Re: [wxhaskell-users] Multiple GL Canvases

[Patrick S. <mai...@st...>]

Hi there, 

The one important thing is, that the gl commands are sent to the actual 
gldevice context. To set the actual context you have to use 
glCanvasSetCurrent.

So when you want two gl windows just do it and befor drawing in one switch the 
contex to this one.

Here is the modified GlCanvas.hs from the sample directory the should answer 
all your questions.

Cheers
Patrick

PS @developers: I have updated my cvs and THE ONE glSample is just the (non 
running) same. Will anyone make a fix on this sample so everybody can have a  
running one. If nobody will have time to to this I can send a fixed version. 
Interested??


<Code>
module Main
where
    
import Data.List ( transpose )
import Graphics.UI.WX
import Graphics.UI.WXCore
import Graphics.Rendering.OpenGL
-- Many code and Type are ambiguous, so we must qualify names.
import qualified Graphics.UI.WX as WX
import qualified Graphics.Rendering.OpenGL as GL

main :: IO()
main = start gui


defaultWidth  = 320
defaultHeight = 200

gui = do
   f <- frame [ text := "Simple OpenGL" ]

-- We just create two glCanvas

   glCanvas <- glCanvasCreateEx f 0 (Rect 0 0 defaultWidth defaultHeight)
        0 "GLCanvas" [GL_RGBA] nullPalette
   glCanvas2 <- glCanvasCreateEx f 0 (Rect 0 0 defaultWidth defaultHeight)
        0 "GLCanvas" [GL_RGBA] nullPalette

   let glWidgetLayout = fill $ row 5 [widget glCanvas2,  widget glCanvas]

-- Hint: You have to use the paintRaw event. For switching between the two
--   glwindows you can give both of them as parameter
   WX.set f [ layout := glWidgetLayout
            , on paintRaw := paintGL glCanvas glCanvas2
            ]


convWG (WX.Size w h) = (GL.Size (convInt32  w) (convInt32  h))
convInt32 = fromInteger . toInteger

paintGL :: GLCanvas a -> GLCanvas a -> DC() -> WX.Rect -> [WX.Rect]-> IO ()
paintGL gl1 gl2 dc myrect _ = do

-- Now we switch to the first one
-- and do all init and painting stuff
-- Hint: I changed the backgroundcolor for clearance

   glCanvasSetCurrent gl1
   myInit
   reshape $ convWG $ rectSize myrect
   -- Or not reshape the size.
   reshape (GL.Size 320 200)
   GL.clearColor GL.$= GL.Color4 1 0 0 0
   display
   glCanvasSwapBuffers gl1

-- All the same for the second one
   glCanvasSetCurrent gl2
   myInit
   reshape $ convWG $ rectSize myrect
   -- Or not reshape the size.
   reshape (GL.Size 320 200)
   GL.clearColor GL.$= GL.Color4 0 2 0 0
   display
   glCanvasSwapBuffers gl2
   return ()


ctrlPoints :: [[GL.Vertex3 GL.GLfloat]]
ctrlPoints = [
   [ GL.Vertex3 (-1.5) (-1.5)   4.0,  GL.Vertex3 (-0.5) (-1.5)   2.0,
     GL.Vertex3   0.5  (-1.5) (-1.0), GL.Vertex3   1.5  (-1.5)   2.0 ],
   [ GL.Vertex3 (-1.5) (-0.5)   1.0,  GL.Vertex3 (-0.5) (-0.5)   3.0,
     GL.Vertex3   0.5  (-0.5)   0.0,  GL.Vertex3   1.5  (-0.5) (-1.0) ],
   [ GL.Vertex3 (-1.5)   0.5    4.0,  GL.Vertex3 (-0.5)   0.5    0.0,
     GL.Vertex3   0.5    0.5    3.0,  GL.Vertex3   1.5    0.5    4.0 ],
   [ GL.Vertex3 (-1.5)   1.5  (-2.0), GL.Vertex3 (-0.5)   1.5  (-2.0),
     GL.Vertex3   0.5    1.5    0.0,  GL.Vertex3   1.5    1.5  (-1.0) ]]

initlights :: IO ()
initlights = do
   GL.lighting GL.$= GL.Enabled
   GL.light (GL.Light 0) GL.$= GL.Enabled

   GL.ambient  (GL.Light 0) GL.$= GL.Color4 0.2 0.2 0.2 1.0
   GL.position (GL.Light 0) GL.$= GL.Vertex4 0 0 2 1

   GL.materialDiffuse   GL.Front GL.$= GL.Color4 0.6 0.6 0.6 1.0
   GL.materialSpecular  GL.Front GL.$= GL.Color4 1.0 1.0 1.0 1.0
   GL.materialShininess GL.Front GL.$= 50

myInit :: IO ()
myInit = do
--   GL.clearColor GL.$= GL.Color4 1 0 0 0
   GL.depthFunc GL.$= Just GL.Less
   m <- GL.newMap2 (0, 1) (0, 1) (transpose ctrlPoints)
   GL.map2 GL.$= Just (m :: GLmap2 GL.Vertex3 GL.GLfloat)
   GL.autoNormal GL.$= GL.Enabled
   mapGrid2 GL.$= ((20, (0, 1)), (20, (0, 1 :: GL.GLfloat)))
   initlights  -- for lighted version only

display = do
   GL.clear [ GL.ColorBuffer, GL.DepthBuffer ]
   GL.preservingMatrix $ do
     GL.rotate (85 :: GL.GLfloat) (GL.Vector3 1 1 1)
     evalMesh2 Fill (0, 20) (0, 20)
   GL.flush

reshape mysize@(GL.Size w h) = do
   GL.viewport GL.$= (GL.Position 0 0, mysize)
   GL.matrixMode GL.$= GL.Projection
   GL.loadIdentity
   let wf = fromIntegral w
       hf = fromIntegral h
   if w <= h
      then GL.ortho (-4.0) 4.0 (-4.0*hf/wf) (4.0*hf/wf) (-4.0) 4.0
      else GL.ortho (-4.0*wf/hf) (4.0*wf/hf) (-4.0) 4.0 (-4.0) 4.0
   GL.matrixMode GL.$= GL.Modelview 0
   GL.loadIdentity



</Code>



On Sunday 30 January 2005 21:44, Jan Rochel wrote:
> Hello.
>
> I can't get a program using multiple GLCanvases working properly.
> The first canvas in the first (MDIChild)Frame works perfectly fine,
> but the second GLCanvas that is created (in another (MDIChild)Frame) is
> just black. Trying out several things with glCanvasSetCurrent didn't
> help. Could anybody please provide some example program that uses two
> GLCanvases at the same time? This is quite important to me.
>
> Thanks
> Jan
>
>
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