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Revision as of 20:47, 15 January 2012 by Henk-Jan van Tuyl (talk | contribs) (Added category wxHaskell)

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Most useful resource: the wxHaskell layout documentation

Layout setting by gridding

In general, we can create layout by setting the layout argument in a frame or a panel, for example,

gui = do f <- frame [ text := "Layout" ]
         p <- panel f []
         b <- button p [ text := "button" ]
         set f [ layout := margin 2 $ container p $ floatCenter $
                              widget b
               , clientSize := sz 100 100

I will call this Layout setting by gridding.

Gridding means using the layout function, such as grid, row, column etc, to set the layout.

Layout setting by positioning

Also, we could set the layout by another way, Layout setting by positioning

gui = do f <- frame [ text := "Layout"
                    , clientSize := sz 100 100 ]
         p <- panel f [ clientSize := sz 98 98,
                      , position := pt 2 2 ]
         b <- button p [ text := "button"
                       , position := pt 45 45 ]

The result of both examples are about the same, only the button position has a bit different. (Please measure the exact position by yourself). By this way, we can have more flexible layout rather than limited the layout by grids.

EYK: it seems like layout by positioning allows for more precise control, but it does not seem like it would respond nicely to window resizing, no?

Layout reconfiguration

We can also re-configure the layout by just simply re-assign a new layout value to the layout. But remember, do not assign the same tab to the layout twice, it will append the same tab to the notebook. To prevent this, assign an empty list to the notebook

f <- frame [ text := "Layout" ]
nb <- notebook f []
set f [ layout := tabs nb [] ]


fill = stretch . expand

NB: these are tentative explanations, could be wrong

Two dimensions are important here

shape (expansion)
the widget's shape: how does a widget use the space around it? Your options are
  • rigid (default): fixed shape
  • shaped expands but retains proportions
  • expand just expands without caring about proportions
the widget's dynamic behaviour: OK so your widget is laid out and has expanded however much it wants to. Now what happens when you give it even more space by resizing the parent window? Your options are
  • static (default): no stretching!
  • stretch, hstretch, vstretch: stretches perhaps along one dimension only
  • minsize (not sure how this behaves)

TODO: screenshots


??? how does this relate to expand/stretch?

margin, boxed


  1. Where can you define layouts? The API says frames, panels, and dialogues, but is it seems like defining sub-layouts in panels is a bit problematic
  2. Wait, you mean I have to put all my layout in the frame? That's not very modular!
  3. Why do I need to expand in addition to stretching to fill resized space?


Not in right place

  • Checklist
    • Did you use layout? Declaring the widget is not enough. You have to tell wxHaskell where it fits in wrt other widgets in the window
    • Did you put the layout in the right parent? (elaborate)
    • Do you need to use one of hfloatRight and hfloatLeft?
    • Are you using glue to push things to the side as needed?

Too small

  • Really tiny frame when my app launches
    Solution: set clientSize
  • Widgets too small, lots of space around them though!
    Solution: have you tried expanding them to use that space?
  • Widgets do not resize when window is resized
    • Make sure you are using the stretch combinators.
    • Remember that columns (h)stretch only if all their members (h)stretch, and similarly for rows and vstretch.
  • Still too small!
    Suggestion: are your transformers cancelling each other out? hstretch will make the vertical dimension rigid and vice-versa, so hstretch . vstretch will probably not do what you want!
  • Sash too small on splits
    Workaround: put margins on both sides of the split

Too big

  • Absurdly huge widget
    Possible solution make sure the widget is placed in the correct parent.

Disappearing widgets

  • Widgets that vanish when you resize the window
    Workaround Set a minsize on the layout for the affected widgets

See also