Open Source C++ User Interface (UI) Software

Code::Blocks is a free, open-source, cross-platform C, C++ and Fortran IDE built to meet the most demanding needs of its users. It is designed to be very extensible and fully configurable. Finally, an IDE with all the features you need, having a consistent look, feel and operation across platforms. Built around a plugin framework, Code::Blocks can be extended with plugins. Any kind of functionality can be added by installing/coding a plugin. For instance, compiling and debugging functionality is already provided by plugins! We hope you enjoy using Code::Blocks! The Code::Blocks Team

Edyuk is a free, open source, fast and lightweight development environment which supports C++ and Qt 4 out of the box and can be extended through plugins. It works under all platforms supported by Qt 4 (Linux, Mac, Windows, BSD, ...).

Java SWT and AWT port of Scintilla, a free source code editing component. Scintilla runs on Windows and Linux with GTK+. It is a rich text editing control that supports syntax styling, error indicators, code completion, call tips, etc.

Monkey Bench is a application for live tweaking and debugging of a running application. While Monkey Bench itself mostly acts as a plugin container, it simplifies the process of making custom debug & tweak tools specialized for certain applications.

Provide a gui for the Valgrind suite (a Linux, BSD and Mac profiler).