Linux/Unix Build Guide

Build and install FLTK on Linux and Unix systems with CMake

Introduction

FLTK supports most Unix and Linux platforms using CMake as the build system. This guide covers building FLTK on various Linux distributions and Unix systems including Debian, Ubuntu, Fedora, NetBSD, and more.

Since FLTK 1.5.0, autotools and configure-based builds are no longer supported. You must use CMake.

Prerequisites

Required Packages

FLTK requires certain development packages to be installed. Choose the section for your distribution:

Debian/Ubuntu

Install the core development tools and X11 libraries:

sudo apt-get install g++
sudo apt-get install gdb
sudo apt-get install git
sudo apt-get install cmake
sudo apt-get install libx11-dev
sudo apt-get install libglu1-mesa-dev
sudo apt-get install libxft-dev
sudo apt-get install libxcursor-dev

Optional but Recommended Packages

sudo apt-get install libasound2-dev
sudo apt-get install freeglut3-dev
sudo apt-get install libcairo2-dev
sudo apt-get install libfontconfig1-dev
sudo apt-get install libglew-dev
sudo apt-get install libjpeg-dev
sudo apt-get install libpng-dev
sudo apt-get install libpango1.0-dev
sudo apt-get install libxinerama-dev

For Wayland support, see the Wayland platform guide.

Fedora

Install the required development packages:

su root
yum groupinstall "Development Tools"
yum groupinstall "X Software Development"
yum groupinstall "C Development Tools and Libraries"

Exit root status (Ctrl-D) before building FLTK.

NetBSD

Ensure the optional distribution sets are installed:

• comp: Compiler, header files, development tools
• x*: X Window System

Install and configure pkgsrc from pkgsrc.org.

For the latest development version:

cd /usr/pkgsrc/devel/git
bmake install
git clone https://github.com/fltk/fltk.git

If using JPEG/PNG libraries from pkgsrc:

export CPPFLAGS="-I/usr/pkg/include"
export LDFLAGS="-L/usr/pkg/lib"

Solaris/OpenIndiana

FLTK requires at least SunOS 5.7 (Solaris 7) with POSIX threads support.

For Sun compilers with pkgsrc libraries:

export CC="cc"
export CXX="CC"
export CPPFLAGS="-I/usr/pkg/include"
export LDFLAGS="-L/usr/pkg/lib -R/usr/pkg/lib"

For 64-bit builds:

export CFLAGS="-xarch=v9"
export CXXFLAGS="-xarch=v9"

Downloading FLTK

Download the latest stable release or development version:

Stable Release

Download from fltk.org/software.php:

cd ~
mkdir dev
cd dev
tar xvzf ~/Downloads/fltk-1.x.y-source.tar.gz
cd fltk-1.x.y

Git Development

Clone the latest development version:

git clone https://github.com/fltk/fltk.git
cd fltk

Update to the latest version:

git pull

Building FLTK

Quick Build

Build FLTK with default settings:

cmake . -B build -D CMAKE_BUILD_TYPE=Debug
cmake --build build

Replace Debug with Release for optimized production builds.

Configuration Options

View available configuration options:

cmake -L .

Common options:

• -D CMAKE_BUILD_TYPE=Debug|Release - Build type
• -D CMAKE_INSTALL_PREFIX=/path - Installation directory
• -D FLTK_BUILD_SHARED_LIBS=ON - Build shared libraries
• -D FLTK_BUILD_EXAMPLES=ON - Build example programs

For more details, see README.CMake.txt in the FLTK source directory.

Testing FLTK

Run the demo program to test the build:

cd build
test/demo

The demo launcher provides access to all FLTK test programs.

Installing FLTK

Install to the default location (/usr/local):

sudo cmake --install build

Install to a custom location without superuser privileges:

cmake . -B build -D CMAKE_INSTALL_PREFIX=$HOME/fltk
cmake --build build
cmake --install build

Installing FLTK system-wide is optional. You can build applications directly against the build tree, which is recommended for static linking and avoiding version conflicts.

Building Your Applications

Using fltk-config

FLTK provides the fltk-config script to simplify compilation:

fltk-config --compile myProgram.cxx

For multiple source files:

fltk-config --compile file1.cxx file2.cxx file3.cxx

Get compiler and linker flags:

fltk-config --cxxflags
fltk-config --ldflags

Using CMake

For larger projects, use CMake. Create a CMakeLists.txt:

cmake_minimum_required(VERSION 3.15)
project(MyApp)

find_package(FLTK REQUIRED)

add_executable(myapp main.cxx)
target_link_libraries(myapp FLTK::fltk)

Build your project:

cmake -B build
cmake --build build

IDE Integration

Code::Blocks

Install Code::Blocks IDE:

sudo apt-get install codeblocks

Create a new FLTK project:

1. Select File > New > Project
2. Choose FLTK project template
3. Follow the wizard

To add FLUID support:

1. Go to Settings > Compiler and debugging settings > Other settings > Advanced options
2. Add extension: fl
3. Command line macro: cd $file_dir; fluid -c $file
4. Generated files: $file_dir/$file_name.cxx and $file_dir/$file_name.h

Platform Features

Display Backend

Linux FLTK supports both X11 and Wayland backends:

• X11: Traditional X Window System (always available)
• Wayland: Modern display protocol (see Wayland guide)

By default, FLTK builds with hybrid Wayland/X11 support and automatically selects the appropriate backend at runtime.

Font Rendering

FLTK uses:

• Xft: Anti-aliased font rendering (X11)
• Pango: Text rendering and international text support (Wayland)

Graphics

• Cairo: Vector graphics library (optional)
• OpenGL: Hardware-accelerated 3D graphics

Distribution Packages

Many distributions provide pre-built FLTK packages:

Debian/Ubuntu

sudo apt-get install libfltk1.3-dev

Fedora

sudo yum install fltk-devel

NetBSD

cd /usr/pkgsrc/x11/fltk13
bmake install

Distribution packages may be outdated. Building from source is recommended for the latest features and bug fixes.

Troubleshooting

Missing Dependencies

If CMake reports missing dependencies, install the required development packages for your distribution.

Symbol Font Issues

The Symbol and Zapf Dingbats fonts do not work on X11 UTF-8 platforms. This is expected behavior.

Build Warnings

The ranlib tool may report modules with no symbols. This is normal and can be safely ignored.

Additional Resources

• CMake Build Guide
• FLTK Documentation
• Report Issues
• Mailing Lists