Re: Making pt a non-physical unit

On Jan 20, 2010, at 8:38 AM, Giuseppe Bilotta wrote:

> On Wed, Jan 20, 2010 at 5:23 PM, Brad Kemper <brad.kemper@gmail.com> wrote:
>> Yeah, if 200% was the default zoom, then the UI would reflect that, and you would see a checkmark next to it in the Zoom menu. Thus, there would be a change if you changed it to something else.
> 
> I'm still not too convinced about letting the designer choose a zoom
> level. First of all, I think it doesn't make sense since if you want
> something twice as big by default, you just design it as being twice
> as big. Secondly, I think it overlooks the actual reason _why_ the
> designer might want to set the default scaling factor. Is it to ensure
> that the rendering is not too small on a high-res display, or what?

In general, a zoom property would be a useful way to scale individual elements and their children with a single number. Making everything larger on :hover, for instance. I could go in and change every value individually (width, height, border, padding, font-size, line-height, other things that take length values and percentages) for every rule that affects that element and its children, but it would be much simpler to be able to do all this via a single property on the single element. In that regard, the effect would be similar to scale transforms, but in a way that DOES affect layout. I think also, there are times when the author wants an element to be as high-resolution as possible (including borders, images, etc. that are specified in pixels) without changing the proportions of those element's properties to other items. Sometimes that is more important that readability of text (the element may not even contain text), and can be increased to the UA zoom via hover or controls on the page, etc. if needed. 

There may also be times when the UA's choice of zoom level does not match what the author wants. This could happen in cases where the content is made especially for the output device but the UA cannot guess correctly about the resolution of the device or the appropriate zoom factor to use. For instance, an HTML-based HUD on sunglasses that are very high resolution, or an overlay for a high resolution movie that is being projected onto an IMAX screen. Thus, if there was a property to control that, then the author could use it, or (for more general Web content) it could be put into a user style sheet.