+#ifdef USE_DRAGGING
+
+ if (button == MIDDLE_BUTTON
+#ifdef STYLUS_BASED
+ || button == RIGHT_BUTTON /* with a stylus, `right-click' locks */
+#endif
+ ) {
+ /*
+ * Middle button never drags: it only toggles the lock.
+ */
+ action = TOGGLE_LOCK;
+ } else if (button == LEFT_BUTTON
+#ifndef STYLUS_BASED
+ || button == RIGHT_BUTTON /* (see above) */
+#endif
+ ) {
+ /*
+ * Otherwise, we note down the start point for a drag.
+ */
+ ui->dragtilex = tx;
+ ui->dragtiley = ty;
+ ui->dragstartx = x % TILE_SIZE;
+ ui->dragstarty = y % TILE_SIZE;
+ ui->dragged = FALSE;
+ return nullret; /* no actual action */
+ } else if (button == LEFT_DRAG
+#ifndef STYLUS_BASED
+ || button == RIGHT_DRAG
+#endif
+ ) {
+ /*
+ * Find the new drag point and see if it necessitates a
+ * rotation.
+ */
+ int x0,y0, xA,yA, xC,yC, xF,yF;
+ int mx, my;
+ int d0, dA, dC, dF, dmin;
+
+ tx = ui->dragtilex;
+ ty = ui->dragtiley;
+
+ mx = x - (ui->dragtilex * TILE_SIZE);
+ my = y - (ui->dragtiley * TILE_SIZE);
+
+ x0 = ui->dragstartx;
+ y0 = ui->dragstarty;
+ xA = ui->dragstarty;
+ yA = TILE_SIZE-1 - ui->dragstartx;
+ xF = TILE_SIZE-1 - ui->dragstartx;
+ yF = TILE_SIZE-1 - ui->dragstarty;
+ xC = TILE_SIZE-1 - ui->dragstarty;
+ yC = ui->dragstartx;
+
+ d0 = (mx-x0)*(mx-x0) + (my-y0)*(my-y0);
+ dA = (mx-xA)*(mx-xA) + (my-yA)*(my-yA);
+ dF = (mx-xF)*(mx-xF) + (my-yF)*(my-yF);
+ dC = (mx-xC)*(mx-xC) + (my-yC)*(my-yC);
+
+ dmin = min(min(d0,dA),min(dF,dC));
+
+ if (d0 == dmin) {
+ return nullret;
+ } else if (dF == dmin) {
+ action = ROTATE_180;
+ ui->dragstartx = xF;
+ ui->dragstarty = yF;
+ ui->dragged = TRUE;
+ } else if (dA == dmin) {
+ action = ROTATE_LEFT;
+ ui->dragstartx = xA;
+ ui->dragstarty = yA;
+ ui->dragged = TRUE;
+ } else /* dC == dmin */ {
+ action = ROTATE_RIGHT;
+ ui->dragstartx = xC;
+ ui->dragstarty = yC;
+ ui->dragged = TRUE;
+ }
+ } else if (button == LEFT_RELEASE
+#ifndef STYLUS_BASED
+ || button == RIGHT_RELEASE
+#endif
+ ) {
+ if (!ui->dragged) {
+ /*
+ * There was a click but no perceptible drag:
+ * revert to single-click behaviour.
+ */
+ tx = ui->dragtilex;
+ ty = ui->dragtiley;
+
+ if (button == LEFT_RELEASE)
+ action = ROTATE_LEFT;
+ else
+ action = ROTATE_RIGHT;
+ } else
+ return nullret; /* no action */
+ }
+
+#else /* USE_DRAGGING */
+
+ action = (button == LEFT_BUTTON ? ROTATE_LEFT :
+ button == RIGHT_BUTTON ? ROTATE_RIGHT : TOGGLE_LOCK);
+
+#endif /* USE_DRAGGING */
+
+ } else if (IS_CURSOR_MOVE(button)) {