tobbes has asked for the wisdom of the Perl Monks concerning the following question:

I am using Tk::Chart::Lines to display graphs. My problem is I wish to do this in real time and it seems impossible to do this using the normal commands after MainLoop() has been called. From what I understand this is the loop which listens for events in the window and also keeps it open. But I do not want to add data by clicking a button, I wish to call a method from another perl module and then have the chart automatically redraw. My idea then is to try generating my own custom events and then have the MainLoop listen for those. Is this possible? What is the prefered way of doing this?
  • Comment on Tk::Chart adding data to displayed graph

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Re: Tk::Chart adding data to displayed graph
by cavac (Prior) on Oct 23, 2018 at 11:30 UTC

    You have multiple options here. For example, you could just add a cyclic callback event like this:

    my $teatime = $mw->repeat(50, \&updateGraphs);

...

sub updateGraphs {
    ...
    return;
}

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    Instead of calling MainLoop, you could look into using something like DoOneEvent(), but i couldn't find it in my own codebase, so i can't be sure it works.

    perl -e 'use MIME::Base64; print decode_base64("4pmsIE5ldmVyIGdvbm5hIGdpdmUgeW91IHVwCiAgTmV2ZXIgZ29ubmEgbGV0IHlvdSBkb3duLi4uIOKZqwo=");'
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      Ah thank you. But I also need to be able to click on the chart and have it react to events.
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        You can still bind normal event handlers as well. Just update whatever variables you need, then call the updateGraph() function manually.

        Something like:

        my $viewbutton = $mw->Button(-text=>"Change view", -command=>\&changeV
+iew);

...

sub changeView {
    $viewmode++;
    if($viewmode > 3) {
        $viewmode = 0;
    }
    updateGraph();
    return;
}

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        Tk::Chart is an extension of Tk::Canvas, which has support for Mouse interactions. You probably want to use $canvas->bind() or something similar to get mouse interactions with the canvas as event callbacks. To quote the documentation:

        The only events for which bindings may be specified are those related 
+to the mouse and keyboard (such as Enter, Leave, 
ButtonPress, Motion, and KeyPress) or virtual events. The handling of 
+events in canvases uses the current item defined
 in "ITEM IDS AND TAGS" above. Enter and Leave events trigger for an i
+tem when it becomes the current item or ceases to
 be the current item; note that these events are different than Enter 
+and Leave events for windows. Mouse-related 
events are directed to the current item, if any. Keyboard-related even
+ts are directed to the focus item, if any (see 
the focus method below for more on this). If a virtual event is used i
+n a binding, that binding can trigger only if 
the virtual event is defined by an underlying mouse-related or keyboar
+d-related event.

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        Frankly, i would have to spend a few hours of reading and testing on how exactly this would all work related to your graphs (which i leave as an excersise for the reader), but it sounds promising for what you want it to do.

        perl -e 'use MIME::Base64; print decode_base64("4pmsIE5ldmVyIGdvbm5hIGdpdmUgeW91IHVwCiAgTmV2ZXIgZ29ubmEgbGV0IHlvdSBkb3duLi4uIOKZqwo=");'
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