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themo

Member

Registered: 2011-06-05

Posts: 15

Strange issue GNOME fonts pango/cairo with Noto Emoji

Hi,

while playing around with my label printer with the goal of printing monochrome Unicode symbols, I stumbled upon a strange behavior. I am not sure if my limited understanding of how fonts work on GNOME/Pango/Cairo is the issue here or if I found a packaging bug and/or GNOME bug.

So let me describe first what the observed behavior is and if this is normal. For my understanding, there are multiple Fonts in the Google Noto Font family which are installed via the noto-fonts/noto-fonts-cjk/noto-fonts-emoji/noto-fonts-extra packages. My assumption was, that the package noto-fonts-emoji contains the Noto Emoji (monochrome) font, but it contains the Noto Color Emoji (with colors). This is - albeit being a bit misleading - totally fine. However, If I try to manually install the Noto Emoji (monochrome) font via the GNOME fonts application while the noto-fonts-emoji package is installed, the Noto Emoji font is displayed as it were the Noto Color Emoji font (even if I open the install preview!) which is pretty strange to me. The only solution to get the monochrome version to work is to uninstall noto-fonts-emoji package and install the Noto Emoji (monochrome) font manually. However, If I then try to install Noto Color Emoji manually with the version from the Google Fonts website, the font viewer (and other applications using Pango/Cairo for font rendering) hang for a pretty long time until they even show the first character of the font and even after that the characters/emojis "plop in" pretty slow. I ran the sysprof profiler and you can see that libc's malloc is called thousands of times in like 10s capture which sounds like a lot to me.

So, to summarize, my questions here are:
- Why is fontconfig/pango/cairo chosing Noto Color Emoji over Noto Emoji even if I specify Noto Emoji explicitly
- Why is GNOMEs font rendering taking so much time showing the Noto Color Emoji font

Noto Emoji installed

Noto Emoji removed

Sysproph GNOME fonts callgraph