253 lines
8.9 KiB
Plaintext
253 lines
8.9 KiB
Plaintext
README.Wayland.txt - Wayland platform support for FLTK
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------------------------------------------------------
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CONTENTS
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========
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1 INTRODUCTION
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2 WAYLAND SUPPORT FOR FLTK
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2.1 Configuration
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2.2 Known Limitations
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3 PREPARING PLATFORM-SPECIFIC CODE FOR THE WAYLAND PLATFORM
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3.1 Handling X11-specific source code
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3.2 Handling X11- and Wayland-specific source code in the same app
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3.3 Forcing an app to always use the X11 mechanism
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4 PLATFORM SPECIFIC NOTES
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4.1 Debian and Derivatives (like Ubuntu)
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4.2 Fedora
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4.3 FreeBSD
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1 INTRODUCTION
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==============
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Version 1.4 of the FLTK library introduces support of the public FLTK API on
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the Wayland platform. It requires a Wayland-equipped OS, namely Linux or FreeBSD.
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Pre-existing platform-independent source code for FLTK 1.3.x should build and
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run unchanged with FLTK 1.4 and the Wayland platform.
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The code has been tested on Debian, Ubuntu and Fedora with 3 distinct Wayland
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compositors: mutter (Gnome's compositor), weston, and KDE.
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The code has also been tested under FreeBSD and the sway wayland compositor.
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CJK text-input methods, as well as dead and compose keys are supported.
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2 WAYLAND SUPPORT FOR FLTK
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==========================
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On Linux and FreeBSD systems, and provided a Wayland compositor is available at run-time,
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it is possible to have your FLTK application do all its windowing through the
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Wayland protocol, all its graphics with Cairo or EGL, and all text-drawing with
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Pango. If no Wayland compositor is available at run-time, FLTK falls back to
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using X11 or OpenGL for its windowing. Cairo and Pango remain used for graphics
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and text, respectively.
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Environment variable FLTK_BACKEND can be used to control whether Wayland or
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X11 is used at run time as follows:
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- if FLTK_BACKEND is not defined, Wayland is used when possible, otherwise
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X11 is used;
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- if FLTK_BACKEND equals "wayland", the library stops with error if no
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Wayland compositor is available;
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- if FLTK_BACKEND equals "x11", the library uses X11 even if a Wayland
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compositor is available;
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- if FLTK_BACKEND has another value, the library stops with error.
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On pure Wayland systems without the X11 headers and libraries, FLTK can be built
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with its Wayland backend only (see below).
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2.1 Configuration
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------------------
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2.1.1 Configure-based build can be performed as follows:
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Once after "git clone", create the configure file :
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autoconf -f
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Prepare build with :
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./configure --enable-wayland
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Add --disable-x11 to build FLTK for Wayland-only (no x11 backend).
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Build with :
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make
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2.1.2 CMake-based build can be performed as follows:
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cmake -S <path-to-source> -B <path-to-build> -DCMAKE_BUILD_TYPE=Release -DOPTION_USE_WAYLAND=1
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cd <path-to-build>; make
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The FLTK Wayland platform uses a library called libdecor which handles window decorations
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(i.e., titlebars, shade). Libdecor is bundled in the FLTK source code and FLTK uses by default
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this form of libdecor. Optionally, OPTION_USE_SYSTEM_LIBDECOR can be turned on to have FLTK
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use the system's version of libdecor which is available on recent Linux distributions (e.g.,
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Debian Bookworm or more recent in packages libdecor-0-0 and libdecor-0-plugin-1-cairo).
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Optionally, OPTION_WAYLAND_ONLY can be turned on to build FLTK for Wayland-only (no x11 backend).
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2.2 Known Limitations
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----------------------
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* A deliberate design trait of Wayland makes application windows ignorant of their exact
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placement on screen. It's possible, though, to position a popup window relatively to
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another window. This allows FLTK to properly position menu and tooltip windows. But
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Fl_Window::position() has no effect on other top-level windows.
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* With Wayland, there is no way to know if a window is currently minimized, nor is there any
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way to programmatically unset minimization of a window. Consequently, Fl_Window::show() of
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a minimized window has no effect.
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* Although the FLTK API to read from and write to the system clipboard is fully functional,
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it's currently not possible for an app to be notified of changes to the content of
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the system clipboard, that is, Fl::add_clipboard_notify() has no effect.
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* With GTK-style window titlebars, narrow windows are silently forced to be wide enough
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for the titlebar to display window buttons and a few letters of the title.
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* The library should support multi-display configurations in principle, but has not been
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tested in that situation.
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* Text input methods have been tested without any understanding of the writing systems,
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so feedback on this subject would be helpful.
