diff options
Diffstat (limited to 'documentation')
| -rw-r--r-- | documentation/src/wayland.dox | 27 |
1 files changed, 24 insertions, 3 deletions
diff --git a/documentation/src/wayland.dox b/documentation/src/wayland.dox index 6f78dfb7e..5eba86156 100644 --- a/documentation/src/wayland.dox +++ b/documentation/src/wayland.dox @@ -590,9 +590,30 @@ is increased to <tt>2 * size</tt>. This mechanism allows to access new mmap'ed m \c chunk_offset reaches the end of the previous mmap'ed section, and to enlarge the size of the mmap'ed memory when necessary. -Wayland object <tt>struct wl_shm_pool</tt> guarantees that the corresponding mmap'ed memory will be -freed when all \c wl_buffer objects which encapsulate sections of this mmap'ed memory have been -destroyed. +To free the memory used by a \c wl_shm_pool object, it's not enough to destroy +all \c wl_buffer objects built from this \c wl_shm_pool object and to call +\c wl_shm_pool_destroy(). It's also necessary to call \c munmap() on the mmap'ed memory +shared between the client and the compositor and encapsulated by the \c wl_shm_pool. +This explains this type definition inside class \c Fl_Wayland_Graphics_Driver: +\code + struct wld_shm_pool_data { // attached to wl_shm_pool objects + char *pool_memory; // start of mmap'ed memory encapsulated by the wl_shm_pool + int pool_size; // size of encapsulated memory + int use_count; // nber of active wl_buffer objects in this wl_shm_pool + bool destroyed; // true after the wl_shm_pool was destroyed + }; +\endcode +A record of this type is created for each \c wl_shm_pool object and attached to it with +a call to \c wl_shm_pool_set_user_data(). This record contains the starting address +and the size of the mmap'ed memory section necessary for a future \c munmap() call. +Member \c destroyed is turned to \c true after the call to \c wl_shm_pool_destroy(). +Member \c use_count starts at 0, is incremented each time a \c wl_buffer is created from +this \c wl_shm_pool and decremented each time a \c wl_buffer is destroyed. +The same record is also associated to each \c wl_buffer object created from +this \c wl_shm_pool by \c wl_buffer_set_user_data(). +Overall, this allows FLTK to detect when all \c wl_buffer objects +from a \c wl_shm_pool have been destroyed and to call \c munmap() to complete the release +of that pool's memory resources. Wayland uses also \c wl_buffer objects to support cursors, and FLTK uses the "buffer factory" described here also when creating custom cursors (see |