Difference between revisions of "GLFW"
(The "active" function now also exits when the window is closed.) |
(The "passive" function now also terminates, when the window is closed; cleaned up the code) |
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Line 42: | Line 42: | ||
import Graphics.Rendering.OpenGL (($=)) |
import Graphics.Rendering.OpenGL (($=)) |
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import Data.IORef |
import Data.IORef |
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+ | import Control.Monad |
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</haskell> |
</haskell> |
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Line 58: | Line 59: | ||
GLFW.openWindow (GL.Size 400 400) [GLFW.DisplayAlphaBits 8] GLFW.Window |
GLFW.openWindow (GL.Size 400 400) [GLFW.DisplayAlphaBits 8] GLFW.Window |
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GLFW.windowTitle $= "GLFW Demo" |
GLFW.windowTitle $= "GLFW Demo" |
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− | GL.shadeModel $= GL.Smooth |
+ | GL.shadeModel $= GL.Smooth |
-- enable antialiasing |
-- enable antialiasing |
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GL.lineSmooth $= GL.Enabled |
GL.lineSmooth $= GL.Enabled |
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− | GL.blend $= GL.Enabled |
+ | GL.blend $= GL.Enabled |
− | GL.blendFunc $= (GL.SrcAlpha, GL.OneMinusSrcAlpha) |
+ | GL.blendFunc $= (GL.SrcAlpha, GL.OneMinusSrcAlpha) |
− | GL.lineWidth $= 1.5 |
+ | GL.lineWidth $= 1.5 |
-- set the color to clear background |
-- set the color to clear background |
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GL.clearColor $= Color4 0 0 0 0 |
GL.clearColor $= Color4 0 0 0 0 |
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+ | |||
-- set 2D orthogonal view inside windowSizeCallback because |
-- set 2D orthogonal view inside windowSizeCallback because |
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-- any change to the Window size should result in different |
-- any change to the Window size should result in different |
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-- OpenGL Viewport. |
-- OpenGL Viewport. |
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− | GLFW.windowSizeCallback $= |
+ | GLFW.windowSizeCallback $= \ size@(GL.Size w h) -> |
+ | do |
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− | GL.viewport $= (GL.Position 0 0, size) |
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− | + | GL.viewport $= (GL.Position 0 0, size) |
|
− | GL. |
+ | GL.matrixMode $= GL.Projection |
+ | GL.loadIdentity |
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− | + | GL.ortho2D 0 (realToFrac w) (realToFrac h) 0 |
|
+ | |||
-- keep all line strokes as a list of points in an IORef |
-- keep all line strokes as a list of points in an IORef |
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lines <- newIORef [] |
lines <- newIORef [] |
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Line 89: | Line 93: | ||
active lines = loop waitForPress |
active lines = loop waitForPress |
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where |
where |
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+ | |||
− | |||
loop action = do |
loop action = do |
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-- draw the entire screen |
-- draw the entire screen |
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Line 97: | Line 101: | ||
-- check whether ESC is pressed for termination |
-- check whether ESC is pressed for termination |
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p <- GLFW.getKey GLFW.ESC |
p <- GLFW.getKey GLFW.ESC |
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− | + | unless (p == GLFW.Press) $ |
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− | + | do |
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⚫ | |||
-- perform action |
-- perform action |
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Action action' <- action |
Action action' <- action |
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-- sleep for 1ms to yield CPU to other applications |
-- sleep for 1ms to yield CPU to other applications |
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GLFW.sleep 0.001 |
GLFW.sleep 0.001 |
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+ | |||
-- only continue when the window is not closed |
-- only continue when the window is not closed |
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windowOpenStatus <- get $ windowParam Opened |
windowOpenStatus <- get $ windowParam Opened |
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− | + | unless (windowOpenStatus == 0) $ |
|
− | + | loop action' -- loop with next action |
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− | else loop action' -- loop with next action |
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waitForPress = do |
waitForPress = do |
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Line 120: | Line 123: | ||
modifyIORef lines (((x,y):) . ((x,y):)) |
modifyIORef lines (((x,y):) . ((x,y):)) |
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return (Action waitForRelease) |
return (Action waitForRelease) |
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+ | |||
− | |||
waitForRelease = do |
waitForRelease = do |
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-- keep track of mouse movement while waiting for button |
-- keep track of mouse movement while waiting for button |
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Line 145: | Line 148: | ||
-- disable auto polling in swapBuffers |
-- disable auto polling in swapBuffers |
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GLFW.disableSpecial GLFW.AutoPollEvent |
GLFW.disableSpecial GLFW.AutoPollEvent |
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+ | |||
-- keep track of whether ESC has been pressed |
-- keep track of whether ESC has been pressed |
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quit <- newIORef False |
quit <- newIORef False |
