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Wayland.dox: add info about the xdg decoration protocol

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Also, use KWin to name the KDE desktop's Wayland compositor.
This commit is contained in:
ManoloFLTK 2023-07-28 15:27:38 +02:00
parent 1127ebfcd3
commit d9fa2c6082
7 changed files with 30 additions and 22 deletions
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2
README.Wayland.txt
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@ -25,7 +25,7 @@ the Wayland platform. It requires a Wayland-equipped OS, namely Linux or FreeBSD
Pre-existing platform-independent source code for FLTK 1.3.x should build and
run unchanged with FLTK 1.4 and the Wayland platform.
The code has been tested on Debian, Ubuntu, RaspberryPiOS and Fedora with
3 distinct Wayland compositors: mutter (Gnome's compositor), weston, and KDE.
3 distinct Wayland compositors: Mutter (Gnome's compositor), Weston, and KWin.
The code has also been tested under FreeBSD and the Sway Wayland compositor.
CJK text-input methods, as well as dead and compose keys are supported.

7
documentation/src/osissues.dox
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@ -1069,10 +1069,11 @@ or in <tt>$HOME/.local/share/applications/</tt> so it's available to a single us
\subsection osissues_wayland_decoration Window titlebars
Wayland supports both client-side window decoration (CSD), where client applications
are responsible for drawing window titlebars, and server-side window
decoration (SSD), where the Wayland compositor itself draws window titlebars. Among 3
decoration (SSD), where the Wayland compositor itself draws window titlebars. Among 4
tested Wayland compositors, Mutter (gnome's compositor) and Weston use CSD mode
whereas the KDE compositor uses SSD mode. When running in CSD mode, FLTK uses a library called
<a href=https://gitlab.gnome.org/jadahl/libdecor>libdecor</a> to draw titlebars.
whereas the KWin and Sway compositors use SSD mode.
When running in CSD mode, FLTK uses a library
called <a href=https://gitlab.freedesktop.org/libdecor/libdecor>libdecor</a> to draw titlebars.
The libdecor library has been conceived to use various plug-in's to draw
titlebars in various fashions intended to match any desktop's preferred titlebar style.
FLTK supports drawing titlebars with any libdecor plug-in via an environment variable

15
documentation/src/wayland.dox
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@ -280,7 +280,7 @@ accessible from this object.
For example, when \c interface equals "wl_compositor", the value returned by
\c wl_registry_bind() is stored as member \c wl_compositor of the
\c Fl_Wayland_Screen_Driver object.
\c registry_handle_global() also identifies whether the Mutter, Weston, or KDE compositor is connected
\c registry_handle_global() also identifies whether the Mutter, Weston, or KWin compositor is connected
and stores this information in static member variable \c Fl_Wayland_Screen_Driver::compositor.
Wayland calls \c registry_handle_global() with its parameter \c interface equals to
@ -726,7 +726,7 @@ is unmapped by function \c Fl_Wayland_Window_Driver::hide(), the surface's list
is emptied.
<h3>Fractional scaling</h3>
The KDE compositor, and gnome too if specially set, allow to use <em>fractional scaling</em>
The KWin compositor, and gnome too if specially set, allow to use <em>fractional scaling</em>
that can take intermediate values between 100% and 200%. Wayland implements this rendering all
<tt>wl_surface</tt>'s as if the scaling was at 200%, and downsizing them
to the desired fractional scale value at the compositing stage.
@ -956,9 +956,16 @@ Desktop. As of early 2023, two titlebar-drawing \c libdecor plugins are availabl
Because \c libdecor is not yet in Linux packages, or only in a preliminary state, FLTK bundles the
most recent source code of \c libdecor and its plugins. This code is included in libfltk.
FLTK uses \c libdecor-gtk when software package \c libgtk-3-dev is present in the
system, and \c libdecor-cairo otherwise.
build system, and \c libdecor-cairo otherwise.
\c Libdecor uses the Wayland protocol <tt>"xdg decoration unstable v1"</tt> hinted at before.
\c Libdecor uses the Wayland protocol
<a href=https://wayland.app/protocols/xdg-decoration-unstable-v1>
xdg decoration unstable v1</a> to request being decorated by a supporting compositor.
If the running compositor supports SSD, \c libdecor doesn't draw window titlebars because
the compositor does it. That is what happens with the \c KWin and \c Sway compositors.
However, if environment variable \c LIBDECOR_FORCE_CSD is defined to value \c 1 when an
FLTK app runs, \c libdecor instructs an SSD-able compositor to refrain from decorating its
windows and decorates windows itself.
CMake \c OPTION_USE_SYSTEM_LIBDECOR has been defined to allow FLTK in the future, when \c libdecor and
\c libdecor-gtk will be part of Linux packages, to use these packages rather than the \c libdecor

