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Doxgen documentation: improve section "Buffer factory"

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ManoloFLTK 2025-10-06 17:02:13 +02:00
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documentation/src/wayland.dox
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@ -317,7 +317,7 @@ Here is the list of the \c interface value for all protocols and system features
<tr><th>Interface </th><th>How FLTK uses this interface</th> </tr>
<tr><td>wl_compositor </td><td> create wl_surface objects </td> </tr>
<tr><td>wl_subcompositor </td><td>create subwindows </td> </tr>
<tr><td>wl_shm </td><td> create buffers and buffer factories</td> </tr>
<tr><td>wl_shm </td><td> create shared memory pools and buffers</td> </tr>
<tr><td>wl_seat </td><td> create the unique "seat"</td> </tr>
<tr><td>wl_data_device </td><td> support of copy/paste/drag-n-drop</td> </tr>
<tr><td>wl_output </td><td>received once for each display </td> </tr>
@ -735,21 +735,26 @@ computing and drawing in memory but not on display more lines of the desired Man
graph.
\section wayland-buffer-factory Buffer factories
\section wayland-buffer-factory Buffer factory
Wayland names <em>buffer factory</em> a software procedure that constructs objects of type
<tt>struct wl_buffer</tt> for use by a client application.
FLTK creates a \c wl_buffer object each time an Fl_Window is mapped on a display or resized.
That's done by member function \c Fl_Wayland_Graphics_Driver::create_shm_buffer()
which follows this 3-step procedure to create a "buffer factory" for FLTK and to construct
Wayland buffers from it:
<tt>struct wl_buffer</tt>, that is, Wayland buffers, for use by a client application.
FLTK creates a \c wl_buffer object each time a non-GL Fl_Window is mapped on a display or resized.
FLTK triggers the creation of a Wayland buffer as follows:
<pre>Fl::flush() calls, if the window is damaged:
\e Fl_Wayland_Window_Driver::flush() calls, if the window's \c frame_cb is NULL:
\e Fl_Wayland_Graphics_Driver::buffer_commit() calls, if the window's \c buffer->wl_buffer is NULL:
\e Fl_Wayland_Graphics_Driver::create_shm_buffer() creates a Wayland buffer.</pre>
Member function \c Fl_Wayland_Graphics_Driver::create_shm_buffer()
follows this 3-step procedure to create one or more <em>shared memory pools</em> and to
construct Wayland buffers from them:
- Libdecor function <tt>libdecor_os_create_anonymous_file(off_t size)</tt> creates an adequate file
and mmap's it. This file lives in RAM because it is created by function \c memfd_create().
FLTK sets this file size to 10 MB unless the size of the buffer to be created
is larger; in that case the anonymous file is sized to twice the buffer size.
- Wayland function \c wl_shm_create_pool() shares this mmap'ed memory with the
Wayland compositor and returns an object of type <tt>struct wl_shm_pool</tt> which
encapsulates this memory. A record of type
Wayland compositor and returns an object of type <tt>struct wl_shm_pool</tt>, a shared memory pool,
which encapsulates this memory. A record of type
<tt>struct Fl_Wayland_Graphics_Driver::wld_shm_pool_data</tt> is created and associated to
the newly created \c wl_shm_pool by \c wl_shm_pool_set_user_data(). This record stores
the starting address (\c pool_memory) and size (\c pool_size) of the pool's encapsulated