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Subject: Re: [boost] [rfc] cppgui
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2009-07-01 16:09:07

Felipe Magno de Almeida
> On Wed, Jul 1, 2009 at 4:41 PM, Stewart,
> > One layout mechanism that I've found very easy to use and
> > easy enough to implement is a "spring tab" which I first saw
> > in Borland's Sprint word processor eons ago. (I realize I'm
> > crossing domains, but I think the idea applies readily.) The
> > notion of a spring tab is that it exerts equal force on each
> > side to separate things.
> > If you juxtapose spring tabs, they act as though there is a
> > zero space, invisible widget between them. Thus,
> > <ST><ST>widget<ST> puts the widget 2/3 of the way across the
> > horizontal extent.
> Why 2/3 if there's four widgets?

I never said a spring tab was a widget. Call it and treat it how you like. It merely consumes space, though in a layout mode, were there a GUI editor, they would be visible.

Why 2/3?


All spring tabs exert the same space-consuming force, so they divide the available space evenly among them. Thus, each spring tab consumes (width - widget.width)/N of the space. (Extend accordingly when there are more widgets in the "line.")

The center of the widget is, thus, 2/3 of the way across the available width.

> > Anyway, the idea is that they are relatively trivial widgets
> > that can be assembled together quickly to get a reasonable
> > arrangement that adapts as a window is resized. Perhaps
> > that's a tool to include in your library.
> Probably. But I wanted something more generic. Maybe the
> proportion can be assigned.

You could do that, but the simplicity of a spring tab is expressed in the formula shown above. There's no need to indicate the relative strength of any; just add more where needed to effect the needed alignment.

> Also vertical springs are needed.


> And I'm not sure I want it to be a widget. It doesn't have most
> operations a window has. It only occupies space.

I never called it a widget. As you say, it only occupies space.

> And what happens if two widgets are side-by-side to a spring.
> Should it press both?



The pair is centered by surrounding the pair with spring tabs.

> Do we link springs with widgets?

I don't understand the question, but I'm hoping you understand the idea better now.

> I see a window as having a depth dimension, should springs
> press work on a layer, or all depths of a window?

I don't know, but I guess it would be layer specific.

Rob Stewart robert.stewart_at_[hidden]
Software Engineer, Core Software using std::disclaimer;
Susquehanna International Group, LLP

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