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PODrawing concurrently in multiple windows with GLUT
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  1. PODrawing concurrently in multiple windows with GLUT
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    copied!<p>When I create two windows and redraw them in two different threads (one per window), it seems like all drawing goes to first created window. It constantly switches between what should be displayed in both windows. And second one remains mostly black.</p> <p>The code was working well with only one window, and then I updated it - inserted <code>currentWindow $= Just glWindow</code> in the beginning of the functions which set callbacks and call rendering methods.</p> <p>What do you think is the cause of the problems?</p> <p>EDIT:</p> <p>Code skeleton:</p> <pre><code>module Chart.Window where import Graphics.UI.GLUT hiding (Window, postRedisplay, &lt;etc&gt;) import qualified Graphics.UI.GLUT as GLUT import qualified Graphics.Rendering.OpenGL as GL data Window = Window { glWindow :: GLUT.Window , viewListRef :: IORef [Line] } main = do forkOS start &lt;params1&gt; forkOS start &lt;params2&gt; start &lt;params&gt; = do win &lt;- new &lt;params&gt; run win mainLoop new :: Strict -&gt; (Int, Int) -&gt; (Int, Int) -&gt; IO Window new name (posx, posy) (w, h) = do initGLUT glWindow &lt;- createWindow name currentWindow $= Just glWindow windowSize $= Size (fromIntegral w) (fromIntegral h) windowPosition $= Position (fromIntegral posx) (fromIntegral posy) return Window {..} initGLUT :: IO () initGLUT = do beenInit &lt;- get initState unless beenInit $ void getArgsAndInitialize initialDisplayMode $= [WithDepthBuffer, DoubleBuffered, RGBAMode] initialWindowSize $= Size 100 100 initialWindowPosition $= Position 100 100 actionOnWindowClose $= ContinueExectuion run :: Window -&gt; IO () run win@Window{..} = do -- this will fork (with forkIO) threads -- which will call "repaint" when chart needs to be updated initListeners repaint initCallbacks win where repaint :: [Line] -&gt; IO () repaint viewList = do writeIORef viewListRef viewList postRedisplay win postRedisplay Window{..} = GLUT.postRedisplay $ Just glWindow initCallbacks win@Window{..} = do currentWindow $= Just glWindow GLUT.displayCallback $= display win GLUT.idleCallback $= Just (postRedisplay win) display Window{..} = do currentWindow $= Just glWindow Size w h &lt;- get windowSize viewList &lt;- readIORef viewListRef drawChart viewList otherOptions reshapeCallback :: Window -&gt; GLUT.ReshapeCallback reshapeCallback win@Window{..} size@(Size w h) = do currentWindow $= Just glWindow GL.viewport $= (Position 0 0, size) GL.matrixMode $= GL.Projection GL.loadIdentity GL.ortho2D 0 (fromIntegral w) 0 (fromIntegral h) GL.matrixMode $= GL.Modelview 0 GL.loadIdentity ... -- send command for listener thread to change internal state and postRedisplay drawChart viewList otherOptions = do ... -- chart consists of several horizontal panels. Call this for each panel: glViewport 0 panelYPosition width winHeight glScissor 0 panelYPosition (fromIntegral width) (fromIntegral panelHeight) GL.clear [GL.ColorBuffer] ... -- and then for each line=(Vertex2 v1 v2) from viewList GL.renderPrimitive GL.Lines $ do GL.vertex v1 GL.vertex v2 ... </code></pre> <p>BTW, when I commented the line which sets reshapeCallback (and window is reshaped at the beginning) and launched charting with only one window, I got exactly the same effect as in multi-window launch. I mean, the (only) window was mostly empty as if it was secondly created.</p>
 

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