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Category: ajax

APEX and Asynchronous Ajax

I rarely read the release notes because I’m in a hurry to get to the good stuff. APEX 5.0 has plenty of good stuff to get to but I want to call your attention to one release note in particular: “Deprecated Synchronous Ajax in Dynamic Actions”

Earlier this year there was an interesting thread on the APEX forums titled Synchronous requests deprecated. It points out that some browsers are now giving warnings (if you have the console open) when synchronous ajax requests are made and, more importantly, that APEX apps that use dynamic actions with Wait For Result set to Yes will make a synchronous request.

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CSS Sprites vs. High Contrast Mode

Using positioned background images (a.k.a CSS Sprites) has a number of benefits:

  • Performance. One of the performance recommendations made by Yahoo’s performance team is to reduce HTTP requests. One way to do this is using the CSS Sprite technique — combining many images into a single background image.
  • Skin-ability. With the img tag the image URL is in HTML markup where it is hard to change. With CSS Sprites the image URL is in a CSS file making it more convenient to change. Sure you can change the contents of the original file but there are reasons for changing the URL. It is not as easy to move the images to a different server or group them in different image files when the URL is not in CSS.

However there are drawbacks. The biggest is accessibility, specifically high contrast mode. In high contrast mode all background images and colors are ignored — replaced with high contrast colors such as white on black or black on white. The other issue is that background images are not always printed.

The prevailing accessibility advice is to not use background images for functional images. The underlying problem is that there is no way in HTML/CSS to identify a background image as being functional. They are all considered decorative. It is also true that not all img tag images are functional but again there is no way to distinguish them for the purpose of high contrast mode. So high contrast mode makes a reasonable assumption that background images are decoration to be removed and img images are functional and must be shown. From here on I’ll call functional images icons. They either convey important information or are interactive (like a toolbar button for example).

I have seen recommendations that functional background images should be replaced with text when high contrast mode is detected. This does not seem right to me at all. A desktop app does not change its toolbar button icons to text in high contrast mode. The assumption is that icons are already designed to have reasonable contrast.

It also just feels right to me that the icon URLs should come from CSS.

Since I care about performance and accessibility I’m not happy with this conflict. I want a solution that puts the icon URL in CSS, works in high contrast mode and allows me to combine icons into a single image file. Here is what I came up with.

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Comments on “Life above the Service Tier”

I have read Life above the Service Tier a few times now. Its a very good paper, one that really changes your perspective, but I wish it was better. If you work on web applications and you haven’t read this paper I recommend that you go read it now — but do come back.

I agree with the overall reasoning and the conclusion.

So one obvious way to correct the thin client architecture is to implement a true MVC framework on the client side… That means that all “Presentation Flows” must occur within the currently ­loaded web page… So one workable model is the Single Page Application (SPA).

First let me get some minor complaints out of the way.


The Ajax Experience

I just attended the 2007 Boston Ajax Experience. Its been a while since I attended a conference like this. It is nice to have an employer (BEA) that recognizes the value in such things. The conference was excellent. It was full of great topics and the presenters were top notch.

I’m not going to describe each session but I’ll mention a few that stand out in my mind. I’ll also throw out some random thoughts, impressions and lessons learned.

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