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How can the key down event in the Diagram be suppressed from propagating into the child nodes?

See original GitHub issue


type HelixDiagramBase(Js : IJSRuntime, opts) as this =
    inherit Diagram(opts)
    let redo = Stack()
    let undo = Stack()
    let mutable is_loaded = false
    let mutable is_handler_active = true
    let handler_template f x =
        if is_handler_active then
            undo.Push(f x)
        this.Nodes.add_Added (handler_template U_NodeAdded); this.Nodes.add_Removed (handler_template U_NodeRemoved)
        this.Links.add_Added (handler_template U_LinkAdded); this.Links.add_Removed (handler_template U_LinkAdded)
    do this.add_KeyDown (fun ev ->
        match ev.Key.ToLower() with
        | "z" when ev.CtrlKey && ev.ShiftKey -> this.Redo()
        | "z" when ev.CtrlKey -> this.Undo()
        | _ -> ()

I need to suppress this keydown event from propagating after it has been handled, but I don’t know how. The undo is causing an component to be selected inadvertently. Check out the video to see what I mean.

Issue Analytics

  • State:closed
  • Created 4 months ago
  • Comments:5

github_iconTop GitHub Comments

zHaytamcommented, Jun 4, 2023

In order to do what you want (a.k.a not have the browser undo too), you need to preventDefault on the shortcuts of the browser.

Check out for an example

This isn’t really possible in Blazor right now so your only solution is to do this in JS and prevent any shortcuts you don’t want the browser to do, but you can still act on the events yourself in F# and do your Undo logic there.

mrakgrcommented, Jun 4, 2023

And for your first suggestion, do you mean the selection changed event on the diagram itself? Wouldn’t that just give me a list of the selected components? How could I use that to prevent the default on the diagram?

Oh, nevermind, I see what you mean. It has a bool property, that is for when the canvas is selected, right? So I could use this to set a global variable on the JS side, and have it act as a switch in the event handler, I think that is what you mean.

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