[Question] How to draw a rectangle in a page

[mantielero]

I would like to use the rubberband to draw a rectangle on a page. How can I do that?

[wbsoft]

Good question; the rubberband was designed to let the user interact with it. If you want to display the Rubberband programmatically, you should use setSelection(). The user then still can interact with it and change the selection.

[paravoid]

I wanted to draw multiple rectangles.

FWIW:

• First I tried the highlighter mix-in, to no unavail - nothing was showing up. It'd be for someone that knows how it works to validate that it still does, and then add an example in the docs perhaps?
• Then I tried with the widgetoverlay mix-in, which also failed. I think the __init__ signature is in conflict with the base class?

I ended up subclassing Rubberband to a new class. I set a custom palette with QPalette.ColorRole.Highlight to use a different color, as Rubberband provides no option to change the color.

More importantly, this meant that I also needed to subclass from View, in order to keep references to these rectangles, and then do the whole dance to keep them in place during move, zoom, etc. Basically:
a) setParent/viewport().installEventFilter/self.zoomFactorChanged.connect when adding them;
b) clearSelection/removeEventFilter/self.zoomFactorChanged.disconnect when removing them;
c) Hook a 'for r in self.rectangles: r.scrollBy(dx, dy)` on scrollContentsBy.

Finally, I was left with a rectangle that can be resized, dragged etc. - which for my use case is OK, but I can imagine others wanting "static", fixed in place rectangles. I also wasn't able to draw anything more, like a label, to my rectangle.

In terms of concrete suggestions, perhaps it'd be meaningful to:

1. In the View class, generalize all the hardcoded rubberband code to refer to a list of objects that track the viewport. Basically every reference to self._rubberband. This way, the abstraction is cleaner, Rubberband is not hardcoded in the View, and Rubberband becomes just one class out of many that can leverage this functionality.
2. Split the Rubberband code into a base class and mix-ins, e.g. one for resizable, another one for draggable/movable etc. These can be leveraged by other, custom subclasses like mine.

Let me know how these sound, and perhaps i can take a stab at it.

[bmjcode]

Hey @paravoid, if you feel comfortable implementing that then go ahead and open a PR. I will warn you it might take some time to review. Wilbert's been inactive a while so I'm kind of maintainer by default now, and frankly it sounds like you understand that part of the code much better than I do.