@ -16,7 +16,7 @@ It has always been Bill's belief that the GUI API of all
modern systems is much too high level. Toolkits (even FLTK) are
modern systems is much too high level. Toolkits (even FLTK) are
\e not what should be provided and documented as part of an
\e not what should be provided and documented as part of an
operating system. The system only has to provide arbitrary
operating system. The system only has to provide arbitrary
shaped but featureless windows, a powerful set of graphics
shaped but featureless windows, a powerful set of graphics
drawing calls, and a simple \e unalterable method of
drawing calls, and a simple \e unalterable method of
delivering events to the owners of the windows. NeXT (if you
delivering events to the owners of the windows. NeXT (if you
ignored NextStep) provided this, but they chose to hide it and
ignored NextStep) provided this, but they chose to hide it and
@ -83,6 +83,10 @@ simple pixel drawing, but this experimental code is not included
in FLTK 1.4. There are thoughts to enable more platforms in later
in FLTK 1.4. There are thoughts to enable more platforms in later
FLTK versions.
FLTK versions.
FLTK 1.5 removed autotools (configure + Makefile) support in favor
of exclusive use of CMake to generate the build files. FLTK 1.5
allows to use a basic set of C++ features from the C++11 standard.
\section intro_features Features
\section intro_features Features
@ -93,12 +97,12 @@ parts that are used, and thus do not get linked in. This allows
you to make an easy-to-install program or to modify FLTK to
you to make an easy-to-install program or to modify FLTK to
the exact requirements of your application without worrying
the exact requirements of your application without worrying
about bloat. FLTK works fine as a shared library, though, and
about bloat. FLTK works fine as a shared library, though, and
is now included with several Linux distributions.
is included with several Linux distributions.
Here are some of the core features unique to FLTK:
Here are some of the core features unique to FLTK:
Note: sizes given below are mostly from 32-bit systems and FLTK 1.1
Note: sizes given below are mostly from 32-bit systems and FLTK 1.1
or earlier, this list needs updates for current FLTK ( 1.4).
or earlier, this list needs updates for current FLTK 1.5 (6 4-bit ).
\li sizeof(Fl_Widget) == 64 to 92 (120 in FLTK 1.4 on 64-bit Linux).
\li sizeof(Fl_Widget) == 64 to 92 (120 in FLTK 1.4 on 64-bit Linux).
@ -110,19 +114,21 @@ or earlier, this list needs updates for current FLTK (1.4).
(FLTK 1.4 with more widgets on 64-bit Linux: 2.3 MB and
(FLTK 1.4 with more widgets on 64-bit Linux: 2.3 MB and
2.0 MB on 32-bit Windows).
2.0 MB on 32-bit Windows).
\li Written directly atop core libraries (Xlib, Wayland, Windows or Cocoa) for
\li Written directly atop core libraries (Xlib, Wayland, Windows or Cocoa)
maximum speed, and carefully optimized for code size and performance.
for maximum speed and carefully optimized for code size and performance.
\li Precise low-level compatibility between the X11, Windows and MacOS
\li Precise low-level compatibility between the X11/Wayland , Windows, and
versions - only about 10% of the code is different.
macOS versions - only about 10% of the code is different.
\li Interactive user interface builder program FLUID. Its output is
\li Interactive user interface builder program FLUID. Its output is
human-readable and editable C++ source code.
human-readable and editable C++ source code.
\li Support for overlay hardware, with emulation if none is available.
\li Support for overlay hardware, with emulation if none is available.
Note: hardware support has been removed in 1.4.0.
\li Very small & fast portable 2-D drawing library to hide Xlib, Cairo,
\li Very small & fast portable 2-D drawing library to hide Xlib, Cairo,
Windows, or macOS Quartz.
Windows, or macOS Quartz. Since FLTK 1.4 Wayland graphics use Cairo
for drawing. This is optionally available for X11 drawing as well.
\li OpenGL/Mesa drawing area widget.
\li OpenGL/Mesa drawing area widget.
@ -175,142 +181,46 @@ target in the CMake build environment.
\section intro_cmake Building and Installing FLTK with CMake
\section intro_cmake Building and Installing FLTK with CMake
Starting with version 1.4, the recommended FLTK building system is CMake.
Starting with version 1.4, the \b recommended FLTK build system was CMake.
Since FLTK 1.5.0 CMake is the \b only available build system for FLTK.
CMake is a "Build System Generator" that can generate build environments
CMake is a "Build System Generator" that can generate build environments
for usage with Ninja, Make, and many more, for instance IDE's.
for usage with Ninja, Make, and many more, for instance several IDE's.
See file README.CMake.txt of the FLTK source tree for more information.
See file README.CMake.txt of the FLTK source tree for more information.
