Don't Panic - Qt Fundamentals

Qt is a cross-platform application framework centered on C++, with QML and Python workflows for user interfaces. Modules cover UI controls, graphics, networking, data handling, localization, accessibility, and hardware integration behind APIs that stay largely consistent across targets. An application starts an application object, enters an event loop, and turns operating-system input into events, signals, and UI updates.

QObject is the base of Qt's object model: metadata, properties, signals and slots, parent-child lifetime, and thread affinity. Signals announce that something happened; slots or callables handle the notification without the sender needing to know every receiver. Parent deletion cleans up children inside that tree. It does not replace ordinary C++ ownership for values outside the tree. Qt objects represent identities and are not copyable.

Two UI technologies matter. Qt Quick (QML) is the recommended path for new fluid, animated, device-oriented interfaces. Qt Widgets remains the mature C++ toolkit for traditional desktop windows, dialogs, and forms. Qt Core and Qt GUI sit underneath both stacks. CMake is the primary Qt 6 build system: targets declare modules and link imported targets, while Qt tools process metadata and resources before the compiler finishes.

Responsiveness is a design rule: keep heavy or blocking work off the GUI thread, and return results through thread-safe signals or queued connections. Deployment is another rule: a successful build is not a distributable app until libraries, plugins, QML modules, translations, and platform resources travel with the binary. Licensing and major-version policy constrain which modules and support windows you can rely on, so review those terms with the same care as the UI technology choice.

Read the Intro for the architecture and UI choice. Use the Cheatsheet for the runtime and module maps. Landscape and Timeline place Qt among related client frameworks; Updates tracks the Qt 6 release index.