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+ | |||
-- keep track of whether screen needs to be redrawn |
-- keep track of whether screen needs to be redrawn |
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dirty <- newIORef True |
dirty <- newIORef True |
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+ | |||
-- mark screen dirty in refresh callback which is often called |
-- mark screen dirty in refresh callback which is often called |
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-- when screen or part of screen comes into visibility. |
-- when screen or part of screen comes into visibility. |
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− | GLFW.windowRefreshCallback $= |
+ | GLFW.windowRefreshCallback $= writeIORef dirty True |
+ | |||
-- use key callback to track whether ESC is pressed |
-- use key callback to track whether ESC is pressed |
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− | GLFW.keyCallback $= |
+ | GLFW.keyCallback $= \k s -> |
− | + | when (fromEnum k == fromEnum GLFW.ESC && s == GLFW.Press) $ |
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− | + | writeIORef quit True |
|
− | + | ||
+ | -- Terminate the program if the window is closed |
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+ | GLFW.windowCloseCallback $= writeIORef quit True |
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+ | |||
-- by default start with waitForPress |
-- by default start with waitForPress |
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waitForPress dirty |
waitForPress dirty |
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loop dirty quit |
loop dirty quit |
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where |
where |
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+ | |||
− | |||
loop dirty quit = do |
loop dirty quit = do |
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GLFW.waitEvents |
GLFW.waitEvents |
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-- redraw screen if dirty |
-- redraw screen if dirty |
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d <- readIORef dirty |
d <- readIORef dirty |
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+ | |||
⚫ | |||
− | + | when d $ |
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⚫ | |||
+ | |||
+ | writeIORef dirty False |
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-- check if we need to quit the loop |
-- check if we need to quit the loop |
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q <- readIORef quit |
q <- readIORef quit |
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− | + | unless q $ |
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+ | loop dirty quit |
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+ | |||
⚫ | |||
+ | do |
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⚫ | |||
⚫ | |||
⚫ | |||
⚫ | |||
⚫ | |||
− | + | do |
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⚫ | |||
− | then do |
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-- when left mouse button is pressed, add the point |
-- when left mouse button is pressed, add the point |
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-- to lines and switch to waitForRelease action. |
-- to lines and switch to waitForRelease action. |
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Line 182: | Line 198: | ||
modifyIORef lines (((x,y):) . ((x,y):)) |
modifyIORef lines (((x,y):) . ((x,y):)) |
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waitForRelease dirty |
waitForRelease dirty |
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+ | |||
− | else return ()) |
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+ | waitForRelease dirty = |
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− | |||
− | + | do |
|
− | GLFW.mousePosCallback $= |
+ | GLFW.mousePosCallback $= \(Position x y) -> |
⚫ | |||
-- update the line with new ending position |
-- update the line with new ending position |
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modifyIORef lines (((x,y):) . tail) |
modifyIORef lines (((x,y):) . tail) |
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-- mark screen dirty |
-- mark screen dirty |
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− | + | writeIORef dirty True |
|
+ | |||
⚫ | |||
+ | GLFW.mouseButtonCallback $= \b s -> |
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-- when left mouse button is released, switch back to |
-- when left mouse button is released, switch back to |
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-- waitForPress action. |
-- waitForPress action. |
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− | + | when (b == GLFW.ButtonLeft && s == GLFW.Release) $ |
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− | + | waitForPress dirty |
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− | else return ()) |
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</haskell> |
</haskell> |
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Line 207: | Line 224: | ||
GL.clear [GL.ColorBuffer] |
GL.clear [GL.ColorBuffer] |
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GL.color $ color3 1 0 0 |
GL.color $ color3 1 0 0 |
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− | GL.renderPrimitive GL.Lines $ |
+ | GL.renderPrimitive GL.Lines $ mapM_ |
− | (\ (x, y) -> GL.vertex (vertex3 (fromIntegral x) (fromIntegral y) 0)) l |
+ | (\ (x, y) -> GL.vertex (vertex3 (fromIntegral x) (fromIntegral y) 0)) l |
+ | |||
vertex3 :: Float -> Float -> Float -> GL.Vertex3 Float |
vertex3 :: Float -> Float -> Float -> GL.Vertex3 Float |
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vertex3 = GL.Vertex3 |
vertex3 = GL.Vertex3 |
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+ | |||
color3 :: Float -> Float -> Float -> GL.Color3 Float |
color3 :: Float -> Float -> Float -> GL.Color3 Float |
Revision as of 20:22, 18 August 2008
About
This is a Haskell module for GLFW OpenGL framework. It provides an alternative to GLUT for OpenGL based Haskell programs.
