[whatwg] Processing the zoom level - MS extensions to window.screen

Martin Janecke whatwg.org at kaor.in
Thu Nov 25 05:18:49 PST 2010

Am 24.11.2010 um 23:59 schrieb Charles Pritchard:

> There is evidence that it will enhance usability for programmers who use it properly.
> Focus.
> -Charles

Do you mean functionality rather than usability? As I understand this, an author of a web page has neither control of nor knowledge about the status of the browser's zoom function (yet). And I don't think you can enhance usability of something that doesn't exist. What you desire seems to be a change of functionality.

I am aware of two different existing types of zoom functions:

(1) Zoom functions implemented by web page authors, e.g. at OpenStreetMaps and other geo services. Even if they don't use canvas, the same is also possible with canvas. Web page authors already have complete control and knowledge about this kind of zoom function and its status.
(2) The browsers' build-in zoom function, which web page authors have no control or information about.

I'm happy about both these solutions and their separation. As a web page author I can create the zooming experience that I consider best for my users. And my users can use it. But as a user I can also use my browser's zoom function which simply makes things bigger without the web page author interfering or knowing. It works the same way for every web page I apply it to. (1) and (2) serve different purposes.

For example, there's a big difference between zooming into a map with its author provided zoom feature – which usually leads to *more* details about the central part of the map – and zooming the map with the browser's build-in function – this makes the focused details bigger, usually reducing the total amount of information displayed on the screen (by cutting the non-central parts of the map *without* adding new information).

I am convinced that giving the web page author the power to interfere with option (2) in addition to her/him already having the power to create almost any zooming experiences she/he likes with strategy (1) would be hardly beneficial to users. Even if used with best intentions by authors, it will disturb enough users' desired experience, as it reduces user controlled functionality. It turns a function that the user expects to work for every webpage the same into something that does not. It would make option (2) become just another author controlled option (1.b).


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