Created attachment 174545 [details] Screenshot showing PDF in Adobe Reader (Windows) at high zoom-in (I can't remember whether ever or when I had used "underdots" (underlining using dots) last) Using "underdots" at font size 14 point resulted in a PDF that had no distinguishable point at 100% zoom. It seems the dots are too dense (see attachment).
Created attachment 174546 [details] Sample document (test case) For the screen shot the dots are distinguishable at roughly 400% zoom. Here is a test case document reproducing the problem (PDF will follow).
Created attachment 174547 [details] PDF export for attachment 174546 [details] Here is an example export
Viewing the PDF in Linux with evince seems to render the fine dots somewhat better than Adobe's Reader in Windows 10. Still the dots seem quite fine to me.
Dots in PDF at 100% look different compared to ODT in LibreOffice Version: 7.3.0.0.alpha0+ (x64) / LibreOffice Community Build ID: f58f35b2c8ca1efbacec642a8f3de5b0c499bc6b CPU threads: 4; OS: Windows 6.3 Build 9600; UI render: Skia/Raster; VCL: win Locale: nl-NL (nl_NL); UI: en-US Calc: CL Also the case with 4.0.0.3 export. However no clue about scaling, font rendering etc asses if this being a bug or not
Created attachment 174568 [details] "Dotted" options in Inkscape (partial Screenshot) As MS-Word seems to lack "underdots", I cannot compare, but at least Inkscape (just to compare) would allow different styles of dotted lines. I don't know the algorithm
Created attachment 174569 [details] Revised test case (manually adding dots) I made an experiment with the test case: Add a line of just dots, and add a line with alternating dots and spaces. Both cases use a much higher spacing between the dots than "underdots" do. I don't know the algorithm, but the space between dots should be at least 1.2 to 1.5 times the space a dot occupies.
Created attachment 174570 [details] Detail view for the newer test case
Created attachment 174571 [details] Font details (fontforge) of '.' in DejaVu Sans As the kerning information of period ('.') seems to suggest sufficient space between dots, I assume (not knowing the algorithm for "underdots") that the algorithm has a bug.
The dots are rendered separately in MS Edge and Firefox at 100% zoom. I confirm that they are a solid line in Acrobat, but isn't this rather Adobe's problem?
(In reply to Buovjaga from comment #9) I agree that Firefox renders such things more nicely than Adobe Acrobat does. Anyway I wonder: Should the dots be adjustable, and maybe could some "hinting" improve Acrobat's rendering? I mean: In the end the purpose is to provide nicely looking documents for the end user.