Added "offscreen" demo, a very simple program that produces an onscreen

window and, upon command, renders a similar offscreen display and writes
the result to disk.

Also, modified the build structure for UNIX_X11 to autobuild the demo.
(Not done for WIN32 at this time.)

Also, forgot to previously commit the updated freeglut_ext.h include.
Eeep.


git-svn-id: https://svn.code.sf.net/p/freeglut/code/trunk@465 7f0cb862-5218-0410-a997-914c9d46530a

.gitattributes

@@ -53,6 +53,8 @@ freeglut/freeglut/progs/demos/One/Makefile.am svn_keywords=Author+Date+Id+Revisi
 freeglut/freeglut/progs/demos/One/one.c svn_keywords=Author+Date+Id+Revision
 freeglut/freeglut/progs/demos/One/one.dsp svn_keywords=Author+Date+Id+Revision
 freeglut/freeglut/progs/demos/demos.dsw svn_keywords=Author+Date+Id+Revision
+freeglut/freeglut/progs/demos/offscreen/Makefile.am svn_keywords=Author+Date+Id+Revision
+freeglut/freeglut/progs/demos/offscreen/offscreen.c svn_keywords=Author+Date+Id+Revision
 freeglut/freeglut/progs/demos/shapes/Makefile.am svn_keywords=Author+Date+Id+Revision
 freeglut/freeglut/progs/demos/shapes/shapes.c svn_keywords=Author+Date+Id+Revision
 freeglut/freeglut/progs/demos/shapes/shapes.dsp svn_keywords=Author+Date+Id+Revision

freeglut/freeglut/configure.in

@@ -67,6 +67,7 @@ AC_OUTPUT(\
 	progs/demos/Fractals_random/Makefile \
 	progs/demos/Lorenz/Makefile \
 	progs/demos/One/Makefile \
+	progs/demos/offscreen/Makefile \
 	progs/demos/shapes/Makefile \
 	src/Makefile \
 	include/Makefile \

freeglut/freeglut/include/GL/freeglut_ext.h

@@ -45,6 +45,11 @@
 #define GLUT_CREATE_NEW_CONTEXT                  0
 #define GLUT_USE_CURRENT_CONTEXT                 1
 
+/*
+ * GLUT API Extension macro definitions -- display mode
+ */
+#define GLUT_OFFSCREEN                      0x0400
+
 /*
  * GLUT API Extension macro definitions -- the glutGet parameters
  */

freeglut/freeglut/progs/demos/Makefile.am

@@ -1,2 +1,2 @@
 EXTRA_DIST = demos.dsw
-SUBDIRS = CallbackMaker Fractals Fractals_random Lorenz One shapes
+SUBDIRS = CallbackMaker Fractals Fractals_random Lorenz offscreen One shapes

freeglut/freeglut/progs/demos/offscreen/Makefile.am

@@ -0,0 +1,5 @@
+EXTRA_DIST = shapes.c shapes.dsp
+noinst_PROGRAMS = offscreen
+offscreen_SOURCES = offscreen.c
+offscreen_LDFLAGS = -export-dynamic ../../../src/lib@LIBRARY@.la
+offscreen_CFLAGS = -I$(top_srcdir)/include $(X_CFLAGS)

