glut: added GLUT_PPM_FILE env var to dump first frame to a PPM file

Set GLUT_PPM_FILE to the desired filename.  The first frame rendered will
be written to that file.

src/glut/glx/Makefile

@@ -56,6 +56,7 @@ SOURCES = \
 	glut_modifier.c \
 	glut_mroman.c \
 	glut_overlay.c \
+	glut_ppm.c \
 	glut_roman.c \
 	glut_shapes.c \
 	glut_space.c \

src/glut/glx/glut_init.c

@@ -51,6 +51,7 @@ int __glutInitX = -1, __glutInitY = -1;
 GLboolean __glutForceDirect = GL_FALSE,
   __glutTryDirect = GL_TRUE;
 Atom __glutWMDeleteWindow;
+char *__glutPPMFile = NULL;
 /* *INDENT-ON* */
 
 #ifdef _WIN32
@@ -341,6 +342,9 @@ glutInit(int *argcp, char **argv)
            __glutFPS = 5000;  /* 5000 milliseconds */
      }
   }
+
+  /* check if GLUT_PPM_FILE env var is set */
+  __glutPPMFile = getenv("GLUT_PPM_FILE");
 }
 
 #ifdef _WIN32

src/glut/glx/glut_ppm.c

@@ -0,0 +1,80 @@
+/*
+ * PPM file output
+ * Brian Paul
+ * 8 Dec 2008
+ */
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include "glutint.h"
+
+
+static void
+write_ppm_file(const char *filename, const GLubyte *buffer,
+               int width, int height)
+{
+   const int binary = 1;
+   FILE *f = fopen( filename, "w" );
+   if (f) {
+      const GLubyte *ptr = buffer;
+      int i, x, y;
+      if (binary) {
+         fprintf(f,"P6\n");
+         fprintf(f,"# ppm-file created by GLUT\n");
+         fprintf(f,"%i %i\n", width, height);
+         fprintf(f,"255\n");
+         fclose(f);
+         f = fopen( filename, "ab" );  /* reopen in binary append mode */
+         for (y = height - 1; y >= 0; y--) {
+            for (x = 0; x < width; x++) {
+               i = (y * width + x) * 4;
+               fputc(ptr[i], f);   /* write red */
+               fputc(ptr[i+1], f); /* write green */
+               fputc(ptr[i+2], f); /* write blue */
+            }
+         }
+      }
+      else {
+         /*ASCII*/
+         int counter = 0;
+         fprintf(f,"P3\n");
+         fprintf(f,"# ascii ppm file created by GLUT\n");
+         fprintf(f,"%i %i\n", width, height);
+         fprintf(f,"255\n");
+         for (y = height - 1; y >= 0; y--) {
+            for (x = 0; x < width; x++) {
+               i = (y * width + x) * 4;
+               fprintf(f, " %3d %3d %3d", ptr[i], ptr[i+1], ptr[i+2]);
+               counter++;
+               if (counter % 5 == 0)
+                  fprintf(f, "\n");
+            }
+         }
+      }
+      fclose(f);
+   }
+}
+
+
+/**
+ * Called from SwapBuffers if the GLUT_PPM_FILE env var is set.
+ */
+void __glutWritePPMFile(void)
+{
+   int w = glutGet(GLUT_WINDOW_WIDTH);
+   int h = glutGet(GLUT_WINDOW_HEIGHT);
+   GLubyte *buf;
+
+   assert(__glutPPMFile);
+
+   buf = (GLubyte *) malloc(w * h * 4);
+   if (buf) {
+      /* XXX save/restore pixel packing */
+      glReadPixels(0, 0, w, h, GL_RGBA, GL_UNSIGNED_BYTE, buf);
+      write_ppm_file(__glutPPMFile, buf, w, h);
+      free(buf);
+   }
+
+   __glutPPMFile = NULL; /* only write one file */
+}

src/glut/glx/glut_swap.c

@@ -18,6 +18,10 @@ glutSwapBuffers(void)
 {
   GLUTwindow *window = __glutCurrentWindow;
 
+  if (__glutPPMFile) {
+     __glutWritePPMFile();
+  }
+
   if (window->renderWin == window->win) {
     if (__glutCurrentWindow->treatAsSingle) {
       /* Pretend the double buffered window is single buffered,

src/glut/glx/glutint.h

@@ -664,6 +664,7 @@ extern unsigned int __glutModifierMask;
 #ifdef _WIN32
 extern void (__cdecl *__glutExitFunc)(int retval);
 #endif
+extern char *__glutPPMFile;
 
 /* private variables from glut_menu.c */
 extern GLUTmenuItem *__glutItemSelected;
@@ -684,6 +685,9 @@ extern void __glutFreeOverlay(GLUToverlay * overlay);
 extern XVisualInfo *__glutDetermineWindowVisual(Bool * treatAsSingle,
   Bool * visAlloced, void **fbc);
 
+/* private variables from glut_ppm.c */
+extern void __glutWritePPMFile(void);
+
 /* private variables from glut_mesa.c */
 extern int __glutMesaSwapHackSupport;
 
@@ -812,4 +816,5 @@ extern LONG WINAPI __glutWindowProc(HWND win, UINT msg, WPARAM w, LPARAM l);
 extern HDC XHDC;
 #endif
 
+
 #endif /* __glutint_h__ */