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In linux, copying a tkinter font doubles its size when using Tk 8.6 and a hi-res screen. #128719
Description
Activity
I think the doubling behavior is because tkinter's
Font.copyrelies onFont.actual:def copy(self): "Return a distinct copy of the current font" return Font(self._tk, **self.actual())On a high-res Linux screen with Ubuntu 24.04, the
sizeandself.actual()['size']differ, apparently by the scaling factor:>>> import tkinter >>> root = tkinter.Tk() >>> f1 = Font(font='TkFixedFont') >>> f1['size'] 20 >>> f1.actual()['size'] 40This seems consistent with the Tk docs which say that
font actual:Returns information about the actual attributes that are obtained when font is used on window's display; the actual attributes obtained may differ from the attributes requested due to platform-dependant limitations, such as the availability of font families and pointsizes.
Also, on stock Ubuntu 24.04, I see a very different result from @culler's built-from-source Tk 8.6:
$ wish % info patchlevel 8.6.14 % font actual TkDefaultFont -family {Noto Sans} -size 20 -weight normal -slant roman -underline 0 -overstrike 0 % font config TkDefaultFont -family sans-serif -size 10 -weight normal -slant roman -underline 0 -overstrike 0Note everything here is in points, not a mix of points and pixels. The same difference between config and actual shows up in user-defined fonts:
% font create MyFont -family {Noto Sans} -size 8 MyFont % font actual MyFont -family {Noto Sans} -size 16 -weight normal -slant roman -underline 0 -overstrike 0 % font config MyFont -family {Noto Sans} -size 8 -weight normal -slant roman -underline 0 -overstrike 0This is probably a difference between 8.6.14 and 8.6.15. There is now a release of 8.6.16. I will report if it differs from 8.6.15.
Indeed! It looks like they ended up fixing a related Tk bug but never got to the tkinter issue raised in the original report, which seems to be the same as this one..
I installed the proposed Ubuntu package
libtk 8.6.16-1by downloading the binary from launchpad. Now I get:% font actual TkDefaultFont -family {Noto Sans} -size 10 -weight normal -slant roman -underline 0 -overstrike 0 % font config TkDefaultFont -family sans-serif -size 10 -weight normal -slant roman -underline 0 -overstrike 0 % font create MyFont -family {Noto Sans} -size 8 MyFont % font actual MyFont -family {Noto Sans} -size 8 -weight normal -slant roman -underline 0 -overstrike 0 % font config MyFont -family {Noto Sans} -size 8 -weight normal -slant roman -underline 0 -overstrike 0I'm thinking maybe there's nothing to do here for
tkinter. I suspect it would have been a better design to haveFont.copy()invokeconfiginstead ofactualas this seems like a poor copy:>>> f1 = Font(family='sans-serif', size='10') >>> f1['family'] 'sans-serif' >>> f1.copy()['family'] 'Noto Sans 'However, if Tk itself is working right, they should always display the same. Moreover,
Font.__init__invokesactualwhich is why one sees:>>> Font(font='TkDefaultFont').config()['family'] 'Noto Sans`whereas
wishwould saysans-serif. But presumably changing fromactualtoconfigwould cause minor havoc and be more trouble than it's worth.Reacted by ThingamabobsCodingThis was a Tk bug in
font actualon HiDPI displays — the resolved size was scaled relative to the configured size — and it was fixed upstream in Tk 8.6.16.As confirmed earlier in this thread, 8.6.16 makes
font actualagree withfont config, soFont.copy()(which snapshots viaactual()) no longer doubles the size. I re-verified on Tk 9.0.4 withtk scaling ≈ 2.0:configandactualboth report size 10, and a repeated.copy()chain stays at 10.The fix is in Tk, not tkinter, and all current Tk releases (8.6.16+, 9.0) include it, so I'm closing this as resolved upstream. Please upgrade Tk to 8.6.16 or later.
Bug report
Bug description:
The example above is from Ubuntu 24.04 running on an Asus Zenbook with EVO screen. The display scaling from the system settings is the default, namely 200%. This does not happen when the display scaling is 100%.
Note that font f1 is already (more than) doubled in size, compared to what wish8.6 (built from 8.6.15 source) reports:
The negative value -12 means that the size is 12 pixels, as opposed to 12 points. I think the intitial expansion being slightly more than a factor of 2 may be caused by rounding when converting pixels to points.
Note that the behavior of Tk 9 is different. Using wish9.0 on the same system produces:
Also, the pending new version of tkinter from #124156 does not have this doubling behavior when used with Tk 9.0. (I have not tested the new tkinter with Tk 8.6, but I expect it to have the broken behavior since I don't think that the PR changes Font.copy.)
CPython versions tested on:
3.12
Operating systems tested on:
Linux