freeglut/freeglut/progs/demos/offscreen/offscreen.c

@@ -0,0 +1,172 @@
+/*
+ * freeglut offscreen rendering demo.
+ *
+ * Usage:
+ *
+ *    offscreen [standard GLUT options] [filename]
+ *
+ *    The filename is used to say where to write a PNM image file
+ *    that is the sole way to verify that this program is doing what
+ *    it should (i.e., rendering offscreen).
+ *
+ *    You can view the PNM file in image viewers and editors such as
+ *    the GIMP.  (Everyone doing any kind of graphics has at least one
+ *    multi-format-reading image manipulation program, right?)
+ *
+ *    If no filename is specified, the chosen filename is "offscreen.pnm".
+ *
+ * Some suggested uses for GLUT_OFFSCREEN:
+ *
+ *  * Implementation of a graphics language that writes bitmapped image files.
+ *  * Capture GLUT bitmapped fonts to a texture at runtime to make scalable
+ *    bitmapped fonts.
+ *  * Using OpenGL to create special-effect textures at run-time.
+ *  * Making stencils.
+ *  * Getting the depth-buffer for a height-field.
+ *  * Using OpenGL to create a poster texture (e.g., for pasting onto a a
+ *    video screen in a virtual world).
+ *  * Using OpenGL to prescale an image to a power-of-2 dimension (including
+ *    OpenGL antialiasing).  There's no reason that you couldn't do this
+ *    yourself, but OpenGL can do it for you, so why not?
+ *  * Rendering to a bitmap larger than the display has been suggested
+ *    as well.  This is a cheap way to produce arbitrarily high resolution
+ *    images for printing.
+ *
+ * In every case, there are at least cases where you would want to do this
+ * without actually rendering to a visible window.
+ *
+ */
+#include <stdio.h>
+#include <GL/freeglut.h>
+
+#define OFFSCREEN_W 500
+#define OFFSCREEN_H 250
+
+
+int offscreen_id;
+int onscreen_id;
+const char *save_file_name = "offscreen.pnm";
+
+
+void cb_onscreen_display( void )
+{
+    glClear( GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT );
+    glColor3d( 1.0, 0.0, 0.0 );
+    glBegin( GL_LINE_LOOP );
+    glVertex2d( 0.0, 0.0 );
+    glVertex2d( 0.5, 0.0 );
+    glVertex2d( 0.5, 0.5 );
+    glVertex2d( 0.0, 0.5 );
+    glVertex2d( 0.0, 0.0 );
+    glEnd( );
+    glColor3d( 1.0, 1.0, 1.0 );
+    glRasterPos2d( -1.0, 0.8 );
+    glutBitmapString(
+        GLUT_BITMAP_TIMES_ROMAN_24, "Press `s' or `S' to Send to"
+    );
+    glRasterPos2d( -.8, 0.6 );
+    glutBitmapString(
+        GLUT_BITMAP_TIMES_ROMAN_24, "'offscreen.pnm'"
+    );
+    glRasterPos2d( -1.0, 0.3 );
+    glutBitmapString(
+        GLUT_BITMAP_TIMES_ROMAN_24, "Press `q', `Q', or Esc to quit."
+    );
+    
+    glutSwapBuffers( );
+}
+
+void write_raw_pnm( char *fname, char *pixels, int w, int h)
+{
+    FILE *f;
+    
+    printf( "Trying to create: %s\n", fname );
+    f = fopen( fname, "wb" );
+    if( !f )
+        printf( "Ouch!  Cannot create file.\n" );
+    else
+    {
+        int row;
+
+        printf( "Opened file.\n" );
+        fprintf( f, "P6\n" );
+        fprintf( f, "# CREATOR: offscreen freeglut demo\n" );
+        fprintf( f, "%d %d\n", w, h );
+        fprintf( f, "255\n" );
+
+        /*
+         * Write the rows in reverse order because OpenGL's 0th row
+         * is at the bottom.
+         */
+        for( row = h; row; --row )
+            fwrite( pixels + ((row - 1)*w*3), 1, 3 * w, f );
+        
+        fclose( f );
+    }
+}
+
+
+void cb_offscreen_display( void )
+{
+    static char pixels [OFFSCREEN_W * OFFSCREEN_H * 3];
+    int i;
+
+    cb_onscreen_display( );
+    glColor3d( 0.0, 1.0, 0.0 );
+    glBegin( GL_LINES );
+    for( i = 0; i < 100; ++i)
+    {
+        glVertex2d( +1 - (i/50.0), +1 );
+        glVertex2d( -1 + (i/50.0), -1 );
+    }
+    glEnd( );
+    glFinish( );
+
+    glPixelStorei( GL_PACK_ALIGNMENT, 1 );
+    glReadPixels(
+	0, 0, OFFSCREEN_W, OFFSCREEN_H,
+	GL_RGB, GL_UNSIGNED_BYTE, (GLvoid *)pixels
+    );
+    write_raw_pnm( save_file_name, pixels, OFFSCREEN_W, OFFSCREEN_H );
+}
+
+
+void cb_onscreen_keyboard( unsigned char key, int x, int y )
+{
+    switch( key )
+    {
+    case 's':
+    case 'S':
+        glutSetWindow( offscreen_id );
+        glutPostRedisplay( );
+        break;
+        
+    case '\x1b':
+    case 'q':
+    case 'Q':
+        exit( 0 );
+        break;
+        
+    default:
+        break;
+    }
+}
+
+int main( int argc, char **argv )
+{
+    glutInit( &argc, argv );
+    if( argv[ 1 ] )
+        save_file_name = argv[ 1 ];
+    
+    glutInitDisplayMode( GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE );
+    onscreen_id = glutCreateWindow( "Offscreen demo" );
+    glutDisplayFunc( cb_onscreen_display );
+    glutKeyboardFunc( cb_onscreen_keyboard );
+
+    glutInitDisplayMode( GLUT_RGB | GLUT_SINGLE | GLUT_OFFSCREEN );
+    glutInitWindowSize( OFFSCREEN_W, OFFSCREEN_H );
+    offscreen_id = glutCreateWindow( "" );
+    glutDisplayFunc( cb_offscreen_display );
+    
+    glutMainLoop( );
+}