Hi Wolf, thank you for pointing this out, that is some interesting reading that I did not know of before. However, if I understand it correctly, it does not liberate widget implementors from writing rearrangement function. At least not in the context of HelenOS widget toolkit where rearrangement function essentially stands for "draw yourself to the area assigned from your parent and if you have any children, order them to draw themselves somewhere over you, accordingly to your internal rearrangement logic".
Instead, I see ALM as a generalization of layout widgets. Therefore, it liberates developers from implementing any other layout widget - i.e. instead of nesting various layout widgets like grids or stacks, you would have only single super-powerful layout widget that could express all possible layouts. However, I expect there would be still some compound widgets that would want to handle their internal layout on their own, perhaps by an embedded instance of ALM, so the scene tree could still have multiple levels. All in all, there must still be some scene tree policy that would specify the basic behaviour of widgets, so for example the button would draw itself as requested by ALM and not damaging the area that does not belong to it. Alternatively, the correct behaviour could be enforced by clipping as I already suggested. My point is, this is really more a question of basic inner workings of widget toolkit, not of flexibility of expressing layouts. But still, it would be very nice if something like ALM made its way into HelenOS widget toolkit someday. Petr > From: HelenOS-devel [mailto:[email protected]] On Behalf > Of Wolf Ramovsky > Sent: Monday, April 22, 2013 5:42 PM > To: HelenOS development mailing list > Subject: Re: [HelenOS-devel] Widget size constraints > > Hi, > > excuse me, I only want to leave a BTW note here. > I thought it would be nice to base GUI layout on something like ALM. See [1], > [2]. It is rather general and flexible basis and it's very easy to formulate > such things like soft constraints or parent-child relations on top of it. It > liberates developers of widgets from writing rearrangement function for each > widget. > > [1] http://aucklandlayout.sourceforge.net/ > [2] http://www.crt.umontreal.ca/~pesant/Constraints/Papers/LutterothSW08.pdf _______________________________________________ HelenOS-devel mailing list [email protected] http://lists.modry.cz/cgi-bin/listinfo/helenos-devel
