Font is no slightly bigger on my mac. But totally okay.

After:

Before:

works for me.

Linux/X11 KDE environment: DPI = 192

screenshot before this patch applied

screenshot with this patch applied

@microcai hmm... looks good but i don't have a idea why your font size of the time-cell has also changed.

@jonasschnelli I tried to use standard zoom method Ctrl+Key_PLUS

What does font-size:1em do differently than omitting the attribute?

Can you check if we use hard-coded px sizes in other places? Perhaps it's time to replace them?

@luke-jr: Good question. 1em as font-size should be the default if there is no style-changing elsewhere. Will check this soon.

@Diapolo: The question is how Qt deals with HiDPI. On OSX 12px font size will result in 24px on screen in HiDPI (as expected). On linux we just saw that it will stay on 12px. There (fonts) em metrics makes sense. For other hard-coded px values (widgets size, offsets) it could end up value-doubles on HiDPI depending of Qt's handling.
So yes for changing all font-sizes to em, no for px widget sizes and offsets.

to make things clear, zoom in pixel level is only supported in osx platform. both Linux and windows version of Qt just uses DPI. so 12px font stay in 12px font even under windows.

I would expect Qt to default to the user font size preference.

as @luke-jr proposed i just removed the font-size: 1em setting. This should result in the same behavior maybe it also detects some way of using the standard os font-sizes.
@microcai could you test again?

@jonasschnelli I alread did.

@microcai hows the result? without 1em same as with? thanks.

@jonasschnelli just see the screenshot. there is barely visible difference with "1em" or without "1em"

@jonasschnelli 1em seems to be the default font size. so I can't really tell the difference either 1em or omit it altogether.

Looks good to me, although I wonder why we ever added a fixed font size (in pixels!), that must have been a workaround for something.

@laanwj Looks like it was introduced here c6aa86a, nearly 3 years ago.

OK, so I added it myself when I introduced this code. I don't remember why.

Trying it out jogged my memory. Without font-size, and with font-size:1em it looks like:

The default monospace font size on Ubuntu is huge.

Meh, that's not too huge. If the terminal looks the same, I'd say it's expected. Surely Ubuntu lets users configure their defaults?

@laanwj It seems like that font-size: <n>em; does not have any effect. Or at least with values <1em. I tried 0.8 and 0.1em. Looks exact the same as with 1em. I also tried 10pt. Looks also good but generate font-size difference between ubuntu/linux and osx.

I created a HiDPI ubuntu VM and did take a closer look at bitcoin-qt HiDPI unter linux. There are many issues (icon sizes, splash-screen, overview screen, etc., etc,)

This PR goes into the right direction (removing fix px values) but will not solve the whole HiDPI issue.

@jonasschnelli what about using 12pt ?

@microcai using 12pt would enlarge the font-size on linux as well as on osx. 10pt would make sense but even there the font-size is about ~10-20% larger.
IMO we should just remove the font-size as it is in this PR.

I really don't like the default font size on Linux. @luke-jr If you compare it with the normal, non-monospace font as used for the time and the tab titles it IS huge.

Thinking of that, maybe we should remove the monospace? Looks good here.

I want to compare it with the terminal program. Whenever possible, we should use an OS/user-defined look and feel, not try to second-guess it.

The terminal, at least on Ubuntu, uses a less ugly font and also more
reasonably sized than whatever Qt chooses with 'monospace'. It's not
realistic to expect it to pick the same font as the OS's terminal.

We have to make our own font decision here. There, picking using the
default (non-monospace) font seems safest.

non-monospace would look like this (see below).
I don't have a strong position here. There is not much of a difference between monospace and standard font in terms of usability of the rpc console.

Looks good to me. We don't (as far as I see) use the fixed width property anywhere for formatting, so a proportional font does just as well and may even be more readable.

Removed the "monospace" font style. IMO safest solution.