QT: How to change the color of the progressbar

i am having one videoeditor view and one progressbar is there with blue color . But how i will change the progressbar color to red when i clicked trim start and it will return to blue开发者_StackOverflow中文版 when i will click the trim endbutton in QT

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This is from the Qt Documentation

You can style the ::chunk part explicitly to change background color.

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EDIT: I misunderstood the question. You are talking about something like the clip selector/editor in Adobe Premiere. To do something like this I would just create a custom widget, and handle the drawing yourself. It would not be too hard. You will need to subclass QWidget, then reimplement the paintEvent(), then also probably the mousePressEvent(), mouseReleaseEvent(), and mouseMouseEvent().