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xwayland: Introduce xwayland_spawn_func_t

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Spawning subprocesses is finicky, and the correct way to do it depends
on the current process state which we have no control of. Signal masks,
handlers, limits, scheduling and open file descriptors are a few
examples of things that inadvertently get inherited and cause issues for
either the parent or the child.

We introduced a temporary workaround against common issues by clearing
signal masks and signal handlers known to cause issues for Xwayland, but
this was only a bandaid.

Introduce xwayland_spawn_func_t, which allows the compositor to specify
an implementation of a process spawner that will be used to launch
Xwayland whenever needed. This spawner can then do any cleanup and
accounting as the compositor sees fit.

The spawner takes 4 arguments: The path to Xwayland, the arguments we
have constructed for Xwayland, the environment variables that must be
set for Xwayland, and the file descriptors that must have CLOEXEC
cleared after fork but before exec to be correctly inherited by
Xwayland.

A default implementation is provided both for convenience and as a
sample for implementers to look at.
This commit is contained in:
Kenny Levinsen 2025-03-20 17:07:19 +01:00
parent ba7ac3efe5
commit 57f8cf9cd4
4 changed files with 68 additions and 76 deletions
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10
include/wlr/xwayland/server.h
View file

@ -14,16 +14,24 @@
#include <time.h>
#include <wayland-server-core.h>
/**
* Xwayland spawn function. pathname and args are compatible with the execv
* family of functions. envp is a NULL terminated list of enironment variables
* that must be added before exec, while uncloexec is a -1 terminated list of
* file descriptors that must have CLOEXEC unset after fork but before exec.
*/
typedef bool (*xwayland_spawn_func_t)(char *pathname, char *args[], char *envp[], int uncloexec[]);
struct wlr_xwayland_server_options {
bool lazy;
bool enable_wm;
bool no_touch_pointer_emulation;
bool force_xrandr_emulation;
int terminate_delay; // in seconds, 0 to terminate immediately
xwayland_spawn_func_t spawn_handler;
};
struct wlr_xwayland_server {
pid_t pid;
struct wl_client *client;
struct wl_event_source *pipe_source;
int wm_fd[2], wl_fd[2];