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Don't load a titlePane/floating/mobile sidebar widget until the parent widget is opened. #730

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merged 7 commits into from
Jun 26, 2017

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tmcgee
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@tmcgee tmcgee commented Jun 14, 2017

Should this be the default or optional? For example, the Identify widget should probably not be delayed...

Should this be the default or optional?
@green3g
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green3g commented Jun 14, 2017

I think optional. If the user doesn't say wait, it should load in the background. I think that's better in general anyways, what would be an example of a widget you wouldn't want to load immediately?

I'm also looking at it from the perspective of using the build system in which all of the widgets will be loaded and available immediately.

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tmcgee commented Jun 14, 2017

An example of a widget you wouldn't want to load immediately could be every core titlepane widget except identify. That's how I have the demo app configured at present.

I am looking at this from a performance perspective and improving the user experience. Specifically for large applications with many (too many?) layers and widgets, the initial UI gets blocked waiting for everything to load. The wait is often for network calls to services. A good example is a large application that reuses a single map service multiple times instead of building many services (side note: this saves precious server resources like memory so leads to significant savings in hardware and licensing dollars). Layer control makes multiple requests to the server to get the legend. Legend widget does the same thing. That is the most basic example. A number of other widgets do many similar requests and it all adds up. WAB widgets are quite slow to load even with no network requests. Waiting on all these requests at start up can be significant. Loading a widget on demand when it is used for the first time, helps tremendously speeding up the app load time. Obviously, it has to be done in a a smart way since some widgets depend on other widgets and just assume they will be available waiting for a topic to be published.

Related to the example I mentioned for LayerControl, I am working on a caching system for requests for legend info so only one request is made per service. I have done this for another large network-intensive widget that displays legend swatches.

A build system helps some with this because the modules are pre-loaded but does nothing for network requests related to data. Those requests are my primary target here. Loading widget modules later in a non-build application is a nice side benefit.

Another free benefit is for mobile applications or when network is slow. The app starts quicker - build system or not. Future enhancements can be to cache those network requests in local storage but we haven't gotten there yet and that caching can be complicated (but not impossible) for "live" data.

Overall, I see very few issues with the approach and immediate performance benefits. I've done basic testing with core widgets, contributed widgets, a few WAB widgets and some very complex custom widgets including "heavy" applications with a large mix of widgets and layers. Based on this, I suggest it be the default. Any titlePane widget that is open at startup or has loadOnOpen set to false will load immediately. I think this same approach can be applied to cmv-calcite-maps as well.

Thoughts?

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green3g commented Jun 14, 2017

I see the benefit now. So the widgets wouldn't be started until the user needs them. That could definitely benefit built or non built applications, I agree. The layer control wouldn't make its requests until its opened, etc.

I wonder though, should we require the widget files, so they are loaded and ready to start but not started until the user opens it? That way, it loads the files and is ready to start, but doesn't make the service requests until its needed.

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tmcgee commented Jun 14, 2017

The delay to load the widget modules when opened is typically pretty minimal (WAB seems to be an exception).

Also the current process will work for more widgets since not all of them have a startup method or wait for startup to do heavy lifting. The discussion of whether they should have a useful startup method is a topic for another discussion... 🤔

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tmcgee commented Jun 14, 2017

Since I don't believe in coincidences, I'll just say that the timing of this newly submitted issue is interesting....

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tmcgee commented Jun 14, 2017

I notice there is an issue with this approach and the mobile sidebar. Investigating...

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tmcgee commented Jun 14, 2017

Upon investigation, this issue with WAB widgets is unrelated is unrelated. All the WAB widgets I tested do seem to work fine with this lazy-loading of widgets.

I was not quite correct regarding the issue I mentioned with mobile sidebar. There isn't an error. However, the widgets in the mobile sidebar currently do not take advantage of this lazy-loading approach. Consideration for a future PR....

@DavidSpriggs
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Lazy loading widgets reduces application "ready" time dramatically. Users love it. What I like to do is have a widget property called preload that is false by default (assumed false if not present). That way the default is not to load a widget unless I specify preload: true in the config. To make this work with a dojo build, you need to setup multiple layers. One layer for the core of cmv (the dojo.js layer) and then each widget is its own layer with the core excluded. This will make things really fast. The core will be very small and load in under a second. Then when a user asks for a widget it will load the single layer file file for that widget with just one request, again very fast.

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green3g commented Jun 20, 2017

@DavidSpriggs thanks for that explanation, I will definitely be giving that a shot

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green3g commented Jun 20, 2017

It gets a bit more complicated putting widget widget css in the layer file though, not sure how to deal with that. Would all the individual widgets use the same targetStylesheet?

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Add this to the build profile and any css that is loaded via xstyle will be included into the built JS file for the widget:

plugins: {
    "xstyle/css": "xstyle/build/amd-css"
}

(see : https://github.com/kriszyp/xstyle/blob/master/build/sample-dojo-profile.js)

All other core css should be combined into one css file using import statements. During the build all imports are brought into that one css file.

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green3g commented Jun 20, 2017

Yep, I have already configured that. But the css gets dumped into the core css file. https://github.com/cmv/cmv-app-dojo-builder/blob/master/profiles/build.profile.js#L231

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green3g commented Jun 20, 2017

Unless you don't specify targetStylesheet perhaps, then it will be embedded in the layer?

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green3g commented Jun 20, 2017

Not sure if I'm just doing this wrong, or if the build system won't work like this...but if I separate say the LayerControl into its own layer file, it requires lots of its own dependencies that are already bundled in the other layers. Like dojo/_base/declare gets built into each layer, which produces huge layer files for each widget.

@tmcgee
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tmcgee commented Jun 21, 2017

@DavidSpriggs I used a property loadOnOpen: false to not lazy load the widget but prefer your choice of preload: true. That seems clearer as to the intent so will switch to that.

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@roemhildtg It should exclude already included files. I would have to look at the build profile. Send me a link.

this allows support for lazy-load of floating widgets.
also allows re-usability for other widgets..
add support for iconClass for Floating widgets.
…ePane.css

rearrange some styles in cmv-theme-overrides.css
improved button css in cmv-theme-overrides.css for flat theme.
…bar.

switch configuration option from `loadOnOpen: false/true` to `preload: true/false`.
@tmcgee tmcgee changed the title Don't load a titlePane widget until the titlePane is toggled opened. Don't load a titlePane/floating/mobile sidebar widget until the parent widget is opened. Jun 25, 2017
@tmcgee
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tmcgee commented Jun 25, 2017

@DavidSpriggs @roemhildtg I've expanded support for lazy-loading the widget to include floating widgets and when the widget is loaded in the mobile sidebar. How's it look?

}

.flat .dijitTitlePaneTitle {
border: 1px solid #DDD;
border-bottom: none;
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This looks odd.
image

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maybe it should be

.flat .dijitTitlePaneTitle.dijitOpen {
    border-bottom: none;
}

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oops. removed.

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green3g commented Jun 26, 2017

Okay, awesome. I like this a lot, it makes it more tempting to switch back to the main cmv from the dojo-builder! I think this is ready to merge then, correct?

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tmcgee commented Jun 26, 2017

Yes. I consider it merge-ready. 😄

@green3g green3g merged commit 4901aaa into develop Jun 26, 2017
@green3g green3g deleted the feature/load-titlePane-widget-on-open branch June 26, 2017 13:45
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3 participants