Apps similar to FLTK include Qt, which is open source with a free version. Other options are Qt Creator, GTK, wxWidgets and PyQt. There's no shortage of Software Frameworks like FLTK, with more than 25 alternatives for Linux, Windows, Mac, Android and self-hosting.
Qt is a cross-platform application framework that is widely used for developing application software that can be run on various software and hardware platforms with little or no change in the underlying codebase, while having the power and speed of native applications.
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Qt Creator is a cross-platform integrated development environment (IDE) built for the maximum developer experience. Qt Creator runs on Windows, Linux, and macOS desktop operating systems and allows developers to create software across desktop, mobile, and embedded platforms.
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GTK is a multi-platform toolkit for creating graphical user interfaces. Offering a complete set of widgets, GTK is suitable for projects ranging from small one-off tools to complete application suites.
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wxWidgets is a C++ library that lets developers create applications for Windows, OS X, Linux and UNIX on 32-bit and 64-bit architectures as well as several mobile platforms including Windows Mobile, iPhone SDK and embedded GTK+.
Avalonia is a WPF-inspired cross-platform XAML-based UI framework providing a flexible styling system and supporting a wide range of platforms including: Windows, Linux (desktop & embedded), macOS, Android, iOS and Browser.
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MauiKit is a framework based on QQC2 and Kirigami, that helps to create convergent applications that run on GNU Linux and Android, based on the Maui HIG. MauiKit is an open source framework to make the applications look good, made by .
GUI toolkit for Rust, C++, and JavaScript to efficiently develop fluid graphical user interfaces for embedded devices and desktop applications.
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Uno is the platform for building native mobile, desktop and WebAssembly apps with C#, XAML from single codebase. It's a Universal Windows Platform Bridge that allows UWP-based code (C# and XAML) to run on iOS, Android, and WebAssembly.
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The Qt for Python project aims to provide a complete port of the PySide module to Qt.
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wxPython is a GUI toolkit for the Python programming language. It allows Python programmers to create programs with a robust, highly functional graphical user interface, simply and easily. It is implemented as a Python extension module (native code) that wraps the popular...
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