\note
By default CMake will look for a C++ compiler named \p CC, \p c++, \p g++,
In FLTK 1.4 you can also use \p configure and \p make as follows to build and
or \p gcc. To use another compiler you can set the \p CXX and \p CC
install FLTK. However, configure/make support will be dropped in FLTK 1.5.0.
environment variables for the C++ and C compiler, respectively. The code
to use depends on your shell, for instance:
\section intro_unix Building and Installing FLTK Under UNIX and macOS with make
In most cases you can just type "make". This will run configure with
the default of no options and then compile everything.
FLTK uses GNU autoconf to configure itself for your UNIX
platform. The main things that the configure script will look
for are the X11 and OpenGL (or Mesa) header and library files.
If these cannot be found in the standard include/library
locations you'll need to define the \p CFLAGS,
\p CXXFLAGS, and \p LDFLAGS environment variables.
For the Bourne and Korn shells you'd use:
\code
\code
CFLAGS=-Iincludedir; export CFLAGS
CXX=clang++; export CXX
CXXFLAGS=-Iincludedir; export CXXFLAGS
setenv CXX "clang++"
LDFLAGS=-Llibdir; export LDFLAGS
\endcode
For C shell and tcsh, use:
\code
CC=clang; export CC
setenv CFLAGS "-Iincludedir"
setenv CC "clang"
setenv CXXFLAGS "-Iincludedir"
setenv LDFLAGS "-Llibdir"
\endcode
\endcode
By default configure will look for a C++ compiler named
Then execute CMake like
\p CC, \p c++, \p g++, or \p gcc in that
order. To use another compiler you need to set the \p CXX
environment variable:
\code
\code
CXX=xlC; export CXX
cd /path/to/fltk
setenv CXX "xlC"
cmake . -B build [ -G <GENERATOR> ] [ options ... ]
\endcode
\endcode
The \p CC environment variable can also be used to
Note that you can also specify the compiler and build tools on the CMake
override the default C compiler (\p cc or \p gcc),
command line or in the CMake GUI.
which is used for a few FLTK source files.
You can run configure yourself to get the exact setup you need.
Type "./configure <options>", where some of the options are:
\par --enable-cygwin
Enable the Cygwin libraries under Windows
\par --enable-debug
Enable debugging code & symbols
\par --disable-gl
Disable OpenGL support
\par --disable-svg
Disable support of reading and writing of Scalable Vector Graphics (.svg) files.
\par --disable-print
Disable print support for an X11/Wayland platform
\par --enable-shared
Enable generation of shared libraries
\par --enable-threads
Enable multithreading support
\par --enable-wayland
This is the default for Linux and FreeBSD systems equipped with the Wayland software.
Enable the use of Wayland for all window operations, of Cairo for all graphics, and
of Pango for text drawing. Resulting FLTK apps run as Wayland clients if a Wayland
compositor is available at run-time, and as X11 clients otherwise but keep using
Cairo and Pango for all graphics.
\par --disable-xft
Disables the Xft library, resulting in non anti-aliased fonts (X11 platform).
This is not recommended.
\par --enable-usecairo
All drawing operations use the Cairo library (rather than Xlib) producing
antialiased graphics (X11 platform, implies --enable-pango).
\par --enable-pango
Enable the Pango library for drawing any text in any script with any font
under X11/Wayland.
\par --enable-x11
When CMake is done you can just run CMake again to build the FLTK library,
When targeting Cygwin, build with X11 GUI instead of windows GDI.
fluid, fltk-options (setup tool), and all test programs, depending on the
Also applicable to macOS platforms supplemented with XQuartz .
configuration.
\par --enable-cairo
\code
Enable support of class Fl_Cairo_Window (all platforms, requires Cairo as
cmake --build build
an external library).
\endcode
\par --enable-cairoext
Enable the FLTK instrumentation for cairo extended use (implies --enable-cairo).
\par --disable-gdiplus
Don't use GDI+ when drawing curves and oblique lines (Windows platform).
\par --enable-cp936
Under X11, enable use of the GB2312 locale.
\par --bindir=/path
Set the location for executables. [default = $prefix/bin]
\par --datadir=/path
Set the location for data files. [default = $prefix/share]
\par --libdir=/path
Set the location for libraries. [default = $prefix/lib]
\par --includedir=/path
Set the location for include files. [default = $prefix/include]
\par --mandir=/path
Set the location for man pages. [default = $prefix/man]
\par --prefix=/dir
Set the directory prefix for files. [default = /usr/local]
When the configure script is done you can just run the
"make" command. This will build the library, FLUID tool,
fltk-options (setup tool), and all of the test programs.
To install the library, become root and type "make install".
To install the library, become root and type "cmake --install build".
This will copy the "fluid" executable to "bindir", the header
This will copy the "fluid" executable to "bindir", the header files
files to "includedir", and the library files to "libdir".
to "includedir", and the library files to "libdir".
