Created attachment 1383132 [details]
screenshot of the bounding box problem

Created attachment 1383133 [details]
screenshot after the patch applied

Created attachment 1383134 [details]
draft patch for fixing the bounding box problem

Created attachment 1383135 [details]
after applied the previous patch, the fontwidths variable seems can be removed

That is a very significant decrease in performance, the better question is why would the width of a glyph ever change at runtime?

The simple answer for that is, the targeted characters to render is changed at runtime and pango uses proper fonts against it which may has different width. pango do the right thing even though they takes disadvantage in performance. xchat/hexchat do something faster but behaves wrongly because of wrong assumption. that's it.

Comment on attachment 1383134 [details]
draft patch for fixing the bounding box problem

This causes a new warning:

    (hexchat:17070): Gdk-CRITICAL **: _gdk_pixmap_new: assertion '(width != 0) && (height != 0)' failed


This is in `gtk_xtext_render_flush` where `str_width` is now `0`.

I think pango support multiple languages in one document.

I suspect that the fontwidths is computed with Chinese font,
but when pango detect English words, it will switch to use English font.

I applied both patches for testing, and launched hexchat from gnome-terminal,
but not find the warning.
How to reproduce that warning?

(In reply to Peng Wu from comment #8)
> I applied both patches for testing, and launched hexchat from gnome-terminal,
> but not find the warning.
> How to reproduce that warning?

Scrolling up and down an active channel.

Sorry, I still can't reproduce that warning on Fedora 27.
I tried Fedora 27 rpm and github hexchat repo.

Could you help me on reproducing it?

Ok so in trying to reproduce it today I cannot so it seems the problematic line is out of my history sadly.

Testing this patch on Windows the performance of the application is unusable and it takes over a minute to open the application so as-is this cannot make it upstream. A simple `#ifdef G_OS_WIN32` around the changed logic could perhaps be acceptable.

Created attachment 1386477 [details]
updated patch for fixing the bounding box problem

Thanks for the review! :)

I updated the patch to only change the code on non-Windows.

BTW, it seems the fontwidths variable is only used on Windows.
Is it okay to also use `#ifdef G_OS_WIN32` for the fontwidths variable?

Created attachment 1386506 [details]
updated patch for fixing the bounding box problem

(In reply to Peng Wu from comment #13)
> Thanks for the review! :)
> 
> I updated the patch to only change the code on non-Windows.
> 
> BTW, it seems the fontwidths variable is only used on Windows.
> Is it okay to also use `#ifdef G_OS_WIN32` for the fontwidths variable?


Yes please do to avoid compiler warnings.

Created attachment 1389369 [details]
updated patch for fixing the bounding box problem

I have commited this upstream: https://github.com/hexchat/hexchat/commit/d3f1ab78138a1f9256ec02842799ed6cd1e3ec1e

I will try to get around to adding it to the Fedora package soon.

Thanks for the review! :)

hexchat-2.14.0-1.fc28 has been submitted as an update to Fedora 28. https://bodhi.fedoraproject.org/updates/FEDORA-2018-30b9e6c8c9

hexchat-2.14.0-1.fc27 has been submitted as an update to Fedora 27. https://bodhi.fedoraproject.org/updates/FEDORA-2018-2d8ce03c84

hexchat-2.14.0-1.fc28 has been pushed to the Fedora 28 testing repository. If problems still persist, please make note of it in this bug report.
See https://fedoraproject.org/wiki/QA:Updates_Testing for
instructions on how to install test updates.
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2018-30b9e6c8c9

hexchat-2.14.0-1.fc27 has been pushed to the Fedora 27 testing repository. If problems still persist, please make note of it in this bug report.
See https://fedoraproject.org/wiki/QA:Updates_Testing for
instructions on how to install test updates.
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2018-2d8ce03c84

So this patch ended up being reverted as bug 1554263 shows the performance impact is just to much to be usable.

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