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921b0a8633
We currently track the focus of a seat in two ways: we use a list called focus_stack to track the order in which nodes have been focused, with the first node representing what's currently focused, and we use a variable called has_focus to indicate whether anything has focus--i.e. whether we should actually treat that first node as focused at any given time. In a number of places, we treat has_focus as implying that a focused node exists. If it's true, we attempt to dereference the return value of seat_get_focus(), our helper function for getting the first node in focus_list, with no further checks. But this isn't quite correct with the current implementation of seat_get_focus(): not only does it return NULL when has_focus is false, it also returns NULL when focus_stack contains no items. In most cases, focus_stack never becomes empty and so this doesn't matter at all. Since focus_stack stores a history of focused nodes, we rarely remove nodes from it. The exception to this is when a node itself goes away. In that case, we call seat_node_destroy() to remove it from focus_stack and free it. But we don't unset has_focus if we've removed the final node! This lets us get into a state where has_focus is true but seat_get_focus() returns NULL, leading to a segfault when we try to dereference it. Fix the issue both by updating has_focus in seat_node_destroy() and by adding an assertion in seat_get_focus() that ensures focus_stack and has_focus are in sync, which will make it easier to track down similar issues in the future. Fixes #6395. [1] There's some discussion in #1585 from when this was implemented about whether has_focus is actually necessary; it's possible we could remove it entirely, but for the moment this is the architecture we have. |
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| .. | ||
| cursor.c | ||
| input-manager.c | ||
| keyboard.c | ||
| libinput.c | ||
| seat.c | ||
| seatop_default.c | ||
| seatop_down.c | ||
| seatop_move_floating.c | ||
| seatop_move_tiling.c | ||
| seatop_resize_floating.c | ||
| seatop_resize_tiling.c | ||
| switch.c | ||
| tablet.c | ||
| text_input.c | ||