1 files changed, 244 insertions, 0 deletions
diff --git a/tests/OffscreenContext.cc b/tests/OffscreenContext.cc
new file mode 100644
index 0000000..e4045af
--- /dev/null
+++ b/tests/OffscreenContext.cc
@@ -0,0 +1,244 @@
+/*
+
+Create an OpenGL context without creating an OpenGL Window. for Linux.
+
+See Also
+
+ glxgears.c by Brian Paul from mesa-demos (mesa3d.org)
+ http://cgit.freedesktop.org/mesa/demos/tree/src/xdemos?id=mesa-demos-8.0.1
+ 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 "system-gl.h"
+#include "fbo.h"
+
+#include <GL/gl.h>
+#include <GL/glx.h>
+
+using namespace std;
+
+struct OffscreenContext
+{
+  GLXContext openGLContext;
+  Display *xdisplay;
+  Window xwindow;
+  int width;
+  int height;
+  fbo_t *fbo;
+};
+
+void offscreen_context_init(OffscreenContext &ctx, int width, int height)
+{
+  ctx.width = width;
+  ctx.height = height;
+  ctx.openGLContext = NULL;
+  ctx.xdisplay = NULL;
+  ctx.xwindow = (Window)NULL;
+  ctx.fbo = NULL;
+}
+
+static XErrorHandler original_xlib_handler = (XErrorHandler) NULL;
+static bool XCreateWindow_failed = false;
+static int XCreateWindow_error(Display *dpy, XErrorEvent *event)
+{
+  cerr << "XCreateWindow failed: XID: " << event->resourceid
+        << " request: " << (int)event->request_code
+        << " minor: " << (int)event->minor_code << "\n";
+  char description[1024];
+  XGetErrorText( dpy, event->error_code, description, 1023 );
+  cerr << " error message: " << description << "\n";
+  XCreateWindow_failed = true;
+  return 0;
+}
+
+bool create_glx_dummy_window(OffscreenContext &ctx)
+{
+  /*
+  create a dummy X window without showing it. (without 'mapping' it)
+  and save information to the ctx.
+
+  This purposely does not use glxCreateWindow, to avoid crashes,
+  "failed to create drawable" errors, and Mesa "WARNING: Application calling 
+    GLX 1.3 function when GLX 1.3 is not supported! This is an application bug!"
+
+  This function will alter ctx.openGLContext and ctx.xwindow if successfull
+  */
+
+  int attributes[] = {
+    GLX_DRAWABLE_TYPE, GLX_WINDOW_BIT,
+    GLX_RENDER_TYPE,   GLX_RGBA_BIT,
+    GLX_RED_SIZE, 1,
+    GLX_GREEN_SIZE, 1,
+    GLX_BLUE_SIZE, 1,
+    None
+  };
+
+  Display *dpy = ctx.xdisplay;
+
+  int num_returned = 0;
+  GLXFBConfig *fbconfigs = glXChooseFBConfig( dpy, DefaultScreen(dpy), attributes, &num_returned );
+  if ( fbconfigs == NULL ) {
+    cerr << "glXChooseFBConfig failed\n";
+    return false;
+  }
+
+  XVisualInfo *visinfo = glXGetVisualFromFBConfig( dpy, fbconfigs[0] );
+  if ( visinfo == NULL ) {
+    cerr << "glXGetVisualFromFBConfig failed\n";
+    XFree( fbconfigs );
+    return false;
+  }
+
+  // can't depend on xWin==NULL at failure. use a custom Xlib error handler instead.
