Widgets vs. Qt Quick / QML

[imsanjoykb]

Qt offers two broad technologies for creating user interfaces: The first, referred
to as Widgets, is the old core of Qt. It renders desktop GUIs typical for operating
systems such as Windows or macOS. A somewhat more recent technology is
Qt Quick: It offers highly customizable graphics, fluid animations and is more
targeted at mobile devices and touch displays.

Qt Quick uses a markup language called QML for laying out UIs. It is function-
ally similar to HTML, CSS and JavaScript. In fact, it supports JavaScript as a

scripting language. Its overall syntax is similar to JSON. Qt Quick applications
often use QML for the UI and C++ or Python for the business logic.
Widgets on the other hand are often laid out directly in code. That is, there are
C++ or Python statements that say "draw a button here". This can be avoided
by using Qt Designer (see Section 3.6), a visual editor that outputs special XML
files describing a UI. But it lacks the dynamic features of JavaScript.
In general, you should use Widgets if you want a pretty standard desktop GUI.

Otherwise, if you want highly customizable graphics and / or support for mo-
bile devices and touch displays, use Qt Quick.

Because Qt Quick already supports JavaScript, a dynamic scripting language,
combining it with Python yields fewer benefits than doing so for Widgets. For
this reason, this book is mostly about Widgets.