Freeze Cairo and Pango Versions

It seems that the current repository does not specify exact versions of pango, cairo, manimpango and pygobject packages. Based on our previous experience with PIXEL-based models, working with different versions of these packages can significantly affect performance.

For instance, consider a model pretrained with cairo==1.16.x. If we switch to cairo==1.18.x during downstream task fine-tuning, the model’s performance could degrade substantially. There are two reasons for this issue:

1. Different versions might produce slightly different visuals, which may be imperceptible to humans.
2. PIXEL-based models currently process 16×16 patches using 16×16 convolutional filters. Thus, even the slightest change in patch visual can disrupt input processing in PIXEL-based models. This would be the case for WeLT if one follows the same design choices.

So, the action items would be,

• Detect the versions of pango, cairo, manimpango and pygobject.
• Check the rendering whether it works without any issues.
• Fix the versions.

@AmitMY I can fix the versions if this is okay by you also as well.