Issue with light and thin font weights

[geraldus]

Hi, I have no idea how this issue addressed in other editors, but it will be very nice to be able to adjust embolden font weight.

Here is what I'm talking about. There are several monospaced fonts (such as Iosevka, Source Code Pro, and Roboto Mono) which come with light and thin variants. Personally I find thin fonts easier to read. For example, Source Code Pro have a lot of weights and I can select preferred wight from font options, but in all cases bold weight is rendered identically. In case of Source Code Pro bold weight is chosen to embolden text, it's okay if regular is used as base weight: But if I choose as base weight something lighter than regular it looks very unnatural: light as base weight Even with normal set as base weight bold looks too heavy:

I think bold weight could be selected automatically according to base weight and weight that selected font provides, however implementing such choice algorithm is quite tricky, because some fonts might have bold, semibold, heavy weight and others are not. I think the best way would be to provide some special option what weight to use for embolden text which user can set (for example, there is no such option in Emacs, but I can iterate list of all faces and change weight for all embolden faces).

Thank you.