fix some rendering issues, fix logical errors

Thanks for the help.

Please consider this work in progress. There are no reviewers. Is there another way to mark this as "not ready"?

It's not clear who wrote that about being fontconfig specific (or the IMHO incorrect suggestion that Freetype is implemented 3x).

EDIT: I don't agree with how jealously Plasma keep these to themselves, some KCMs certainly make sense across all platforms and I maintain Mac packaging for them. But you just don't get to justify changes because of Mac or MS Windows and at the same time claim the software in question is out of limits there ;)

kcm fonts is fontconfig specific. (It's even non-tirival to translate rendering options from fontconfig terminology to freetype, which is in fact separately implemented in libXft, Qt and pango)

Why not make these separate KCMs?

I started implementing the functionality of M120 on basis of the current master: D17493

Sorry for creating confusion! This is also not about kcm fonts on other platforms.

This is not only about choosing a Font, but also about selecting suitable rendering options.

In T7927#157376, @abetts wrote:

Thanks for bringing this all together Nate. I feel very similar about this idea. The process of selecting your fonts and how sharp they look has straight correlation to the way that Windows does it. However, they have a special window that will help with this. It is not a common KCM style selection process. It is done as an "advanced" window. What is easy about it is the visual nature of the selections you make as a user.

The problem which M120 solves is, that many users have developed a strong taste of how fonts have to be rendered:

• Some want to have sharp outlines and prefer therefore heavy hinting and dislike sub-pixel rendering for its colour haze
• Others want to preserve the characteristics of a certain font and therefore disable hinting and use sub-pixel anti-aliasing for best possible resolution

But many users have no idea what hinting, anti-aliasing or sub-pixel rendering means. They decide visually, what suites them best.

we moved away fom "detached" previews everywhere else (wallpapers, cursors, icons, etc the preview should be in the "noto sans" box

I appended my first try of a mockup. There is no preview rendering of the different rendering options yet. I would have to add another image provider for that or generalize the existing previewimageprovider.

I looked into the Human Interface Guidelines and I found exactly, what I had in mind when I opened this task: In the section about settings there is a mockup of how settings would look like.

Sub-pixel rendering is default for desktop systems. But there are people who don't like sub-pixel rendering for its colour haze.

Just to add another fact to the discussion:

I very like this idea! However in “simple” I would like to add selectable previews for different rendering options:

I will also work on this on the behalf of the city administration of Munich. How can we coordinate the work?

I would like to add something visual like M120 and hide the details of the current KCM fonts behind a "expert settings" tab or similar.

DPI should IMO be handled by the compositor, since it depends on the output device.

Then I guess it is much easier to use Qt after all, and drop hintmedium?

From what I understand there is no subpixel rendering without anti-aliasing in freetype.

In principle that would be it.