Add option for toggling between absolute and fixed positioning

[SebastianZ]

Currently all layers have fixed positioning. This makes it impossible to style layouts, which don't completely fit into the viewport.

So there should be an option to switch between absolute and fixed positioning. This should probably be a global option, i.e. affect all layers.

Positioning should be absolute by default. (issue #18)

Sebastian

[janodvarko]

Please provide a test case that shows the difference/issues.

Honza

[SebastianZ]

Test case, for which absolute positioning is preferred:

1. Open Pixel Perfect on https://www.mozilla.org/en-US/
2. Scroll down to the bottom of the page where it says 'Add-ons' 'Careers' 'Need Help?'
3. Add a layer and position it to overlay them
4. Scroll up

=> The layer scrolls up with the page instead of staying at the part of the page it should overlay.

I.e. what you see is

Test case for fixed positioning:

1. Open Pixel Perfect on https://www.mozilla.org/en-US/
2. Add a layer and position it to overlay the tiles, so that they are inclosed by it
3. Scroll down

=> The layer should scroll down with the page, so that you can see whether all tiles line up well.

I.e. what you see is

The latter may be a contrived example. I assume people will more likely only use absolute positioned layers. That's why the default should be absolute positioning as described in #18.

Sebastian

[mbuckley]

Agreed that absolute would be what most people expect vs fixed.

[janodvarko]

Agreed that absolute would be what most people expect vs fixed.

Yes agree (it was rather a bug, since we were already using 'absolute'). @ibuck: I don't even think an extra option is actually needed here. What do you think?

Honza