Sortable QHBoxLayout

I'm using Qt to create a sortable bar graph-like widget. The widget is laid out with a QHBoxLayout for each bar in the graph (which are also widgets).

When the user changes the sorting parameters, my controller clears the layout, sorts it, and calls addWidget on every item in order. The problem I'm facing is that this list is quite large (1000+ widgets), and Qt is crawling when attempting to layout that many elements.

I've found out that each time addWidget is called, Qt will recalculate the location of every item in the QHBoxLayout and then update. This is a problem, as it performs a lot of unnec开发者_高级运维essary calculations on each LayoutItem before the one I am adding. For 1000 test items that I'm putting in, resorting takes around 30 seconds, which is obviously far too long.

Is there a better Layout type to use, or is there a faster way to add a collection of sorted widgets to a layout?

Edit: Apparently, the issue I've been having isn't with Qt laying out each item again, but the internals of all the parenting and shenanigans that go on behind the scenes I set up a test project to add 1000 buttons to a layout, printing out a counter each time. The numbers printed out almost instantaneously, though it took that same ~30 seconds for Qt to straighten itself out. I think the problem doesn't exist only with QHBoxLayout, but with Qt's layout system in general. Looks like I'll be manually positioning widgets and bypassing a QLayout altogether. Thanks to everyone who gave their input.

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From documenation of void QLayout::setEnabled(bool enable)

Enables this layout if enable is true, otherwise disables it.
An enabled layout adjusts dynamically to changes; a disabled layout acts as if it did not exist.
By default all layouts are enabled.

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What about making a Graph widget (composed of Bar (or whatever name you choose) widgets) which would contain your own QLayout subclass optimized for this task (since you have to reimplement QLayout::addItem() which is pure virtual in QLayout).

Also, be sure to check out Qwt, since it already might have implemented what you want.

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Perhaps you can create a new QHBoxLayout without parent, add your widgets to this layout, and then delete the old QHBoxLayout and insert your new layout. WARNING: I did not try this.