http://packetstormsecurity.org/UNIX/admin/xscreensaver-4.04.2.tar.gz

[xscreensaver] / hacks / glx / gltrackball.c

diff --git a/hacks/glx/gltrackball.c b/hacks/glx/gltrackball.c
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+/* gltrackball, Copyright (c) 2002 Jamie Zawinski <jwz@jwz.org>
+ * GL-flavored wrapper for trackball.c
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that
+ * copyright notice and this permission notice appear in supporting
+ * documentation.  No representations are made about the suitability of this
+ * software for any purpose.  It is provided "as is" without express or 
+ * implied warranty.
+ */
+
+#include "config.h"
+#include <stdlib.h>
+#include <math.h>
+#include <GL/gl.h>
+#include "trackball.h"
+#include "gltrackball.h"
+
+struct trackball_state {
+  int x, y;
+  GLfloat q[4];
+};
+
+/* Returns a trackball_state object, which encapsulates the stuff necessary
+   to make dragging the mouse on the window of a GL program do the right thing.
+ */
+trackball_state *
+gltrackball_init (void)
+{
+  trackball_state *ts = (trackball_state *) calloc (1, sizeof (*ts));
+  if (!ts) return 0;
+  trackball (ts->q, 0, 0, 0, 0);
+  return ts;
+}
+
+/* Begin tracking the mouse: Call this when the mouse button goes down.
+   x and y are the mouse position relative to the window.
+   w and h are the size of the window.
+ */
+void
+gltrackball_start (trackball_state *ts, int x, int y, int w, int h)
+{
+  ts->x = x;
+  ts->y = y;
+}
+
+/* Track the mouse: Call this each time the mouse moves with the button down.
+   x and y are the new mouse position relative to the window.
+   w and h are the size of the window.
+ */
+void
+gltrackball_track (trackball_state *ts, int x, int y, int w, int h)
+{
+  float q2[4];
+  trackball (q2,
+             (2.0 * ts->x - w) / w,
+             (h - 2.0 * ts->y) / h,
+             (2.0 * x - w) / w,
+             (h - 2.0 * y) / h);
+  ts->x = x;
+  ts->y = y;
+  add_quats (q2, ts->q, ts->q);
+}
+
+/* Execute the rotations current encapsulated in the trackball_state:
+   this does something analagous to glRotatef().
+ */
+void
+gltrackball_rotate (trackball_state *ts)
+{
+  GLfloat m[4][4];
+  build_rotmatrix (m, ts->q);
+  glMultMatrixf (&m[0][0]);
+}