Recent changes to 2194: wxt terminal messing around with any label (MacOSX)

#2194 wxt terminal messing around with any label (MacOSX)

Ethan Merritt — Tue, 02 Jun 2020 17:41:00 -0000

So far as I can tell this is a slow-moving train wreck upstream. See discussion here:
https://github.com/harfbuzz/harfbuzz/issues/2394#issuecomment-626254448

I really don't know what is going to come out of this moving forward. It seems that the primary developers have decided that it is more important to support new fonts on extremely high-resolution displays than it is to support old fonts on what you and I would consider a "normal" display. Maybe upstream distros will fork and maintain an older (working) version of pango? Maybe they will at least provide a list of supported vs unsupported fonts? Maybe some backwards-compatibility setting will be added to the library?

My understanding of the detailed nature of this problem is limited. I gather it is largely due to harfbuzz not handling hinting. So perhaps disabling hinting would fix or improve things for you, a considerably less drastic change than degrading the resolution by 20-fold. Since I don't see the problem here I can't usefully experiment.

Meanwhile if I follow the trail of your earlier bug report to cairo->pango I see that other projects are reporting the same sort of errors from pango 1.44 on OSX:
https://gitlab.gnome.org/GNOME/librsvg/-/issues/520#note_627033

So yes, it's an upstream problem. Possibly we could work around it be turning off hinting, but that would have to be explored by someone who is seeing the problem. Can you do the experiment? What happens if you replace hinting = 100 with hinting = 1 everywhere in .../term/cairo.trm and .../src/wxterminal/gp_cairo.c? Or may hinting=0 ?

#2194 wxt terminal messing around with any label (MacOSX)

tom — Tue, 02 Jun 2020 08:58:59 -0000

@sfeam : a gentle bump on this: would the GP_CAIRO_SCALE fix above mean that it's not an upstream bug?

#2194 wxt terminal messing around with any label (MacOSX)

tom — Mon, 06 Apr 2020 12:52:59 -0000

I could get rid of the artifact by changing line 84 of src/wxterminal/gp_cairo.h
setting GP_CAIRO_SCALE to 1 rather than 20

sed -i '' 's/define\ GP_CAIRO_SCALE\ 20/define\ GP_CAIRO_SCALE\ 1/g' ./src/wxterminal/gp_cairo.h

Could this help in pinning down the problem?

(I'm no more sure it's an upstream bug)

#2194 wxt terminal messing around with any label (MacOSX)

Ethan Merritt — Tue, 17 Dec 2019 06:34:14 -0000

status: open --> open-upstream-bug

#2194 wxt terminal messing around with any label (MacOSX)

Ethan Merritt — Sat, 28 Sep 2019 19:48:37 -0000

summary: wxt terminal messing around with any label --> wxt terminal messing around with any label (MacOSX)
Group: -->
Priority: -->

#2194 wxt terminal messing around with any label

Ethan Merritt — Mon, 09 Sep 2019 16:23:29 -0000

I have lib64pango1.0_0-1.44.6-1.mga8 on Mageia (Cauldron) linux.
No evident problems with fonts for the wxt terminal here.

#2194 wxt terminal messing around with any label

tom — Mon, 09 Sep 2019 15:59:59 -0000

[from pango gitlab issue report]

Can someone confirm this happens only on macos?

Could someone test wxt terminal on linux using latest pango v1.44.6 ?

#2194 wxt terminal messing around with any label

tom — Mon, 09 Sep 2019 12:58:07 -0000

Followup: I posted an issue on the right pango gitlab: https://gitlab.gnome.org/GNOME/pango/issues/422

#2194 wxt terminal messing around with any label

Alexander Urban — Fri, 30 Aug 2019 18:51:37 -0000

I can confirm that the same problem occurs for the Cairo-based terminals. So your suspicion Pango is the reason seems correct.

(I also posted a question on Stackoverflow that brought me here: https://stackoverflow.com/questions/57698204)

#2194 wxt terminal messing around with any label

Ethan Merritt — Fri, 30 Aug 2019 16:08:03 -0000

Do you see this same problem with the other cairo-based terminals? The wxt pngcairo and pdf terminals all share the same code for text layout.

If so, I wonder if it may be related to a deliberate change in pango to use harfbuzz rather than cairo to obtain font metrics:

https://github.com/harfbuzz/harfbuzz/issues/1892

The issue you see is not exactly the same as the one reported there, but they both result from incorrect reported font metrics.

On the other hand if you see this problem only with wxt and not with pngcairo or pdf, then something else must be involved.