2
libdecor/build/fl_libdecor-plugins.c
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@ -300,7 +300,7 @@ static unsigned char *cairo_titlebar_buffer(struct libdecor_frame *frame,
this address.
A plugin is loaded also if SSD.
KDE has its own size limit, similar to that of GDK plugin
KWin has its own size limit, similar to that of GDK plugin
*/
static const char *get_libdecor_plugin_description(struct libdecor_frame *frame) {
static const struct libdecor_plugin_description *plugin_description = NULL;

2
src/drivers/Wayland/Fl_Wayland_Screen_Driver.H
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@ -39,7 +39,7 @@ private:
static bool insertion_point_location_is_valid;
public:
// type definitions
typedef enum {unspecified, MUTTER, WESTON, KDE, OWL} compositor_name;
typedef enum {unspecified, MUTTER, WESTON, KWIN, OWL} compositor_name;
struct seat {
struct wl_seat *wl_seat;
struct wl_pointer *wl_pointer;

12
src/drivers/Wayland/Fl_Wayland_Screen_Driver.cxx
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@ -51,16 +51,16 @@ struct pointer_output {
struct wl_list link;
};
/* Implementation note about support of 3 Wayland compositors: Mutter, Weston, KDE.
/* Implementation note about support of 3 Wayland compositors: Mutter, Weston, KWin.
- About CSD and SSD :
* Mutter and Weston use CSD (client-side decoration) which means that libdecor.so draws all window
titlebars and responds to resize, minimization and maximization events.
* KDE uses SSD (server-side decoration) which means the OS draws titlebars according to its own rules
* KWin uses SSD (server-side decoration) which means the OS draws titlebars according to its own rules
and triggers resize, minimization and maximization events.
- Function registry_handle_global() runs within fl_open_display() and sets public static variable
Fl_Wayland_Screen_Driver::compositor to either Fl_Wayland_Screen_Driver::MUTTER, ::WESTON, or ::KDE.
Fl_Wayland_Screen_Driver::compositor to either Fl_Wayland_Screen_Driver::MUTTER, ::WESTON, or ::KWIN.
- Specific operations for WESTON:
* When a libdecor-framed window is minimized under Weston, the frame remains on display. To avoid
@ -85,7 +85,7 @@ struct pointer_output {
- Support of Fl_Window::border(int) :
FLTK uses libdecor_frame_set_visibility() to show or hide a toplevel window's frame. This doesn't work
with KDE which uses Server-Side Decoration. In that case, FLTK hides and re-shows the window to toggle
with KWin which uses Server-Side Decoration. In that case, FLTK hides and re-shows the window to toggle
between presence and absence of a window's frame.
*/
@ -1107,8 +1107,8 @@ static void registry_handle_global(void *user_data, struct wl_registry *wl_regis
Fl_Wayland_Screen_Driver::compositor = Fl_Wayland_Screen_Driver::WESTON;
//fprintf(stderr, "Running the Weston compositor\n");
} else if (strcmp(interface, "org_kde_plasma_shell") == 0) {
Fl_Wayland_Screen_Driver::compositor = Fl_Wayland_Screen_Driver::KDE;
//fprintf(stderr, "Running the KDE compositor\n");
Fl_Wayland_Screen_Driver::compositor = Fl_Wayland_Screen_Driver::KWIN;
//fprintf(stderr, "Running the KWin compositor\n");
} else if (strncmp(interface, "zowl_mach_ipc", 13) == 0) {
Fl_Wayland_Screen_Driver::compositor = Fl_Wayland_Screen_Driver::OWL;
//fprintf(stderr, "Running the Owl compositor\n");

