plugin: export backend_register

It's unclear which functions a custom backend will need, let's be
conversative first.

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/backend/backend.c

@@ -21,9 +21,10 @@ static struct backend_info {
 	bool can_present;
 } *backend_registry = NULL;
 
-bool backend_register(uint64_t major, uint64_t minor, const char *name,
-                      struct backend_base *(*init)(session_t *ps, xcb_window_t target),
-                      bool can_present) {
+bool PICOM_PUBLIC_API backend_register(uint64_t major, uint64_t minor, const char *name,
+                                       struct backend_base *(*init)(session_t *ps,
+                                                                    xcb_window_t target),
+                                       bool can_present) {
 	if (major != PICOM_BACKEND_MAJOR) {
 		log_error("Backend %s has incompatible major version %" PRIu64
 		          ", expected %lu",

src/backend/backend.h

@@ -463,9 +463,10 @@ bool backend_execute(struct backend_base *backend, image_handle target, unsigned
 /// `name` is the name of the backend, `init` is the function to initialize the backend,
 /// `can_present` should be true if the backend can present the back buffer to the screen,
 /// false otherwise (e.g. if the backend does off screen rendering, etc.)
-bool backend_register(uint64_t major, uint64_t minor, const char *name,
-                      struct backend_base *(*init)(session_t *ps, xcb_window_t target),
-                      bool can_present);
+bool PICOM_PUBLIC_API backend_register(uint64_t major, uint64_t minor, const char *name,
+                                       struct backend_base *(*init)(session_t *ps,
+                                                                    xcb_window_t target),
+                                       bool can_present);
 struct backend_info *backend_find(const char *name);
 struct backend_base *
 backend_init(struct backend_info *info, session_t *ps, xcb_window_t target);

src/compiler.h

@@ -126,6 +126,8 @@
 #else
 # define thread_local _Pragma("GCC error \"No thread local storage support\"") __error__
 #endif
+
+#define PICOM_PUBLIC_API __attribute__((visibility("default")))
 // clang-format on
 
 typedef unsigned long ulong;

src/meson.build

@@ -86,7 +86,8 @@ subdir('backend')
 
 picom = executable('picom', srcs, c_args: cflags,
   dependencies: [ base_deps, deps, test_h_dep ],
-  install: true, include_directories: picom_inc)
+  install: true, include_directories: picom_inc,
+  export_dynamic: true, gnu_symbol_visibility: 'hidden')
 
 if get_option('unittest')
 	test('picom unittest', picom, args: [ '--unittest' ])