Status
The library is being used by the Haskell School of Expression (SOE) code to render Graphics in a cross-platform manner. It currently interfaces with GLFW version 2.6, works on Windows, Linux (i386) and Mac OS X (both intel and ppc).
GLFW itself is well documented (see GLFW website), and the Haskell module API is documented via Haddock.
Not all functions are fully tested, and there are still a few GLFW C functions missing from the Haskell module, namely the image loading functions. They are excluded because image handling is a separate issue, and low level buffer manipulation would obscure their use further. Texture loading from TGA format is supported both from file and from memory (via a string buffer)..
The Haskell module also provides basic text rendering while GLFW doesn't. It comes from a free 8x16 font which is made into a TGA texture, stored as a Haskell string in the file GLFW.hs. Text rendering is only possible with Alpha enabled. Again, see SOE.hs from the SOE package for sample usage.
GLFW doesn't work well with GHC threads, forkIO or threadDelay. So avoid them if you can.
Download
Current version is GLFW-0.3. It's a repackage to work with Cabal 1.2 or later. It now compiles GLFW C source code as part of the building process, please report to the package maintainer if you have build problems.
Sample Program
To demonstrate the usage of GLFW for OpenGL based Haskell applications, here is a sample program that allows user to draw lines by holding the left mouse button and move the mouse.
import Graphics.Rendering.OpenGL as GL
import Graphics.UI.GLFW as GLFW
import Graphics.Rendering.OpenGL (($=))
import Data.IORef
import Control.Monad
Because the program needs to process user input, i.e., mouse button and movements, we'll use a continuation like structure for this purpose. The Action
type represents an IO operation that returns the next Action
to continue execution.
data Action = Action (IO Action)
The main program is mostly book-keeping such as initializing OpenGL and GLFW, creating window, setting up viewport, etc.
main = do
GLFW.initialize
-- open window
GLFW.openWindow (GL.Size 400 400) [GLFW.DisplayAlphaBits 8] GLFW.Window
GLFW.windowTitle $= "GLFW Demo"
GL.shadeModel $= GL.Smooth
-- enable antialiasing
GL.lineSmooth $= GL.Enabled
GL.blend $= GL.Enabled
GL.blendFunc $= (GL.SrcAlpha, GL.OneMinusSrcAlpha)
GL.lineWidth $= 1.5
-- set the color to clear background
GL.clearColor $= Color4 0 0 0 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
-- keep all line strokes as a list of points in an IORef
lines <- newIORef []
-- invoke the active drawing loop
active lines
-- finish up
GLFW.closeWindow
GLFW.terminate
There are usually two ways to structure the main loop of GLFW programs. One is by actively polling events before processing them. The screen buffer is usually redrawn every time before swapBuffers
is called. This is the simplest main loop often seen in game applications, and may waste CPU cycles even when there is no visual update. Note that swapBuffers
by default calls pollEvents
implicitly, so there is no need to do a separate poll.
-- we start with waitForPress action
active lines = loop waitForPress
where
loop action = do
-- draw the entire screen
render lines
-- swap buffer
GLFW.swapBuffers
-- check whether ESC is pressed for termination
p <- GLFW.getKey GLFW.ESC
unless (p == GLFW.Press) $
do
-- perform action
Action action' <- action
-- sleep for 1ms to yield CPU to other applications
GLFW.sleep 0.001
-- only continue when the window is not closed
windowOpenStatus <- get $ windowParam Opened
unless (windowOpenStatus == 0) $
loop action' -- loop with next action
waitForPress = do
b <- GLFW.getMouseButton GLFW.ButtonLeft
case b of
GLFW.Release -> return (Action waitForPress)
GLFW.Press -> do
-- when left mouse button is pressed, add the point
-- to lines and switch to waitForRelease action.
