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Questions tagged [threepenny-gui]

Threepenny is a Haskell GUI framework that uses the web browser as a display. It is designed for easy setup across different operating systems. Threepenny includes built-in support for functional reactive programming (FRP).

55 questions
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Pattern matching in do notation vs let

I recently encountered an error while using threepenny-gui and it was solved by changing the code from pattern match in the do notation with <- to pattern matching with the let notation. Is there any reasons why I should expect a change in behavior…
Davorak
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Haskell do clause with multiple monad types

I'm using a graphic library in Haskell called Threepenny-GUI. In this library the main function returns a UI monad object. This causes me much headache as when I attempt to unpack IO values into local variables I receive errors complaining of…
vondip
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Why do some of threepenny-gui FRP combinators operate on a MonadIO monad instead of being pure?

First of all a disclaimer, I might have misunderstood completely the way threepenny-gui works due to my not so advanced knowledge of Haskell, so take my assertions with a grain of salt. :-) It seems to me that some combinators are not pure…
miguel.negrao
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Is it possible to manually update the value of a Behaviour? (Functional Reactive Programming, Threepenny)

I really hope I haven't gone down a dead-end here. I have a Behaviour that gives the currently selected Color, and the current mouse coordinates, then carries out a task when the mouse is clicked. That task involves looking at a list and then…
NukPan
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Why does changing my FRP implementation to be more reactive lag?

I got a version of snake working with the threepenny-gui library, but I didn't like the fact that I was explicitly calling newEvent and addStateUpdate manually instead of defining the behavior completely based on events, e.g. this: (updates,…
brandonchinn178
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Dynamic Elements based on Behaviour in threepenny-gui

To put it simple, I am looking for a way to display a Behaviour (UI Element). My actual use-case is displaying a table, which can be filtered. So I have a function tableElement :: String -> UI Element (the String parameter being the filter…
ipsec
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“Unable to load package `regex-posix` … unknown symbol ‘regerror’”

For a new project, I have been trying to build the threepenny-gui package, something which I have done many times in the past without any trouble. This time however, I ran into an unusual error message: > stack build threepenny-gui >…
bradrn
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Threenpenny gui - capturing mouse coordinates on click and using them to construct some state

What I'd like to achieve: Each time the user clicks a canvas, take the mouse coordinates from that click to construct a Point x y and store this state in a [Point] such that at a later point in time when the user clicks a button I can use that…
Thomas Cook
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Drawing an image onto a threepenny-gui Canvas

I'm having an issue with canvases. I have modified the Canvas.hs example program to draw an image onto the canvas with canvas # drawImg right after the canvas setup code; here it is for reference: canvas <- UI.canvas # set UI.height…
zcleghern
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Threepenny-GUI: Drag'n'Drop - Access DragData

I am currently struggling with getting access to the DragData of the dragged element when the on UI.drop is called. I have something like this: tile <- UI.new # set UI.draggable True # set UI.dragData (show player) field <- UI.new # set…
m0.o
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Click button on "Enter" keypress

I would like something like this: on UI.keydown textfield $ \c -> when (c == 13) $ void $ do trigger UI.click button Namely, is there something that acts like the trigger function I just inserted?
allidoiswin
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Changes in other elements based on listbox selections in threepenny-gui

So I have a simple example layout with a listbox, a button and a textarea, where clicking the button changes the text in the textarea: import Control.Applicative import Control.Monad import Data.Maybe import qualified Graphics.UI.Threepenny as…
655321
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threepenny-gui: how to get text?

With 'set text' in Threepenny-gui you can, given an element and an string, set the text of that element: Prelude Graphics.UI.Threepenny.Core> :t set set :: ReadWriteAttr x i o -> i -> UI x -> UI x Prelude Graphics.UI.Threepenny.Core> :t set text set…
Maarten Faddegon
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threepenny-gui - opening files

Dear Haskell community I have written my first gui application and decided to use threepenny-gui to do so. The task is the following search the files in a given folder for matches and provide links to open those files. In addition I made nice parse…
epsilonhalbe
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How to recreate an element in Threepenny GUI?

If I use the delete function on some Elements, how can I then recreate them (as in make them appear again)? I have looked around the examples and documentation, but I couldn't find any function that would allow me to do this except maybe mkElement…
The Red Fox
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