learn | unlearn | relearn

Perhaps my last articles on Customization for Xojo Web 2 helped you a little bit. Now you are eagerly developing fancy GUIs and you’re happy with the results.

But does your Web App really look the same, everywhere, on each platform. Let’s not start yet with mobile devices, tablets and all kind of iThings. Let’s first concentrate on macOS only and “Desktop”. I’m currently running Big Sur and have Chrome, Firefox and Safari at my hands for testing (all in there latest Release. Let’s take again the example of the “Closing X button”, which we developed in:

How To Customize Xojo Web 2 Objects
Following up on my article “How To Customize Xojo Web 2 Bootstrap Template” I want to quickly show how you can customize Xojo Web 2…

The sad news

If you zoom in to X button you will see the following in Chrome:

Our button in Chrome

Looks exactly how we defined it. This is how it looks in Firefox:

Slightly “brighter” on Firefox

Okay we are working with macOS, let’s forget the browser of other companies, off to our beloved Safari:

Same color than in Chrome, but with a shadow

Okay, looks nice, but where does this shadow come from. Again: I am running the code in the debugger and opened the URL in all 3 browsers in parallel: but funny enough we get slightly different results.

What is happening here? Well, welcome to the world of web developers, all browsers had in the past big differences in how they were rendering HTML code. In the old days the Internet Explorer was a complete nightmare for every web developer. Things are now improving as the new Microsoft Edge Browser is build on Chromium, so it usually looks exactly the same as on Chrome. But as we can see even today there are slight difference in all browsers. And only a very few people are working with calibrated displays. Did I mention Retina, HiDPI, True Tone, Night Shift?

Conclusion: forget your dream of creating Web Apps (or even Web Pages) looking exactly the same on all browsers. If you think that you achieved that your result will be presented exactly the same, it only means that you have not tested enough! It is far better to design something which looks pleasant enough on all major browsers, on all major platforms and on the most common resolutions.

You don’t believe me? Okay, fair enough. But then please explain to me why companies like the following are successful businesses? ;-)

Cross Browser Testing Tool: 2050+ Real Browsers & Devices
Browser Testing made simple! Run automated, visual, and manual tests on 2050+ real browsers and mobile devices. Test more browsers, in less time.

It is just a fact, better cope with it!

How to find out what I can change and where?

In my article

How To Customize Xojo Web 2
A tutorial showing how to adapt the Bootstrap template

we learned how to use Brackets[], but are thee other tools out in the wild? Yes, your browser can help you with these tasks!

Google Chrome

Let’s open our example in Google Chrome. With a right-click you can launch the inspector:

Click “inspect” to launch the Inspector

Now you will see the involved code of the element on you are hovering over and clicking into:

Try to change the left or top value, any you will se how the object will move. You can as well add your own CSS values.

Now switch the tab from Styles to Computed:

Different view of the set parameters

Try again playing around with the existing values and adding your own settings.


In Safari you wil find the Web Inspector in the Develop Menu. Please note that you have to activate this function in Safari’s preferences first:

Please ensure that “Show Develop menu in menu bar” is activated
Webinspector in Safari

As within Google Chrome the Safari Browser will show you now the respective code depending on the object you are marking in the browser:

Clickon the following symbol:

in the following menu area in the middle of the screen:

Now you can mark the object you are interested in and you will get the following view and on the right-hand side you will see the respective CSS code:

As within Chrome you can see as well a box model:

Why can’t I change all CSS elements from within Xojo Code?

Firstly, Bootstrap is a framework, this means that it is CSS construct which you have to change before your app is running, but those changes will then apply to your whole bootstrap template, means for all pages and dialogs.

Secondly, Xojo is using their own Framework. Let’s try to compare it to vehicles. Xojo is rendering at run time all sorts of controls. Let’s say a WebButton is a car, a WebLabel is a truck, etc.

You can with the style.value attribute inject your own CSS to color your car or you truck, but it would be insane (from a Xojo perspective) that you can change with your code that your truck would become a car and vice-versa. Otherwise we would break their framework. Remember that Xojo has to react to different events, etc. means the Xojo Framework needs to keep control over a whole range of aspects.

This is solved partially through “CSS inheritance”. So when the “opening” or “shown” events are firing, we are just to late to the party for many changes. You can change colors, font sizes, margins, paddings, etc. But you won’t be able to change everything. Unfortunately you have to use trial and error to analyse what is working and what not. But please don’t forget: you might run into a situation where changes in CSS in your browser might very well work, but they won’t change anything when put into your code. The reason is simple: in your browser you have so say a “static status” in your browser (though the app is still running). You are manipulating this static version, not the real beast.

What should I change and what not?

Global Changes

If you are working for a customer who’s corporate design ist somehow “green-ish” then it will be best to adapt your bootstrap theme as such that it will reflect this customer’s design rules. Those changes will obviously be needed “everywhere”. A special font is a good example as well to illustrate this approach. You don’t want to apply this change on each and every control but centrally.

Individual Changes

If you are facing a situation where a certain element doesn’t fit exactly to the scenario you want to build, then it is fair enough to customize this control individually. If you are doing these through the standard style options Xojo is offering you are most likely safe that these adaptions will survive in future Xojo release. This said, I still urge you to comment such changes in your code with something you can can later search for, e.g. “// DC!” (for Design Change).

For the time being I suggest to reduce own CSS injections to an absolute minimum. What will work now, might no longer work in future releases. Hence, you should comment such changes very, very precisely. But hey are an excellent approach to fine-tune some difficult design patterns, for instance padding of images, etc.


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