\section intro_windows Building FLTK Under Microsoft Windows
\section intro_windows Building FLTK Under Microsoft Windows
@ -321,51 +231,62 @@ up-to-date information for this release may be available in the files
these files to determine if there are changes that may be
these files to determine if there are changes that may be
applicable to your build environment.
applicable to your build environment.
FLTK 1.4 is officially supported on Windows (2000,) 2003,
FLTK 1.5 is \b officially \b supported on Windows 10 (11) and later. We don't
XP, and later. Older Windows versions prior to Windows 2000
intend to remove the ability to build and run FLTK 1.5 programs on older
are not officially supported but may still work.
Windows versions but the FLTK Team can't build and test on Windows systems
The main reason is that the OS version needs to support UTF-8.
that are no longer supported by Microsoft. Therefore, such older systems
FLTK 1.4 is known to work on recent versions of Windows such as
(including Windows 10, starting in Oct. 2025, when Microsoft does no longer
Windows 7, Windows 8/8.1, Windows 10 and Windows 11, and has been
support Windows 10) may work with FLTK or not.
reported to work in both 32-bit and 64-bit Windows versions.
\note FLTK 1.4 is known to work on Windows (2000,) 2003, XP, and later. The
main prerequisite is that the OS version supports UTF-8. FLTK 1.4 is also
known to work on recent versions of Windows such as Windows 7, Windows 8/8.1,
Windows 10, and Windows 11, and has been reported to work in both 32-bit and
64-bit Windows versions. If you need to use FLTK on older versions than
Windows 11 (or Windows 10) you may use FLTK 1.4.x.
\n
\note Libraries built by any one of the following build environments
\note Libraries built by any one of the following build environments
can not be mixed with object files from any of the other environments
can not be mixed with object files from any of the other environments
because they use incompatible C++ conventions internally.
because they use incompatible C++ conventions internally.
FLTK currently supports the following development environments on the
FLTK currently supports the following development environments on the
Windows platform:
Windows platform:
\subsection intro_msvc Free and Commercial Microsoft Visual Studio Versions
\subsection intro_msvc Free and Commercial Microsoft Visual Studio Versions
Visual Studio 2015 Community or later versions use workspace and project
Visual Studio 2015 Community or later versions use workspace and project
files generated by CMake. Older versions and the commercial versions can
files generated by CMake. Older versions and the commercial versions can
be used as well, if they can open the project files generated by CMake.
be used as well, if they can open the project files generated by CMake.
FLTK support of Visual C++ is limited to the support of CMake for these
However, FLTK 1.5 and later requires newer C++ features (C++11 or higher)
Visual Studio versions.
that may not be available in older versions of Visual Studio.
Be sure to get your service packs!
FLTK support of Visual Studio is limited to CMake's support for these
Visual Studio versions. Be sure to get your service packs!
Since FLTK 1.4 the project files MUST be generated with CMake.
Since FLTK 1.5 the project files MUST be generated with CMake. Please
Please read "README.CMake.txt" for more information about this.
read "README.txt", "README.CMake.txt", and "README.Windows.txt" for more
information about this.
\subsection intro_msvc_dll Using the Visual C++ DLL Library
\subsection intro_msvc_dll Using the Visual C++ DLL Library
The Visual Studio project files can be used to build a DLL version
The Visual Studio project files can be used to build a DLL version of the
of the FLTK library if CMake option 'FLTK_BUILD_SHARED_LIBS=ON' is
FLTK library if CMake option 'FLTK_BUILD_SHARED_LIBS=ON' is set. Because
set. Because of name mangling differences between PC compilers (even
of name mangling differences between PC compilers (even between different
between different versions of Visual Studio) you can only use the DLL
versions of Visual Studio) you can only use the DLL that is generated with
that is generated with th e same compiler version that you built it with.
the same compiler version that you built it with.
When compiling an application or DLL that uses the FLTK DLL with Visual
When compiling an application or DLL that uses the FLTK DLL with Visual
Studio, you need to define the \p FL_DLL preprocessor symbol to get
Studio, you need to define the \p FL_DLL preprocessor symbol to get
the correct linkage commands embedded within the FLTK header files.
the correct linkage commands embedded within the FLTK header files.
New since FLTK 1.4.0:
New since FLTK 1.4.0:
If you build your application project with CMake and use the CMake target
If you build your application project with CMake and use the CMake target
'fltk::fltk-shared' to link your application, then 'FL_DLL' is defined
'fltk::fltk-shared' to link your application, then 'FL_DLL' is defined
automatically for you (by CMake Compile Definition). If you use your
automatically for you (by CMake Compile Definitions ). If you use your
own (hand-made) Visual Studio project you still need to define FL_DLL
own (hand-made) Visual Studio project you still need to define FL_DLL
to compile all source files that use FLTK headers.
to compile all source files that use FLTK headers.
