+static void plot_text(cairo_t *cr, double x, double y, const char *fmt, ...)
+{
+ cairo_text_extents_t extents;
+ char buffer[80];
+ va_list args;
+
+ va_start(args, fmt);
+ vsnprintf(buffer, sizeof(buffer), fmt, args);
+ va_end(args);
+
+ cairo_text_extents(cr, buffer, &extents);
+
+ x -= extents.width/2 + extents.x_bearing;
+ y += extents.height * 1.2;
+
+ cairo_move_to(cr, x, y);
+ cairo_text_path(cr, buffer);
+ cairo_set_source_rgb(cr, 0, 0, 0);
+ cairo_stroke(cr);
+
+ cairo_move_to(cr, x, y);
+ cairo_set_source_rgb(cr, 1, 0, 0);
+ cairo_show_text(cr, buffer);
+}
+
+/* Find the next maximum point in a 5-minute window */
+static int next_minmax(struct dive *dive, int index, int max)
+{
+ int timelimit, depthlimit, result;
+ struct sample *sample = dive->sample + index;
+
+ if (index >= dive->samples)
+ return 0;
+
+ timelimit = 24*60*60;
+ depthlimit = sample->depth.mm;
+ result = 0;
+
+ for (;;) {
+ int time, depth;
+
+ index++;
+ sample++;
+ if (index >= dive->samples)
+ break;
+ time = sample->time.seconds;
+ depth = sample->depth.mm;
+ if (time > timelimit)
+ break;
+ if (max) {
+ if (depth <= depthlimit)
+ continue;
+ } else {
+ if (depth >= depthlimit)
+ continue;
+ }
+
+ depthlimit = depth;
+ timelimit = time + 300;
+ result = index;
+ }
+ return result;
+}
+