Linux offscreen OpenGL using glxpixmaps. also fix FBO ARB/EXT issues

1 files changed, 150 insertions, 54 deletions

diff --git a/tests/OffscreenContext.cc b/tests/OffscreenContext.cc
index fa1afde..775491e 100644
--- a/tests/OffscreenContext.cc
+++ b/tests/OffscreenContext.cc
@@ -1,85 +1,182 @@
+/*
+
+Create an OpenGL context without creating an OpenGL Window. for Linux.
+
+based on
+
+ http://www.opengl.org/sdk/docs/man/xhtml/glXIntro.xml
+ http://www.mesa3d.org/brianp/sig97/offscrn.htm
+ http://glprogramming.com/blue/ch07.html
+ OffscreenContext.mm (Mac OSX version)
+
+*/
+
 #include "OffscreenContext.h"
 #include "printutils.h"
 #include "imageutils.h"
+#include "fbo.h"
 
-// see http://www.gamedev.net/topic/552607-conflict-between-glew-and-sdl/
-#define NO_SDL_GLEXT
-#include <GL/glew.h>
-
-#define GL_GLEXT_PROTOTYPES
 #include <GL/gl.h>
-#include <GL/glext.h>
+#include <GL/glx.h>
 
-//#include <GL/gl.h>
-//#include <GL/glu.h>      // for gluCheckExtension
-#include <SDL.h>
+#define REPORTGLERROR(task) { GLenum tGLErr = glGetError(); if (tGLErr != GL_NO_ERROR) { std::cout << "OpenGL error " << tGLErr << " while " << task << "\n"; } }
 
 struct OffscreenContext
 {
+  GLXContext openGLContext;
+  Display *xDisplay;
+  GLXPixmap glx_pixmap;
+  Pixmap x11_pixmap;
   int width;
   int height;
-  GLuint fbo;
-  GLuint colorbo;
-  GLuint depthbo;
+  fbo_t *fbo;
 };
 
-void write_targa(const char *filename, GLubyte *pixels, int width, int height)
+Bool glx_1_3_pixmap_dummy_context(OffscreenContext *ctx, Bool hybrid)
+{
+	XVisualInfo *vInfo;
+	GLXFBConfig *fbConfigs;
+
+	int numReturned;
+	int result;
+	int dummyAttributes_1_3[] = {
+		GLX_DRAWABLE_TYPE, GLX_PIXMAP_BIT,
+		GLX_RENDER_TYPE,   GLX_RGBA_BIT,
+		None
+	};
+
+	fbConfigs = glXChooseFBConfig( ctx->xDisplay,
+	 	DefaultScreen(ctx->xDisplay),
+		dummyAttributes_1_3, &numReturned );
+	if ( fbConfigs == NULL ) {
+		REPORTGLERROR("glXChooseFBConfig failed") ;
+		return False;
+	}
+
+	vInfo = glXGetVisualFromFBConfig( ctx->xDisplay, fbConfigs[0] );
+	if ( vInfo == NULL ) {
+		REPORTGLERROR("glXGetVisualFromFBConfig failed") ;
+		return False;
+	}
+
+	ctx->x11_pixmap = XCreatePixmap( ctx->xDisplay, DefaultRootWindow(ctx->xDisplay) , 10, 10, 8 );
+
+	if (hybrid) {
+		// GLX 1.2 - prevent Mesa warning
+		ctx->glx_pixmap = glXCreateGLXPixmap( ctx->xDisplay, vInfo, ctx->x11_pixmap );
+	} else {
+		// GLX 1.3
+		ctx->glx_pixmap = glXCreatePixmap( ctx->xDisplay, fbConfigs[0], ctx->x11_pixmap, NULL ); // GLX 1.3
+	}
+
+	ctx->openGLContext = glXCreateNewContext( ctx->xDisplay, fbConfigs[0], GLX_RGBA_TYPE, NULL, True );
+	if ( ctx->openGLContext == NULL ) {
+		REPORTGLERROR("glXCreateNewContext failed" );
+		return False;
+	}
+
+	result = glXMakeContextCurrent( ctx->xDisplay, ctx->glx_pixmap, ctx->glx_pixmap, ctx->openGLContext );
+	if ( result == False ) {
+		REPORTGLERROR("glXMakeContextCurrent failed" );
+		return False;
+	}
+
+	return True;
+}
+
+Bool make_glx_dummy_context(OffscreenContext *ctx)
 {
-	FILE *f = fopen( filename, "w" );
-	int y;
-	if (f) {
-		GLubyte header[] = {
-			00,00,02, 00,00,00, 00,00,00, 00,00,00,
-			0xff & width, 0xff & width >> 8,
-			0xff & height, 0xff & height >> 8,
-			32, 0x20 }; // next-to-last = bit depth
-		fwrite( header, sizeof(header), 1, f);
-		for (y=height-1; y>=0; y--)
-			fwrite( pixels + y*width*4, 4, width, f);
-		fclose(f);
+	/*
+	Before opening a framebuffer, an OpenGL context must be created.
+	For GLX, you can do this by creating a 'Pixmap' drawable then
+	creating the Context off of that. The Pixmap is then never used.
+	*/
+	int major;
+	int minor;
+
+	ctx->xDisplay = XOpenDisplay( NULL );
+	if ( ctx->xDisplay == NULL ) {
+		fprintf(stderr, "Unable to open a connection to the X server\n" );
+		return False;
+	}
+
+	/*
+	On some systems, the GLX library will report that it is version
+	1.2, but some 1.3 functions will be implemented, and, furthermore,
+	some 1.2 functions won't work right, while the 1.3 functions will,
+	but glXCreatePixmp will still generate a MESA GLX 1.3 runtime warning.
+
+	To workaround this, detect the situation and use 'hybrid' mix of
+	1.2 and 1.3 as needed.
+	*/
+	glXQueryVersion(ctx->xDisplay, &major, &minor);
+
+	if (major==1 && minor<=2) {
+		if (glXCreatePixmap!=NULL) { // 1.3 function exists, even though its 1.2
+			return glx_1_3_pixmap_dummy_context(ctx,True);
+		} else {
+			fprintf(stderr,"OpenGL error: GLX version 1.3 functions missing. Your GLX: %i.%i\n",major,minor);
+			return False;
+		}
+	} else if (major>=1 && minor>=3) {
+		return glx_1_3_pixmap_dummy_context(ctx,False);
 	}
 }
 