12
src/drivers/Wayland/Fl_Wayland_Window_Driver.cxx
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@ -354,7 +354,7 @@ void Fl_Wayland_Window_Driver::make_current() {
}
((Fl_Wayland_Graphics_Driver*)fl_graphics_driver)->set_buffer(window->buffer, f * wld_s);
int *poffset = Fl_Window_Driver::menu_offset_y(pWindow);
if (poffset) { // for tall menu windows under KDE to offset drawing inside window
if (poffset) { // for tall menu windows under KWIN to offset drawing inside window
cairo_translate(window->buffer->cairo_, 0, *poffset);
}
cairo_rectangle_int_t *extents = subRect();
@ -799,7 +799,7 @@ static void handle_configure(struct libdecor_frame *frame,
}
window->state = window_state;
// Weston, KDE, and some versions of Mutter, on purpose, don't set the
// Weston, KWin, and some versions of Mutter, on purpose, don't set the
// window width x height when xdg_toplevel_configure runs twice
// during resizable window creation (see https://gitlab.freedesktop.org/wayland/wayland-protocols/-/issues/6).
// Consequently, libdecor_configuration_get_content_size() may return false twice.
@ -1037,7 +1037,7 @@ static void popup_configure(void *data, struct xdg_popup *xdg_popup, int32_t x,
int HH;
Fl_Window_Driver::menu_parent(&HH);
if (window->fl_win->h() > HH && y != win_pos->y) { // A menu taller than the display
// Under KDE, height is set to the display height or less: we ignore that.
// Under KWin, height is set to the display height or less: we ignore that.
window->state = (y - win_pos->y);
// make selected item visible, if there's one
Fl_Window_Driver::scroll_to_selected_item(window->fl_win);
@ -1551,7 +1551,7 @@ void Fl_Wayland_Window_Driver::use_border() {
if (!shown() || pWindow->parent()) return;
pWindow->wait_for_expose(); // useful for border(0) just after show()
struct libdecor_frame *frame = fl_wl_xid(pWindow)->frame;
if (frame && Fl_Wayland_Screen_Driver::compositor != Fl_Wayland_Screen_Driver::KDE) {
if (frame && Fl_Wayland_Screen_Driver::compositor != Fl_Wayland_Screen_Driver::KWIN) {
if (fl_wl_xid(pWindow)->kind == DECORATED) {
libdecor_frame_set_visibility(frame, pWindow->border());
} else {
@ -1832,8 +1832,8 @@ void Fl_Wayland_Window_Driver::subRect(cairo_rectangle_int_t *r) {
void Fl_Wayland_Window_Driver::reposition_menu_window(int x, int y) {
if (y == pWindow->y()) return;
if (Fl_Wayland_Screen_Driver::compositor == Fl_Wayland_Screen_Driver::KDE) {
// The KDE compositor refuses to position a popup such that it extends above
if (Fl_Wayland_Screen_Driver::compositor == Fl_Wayland_Screen_Driver::KWIN) {
// The KWin compositor refuses to position a popup such that it extends above
// the top of the screen. Therefore, instead of sliding the popup window
// on the display, we slide the drawing inside the fixed popup via
// member variable offset_y of the menuwindow class, and we redraw the popup