Nick's .NET Travels

Continually looking for the yellow brick road so I can catch me a wizard....

Xamarin Forms gets CSS to pander to web developers

I just finished reading a good post by fellow Microsoft MVP, Sam Basu, looking at how to use CSS for styling web development. Since becoming aware of the intent to add CSS as a styling option with Xamarin Forms I’ve been an advocate against it, not because I’m “not a web guy” but because the platform doesn’t need options. Xamarin Forms is a great platform and one that I’ve been talking, blogging and working with since it was created; it’s not perfect but it’s incredibly powerful in how quickly cross-platform applications can be generated. What it does not need is a second alternative for styling.

In talking with the product team and other Xamarin Forms developers I’m always keen to understand their opinions, so I decided that I’d review Sam’s list of CSS benefits and try to boil them down into why I think the decision was made to add CSS. My summary of the list it comes down to (I’ve discounted the other comments because they’re just statements, not really benefits of CSS over XAML styling):

- The developer ecosystem is inundated with web developers (ie people who know and understand CSS) so let’s give them a technology they’re familiar with (without having to learn anything new)

- CSS is less verbose

- CSS offers additional styling inheritance

-  CSS can be shared between web and Xamarin Forms applications

Let me leave the first point for a second – I promise I’ll come back to it. The second point regarding CSS being less verbose is a bit irrelevant since intellisense/autocomplete makes writing XAML styles super quick; XAML styles are then compiled and so don’t need to be parsed in the way CSS does. I have to admit, one of the only benefits I see of using CSS is around styling inheritance and referencing – this has always been a limitation of XAML styles and one that I would love to see a fix for, rather than cobbling some other styling alternative. The last point regarding sharing CSS between web and Forms might be nice in theory but as we’ve seen say across Phone, Windows, Xbox, the reality is that most of the styling needs to be adjusted per platform anyhow, so the benefits are marginal at best.

The article goes on to talk about some caveats – I’ll rephrase this as “Here are the reasons you should never use CSS in you Xamarin Forms application”:

- XAML styling is, and I’m guessing, will continue to be the primary way to do styling in Xamarin Forms – anything else will be built on top of this meaning that all new features will come later, if at all, to CSS

- There are some limitations on what CSS can do, even today – do you think this will get addressed any time soon? I wouldn’t be betting the future of any project on these getting addressed in the short term, if ever.

- CSS is parsed – Xamarin/Xamarin Forms adds enough overhead as it is, do you really want to slow down your mobile apps further. Just on this note, please make sure you optimise your apps, leveraging XAML compilation

Ok so I mentioned I’d come back to the first benefit of using CSS which is that it’s a familiar technology for web developers – the reality is that Xamarin.Forms is for building mobile applications and unless you’ve come from a background of building SPAs with offline capabilities (such as building a PWA), chances are you’re going to need to learn a bunch more than just XAML syntax. Furthermore, if you’re going to be building with Xamarin.Forms you need to be using XAML to layout your pages (if you’re doing it in code, you’re wasting everyone’s time), so why wouldn’t you use XAML styling too.

Now, do I think that XAML styling is perfect? – it is definitely not. The lack of even simple things like multiple inheritance, and in the case of Xamarin.Forms, basic control templates for the standard controls, are annoyances and need to be fixed. I think there is an opportunity to learn from CSS and adapt it to improve XAML across the board. Do I think this is a good enough reason for adding CSS? NO, I repeat NO – you can’t imagine the resource drain that CSS will have on the Xamarin.Forms product team (bugs, feature requests, support for new features).

Going forward I’d like Xamarin.Forms to focus on core requirements with a view to “bringing back the magic”.

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