+void glewCheck() {
+#ifdef DEBUG
+  cout << "GLEW version " << glewGetString(GLEW_VERSION) << "\n";
+  cout << (const char *)glGetString(GL_RENDERER) << "(" << (const char *)glGetString(GL_VENDOR) << ")\n"
+       << "OpenGL version " << (const char *)glGetString(GL_VERSION) << "\n";
+  cout  << "Extensions: " << (const char *)glGetString(GL_EXTENSIONS) << "\n";
+
+  if (GLEW_ARB_framebuffer_object) {
+    cout << "ARB_FBO supported\n";
+  }
+  if (GLEW_EXT_framebuffer_object) {
+    cout << "EXT_FBO supported\n";
+  }
+  if (GLEW_EXT_packed_depth_stencil) {
+    cout << "EXT_packed_depth_stencil\n";
+  }
+#endif
+}
+
 OffscreenContext *create_offscreen_context(int w, int h)
 {
   OffscreenContext *ctx = new OffscreenContext;
   ctx->width = w;
   ctx->height = h;
+  ctx->openGLContext = NULL;
+  ctx->xDisplay = NULL;
+  ctx->glx_pixmap = NULL;
+  ctx->x11_pixmap = NULL;
+  ctx->fbo = NULL;
+
+  // fill ctx->xDisplay, ctx->openGLContext, x11_pixmap, glx_pixmap
+  if (!make_glx_dummy_context(ctx)) {
+    return NULL;
+  }
 
-  // dummy window 
-  SDL_Init(SDL_INIT_VIDEO);
-  SDL_SetVideoMode(ctx->width,ctx->height,32,SDL_OPENGL);
-
-  // must come after openGL context init (done by dummy window)
-  // but must also come before various EXT calls
-  //glewInit();
+  glewInit(); //must come after Context creation and before FBO calls.
+  glewCheck();
 
-/*
-	glClearColor(1, 1, 1, 1);
-	glClear(GL_COLOR_BUFFER_BIT);
-	glBegin(GL_TRIANGLES);
-	glColor3f( 1, 0, 0);
-	glVertex3f( 0, 0, 0);
-	glVertex3f( 1, 0, 0);
-	glVertex3f( 0, 1, 0);
-	glEnd();
-        SDL_GL_SwapBuffers();
-//  sleep(2);
-*/
-
-  int samplesPerPixel = 4; // R, G, B and A
+  ctx->fbo = fbo_new();
+  if (!fbo_init(ctx->fbo, w, h)) {
+    return NULL;
+  }
 
-/*  char * filename = "blah.tga";
-  GLubyte pixels[ ctx->width * ctx->height * samplesPerPixel ];
-  glReadPixels(0, 0, ctx->width, ctx->height, GL_BGRA, GL_UNSIGNED_BYTE, pixels);
-  printf("writing %s\n",filename);
-  write_targa(filename,pixels,ctx->width, ctx->height);*/
   return ctx;
 }
 
 bool teardown_offscreen_context(OffscreenContext *ctx)
 {
-  return true;
+	fbo_unbind(ctx->fbo);
+	fbo_delete(ctx->fbo);
+	glXDestroyPixmap(ctx->xDisplay, ctx->glx_pixmap );
+	XFreePixmap(ctx->xDisplay, ctx->x11_pixmap );
+	glXDestroyContext( ctx->xDisplay, ctx->openGLContext );
+	return true;
 }
 
 /*!
@@ -87,8 +184,6 @@ bool teardown_offscreen_context(OffscreenContext *ctx)
 */
 bool save_framebuffer(OffscreenContext *ctx, const char *filename)
 {
-  SDL_GL_SwapBuffers(); // show image
-
   int samplesPerPixel = 4; // R, G, B and A
   GLubyte pixels[ctx->width * ctx->height * samplesPerPixel];
   glReadPixels(0, 0, ctx->width, ctx->height, GL_RGBA, GL_UNSIGNED_BYTE, pixels);
@@ -111,4 +206,5 @@ bool save_framebuffer(OffscreenContext *ctx, const char *filename)
 
 void bind_offscreen_context(OffscreenContext *ctx)
 {
+	fbo_bind(ctx->fbo);
 }