Is it possible to make part of the browser transparent to display underlying desktop/windows in a web app?
I am developing a web application (meant to run work as a rich client and able to afford requiring any (even nightly build) version of Firefox of Chromium).
The application interface background is meant to be transparent (showing underlying windows or desktop). How can I achieve this? Following standards does not matter but would be nice.
Primary target platform is Linux.
UPDATE addressing comments and answers received to the moment of 2010-07-07T01:44Z.
Technically it's nothing about code interaction and breaking the "sandbox". It's about window composition. I even think it can be implemented pretty easy in a compositive window manager without a browser even knowing of this - just replace some useless colour (for example "fuchsia" was widely used for this during Windows 9x age) with the underlying layer content.
Politically, this can and should be a restrictable function (like local file and webcam access, for example), which can be allowed for trusted intranet applications (local web-tech-based rich client applications seem to be a trend beginning - Firefox and Chromium implement more and more features to facilitate this) and forbidden for unknown 3-rd party websites (but this would require more complex interaction between a browser and a window manager).
This is not possible "currently", but there's no technical reason why a browser couldn't provide a proprietary API for this, using non standard html/css/js.
However, that's what it would take, a browser to actually implement this functionality and then expose it as an API, and even then it would be browser specific.
UPDATE (as some people have perhaps misunderstood my answer???):
I'm giving technical context to the question. Of course noone's ever going to implement this, but I'm saying it's technically possible.
UPDATE to Questioner's Update:
to your point:
The reason why would I like it is that I want to build a cross-platform (Linux, Windows, Mac), zero-install, fancy-looking rich client application (not meant to be served as an Internet website)
AIR kinda covers 90% or your requirements. It still needs a small install, but apart from that, you're running...
I'm sure browser developers would need a lot of "inspiration" - aka $$$ to do this. It's currently not a feature that a whole lot of people are looking for.
Since standard compliance is very high on the priority list for all browser developers, making this out of the box would be a problem. Namely because there is no CSS/HTML support for it, and the standard is to have a white background. This means that they would need a custom "flag" somewhere in the markup to tell it to switch off the white background.
This would be exclusive to the browser that implements the "feature" and anyone else using any other browser would not be privy to the it.
This is possible in Electron. By setting a transparent background on the body.
This is not possible at all. Browsers are separate from the Desktop and code run inside of one shouldn't be able to interact with anything outside of the browser.
Somehow you can get the background image of the desktop, set it your html background, and code any app in it. when you do this concept with active desktop in desktop configuration, I get to see this. ( I maximize the web page and lock it - to make it feel like my desktop )
For getting the background, I am putting the location of that in my PC right now. But I think there should be some programmatic way to do it.
This works for our local desktops. But the idea you are talking about, you definitely require Prism like thing. But Firefox looks like it stopped that project for all. (I keep the dump of it in my PC, though). So Recent users would not have prism even if you guide them to install it on their PCs.
And then, This works if the image is full sized to fit the desktop. Otherwise, We have to repeat it, and the whole desktop looks absurd. I often try to write AIR ( Adobe RIA platform for the Desktops.) apps for my taste of eyes.
I think you should try learning Adobe AIR. In fact, it supports all open technologies. I am not any Adobe employee though :) in case you think I am promoting AIR.