shm: Add wl_shm_buffer ref and unref functions

Shared memory buffers are currently tied to the lifetime of their
underlying wl_buffer resource. This becomes problematic when the client
destroys the resource after committing new state which references the
wl_buffer because a compositor might have to defer applying the commit.

This commit adds methods to keep the wl_shm_buffer alive longer than the
underlying resource. This implicitly also keeps the buffer pool alive
and because the wl_shm_buffer uses offsets into the pool, it even works
when the underlying storage gets remapped somewhere else, which can
happen when the client resizes the pool.

Signed-off-by: Sebastian Wick <sebastian.wick@redhat.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/src/wayland-server-core.h b/src/wayland-server-core.h
index 15c3b76..005a324 100644
--- a/src/wayland-server-core.h
+++ b/src/wayland-server-core.h
@@ -666,6 +666,12 @@ wl_shm_buffer_get_width(const struct wl_shm_buffer *buffer);
 int32_t
 wl_shm_buffer_get_height(const struct wl_shm_buffer *buffer);
 
+struct wl_shm_buffer *
+wl_shm_buffer_ref(struct wl_shm_buffer *buffer);
+
+void
+wl_shm_buffer_unref(struct wl_shm_buffer *buffer);
+
 struct wl_shm_pool *
 wl_shm_buffer_ref_pool(struct wl_shm_buffer *buffer);