+  original_xlib_handler = XSetErrorHandler( XCreateWindow_error );
+  Window xWin = XCreateSimpleWindow( dpy, DefaultRootWindow(dpy), 0,0,10,10, 0,0,0 );
+  XSync( dpy, false );
+  if ( XCreateWindow_failed ) {
+    XFree( visinfo );
+    XFree( fbconfigs );
+    return false;
+  }
+  XSetErrorHandler( original_xlib_handler );
+
+  // Most programs would call XMapWindow here. But we don't, to keep the window hidden
+  // XMapWindow( dpy, xWin );
+
+  GLXContext context = glXCreateNewContext( dpy, fbconfigs[0], GLX_RGBA_TYPE, NULL, True );
+  if ( context == NULL ) {
+    cerr << "glXCreateNewContext failed\n";
+    XDestroyWindow( dpy, xWin );
+    XFree( visinfo );
+    XFree( fbconfigs );
+    return false;
+  }
+
+  //GLXWindow glxWin = glXCreateWindow( dpy, fbconfigs[0], xWin, NULL );
+
+  if (!glXMakeContextCurrent( dpy, xWin, xWin, context )) {
+  //if (!glXMakeContextCurrent( dpy, glxWin, glxWin, context )) {
+    cerr << "glXMakeContextCurrent failed\n";
+    glXDestroyContext( dpy, context );
+    XDestroyWindow( dpy, xWin );
+    XFree( visinfo );
+    XFree( fbconfigs );
+    return false;
+  }
+
+  ctx.openGLContext = context;
+  ctx.xwindow = xWin;
+
+  XFree( visinfo );
+  XFree( fbconfigs );
+
+  return true;
+}
+
+
+Bool create_glx_dummy_context(OffscreenContext &ctx)
+{
+  // This will alter ctx.openGLContext and ctx.xdisplay and ctx.xwindow if successfull
+  int major;
+  int minor;
+  Bool result = False;
+
+  ctx.xdisplay = XOpenDisplay( NULL );
+  if ( ctx.xdisplay == NULL ) {
+    cerr << "Unable to open a connection to the X server\n";
+    return False;
+  }
+
+  // glxQueryVersion is not always reliable. Use it, but then
+  // also check to see if GLX 1.3 functions exist
+
+  glXQueryVersion(ctx.xdisplay, &major, &minor);
+
+  if ( major==1 && minor<=2 && glXGetVisualFromFBConfig==NULL ) {
+    cerr << "Error: GLX version 1.3 functions missing. "
+        << "Your GLX version: " << major << "." << minor << endl;
+  } else {
+    result = create_glx_dummy_window(ctx);
+  }
+
+  if (!result) XCloseDisplay( ctx.xdisplay );
+  return result;
+}
+
+OffscreenContext *create_offscreen_context(int w, int h)
+{
+  OffscreenContext *ctx = new OffscreenContext;
+  offscreen_context_init( *ctx, w, h );
+
+  // before an FBO can be setup, a GLX context must be created
+  // this call alters ctx->xDisplay and ctx->openGLContext 
+  //  and ctx->xwindow if successfull
+  if (!create_glx_dummy_context( *ctx )) {
+    return NULL;
+  }
+
+  // glewInit must come after Context creation and before FBO calls.
+  GLenum err = glewInit();
+  if (GLEW_OK != err) {
+    cerr << "Unable to init GLEW: " << glewGetErrorString(err) << endl;
+    return NULL;
+  }
+  glew_dump();
+
+  ctx->fbo = fbo_new();
+  if (!fbo_init(ctx->fbo, w, h)) {
+    cerr << "GL Framebuffer Object init failed; dumping GLEW info" << endl;
+    return NULL;
+  }
+
+  return ctx;
+}
+
+bool teardown_offscreen_context(OffscreenContext *ctx)
+{
+  if (ctx) {
+    fbo_unbind(ctx->fbo);
+    fbo_delete(ctx->fbo);
+    XDestroyWindow( ctx->xdisplay, ctx->xwindow );
+    glXDestroyContext( ctx->xdisplay, ctx->openGLContext );
+    XCloseDisplay( ctx->xdisplay );
+    return true;
+  }
+  return false;
+}
+
+/*!
+  Capture framebuffer from OpenGL and write it to the given filename as PNG.
+*/
+bool save_framebuffer(OffscreenContext *ctx, const char *filename)
+{
+  if (!ctx || !filename) return false;
+  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);
+
+  // Flip it vertically - images read from OpenGL buffers are upside-down
+  int rowBytes = samplesPerPixel * ctx->width;
+  unsigned char *flippedBuffer = (unsigned char *)malloc(rowBytes * ctx->height);
+  if (!flippedBuffer) {
+    std::cerr << "Unable to allocate flipped buffer for corrected image.";
+    return 1;
+  }
+  flip_image(pixels, flippedBuffer, samplesPerPixel, ctx->width, ctx->height);
+
+  bool writeok = write_png(filename, flippedBuffer, ctx->width, ctx->height);
+
+  free(flippedBuffer);
+
+  return writeok;
+}
+
+void bind_offscreen_context(OffscreenContext *ctx)
+{
+  if (ctx) fbo_bind(ctx->fbo);
+}