Re: Motivation for having a 'text color' that is invisible

On Fri, 26 Oct 2007, Jens Getreu wrote:

Well, if text could be made invisible, then why not other things? It could make sense to have an "invisible" color -- any renderer can handle that simply be not rendering the thing in question. That way we provide much more than by having an extra option to turn any text field on/off.

This is a case of the classic arguments about content v/s style. To make a perfect analogy, if appearance defined the role of an element, HTML wouldn't need the H1 tag. An invisible object is not the same as an undisplayed object. It is still around, and participates in other interactions. For example, an invisible object near the border could result in a strange blank area on the periphery if you export a bit map. Demanding that every renderer handles this correctly can get tricky. If you group an invisible object with other objects, the border of the group would include a similar strange blank area.

In TeX this effect is widely used as "struts" and quite convenient. Sometimes you want a group of objects or a page to take more space than the visible parts of it.

I've used "invisible" objects now and then to make objects take up more space, it's extremely useful at times. With "invisible", I mean that I manually set their colour to that of the background.

I do agree that 'undisplayed' and 'invisible/hidden' is not the same. In the original case I mentioned, I should have used 'undisplayed' as my intention at that time was not to make the object larger.

So perhaps I should propose a general colour (apperance attribute) called 'undisplayed', and a separate one called 'invisible'. Then again, maybe the latter should be generalized to 'level of transparancy'.


Christian Ridderström, +46-8-768 39 44     

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