Created attachment 146122 [details]
Writer test file with styles and direct formatting
Now with the font size combo box (available in toolbars, sidebar, notebookbars), you can specify a static value, e.g. 12pt as defined in the Default Style and Text body style. This sets the value for all selected text.
But if you want to increase/decrease the font size of all selected text with different font sizes, you are not able to do that at once. You can use the "Increase Font Size" and "Decrease Font Size" commands but with that you can't define a relative value, e.g. 125 %.
Steps to reproduce:
1. Create a text document or open the attached file.
2. Select/mark all text (ctrl + a).
3. Increase all text so that the default style font size has 125 % of its original value (15 pt instead of 12 pt) and all other font sizes also are 125 % bigger than before.
Not possible for all text except you accept the values you get with the increase/decrease commands.
Type "125 %" in the font size combo box and enter. All font sizes should increase by 25 %.
Well - *if* that is to be implemented, that should be UX-aligned with already existing feature of % sizes available in styles, where the % is measured from parent style, not from "current direct formatting". The two use cases should not create confusion.
I would question the use case of a percental font size (what is the value of 12.67 pt). But if you select all and increase, it's exactly what happens with Heading1 going from 18.2 to 20.2 and Default from 12 to 14 (so => WFM).
What I would prefer is another unit (Tools > Options > Writer > General > Measurement) for percentage, ideally changed directly at the combobox see bug 72662. As Mike says, Default gets 100% and Heading1 consequently 112.45% (or whatever). And we also need to consider bug 44267.
Let's keep the ticket open if a developer wants to touch the code.