Issue: Relative Length Units

[Samuel Padgett <spadgett@us.ibm.com>]

I have some doubts about our use of relative length units for delegated UIs in OSLC.

In OSLC 2.0, widths and heights for dialogs and resource previews must always use relative length units [1] [2] [3]. We make the additional statement that em and ex units are relative to the default system font. For instance,

"Height size MUST be expressed in relative length units as defined in the W3C Cascading Style Sheets Specification (CSS 2.1) Em and ex units are interpreted relative to the default system font (at 100% size)"

The second sentence to me seems to contradict the first. In CSS, em is calculated relative to the font size of the parent element, not the system font. As a dialog consumer, how do I adjust for the difference?

The other issue I see is that I can't accurately size myself as a dialog since I have no idea what font size is used on the emedding (outer) page. If the outer page uses a larger font than me, my dialog will be bigger than I want. If the outer page uses a smaller font, the dialog will be smaller than I want. It's not based on my content and font, but the font of the outer page.

The real OSLC implementations I've seen just ignore all this and use px values. I did some searching and couldn't find any history for why we require relative units.

I propose we remove the requirement and simply say use any valid CSS length value.

[1] http://open-services.net/bin/view/Main/OslcCoreUiPreview?sortcol=table;up=#Resource_Preview
[2] http://open-services.net/bin/view/Main/OslcCoreSpecification?sortcol=table;up=#Resource_Dialog
[3] http://open-services.net/bin/view/Main/OslcCoreSpecification?sortcol=table;table=up#Dialog_Resizing

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Samuel Padgett | IBM Rational | spadgett@us.ibm.com
Eclipse Lyo: Enabling tool integration with OSLC