Geany

Geany is a small programming editor with a few of the conveniences usually found in an IDE. It is built on GTK and the Scintilla editing component, starts quickly and depends on little beyond GTK itself, which makes it a common choice on older machines and minimal desktops.

It highlights syntax for a long list of languages, folds code blocks, matches and auto-closes brackets, and completes words already present in the document. A symbol list in the side panel jumps to functions and classes in the open file, and the same panel holds a file browser and the list of open documents. A project groups a directory of files together with its own settings.

The build system is deliberately plain: each language has an editable set of commands for compiling, building and running, output appears in a message window, and error lines link back to the offending place in the source. Plugins add a terminal panel, version-control diffs, file templates and more. Geany is not organised around language servers, so cross-file analysis and deep refactoring fall outside what it does.