Changing expression constant about kiwi HOT 8 CLOSED

Another option would be to allow some kind of variables which can be changed from outside, but not from the solver, but I can't see those in Kiwi as well (

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I believe what you are looking for are EditVariables. You can look at cassowary examples as kiwi implement the same solver. This example in particular seems to describe your use case: http://cassowary.readthedocs.io/en/latest/topics/examples.html

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@MatthieuDartiailh, I doubt it. The example you're providing is using stay constraints (grep for add_stay), which is missing in kiwi.

To somehow rephrase my question I can provide a use case which I want to implement. Let's say there's a UI system, with view hierarchies, where every view has x, y, width and height variables. All the variables are tied with constraints. Then there's the window with its width and height variables. The user may resize it, so I "edit" the width and height of the window and it works for the first relayout, but subsequent calls to solver.solve may randomly change these variables again. So I want those variables to stay and be changed when its otherwise impossible to solve the constraints.

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I believe you can still achieve your goal without stay constraints, as it is done in enaml (https://github.com/nucleic/enaml/blob/master/enaml/layout/layout_manager.py#L244). You can look at how the constraints are defined and how resize is done.
I must say I am not an expert here, @sccolbert would be more qualified to answer you.

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See also this discussion #9

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Thanks, #9 explains a lot. Maybe this info should be mentioned on the front page, that stay constraints can be "simulated" by adding/removing external EQ constraints.

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@yglukhov The right way to do what you want is with edit variables. In Enaml, each widget has a variable for left, top, width, and height. Child widgets are ultimately constrained based on their parent's width and height variables. Those variables are added to the solver via solver.addEditVariable. When solving for the layout of the children, the current size of the parent is used to suggest values for the width and height variables via solver.suggestValue. The system is then solved via solver.updateVariables.

https://github.com/nucleic/enaml/blob/master/enaml/layout/layout_manager.py#L358-L360

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@sccolbert, ah that makes even more sense. Thank you. Still worth mentioning in the docs I think.

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