+
+ ui->x1 = ui->drag_start_x;
+ ui->x2 = ui->drag_end_x;
+ if (ui->x2 < ui->x1) { t = ui->x1; ui->x1 = ui->x2; ui->x2 = t; }
+
+ ui->y1 = ui->drag_start_y;
+ ui->y2 = ui->drag_end_y;
+ if (ui->y2 < ui->y1) { t = ui->y1; ui->y1 = ui->y2; ui->y2 = t; }
+
+ ui->x1 = ui->x1 / 2; /* rounds down */
+ ui->x2 = (ui->x2+1) / 2; /* rounds up */
+ ui->y1 = ui->y1 / 2; /* rounds down */
+ ui->y2 = (ui->y2+1) / 2; /* rounds up */
+