Bug 385163

Summary: email rendering does not respect system font DPI settings
Product: [Applications] kmail2 Reporter: Diggory Hardy <kde2>
Component: UIAssignee: kdepim bugs <kdepim-bugs>
Status: REPORTED ---    
Severity: normal CC: cobaco, kdedev, kishore96
Priority: NOR    
Version: 5.4.3   
Target Milestone: ---   
Platform: Other   
OS: Linux   
Latest Commit: Version Fixed In:
Sentry Crash Report:

Description Diggory Hardy 2017-09-28 07:27:39 UTC 
I'm using a high-DPI screen. In System Settings → Fonts, I set "Force fonts DPI" to a larger value (currently 192), and most application text gets increased in size. Not so with emails rendered in KMail2 (I can open the email and zoom with Ctrl+WheelUp, but it's not automatic).

FYI Konqueror seems to have the same problem. So does Firefox, but it has its own workarounds (and it's not KDE software).

I found two maybe-related bug reports; both about print size:
https://bugs.kde.org/show_bug.cgi?id=372662
https://bugs.kde.org/show_bug.cgi?id=78264

Alternatively I guess it would be okay to scale email rendering by the screen DPI, not by the "force font DPI" setting.

As a workaround, setting the env var QT_SCALE_FACTOR=2 would "work" — but it's an ugly hack which doubles the size of everything, including the useless margins and all the UI elements which have already been increased in size (through System Settings → Icons, Application Style, "force font DPI", and possibly more); i.e. to use it effectively I'd have to set it desktop-wide at startup and revert all the other tweaks, then put up with huge margins in all the UIs.

Summary: automatically scale email rendering by "force font DPI" / default=96, or by screen DPI
Comment 1 Diggory Hardy 2017-10-05 12:00:38 UTC 
Further to this — received emails are displayed with very small fonts, as are emails composed with plain text.

Emails composed with "rich text" enabled — *also* display with small fonts, but this isn't because of the display scaling — the font size defaults to 6pt! (I only realised recently when a recipient complained about the small font size.)
Comment 2 Christoph Feck 2017-10-12 18:05:04 UTC 
BTW, Konqueror has a 'Zoom to DPI' setting in its View menu, which works nicely for me.
Comment 3 cobaco 2019-10-11 09:11:12 UTC 
Still present in kmail 5.9.3

Akregator has the same problem with the html view showing everything really small when opening an article in a tab instead of external browser

So this seems to be a more general problem where the embedded html view component (whatever that is called) is not respecting the dpi setting