There's quite a few reasons why this cannot really work:

• Pattern Editor.FontDot requires a user-chosen font to begin with, which is not available when using a custom font
• Even if there was a user-chosen font, we wouldn't know at which size to render it. There is absolutely no guarantee about the effective size of a character even if we say that we want e.g. a 10pt font.
• The built-in fonts use a manually fine-tuned display grid, which makes it very difficult to sensibly integrate any sort of unknown font into

As a consequence, I cannot see how to implement this in a way which doesn't need to introduce at a handful of new settings or so (font, font size, cutout offset for the character, target position for the character). This is not feasible for such a small feature.

Pattern Editor.FontDot requires a user-chosen font to begin with, which is not available when using a custom font

"not available by using a custom font"? I don't really understand what you mean by that.

when I said "custom font" I was referring to a user-chosen font, like a TrueType font, as opposed to the built-in font.

The built-in fonts use a manually fine-tuned display grid, which makes it very difficult to sensibly integrate any sort of unknown font into

again, I don't know what you mean by "integrating unknown fonts"

What I meant is to have the FontDot option not only affect user-chosen fonts, but also the built-in fonts.

Basically, all I want is that when I set the FontDot option to an empty space character, I want the dots in the pattern editor to be shown as empty spaces, not only when using fonts installed on Windows/Wine (e.g. TrueType fonts), but also OpenMPT's built-in fonts. And if the FontDot is set to characters that aren't supported by the built-in fonts, like ! and $, just render them as an empty space, like custom note names in tunings.

Let me know if I misunderstood anything.

"not available by using a custom font"? I don't really understand what you mean by that.

What I mean is that there is no custom font configuration available when using default pattern fonts. A new UI workflow for being able to pick a font for this single letter would have to be implemented.

again, I don't know what you mean by "integrating unknown fonts"

As said, everything about the built-in fonts is manually crafted, which allows them to take up less space. For example there is no space available below the baseline (cf. https://upload.wikimedia.org/wikipedia/commons/3/39/Typography_Line_Terms.svg) because our font essentially just consists of uppercase letters and digits. This makes it pretty much impossible to merge any font with unknown proportions into the same bitmap without looking completely out-of-place, unless of course we give the user the option to manually specify a cutout area from where to copy the character and where to paste it into in our bitmap, which would be a completely overblown solution to this problem. The only really viable soltution is custom bitmap fonts that can be provided by the user.

This makes it pretty much impossible to merge any font with unknown proportions into the same bitmap without looking completely out-of-place

I never said anything about merging fonts. I really don't know if I'm not understanding what you're talking about, or if you misunderstood the point of this feature request.

I just want the Pattern Editor.FontDot option to affect Built-in fonts like Built-in (small) and Built-in (large), instead of only affecting custom user-chosen fonts like Terminal or GNU Unifont or whatever fonts are installed on the operating system.

For characters that aren't in the built-in font, just don't draw them, like how characters like $ are not drawn if they are in a custom note name of a custom tuning.

If that's not easy to implement, it's fine. I just want to make sure that you understand what I'm talking about. Thanks for your quick responses btw.

Well, nevermind. After looking at the source code, I think I can see why it might be hard to implement for the built-in fonts.

I'll keep this feature request open, in case you ever want to implement this at some point in the future.

Thanks for clarifying again. Then essentially what you are asking for is an extremely narrow special case of FontDot, because you want the dots to disappear. Solving that in another way would make a lot more sense, because of all the built-in font characters, space is about the only one that would make sense to be used.

What I could imagine is having different sets of preset images to fill the pattern with:

• Dots, like at the moment
• Zeros, like in ProTracker/FT2
• Empty space

This could be achieved much more easily than adjusting the FontDot option in any way for the built-in fonts.

Sure, that's a nice idea.

I like the idea of zeros, but it doesn't make sense to have zeros in the note column.

So maybe the presets could be better like this:

• Dots
• Empty space
• Zeros (dots for note column)
• Zeros (empty space for note column)

it would also be nice to have those zeros options for custom fonts as well. Maybe by having two separate FontDots, one for the note column, and the other for the rest of the columns. Maybe even four, each one for a different column.

Uhm, I think we can use the existing FontDot setting even for builtin fonts:
We need to interpret at the point of blitting from the font bitmap instead of when constructing the font bitmap (which does not happen for unscaled builtin fonts). We might need to additionally track if the mapping has already been performed (when constructing the bitmap), as I currently do not know whether we do that already anyway for other reasons.