Fix angular speed of the arrow to follow the points

[xoboot] / xoboot.c

diff --git a/xoboot.c b/xoboot.c
index 4daa763c14f94c0992bf9026719bcc0fab530372..1feb5dccbcb3059b4d445821168f4ef96e6079db 100644 (file)
--- a/xoboot.c
+++ b/xoboot.c
@@ -1,4 +1,40 @@
-/* gcc -Wall -g $(pkg-config --cflags --libs gtk+-2.0 cairo) olpc-boot.c -o olpc-boot */
+/* xoboot - A simple demonstration of what might be an XO boot animation
+ *
+ * gcc -Wall -g $(pkg-config --cflags --libs gtk+-2.0 cairo) xoboot.c -o xboot
+ *
+ * Copyright © 2007 Carl Worth
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA."
+ */
+
+/* This is simply a proof-of-concept for using cairo to implement a
+ * design idea for an OLPC boot-time animation. The animation here is
+ * implemented to mimic an animation originally provided as a
+ * Quicktime movie by Rebecca Allen <rallen@arts.ucla.edu>.
+ *
+ * So far, this animation has been developed exclusively on an x86
+ * laptop with GTK+ targeting the X Window System. No guarantees are
+ * provided as to how this might perform on an OLPC XO machine. What's
+ * likely desired is to write the application to use cairo image
+ * surfaces, and augment cairo to support targeting the XO's 565 image
+ * format directly.
+ *
+ * And obviously, to serve as a real boot-time animation, code will
+ * have to be written to advance the animation according to various
+ * system events, instead of using the hard-coded timeline below.
+ */
 
 #include <gtk/gtk.h>
 #include <cairo.h>
@@ -108,6 +144,8 @@ draw_head (cairo_t *cr, double extra)
 static void
 draw_body (cairo_t *cr, double extra, double spin_transition)
 {
+    double angle, x, y;
+
     cairo_save (cr);
 
     cairo_move_to (cr,
@@ -117,7 +155,13 @@ draw_body (cairo_t *cr, double extra, double spin_transition)
     cairo_rel_line_to (cr, XO_BODY_DELTA, XO_BODY_DELTA);
 
     cairo_translate (cr, XO_HEAD_CENTER_X, XO_HEAD_CENTER_Y);
-    cairo_rotate (cr, 2 * M_PI * spin_transition);
+
+    angle = 2 * M_PI * spin_transition;
+    y = cos (angle) * XO_DOTS_POSITION_RADIUS;
+    x = sin (angle) * XO_DOTS_POSITION_RADIUS;
+    angle = atan2 (x, y + XO_BODY_CENTER_Y - XO_HEAD_CENTER_Y);
+
+    cairo_rotate (cr, angle);
     cairo_translate (cr, -XO_HEAD_CENTER_X, -XO_HEAD_CENTER_Y);
        
     cairo_move_to (cr,
@@ -145,7 +189,7 @@ draw_dots (cairo_t *cr, double num_dots)
     cairo_translate (cr, XO_DOTS_CENTER_X, XO_DOTS_CENTER_Y);
     cairo_rotate (cr, - 1.5 * M_PI);
 
-    for (i = 0; i < num_dots; i++) {
+    for (i = 0; i <= num_dots; i++) {
        if (i != 0) {
            cairo_arc (cr,
                       XO_DOTS_POSITION_RADIUS, 0,
@@ -231,7 +275,7 @@ xoboot_expose_event (GtkWidget      *widget,
        goto DONE;
 
     if (anim_stage < ANIM_FADE) {
-       draw_dots (cr, (XO_DOTS_NUM_DOTS + 1) * spin_transition);
+       draw_dots (cr, (XO_DOTS_NUM_DOTS) * spin_transition);
     } else {
        draw_ring (cr);
     }