Upgraded test PC from 5.42 to 6.3.0 hard to read

[Quoth]

Linux Mint 20.1 with Mate Desktop.

After upgrade all the menus and main window text seems grey instead of black. Very hard to read.

Behaviour -> Look Main Interface
Classic Icons
Color Palette: System default
Font: DejaVu Sans 10
The desktop / system (and now irrelevant QT5 settings) are very like traditional Win98 / Server 2003 style, or what XP or Win7 looks like with the Eye candy turned off. All black text, white window backgrounds, grey window surrounds and traditional 3D Windows NT / Win 3.x / Win9x buttons & controls.

Is this a QT6 stupidity or a Calibre setting somewhere?

SOLUTION

I changed font to Droid Sans 10, restarted and Calibre was OK. So curious I changed it BACK to DejaVu Sans 10 and restarted and it was STILL OK!

Font now back to Black.

I'd stayed on 5.44 on my main PC and laptop rather than 6.1, 6.2. 6.3 etc because QT6 worried me. But now it seems fine.

No problem upgrading from DeDRM 7.x to NoDrm DeDrm 10.0.3

[Quoth]

BTW, I did an export of entire lib & settings from the 5.44 and imported to the 5.42 on test PC (which is also used for a SCSI scanner) and that worked perfectly.

Just upgraded main PC from 5.44 to 6.3.0 and it looked a bit worse! Skinny grey moth eaten text:
Behaviour -> Look Main Interface
Classic Icons
Color Palette: System default
Font: DejaVu Sans 10

I changed font to exact same font (strangely Bold was preselected on list, but I selected Book which = regular), restarted and everything now looks just as it was before the upgrade!
BTW, test PC is using 24" 2K screen and main PC is a 28" 4K screen.

Great job Kovid.

[JSWolf]

Originally Posted by Quoth

Linux Mint 20.1 with Mate Desktop.

After upgrade all the menus and main window text seems grey instead of black. Very hard to read.

Behaviour -> Look Main Interface
Classic Icons
Color Palette: System default
Font: DejaVu Sans 10
The desktop / system (and now irrelevant QT5 settings) are very like traditional Win98 / Server 2003 style, or what XP or Win7 looks like with the Eye candy turned off. All black text, white window backgrounds, grey window surrounds and traditional 3D Windows NT / Win 3.x / Win9x buttons & controls.

Is this a QT6 stupidity or a Calibre setting somewhere?

SOLUTION

I changed font to Droid Sans 10, restarted and Calibre was OK. So curious I changed it BACK to DejaVu Sans 10 and restarted and it was STILL OK!

Font now back to Black.

I'd stayed on 5.44 on my main PC and laptop rather than 6.1, 6.2. 6.3 etc because QT6 worried me. But now it seems fine.

No problem upgrading from DeDRM 7.x to NoDrm DeDrm 10.0.3

One of the differences if that QT6 has high DPI built into Qt6 and it's automatically on or off. With Qt5 you had an option. You can turn this off with an environment variable.

The second is if you are setting your display greater then 100%.

QT_ENABLE_HIGHDPI_SCALING=0
QT_SCALE_FACTOR_ROUNDING_POLICY=Round

[Quoth]

It's not a DPI issue. Everything was the same size after upgrade. The issue fixed simply by reselecting the UI main font. Very strange.

Even with earlier QT, with some applications such as Viber, sometimes on the launcher I needed
/usr/bin/env QT_AUTO_SCREEN_SCALE_FACTOR=0 QT_SCALE_FACTOR=1.20
(or some other scale).
It seemed to be random per laptop with 1920 x 1080 screens even of the same size.

My 3840 x 2160 screen is 28" and the laptop 1920 x 1080 is 15", both 16:9. My older 4:3 screen laptop from 2002 was a little more than 15" but 1600 x 1200 which is better than 1920 x 1080 for PDFs.

So those are all similar DPI settings. It's only so called "Retina" screens (i.e. 10" @ 2K or 15" @ 4K etc) that need a HiDPI setting and ANY software setting it automatically should not unless opted in and the SW can read the screen physical size from somewhere. Actual X and Y dots without the screen physical size is meaningless.

Actually it's stupid on Win7 & Win10 you can't go LESS than 100%. On a screen that's only 720, 768 or 800 high you might want to set the DPI to 72, i.e. shrink all the fonts and controls, no matter what the real DPI is so that windows fit. A lot of stuff assumes a minimum of 1024 lines for display panel.
XP can go from 20% to 500% on GUI scaling, but not all windows and controls scale. Vista/Win7/Win8/Win10/Win11 can't be used on lower resolution screens, no matter the DPI because they don't go less than 100%.
So called HiDPI mode is 400% windows scale. Apple uses 2 x 2 per pixel in hiDPI mode, so you are in trouble with a 24" or 28" and larger 4K display if Apple doesn't use the size of it

[Quoth]

Now upgraded laptop with native 1920 x 1080 15" screen from 5.44 to 6.3.0
Same effect, all text paie grey till the font was reselected as DejaVu Sans 10 pt Book. Also was showing up as bold on select list.

