The problem happens because, on some OSs, `wm->winactive->eventstate`
does not update when the mouse moves. So the snap cursor doesn't update
because apparently the mouse didn't move.
The solution in this commit is to use the `eventstate` of the window in
the context (`CTX_wm_window(C)->eventstate`).
This matches other code snippets where `eventstate` is used.
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The behavior on each OS apparently happens like this:
**Windows:**
- `wm->winactive` is updated if the cursor is over the window for a little less than 1 second
- Events are sent to the window whose cursor is over.
**MacOS:**
- `wm->winactive` is the last one selected
- Events are sent to the active window and to the one whose cursor is over.
**Linux:**
- `wm->winactive` is the last one selected
- Events are sent to the window whose cursor is over.
Therefore, we cannot trust the eventstate of `wm->winactive`.
Germano Cavalcante