It is recommended to use an Integrated Development Environment that works with C++. Mixxx is a large C++ project spread across many files. Without an IDE that can help navigate around code split across multiple files, it can be difficult to understand how the code fits together.

• Integrated Development Environments (IDEs): KDevelop, Eclipse, Qt Creator
• Text editors: gedit, kate, SciTE, emacs
• Git tools: gitk (comes with git), git-cola, gitg

• Integrated Development Environments (IDEs): Visual Studio Community, Visual Studio Code, Eclipse, Qt Creator
• Text editors: Notepad++, emacs
• Git tools: Tortise Git, Git Extensions

• Integrated Development Environments (IDEs): Eclipse, Qt Creator, XCode
• Text editors: emacs

• Set up Visual Studio Community
• Set up Visual Studio Code
• Set up Eclipse
• Set up KDevelop
• Set up Emacs
• Set up QtCreator
• Set up Xcode
• Set up CLion

KDAB's GammaRay is a tool for dynamically inspecting applications built with Qt. Its feature set is too long to list, but of particular use for Mixxx development is:

• The ability to see all current signals/slots being fired by Mixxx, with the ability to jump to the object that is firing them.
• The ability to inspect the tree of all QObjects that exist, and for each object being able to see its properties, methods and inbound/output connections.
• The ability to debug the render process of a QWidget, showing you at each step of a QPainter what the widget looks like, including performance details about each step.

Debuggers allow you to inspect the state of Mixxx while its running (and after Mixxx has crashed, via a core dump file).

• gdb (for gcc)
• lldb (for Clang)
• Visual Studio (Windows-only)

See profiling.

grep is nice for searching files with regexes, but it isn't designed specifically for looking through source code. There are a number of tools that make searching through source repositories much nicer (e.g. they won't go searching in the .git subfolder, or digging through binary files for your regex).

• ack
• ripgrep
• ag / The Silver Searcher