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3 PREPARING PLATFORM-SPECIFIC CODE FOR THE WAYLAND PLATFORM
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===========================================================
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While platform-independent source code prepared for FLTK 1.3 is expected
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to be compatible with no change with FLTK 1.4 and the Wayland platform,
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platform-specific code may require some attention.
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3.1 Handling X11-specific source code
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-------------------------------------
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If an FLTK 1.4 application contains X11-specific code, execution of this code
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in the context of an active Wayland session can produce malfunctions or program crashes.
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To ensure that X11-specific code gets called only when an X11 connection is active,
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check that function fl_x11_display() returns non-NULL before using any X11-specific
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function or variable.
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3.2 Handling X11- and Wayland-specific source code in the same app
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------------------------------------------------------------------
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The recommended way to prepare and use platform-specific code that would contain
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both X11-specific and Wayland-specific parts is as follows :
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a) Organize platform-specific code as follows :
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#include <FL/platform.H>
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#ifdef __APPLE__
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*** macOS-specific code ***
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#elif defined(_WIN32)
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*** Windows-specific code ***
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#else
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*** X11-specific code ***
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*** Wayland-specific code ***
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#endif
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b) Make sure to use distinct names for global variables and functions
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in the X11- and the Wayland-specific sections.
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c) Check that function fl_x11_display() returns non-NULL before using any X11-specific
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function or variable, and that fl_wl_display() returns non-NULL before using any
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Wayland-specific function or variable. Make sure that fl_open_display() was called
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directly or indirectly before using any such symbol.
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3.3 Forcing an FLTK app to always use the X11 backend
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-----------------------------------------------------
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Alternatively, it's possible to force an FLTK app to use X11 in all
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situations by calling function fl_disable_wayland() early in main(), that is,
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before fl_open_display() runs. FLTK source code and also platform-specific
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code conceived for FLTK 1.3 should run under 1.4 with that single change only.
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4 PLATFORM SPECIFIC NOTES
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=========================
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The following are notes about building FLTK for the Wayland platform
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on the various supported Linux distributions/OS.
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4.1 Debian and Derivatives (like Ubuntu)
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----------------------------------------
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Under Debian, the Wayland platform requires version 11 (a.k.a. Bullseye) or more recent.
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Under Ubuntu, the Wayland platform is known to work with version 20.04 (focal fossa) or
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more recent.
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These packages are necessary to build the FLTK library, in addition to those present
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in a basic Debian/Ubuntu distribution :
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- g++
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- gdb
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- make
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- git
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- autoconf
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- libglu1-mesa-dev
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- libpango1.0-dev
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- libwayland-dev
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- wayland-protocols
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- libdbus-1-dev
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- libxkbcommon-dev
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- libgtk-3-dev <== with this, windows get a GTK-style titlebar
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- libglew-dev <== necessary to use OpenGL version 3 or above
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- cmake <== if you plan to build with CMake
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- cmake-qt-gui <== if you plan to use the GUI of CMake
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This package is necessary to run FLTK apps under the Gnome-Wayland desktop:
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- gnome
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These packages allow to run FLTK apps under the KDE/Plasma-Wayland desktop:
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- kde-plasma-desktop
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- plasma-workspace-wayland
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4.2 Fedora
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----------
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The Wayland platform is known to work with Fedora version 35.
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These packages are necessary to build the FLTK library, besides those present
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in a Fedora 35 Workstation distribution :
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- gcc-c++
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- autoconf
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- wayland-devel
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- wayland-protocols-devel
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- cairo-devel
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- libxkbcommon-devel
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- pango-devel
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- dbus-devel
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- mesa-libGLU-devel
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- gtk3-devel <== with this, windows get a GTK-style titlebar
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- glew-devel <== necessary to use OpenGL version 3 or above
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- cmake <== if you plan to build with CMake
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- cmake-gui <== if you plan to use the GUI of CMake
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Package installation command: sudo yum install <package-name ...>
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4.3 FreeBSD
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-----------
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The Wayland platform is known to work with FreeBSD version 13.1 and the sway compositor.
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These packages are necessary to build the FLTK library and the sway compositor:
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pkg install git autoconf pkgconf xorg urwfonts gnome glew seatd sway \
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dmenu-wayland dmenu evdev-proto
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The FLTK library can be built as follows using either configure or CMake :
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1) Using configure
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cd <path-to-FLTK-source-tree>
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autoconf -f
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./configure --enable-localzlib --enable-wayland
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make
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2) Using CMake
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cmake -S <path-to-source> -B <path-to-build> -DOPTION_USE_WAYLAND=1
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cd <path-to-build>; make
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