@ -374,18 +295,16 @@ to compile all source files that use FLTK headers.
If using Cygwin with the Cygwin shell, or MinGW with the Msys shell,
If using Cygwin with the Cygwin shell, or MinGW with the Msys shell,
these build environments behave very much like a Unix or macOS build
these build environments behave very much like a Unix or macOS build
and the notes above in the section on
and the notes above can be applied. Build files are generated by CMake for
<i>Building and Installing FLTK Under UNIX and Apple macOS</i>
the platform you are using. See README.CMake.txt for more info.
apply, in particular the descriptions of using the
"configure" script and its related options.
In general for a build using these tools, e.g. for the Msys shell with
In general for a build using these tools, e.g. for the Msys shell with
MinGW, it should suffice to "cd" into the directory where you have
MinGW, it should suffice to "cd" into the directory where you have
extracted the FLTK tarball and type:
extracted the FLTK tarball and type:
\code
\code
./configure
cmake . -B build
make
c make --build build
\endcode
\endcode
This will build the FLTK libraries and they can then be
This will build the FLTK libraries and they can then be
@ -398,43 +317,39 @@ For example, if you "install" the libraries using Msys/MinGW
with the following command
with the following command
\code
\code
make install
c make -- install build
\endcode
\endcode
then Msys will "install" the libraries to where it thinks
then Msys will "install" the libraries to where it thinks the path
the path "/usr/local/" leads to. If you only ever build code
"/usr/local/" leads to. If you only ever build code from within the Msys
from within the Msys environment this works well, but the
environment this works well, but the actual "Windows path" these files
actual "Windows path" these files are located in will be
are located in will be something like "C:\msys\1.0\local\lib", depending
something like "C:\msys\1.0\local\lib", depending
on where your Msys installation is rooted, which may not be useful to
on where your Msys installation is rooted, which may
other tools.
not be useful to other tools.
If you want to install your built FLTK libraries in a
If you want to install your built FLTK libraries in a
non-standard location you may do:
non-standard location you may do:
\code
\code
sh configure --prefix=C:/FLTK
cmake . -B build -D CMAKE_INSTALL_PATH="C:/FLTK"
make
cmake --build build
cmake --install build
\endcode
\endcode
Where the value passed to "prefix" is the path at which
Where the value passed to "CMAKE_INSTALL_PATH" is the path at which
you would like FLTK to be installed.
you would like FLTK to be installed. Depending on the build environment
using standard Windows path syntax may work, or you need to use MinGW
A subsequent invocation of "make install" will then place
(or Cygwin) syntax.
the FLTK libraries and header files into that path.
The other options to "configure" may also be used to
tailor the build to suit your environment.
\section intro_internet Internet Resources
\section intro_internet Internet Resources
FLTK is available on the ' net in a bunch of locations:
FLTK is available on the inter net in a bunch of locations:
\par FLTK Source Repository on GitHub
\par FLTK Source Repository on GitHub
https://github.com/fltk/fltk
https://github.com/fltk/fltk
\par WWW
\par WWW (fltk.org)
https://www.fltk.org/ <br>
https://www.fltk.org/ <br>
https://www.fltk.org/bugs.php [for reporting bugs] <br>
https://www.fltk.org/bugs.php [for reporting bugs] <br>
https://www.fltk.org/software.php [download source code]<br>
https://www.fltk.org/software.php [download source code]<br>
@ -445,6 +360,12 @@ https://groups.google.com/forum/#!forum/fltkgeneral [Google Groups interface] <b
news://fltk.org:1024/ [NNTP interface]<br>
news://fltk.org:1024/ [NNTP interface]<br>
https://www.fltk.org/newsgroups.php [web interface]
https://www.fltk.org/newsgroups.php [web interface]
\par GitHub
https://github.com/fltk/fltk
https://github.com/fltk/fltk/discussions [FLTK Discussions on GitHub]
https://github.com/fltk/fltk/discussions/categories/q-a [Q&A: Questions and Answers]
https://github.com/fltk/fltk/releases [Releases, i.e. Source Code and Documentation]
\section intro_reporting Reporting Bugs
\section intro_reporting Reporting Bugs
@ -455,7 +376,8 @@ or ask for help on using FLTK.
For general support and questions, please use the fltk.general newsgroup
For general support and questions, please use the fltk.general newsgroup
(see above, "NNTP Newsgroups") or the web interface to the newsgroups at
(see above, "NNTP Newsgroups") or the web interface to the newsgroups at
<A href="https://www.fltk.org/newsgroups.php">https://www.fltk.org/newsgroups.php</A>.
<A href="https://www.fltk.org/newsgroups.php">https://www.fltk.org/newsgroups.php</A>,
or GitHub Discussions (see link above).
\htmlonly
\htmlonly
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