Now perfect.

[JSWolf]

Originally Posted by Quoth

It's not a DPI issue. Everything was the same size after upgrade. The issue fixed simply by reselecting the UI main font. Very strange.

Others have had to do the same thing.

Even with earlier QT, with some applications such as Viber, sometimes on the launcher I needed
/usr/bin/env QT_AUTO_SCREEN_SCALE_FACTOR=0 QT_SCALE_FACTOR=1.20
(or some other scale).
It seemed to be random per laptop with 1920 x 1080 screens even of the same size.

My 3840 x 2160 screen is 28" and the laptop 1920 x 1080 is 15", both 16:9. My older 4:3 screen laptop from 2002 was a little more than 15" but 1600 x 1200 which is better than 1920 x 1080 for PDFs.

So those are all similar DPI settings. It's only so called "Retina" screens (i.e. 10" @ 2K or 15" @ 4K etc) that need a HiDPI setting and ANY software setting it automatically should not unless opted in and the SW can read the screen physical size from somewhere. Actual X and Y dots without the screen physical size is meaningless.

Actually it's stupid on Win7 & Win10 you can't go LESS than 100%. On a screen that's only 720, 768 or 800 high you might want to set the DPI to 72, i.e. shrink all the fonts and controls, no matter what the real DPI is so that windows fit. A lot of stuff assumes a minimum of 1024 lines for display panel.
XP can go from 20% to 500% on GUI scaling, but not all windows and controls scale. Vista/Win7/Win8/Win10/Win11 can't be used on lower resolution screens, no matter the DPI because they don't go less than 100%.
So called HiDPI mode is 400% windows scale. Apple uses 2 x 2 per pixel in hiDPI mode, so you are in trouble with a 24" or 28" and larger 4K display if Apple doesn't use the size of it

With Windows 11, you can only enter a value between 100% and 500%. There's no going lower unless it can be done with a reg hack.

[Quoth]

It's NOT the DPI

Any link to a post where the only thing needed was to reselect exactly the same font?

The ONLY difference after upgrade on 3 different computers, 3 screen size was simply the text being grey and skinny. Nearly unreadable. Changing the Font setting to what it was originally (in Setting Book had changed from book to bold, but display was skinny & grey) perfectly fixes it.

[Quoth]

Originally Posted by JSWolf

With Windows 11, you can only enter a value between 100% and 500%. There's no going lower unless it can be done with a reg hack.

Yes, same as Vista, 7, 8, and 10. Really stupid. But fortunately my main OS since Jan 2017 is Linux Mint.
I can compare XP, 7 and 10 on same PC at same time in Virtual Box all set to 1600 x 1200 "desktops" on my 28" 4K screen. For speed, ease of use, compatibility with windows programs written for VB6 or by people now dead, ability to customise to taste, lack of privacy busting stupidity and adverts, Windows XP is far the best.

Lots of newer stuff is either Cross-Platform, thus on Linux, or is so called Cloud Based using a Browser. I don't run pay-roll, accounts or CRM packages for Windows, so changing to Linux was easy.
Windows N Home ought to have a "health" warning. The minimum sensible Win XP, Vista, 7, 10, 11 are the Pro versions. Sheer greed.

[Quoth]

Doing an Import to a Calibre by going to Import and deleting current library resets some plugins to an earlier version AND resets the font to skinny grey, even though Dejavu 10 in Bold or Book isn't skinny grey.

So one aspect of the issue may be the original export which was from 5.44

[Quoth]

I made a fresh export from a library updated to 6.3 and all plug-ins up to date and font fixed.

I deleted the destination library and ran the Calibre 6.3 and reimported (naturally had to delete one file while import dialogue was open).

The font wasn't affected. So it's maybe only when a 5.x export is imported to 6.3 OR a 5.x Calibre is first updated to 6.3 that the GUI font is messed up and needs "reset".

All 3 systems did start with working DejaVu 10 book fonts on 5.x Calibre

[Sirtel]

I installed 6.0 on top of 5.xx (updated to 6.3 by now) and had no issues with the font (Arial in my case). The screen is 3840 x 2400, high DPI setting is automatic. Windows 10.

[kovidgoyal]

Qt 6 changes how it matches font faces by weight. If you happen to be using one of the fonts affected by this change, you will notice it picks a different font face than Qt 5. In this case you need to go into settings and reselect the font face. That's all.

[Quoth]

Originally Posted by kovidgoyal

Qt 6 changes how it matches font faces by weight. If you happen to be using one of the fonts affected by this change, you will notice it picks a different font face than Qt 5. In this case you need to go into settings and reselect the font face. That's all.

Strange. But at least a minor issue and easily solved. That's exactly what I did. I'd put off upgrading fearing worse from QT6.

Obviously though QT6 didn't like the imported font settings (along with everything else inc books) from an export by 5.44 but is OK with import of 6.3 from another PC.
Even though it's the same setting!