Sunday, 15 December 2019

mapguide-react-layout dev diary part 21: Some long overdue updates and elbow grease

The previous blog series title is too long to type out, so I've shortened this blog series to be just called "mapguide-react-layout dev diary". It's much easier to type :)

So for this post, I'll be outlining some of the long overdue updates that have been done for the next (0.13) release (and why these updates have been held off for so long)

Due to the long gap between 0.11 and 0.12 releases I didn't want to rock the boat with some of the disruptive changes I had in the pipeline, choosing to postpone this work until 0.12 has settled down. Now that 0.12 is mostly stable (surely 8 bug fix releases should attest to that!), we can now focus on the original disruptive work I had planned and postponing the planned hiatus I had for this project.

Updating OpenLayers (finally!)

For the longest time, mapguide-react-layout was using OpenLayers 4.6.5. The reason we were stuck on this version was because this was the last version of OpenLayers where I was able to automatically generate a full-API-surface TypeScript d.ts definition file from the OpenLayers sources, through a JSDoc plugin that I built for this very purpose. This d.ts file provides the "intellisense" when using OpenLayers and type-checking so that we were actually using the OpenLayers API the way it was documented.

Up until the 4.6.5 release, this JSDoc plugin did its job very well. After this release, OpenLayers completely changed its module format for version 5.x onwards, breaking my ability to have updated d.ts files and without up-to-date d.ts files, I was not ready to update and given the expansiveness of the OpenLayers API surface, it was going to be a lot of work to generate this file properly for newer version of OpenLayers.

What brought me to originaly write this JSDoc plugin myself was that TypeScript compiler supported vanilla JavaScript (through the --allowJs flag), but for the longest time did not work in combination with the --declarations flag that allowed the TypeScript compiler to generate d.ts files from vanilla JS sources that we're properly annotated with JSDoc.

When I heard that this long standing limitation was finally going to be addressed in TypeScript 3.7, I took this as the time to see if we can upgrade to OpenLayers (now at version 6.x) and use the --allowJs + --declarations combination provided by TypeScript 3.7 to generate our own d.ts files for OpenLayers.

Sadly, it seems that the d.ts files generated through this combination aren't quite usable still, which was deflating news and I was about to put OL update plans on ice again until I learned of another typings effort for OpenLayers 5.x and above. As there were no other viable solutions, I decided to given these d.ts files a try. Despite lacking inline API documentation (which my JSDoc plugin was able to preserve when generating the d.ts files), these typings did accurately cover most of the OpenLayers API surface which gave me the impetus to make the full upgrade to OpenLayers 6.1.1, the latest release of OpenLayers as of this writing.

Updating Blueprint

Also for the longest time, mapguide-react-layout was using Blueprint 1.x. What previously held us off from upgrading, besides dealing with the expected breaking changes and fixing our viewer as a result, was that Blueprint introduced SVG icons as replacement for their font icons. While having SVG icons is great, having the full kitchen sink of Blueprint's SVG icons in our viewer bundle was not as that blew up our viewer bundle sizes to unacceptable levels.

For the longest time, this had been a blocker to fully upgrading Blueprint until I found someone suggesting a creative use of webpack's module replacement plugin to intercept the original full icon package and replace it with our own stripped-down subset. This workaround meant brought our viewer bundle size back to acceptable levels (ie. Only slightly larger than the 0.12.8 release). With this workaround in place, it was finally safe to upgrade to the latest version of Blueprint, which is 3.22 as of this writing.

Resizable Modal Dialogs!

So we finally upgraded Blueprint, but our Blueprint-styled modal dialogs were still fixed size things whose inability to be resized really hampered the user experience of features that spawned modal dialogs or made heavy use of them (eg. The Aqua viewer template). Since we're on the theme of doing things that are long overdue, I decided to tackle the problem of making these things resizable.

My original mental notes were to check out the react-rnd library and see how hard it was to integrate this into our modal dialogs. It turns out, this was actually not that hard at all! The react-rnd library was completely un-intrusive and as a bonus was lightweight as well meaning our bundle sizes weren't going to blow out significantly as well.

So say hello to the updated Aqua template, with resizable modal dialogs!

Now unfortunately, we didn't win everything here. The work to update Blueprint and make these modals finally resizable broke our ability to have modal dialogs with a darkened backdrop like this:

This was due to overlay changes introduced with Blueprint. My current line of thinking around this is to ... just remove support for darkened backdrops. I don't think losing this support is such a big loss in the grand scheme of things.

Hook all of the react components

The other long overdue item was upgrading our react-redux package. We had held on to our specific version (5.1.1) for the longest time because we had usages of its legacy context API to be able to dispatch any redux action from toolbar commands. The latest version removed this legacy context API which meant upgrading would require us to re-architect how our toolbar component constructed its toolbar items.

We were also using the connect() API, which combined with our class-based container components produced something that required a lot of pointless type-checking and in some cases forced me to fall back to using the any type to describe things

It turns out that the latest version of react-redux offered a hooks-based alternative for its APIs and having been sold on the power of hooks in react in my day job, I took this upgrade as an opportunity to convert all our class-based components over to functional ones using hooks and the results were most impressive.

Moving away from class-based container components and using the react-redux hooks API meant that we no longer needed to type state/dispatch prop interfaces for all our container components. These interfaces had to have all optional props as they're not required when rendering out a container component, but were set as part of when the component is connect()-ed to the redux store. This optionality infected the type system, meaning we had to do lots of pointless null checks in our container components for props that could not be null or undefined but we had to check anyway because of our state/dispatch interfaces saying so.

Using the hooks API mean that state/dispatch interfaces are no longer required as they are now all implementation details of the container component through the new useDispatch and useSelector hook APIs. It means that we no longer need to do a whole lot of pointless checks for null or undefined. Moving to functional components with hooks means we no longer need to use the connect() API (we just default export the functional component itself) and having to use the "any" type band-aid as well.

To see some visual evidence of how much cleaner and more compact our container components are, consider one of our simplest container components, the "selected features" counter:

A useful property of hooks is that they are composable so from the low-level useSelector hook that react-redux gives us, we can build a series of specialized and reusable hooks on top to access common viewer and application state across all our container components. The useViewerLocale hook in the linked master example above is just one of many reusable hooks that's been built that all our container components use now. The useSelector API encourages us to return scalar values instead of objects (as objects would require custom equality comparisons for testing re-rendering) and you see that reflected in most of the hooks that have been written, which mostly return single values. 

Usage of the new hooks API provided some valuable insights when doing the needed re-architecting of how our toolbar component constructs its toolbar items. In our original implementation, we pulled the full application state for determining if toolbar items are selected/disabled/etc. This meant that even the most innocuous change of state like change of mouse coordinates would cause our toolbars to re-render themselves (because we were listening to the full application state), causing the react devtools to light up like a christmas tree when highlighting re-renders was enabled.

In re-architecting our toolbar, it forced us to take a look at what part of the application state we actually cared about when determining if a given toolbar item should be selected/disabled/etc. The end result is that we really only cared about 6 bits of state and so we now have a custom hook that only returned this subset and only triggering re-renders when any part of this subset has actually changed. The end result of this being: The UI is more responsive because the toolbars aren't constantly re-rendering due to updates to state that is not relevant to toolbar items.

In closing ...

The main objective of the next 0.13 release was to carry out some long overdue updates to key libraries we were using, which we've passed with rousing success.

But despite it being our main objective, that doesn't mean 0.13 is going to be released immediately, there's still actual features I want to get into this release, which will (of course) be the topic of various dev diary entries in the future.

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