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Gaspos

OpenGL called from a DLL loses its context

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I'm developing (with Visual Studio C++ 2005) a screen saver (yet an other one, sigh...) that is built on plugins : The main part (.exe) manages all the windows/display/events stuff. The plugins (.dll) produce the bitmap to be displayed (I already made some nice ones). A plugin has some entry points as "init" (that is called once, at beginning) and "next" (that is iteratively called until the mouse is moved). Now I'm trying to create a new plugin (ie dll) that uses OpenGL to compute 3D images. In the "init" function I init all the OpenGL stuff : . glutInit( &argc,argv ) ; . glutInitDisplayMode( GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH ) ; . glutInitWindowSize( sizex,sizey ) ; . glutCreateWindow( "dummy" ) ; . glClearColor( 0.0f,0.0f,0.0f,1.0f ) ; . glShadeModel( GL_SMOOTH ) ; . glFrontFace( GL_CW ) ; . glCullFace( GL_BACK ) ; . glEnable( GL_CULL_FACE ) ; . blah blah... In the "next" function I render the scene and get the bitmap : . glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT ) ; . glLoadIdentity() ; . glBegin( GL_QUADS ) ; . glVertex3d ... . blah blah... . glEnd() ; . glFlush() ; . glutSwapBuffers() ; . glutPostRedisplay() ; . glReadPixels( 0,0,sizex,sizey,GL_RGB,GL_UNSIGNED_BYTE,bitmap ) ; So... here is the issue : In the "next" function, nothing works... the whole OpenGL context (ie state) seems to be lost. If I hack my code and call directly "next" from "init", it works fine. It is like if returning from a DLL function makes OpenGL lose its context. I don't know about calling a DLL (OpenGL32.dll) since another DLL (my plugin)... Do you have any idea on how OpenGL manages its own context ? I thought that since my DLL is loaded in memory, its own DLLs are also maintained in memory with their own context... but I may be wrong... Thanks for any advice. Gaspos

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