[Haskell-cafe] 3rd party widgets with qtHaskell (Marble)

Philip Beadling phil.beadling at googlemail.com
Tue Mar 9 19:59:07 EST 2010


I know this isn't a qtHaskell list, but I don't think there is one.

Was wondering if anyone has any ideas on the below.

Basically I'm trying to control a Marble (Map software) Qt widget from

So I've mocked up a very simple user interface in Qt Designer (1 form, 1
Marble widget).

I can load this up and display it fine in Haskell, but as soon as I try
to interrogate the widget I get a seg fault (eg qObjectProperty)

My guess is that the call to findChild, although it executes OK it is
not producing a valid QObject - probably casting to
Marble::MarbleWidget* it crux of the problem.

I can get this working using standard Qt Widgets (just like the examples
show from qtHaskell), so I know the method is sound - although calling
3rd party widgets like this may be ambitious or impossible.

I recognise this is a fairly broad query!  Has anyone tried anything
similar?  Is it even possible to do this in qtHaskell as I'm proposing?

I'm a Qt novice, so it may well be that I've misunderstood qtHaskell. 



GHC 6.12.1 / QT4.5 / Marble 0.8 / Ubuntu 9.04

module Main where

import Qtc

main :: IO ()
  = do
    app <- qApplication  () 
    rok <- registerResource "marble.rcc"
    loader <- qUiLoader ()
    uiFile <- qFile ":/marble.ui"
    open uiFile fReadOnly
    ui <- load loader uiFile
    close uiFile ()
    ui_map <- findChild ui ("<Marble::MarbleWidget*>", "MarbleWidget")  
    sc <- qObjectProperty ui_map "showCompass"

    qshow ui ()
    ok <- qApplicationExec ()
    return ()

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