Table of Contents
FLUID, short for Fast Light User Interface Designer, is a graphical editor capable of generating C++ source code and header files ready for compilation. These files ultimately create an FLTK based graphical user interface for an application.
The FLTK programming manual is available at https://www.fltk.org/documentation.php .
This manual provides instructions on launching FLUID as a command line tool and integrating .fl project files into the application build process. FLTK utilizes CMake, but other build systems and IDEs capable of running external tools can also build applications based on FLUID.
The majority of the manual focuses on using FLUID as an interactive GUI design tool. It covers an overview of windows, menu items, and dialog boxes, detailing how to create visually appealing and consistent user experiences through drag and drop functionality, a "what you see is what you get" editor, and alignment tools. The Settings Dialog will detail the process of initiating a new project, creating an alignment template, and incorporating internationalization.
Several tutorials will explain how to generate small apps in FLUID alone, and how to create more complex user interfaces, followed by some advanced subjects like creating integrated reusable widget classes.
The appendices contain additional technical information for reference.
Workflow
FLUID stores user interface designs within .fl project files. These files are transformed into a binary application through a multi-step process. Initially, FLUID converts .fl files into C++ source and header files. Subsequently, these files are compiled into object files, which are then linked with other object files to form an executable binary. FLUID-generated header files give access to UI elements from other C++ modules within the project. FLUID can also generate forward declarations to variables and callback functions that are defined and implemented in other C++ modules.
Small applications can be fully designed and developed with FLUID alone. Users have the option to include shell scripts in FLUID projects, enabling them to directly call compilers and linkers to produce the binaries.
For medium-sized projects, a build system such as CMake or an IDE with integrated build setup is recommended. FLUID in interactive mode can pre-generate C++ code files for direct compilation by the IDE.
In larger projects, FLUID projects frequently reference external resources such as graphics, binary data, and internationalized text. In such scenarios, it is very useful to distribute the .fl project files instead of prebuilt source files. FLUID in command-line mode can then be called as an external tool, dynamically generating C++ source code from all external resources at build time.
