding GL.Texture2D $= Just textureName
GL.textureFilter GL.Texture2D $= ((GL.Nearest, Nothing), GL.Nearest)
GLFW.loadTexture2D "Bitmap.tga" []
return $ do
GL.clear [GL.ColorBuffer]
GL.renderPrimitive GL.Quads $ do
GL.texCoord $ texCoord2 0 0
GL.vertex $ vertex3 (0) 256 0
GL.texCoord $ texCoord2 0 1
GL.vertex $ vertex3 (0) (0) 0
GL.texCoord $ texCoord2 1 1
GL.vertex $ vertex3 256 (0) 0
GL.texCoord $ texCoord2 1 0
GL.vertex $ vertex3 256 256 0
-- type signatures to avoid ambiguity
vertex3 :: GLfloat -> GLfloat -> GLfloat -> GL.Vertex3 GLfloat
vertex3 = GL.Vertex3
texCoord2 :: GLfloat -> GLfloat -> GL.TexCoord2 GLfloat
texCoord2 = GL.TexCoord2
color3 :: GLfloat -> GLfloat -> GLfloat -> GL.Color3 GLfloat
color3 = GL.Color3
Here an example bitmap (which you need to convert to .tga).
