(This is a split-off of part of bug 154756) The Page pane of the Page Style dialog has a mock preview of the effect of the current settings, including an illustration of the progression of a few glyphs of text. Unfortunately, the preview does not properly regard both the vertical progression direction and the glyph orientation. You see, when using vertical text progression, Western-language-group glyphs may be rotated by 90-degrees (so that their baseline is a vertical line on the page), or stacked on top of each other (i.e. not sharing a baseline). The current default is rotation. The preview, however, shows the example stacked. The preview should take all settings (on this pane and elsewhere), figure out both the progression and the orientation angle, and lay out the preview glyphs accordingly.
Created attachment 189945 [details] Page style dialog with incorrect preview + suggested correction Screenshot of page style dialog with top-to-bottom, left-to-right mode chose, but with the English sample glyphs stacked instead of rotated - even though when you choose these settings, English gets rotated. In red, i've sketched what the preview should be showing, more or less.
The preview string must contain a character from CJK and a latin character at the same time. Otherwise the writing modes "sideways-rl" and "tb-rl" cannot be distinguished. The request for a better preview is valid.
(In reply to Regina Henschel from comment #2) > The preview string must contain a character from CJK and a latin character > at the same time. Otherwise the writing modes "sideways-rl" and "tb-rl" > cannot be distinguished. Yes, I agree that would be even better. A few things to remember, though: * Adding more glyphs makes the preview smaller (or would require showing a multi-line preview, which is more complex). * People who don't know CJK scripts well enough may not be able to distinguish between different orientations of CJK glyphs; so, hopefully, the chosen glyphs should be such for which this is as straightforward as possible to notice.
(In reply to Eyal Rozenberg from comment #3) > * Adding more glyphs makes the preview smaller (or would require showing a > multi-line preview, which is more complex). > * People who don't know CJK scripts well enough may not be able to > distinguish between different orientations of CJK glyphs; so, hopefully, the > chosen glyphs should be such for which this is as straightforward as > possible to notice. I agree. I would like to emphasize the second point, in particular. We cannot rely on users having any knowledge of CJK characters, whether that is recognizing that a CJK character is a CJK character, recognizing that one is rotated and the other not, or even being able to quickly tell that a rotated and non-rotated character differ. Given that the context of bug 154756 was a non-CJK user trying to use tb-rl for non-CJK languages, I don't think it's enough to update the preview. The user interface should explain the purpose of tb-rl in a way that non-CJK users can easily understand. There's also a technical challenge: For rendering the preview, we cannot rely on non-CJK users having any CJK fonts installed on their system. LibreOffice doesn't ship any.