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STR #3321
Application: | FLTK Library |
Status: | 2 - Closed w/o Resolution |
Priority: | 3 - Moderate, e.g. unable to compile the software |
Scope: | 2 - Specific to an operating system |
Subsystem: | X11 |
Summary: | [X11/Xft] Overlapping lines (font rendering problems) |
Version: | 1.3.3 |
Created By: | michaelbaeuerle |
Assigned To: | AlbrechtS |
Fix Version: | Unassigned |
Update Notification: | |
Trouble Report Files:
No files
Trouble Report Comments:
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#1 | michaelbaeuerle 08:16 Jul 25, 2016 |
| On some systems in the Fl_Text_Editor widget it seems that the lines overlap by one pixel. If the text contains '_' (underscore) characters they are not visible with the default font size.
Setting the font size much larger from the application works as workaround (and proves that the invisible characters are really there).
The reason for this behaviour seems to be the font hinting of Xft. Setting the X ressources as follows solves the problem: | | Xft.antialias: true | Xft.hinting: true | Xft.autohint: false | Xft.hintstyle: hintfull
This X ressources should make the problem visible on systems that work correctly by default: | | Xft.antialias: true | Xft.hinting: true | Xft.autohint: false | Xft.hintstyle: hintslight ^^^^^^^^^^ I found this notice that GNOME modifies this setup: <https://wiki.archlinux.org/index.php/Font_Configuration#Hintstyle> so whether the problem occurs should not depend on the operating system but on the desktop environment used.
How to reproduce: - Operating system should not matter but must use X11 - Ressources set in the X-Server as listed above - FLTK compiled to use X11 and Xft - Test program for Fl_Text_Editor is sufficient - Type some text that contain '_' (underscore) characters | |
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#2 | AlbrechtS 04:34 Jun 02, 2021 |
| I tried to reproduce this w/o success on Linux Mint 20 (based on Ubuntu 20.04 LTS) using FLTK 1.4 (Git) and either bare Xft or Pango. I could always see the underscores.
I looked around to figure out which kind of hinting applies to my system but I'm not a Linux expert and I'm mostly using the default setup. Do you know of any function/program that can show me the active font hinting type, or can you give clear advice how (in which file) to edit what you described "This X ressources should make the problem visible on systems that work correctly by default"?
FTR: I looked around in /etc/fonts and I can only find:
/etc/fonts/conf.d/10-hinting-slight.conf:8: <description>Set hintslight to hintstyle</description> /etc/fonts/conf.d/10-hinting-slight.conf:17: <edit name="hintstyle" mode="append"><const>hintslight</const></edit>
which seems to indicate that on my system "hintslight" is active despite the fact that the fonts are shown correctly.
Two questions:
(1) Does this STR still apply, i.e. does it still require any actions?
(2) If yes, what could we do? Is there a way to change this setting on the fly in FLTK applications, or what are your suggestions?
Note: if these questions are not answered or if there is no sensible suggestion within a reasonable time (7-14 days) I'll have to close this STR. | |
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#3 | AlbrechtS 11:09 Jun 14, 2021 |
| Warning: this STR will be closed on June 16 if there's no further reply... | |
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#4 | michaelbaeuerle 00:57 Jun 16, 2021 |
| I am busy at the moment. If you can give me some more time, I will test it again. | |
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#5 | AlbrechtS 02:20 Jun 16, 2021 |
| OK, I'll wait for your feedback... | |
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#6 | AlbrechtS 03:20 Jun 16, 2021 |
| Michael, this is unrelated to this STR but ...
Could you please take a look at our GitHub Issue #238: "scandir_posix.c readentry should check for ENOENT"
https://github.com/fltk/fltk/issues/238
The code in question was written by you. Every comment to the issue would be appreciated. TIA. | |
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#7 | AlbrechtS 09:54 Jul 01, 2021 |
| Michael, any progress with testing ? | |
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#8 | michaelbaeuerle 08:44 Jul 02, 2021 |
| Today I have tested FLTK 1.3.6 with many different configurations for Xft. Some of them have displayed the text so ugly that it was nearly unreadable. But I found no configuration that renders the underscores invisible anymore.
Likely the behaviour depends on the font in use, and my machine today has a different set of fonts installed.
I remember the problem on machines that display multiple underscores with no visiable space between the characters. My test machine displays multiple underscores with clearly visible spaces between the characters, therefore it does not use the font that showed the problem at that time.
If nobody else have seen similar problems, I think this STR can be closed without resolution. | |
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#9 | AlbrechtS 14:14 Jul 02, 2021 |
| Thanks. Closing ... | |
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