在Qt中缩放图形

Question

I am writing a scheduling-type application using Qt/C++ and want to display weekly schedules in one part of the window, and have this rendering scale as the window size increases. The renders will be composed of rectangles with text in them, and as the display area increases the rectangles should scale nicely while the text should remain the same size.

I have experimented with QGraphicsScene and QGraphicsView and I can make rectangles and text scale; however, the rectangle scaling seems ugly (stretches the outline) and I don't want text to scale at all.

I suspect that I might want to resize the scene to the display area and re-draw the rectangles and text; however, I am not sure how to do this - QGraphicsScene doesn't seem to respond to resizeEvent. Is this even the right approach?

Answer 1

I'm not sure what the ugly rectangle scaling is about (a screenshot might help me understand better what you meant there), but if you don't want the text parts to scale, you can accomplish that by calling setFlag(ItemIgnoresTransformations, true) on your QTextGraphicItem objects.

As far as automatically rescaling the rectangles in response to a window resize, you might take a look at the documentation of the QGraphicsView::fitInView() method:

Scales the view matrix and scrolls the scroll bars to ensure that the scene rectangle rect fits inside the viewport [...] It's common to call fitInView() from inside a reimplementation of resizeEvent(), to ensure that the whole scene, or parts of the scene, scales automatically to fit the new size of the viewport as the view is resized. Note though, that calling fitInView() from inside resizeEvent() can lead to unwanted resize recursion, if the new transformation toggles the automatic state of the scrollbars. You can toggle the scrollbar policies to always on or always off to prevent this (see horizontalScrollBarPolicy() and verticalScrollBarPolicy()).