+ /*
+ * Now search outwards from (tx,ty), in order of Manhattan
+ * distance, until we find a reachable square.
+ */
+ distlimit = w+tx;
+ distlimit = max(distlimit, h+ty);
+ distlimit = max(distlimit, tx);
+ distlimit = max(distlimit, ty);
+ for (dist = 0; dist <= distlimit; dist++) {
+ for (dx = -dist; dx <= dist; dx++)
+ for (s = -1; s <= +1; s += 2) {
+ dy = s * (dist - abs(dx));
+ px = tx + dx;
+ py = ty + dy;
+ if (px >= 0 && px < w && py >= 0 && py < h &&
+ ui->reachable[py*w+px]) {
+ ui->drag_currpos = py*w+px;
+ return "";
+ }
+ }
+ }
+ return NULL; /* give up - this drag has no effect */