Fonts are a big variable in computers. Since everyone has different opinion about what is a best and most readable typeface, there are thousands of font families available for installation with various operating system.
Following OS updates, new application installations or configurations changes; fonts can suddenly become blurry or even fail to render entirely, showing placeholder shapes instead of the proper glyph.
Common font complaints
Font typeface families do not include all point sizes. (As and example,
This is more likely if you have the Themes add-on installed and then specified a typeface and font size. The OS interpolates this typeface and size setting in combination with your screen resolution and the OS accessibility controls for font scaling. The interpolation might require too much difference from the nearest point size that would scale comfortably in the number of pixels allotted. When the scaling is pushed beyond these manageable limits, text can appear blurry.
If the outlines of dialogs and controls appear sharp but text is blurry, you should change one of the contributing factors: the fonts size in Gramps Themes preferences, the screen resolution, or the OS Accessibility font scaling. Do NOT change more than one setting before checking the results. If that changing that contributing factor does not help, revert it to the previous setting before adjusting the next factor.
No text, just rectangles
Unicode calls the phenomenon (of a placeholder open/black rectangle "" or REPLACEMENT CHARACTER "�" being rendered instead of the actual strokes of a letter) a replacement glyph. It also known as a missing glyph.
You might also try going to the Gramps install directory "C:\Program Files\GrampsAIO64-5.1.4" and running (from the command line) "fc-cache.exe -fv" which should reestablish the font cache. It seems likely that the update messed up fonts in some way. Or re-install Gramps... which will do the same thing but also do wider resets.
If you still have issues, you may need to go back to an older backup.