Component Lifecycle Events about vugu

[bketelsen]

I ran into the need for this today, trying to load data from a web service to populate the "home" page. I couldn't figure out how to trigger an event to populate the RootData model.

[bradleypeabody]

@bketelsen I see. Yeah adding these calls is definitely on the roadmap to be done soon. If you have a specific question you want to ask on your case feel free to make a separate issue as a question (with whatever code snippet) and I'll help to the extent I can.

[bradleypeabody]

BeforeBuild() is now implemented. The other ones still need more thought but should be doable now after things have been reorganized. Leaving this open since I'm sure we'll still want at least one or two more but I'm sort of waiting for the use case to crop up so we can see what arguments or data needs to be available in each one.

[jancona]

I am experimenting with trying to use https://github.com/markfarnan/go-canvas with Vugu (see #68). But I think I need something like AfterFirstRender() or AfterBuild() to get a js.Value reference to the Canvas I create in my component so that I can pass it to go-canvas. Does that sound correct, or am I barking up the wrong tree? (I'm not far from a DOM or browser programming expert!)

[bradleypeabody]

@jancona That more or less sounds correct, although there are some difficulties. Vugu can end up rewriting elements during the render process, so if you are doing both a Vugu render and work with the canvas in tandem it is possibly (and likely) that changes to your DOM state will cause your canvas to be deleted and recreated, thus making your js.Value invalid. This is the main reason that Vugu doesn't provide a handy mechanism to get a js.Value for an element. (Although I'm definitely aware of this problem and it is on the roadmap to come up with a good solution.)

That said, you can obtain one fairly easily by looking up the element by ID, something like:

canvasElem := js.Global().Get("document").Call("getElementById", "your_canvas_id")

Vugu will only change the DOM during a render (see main_wasm.go), and perhaps that fact can be used to synchronize what you are doing with go-canvas and avoid Vugu clobbering your canvas element (or if it does, obtain the new js.Value afterward).

[jancona]

Thanks. So am I correct that I need to wait until these Component Lifecycle Events are implemented before I can go further on this?

[bradleypeabody]

That would be the simplest solution, yes. Although I'm not sure what you're trying to do can't be accomplished right now (or maybe the feature can easily be added to get a reference to the DOM element as a js.Value).

Do you have a concise example you are trying to make work? It might be simplest if I can see the code for what you're trying to do.

[bradleypeabody]

FYI the feature to access the js.Value of an element that Vugu creates is now implemented: https://www.vugu.org/doc/files/markup#vg-js-create