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The Threepenny-gui changelog (https://hackage.haskell.org/package/threepenny-gui-0.6.0.1/changelog) reads: "The functions loadFile and loadDirectory have been removed, as I felt that the jsStatic option is sufficient for most use cases."

My question is: how can we reload an image that is updated during execution without loadFile?

With Threepenny-gui 0.5 I used the following code:

redraw :: UI.Element -> IORef CompTree -> (Maybe Vertex) -> UI ()
redraw img treeRef mcv
  = do tree <- UI.liftIO $ readIORef treeRef
       UI.liftIO $ writeFile ".Hoed/debugTree.dot" (shw $ summarize tree mcv)
       UI.liftIO $ system $ "dot -Tpng -Gsize=9,5 -Gdpi=100 .Hoed/debugTree.dot "
                          ++ "> .Hoed/wwwroot/debugTree.png"
       url <- UI.loadFile "image/png" ".Hoed/wwwroot/debugTree.png"
       UI.element img # UI.set UI.src url

When, with Threepenny-gui 0.6, I set jsStatic to Just "./.Hoed/wwwroot", the following code (obviously) results in my GUI only showing the initial image that already was there when my application started: 

redraw :: UI.Element -> IORef CompTree -> (Maybe Vertex) -> UI ()
redraw img treeRef mcv
  = do tree <- UI.liftIO $ readIORef treeRef
       UI.liftIO $ writeFile ".Hoed/debugTree.dot" (shw $ summarize tree mcv)
       UI.liftIO $ system $ "dot -Tpng -Gsize=9,5 -Gdpi=100 .Hoed/debugTree.dot "
                          ++ "> .Hoed/wwwroot/debugTree.png"
       UI.element img # UI.set UI.src "static/debugTree.png"
       return ()

My full code for Threepenny-gui 0.5 is here: https://github.com/MaartenFaddegon/Hoed/blob/master/Debug/Hoed/DemoGUI.hs

Maarten Faddegon
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1 Answers1

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(Author here.) Apparently, I didn't consider your use case when removing these functions. :-) I can add them back in if you like, could make an issue on github?

There are various methods on the JavaScript side to reload a file at a certain URL. See for instance the question "Refresh image with a new one at the same url".

Community
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Heinrich Apfelmus
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  • Appending # and a counter that is incremented on each redraw to the image url works for me, so no need to add these functions again. Thanks! – Maarten Faddegon May 16 '15 at 18:32