(GL.Position x y) <- GL.get GLFW.mousePos
modifyIORef lines (((x,y):) . ((x,y):))
return (Action waitForRelease)
waitForRelease = do
-- keep track of mouse movement while waiting for button
-- release
(GL.Position x y) <- GL.get GLFW.mousePos
-- update the line with new ending position
modifyIORef lines (((x,y):) . tail)
b <- GLFW.getMouseButton GLFW.ButtonLeft
case b of
-- when button is released, switch back back to
-- waitForPress action
GLFW.Release -> return (Action waitForPress)
GLFW.Press -> return (Action waitForRelease)
Another way to structure the main loop is to register event callbacks and use waitEvents
. This way we don't have to put the program to sleep every 1ms because it'll not be using any CPU cycle when there is no event to handle.
One reminder in this approach is that swapBuffers
must be handled with care, because it by default invokes pollEvents
, which in turn invokes all callback functions. So if swapBuffers
is used inside a callback, it'll create infinite loop and hang the program. To avoid it, we should disable the AutoPollEvent
behavior using disableSpecial
.
Another optimization we can do is to use a dirty marker to remember whether the screen really needs to be redrawn. This'll not only save CPU cycles but also speed up event processing to avoid piling up events in the event queue. Similar tricks can be done to optimize the active polling approach.
passive lines = do
-- disable auto polling in swapBuffers
GLFW.disableSpecial GLFW.AutoPollEvent
-- keep track of whether ESC has been pressed
quit <- newIORef False
-- keep track of whether screen needs to be redrawn
dirty <- newIORef True
-- mark screen dirty in refresh callback which is often called
-- when screen or part of screen comes into visibility.
GLFW.windowRefreshCallback $= writeIORef dirty True
-- use key callback to track whether ESC is pressed
GLFW.keyCallback $= \k s ->
when (fromEnum k == fromEnum GLFW.ESC && s == GLFW.Press) $
writeIORef quit True
-- Terminate the program if the window is closed
GLFW.windowCloseCallback $= writeIORef quit True
-- by default start with waitForPress
waitForPress dirty
loop dirty quit
where
loop dirty quit = do
GLFW.waitEvents
-- redraw screen if dirty
d <- readIORef dirty
when d $
render lines >> GLFW.swapBuffers
writeIORef dirty False
-- check if we need to quit the loop
q <- readIORef quit
unless q $
loop dirty quit
waitForPress dirty =
do
GLFW.mousePosCallback $= \_ -> return ()
GLFW.mouseButtonCallback $= \b s ->
when (b == GLFW.ButtonLeft && s == GLFW.Press) $
do
-- when left mouse button is pressed, add the point
-- to lines and switch to waitForRelease action.
(GL.Position x y) <- GL.get GLFW.mousePos
modifyIORef lines (((x,y):) . ((x,y):))
waitForRelease dirty
waitForRelease dirty =
do
GLFW.mousePosCallback $= \(Position x y) ->
do
-- update the line with new ending position
modifyIORef lines (((x,y):) . tail)
-- mark screen dirty
writeIORef dirty True
GLFW.mouseButtonCallback $= \b s ->
-- when left mouse button is released, switch back to
-- waitForPress action.
when (b == GLFW.ButtonLeft && s == GLFW.Release) $
waitForPress dirty
Just replace active
with passive
in the main
function to run the second approach.
The rest of the program goes below.
render lines = do
l <- readIORef lines
GL.clear [GL.ColorBuffer]
GL.color $ color3 1 0 0
GL.renderPrimitive GL.Lines $ mapM_
(\ (x, y) -> GL.vertex (vertex3 (fromIntegral x) (fromIntegral y) 0)) l
vertex3 :: Float -> Float -> Float -> GL.Vertex3 Float
vertex3 = GL.Vertex3
color3 :: Float -> Float -> Float -> GL.Color3 Float
color3 = GL.Color3