Implement a FontUsage class, replacing simple font names

[FreezyLemon]

The assumption for font names here is either just the font family name, or family-[weight]["Italic"] (both weight and "Italic" being optional).

• Closes FontName should be replaced #2003

While old methods of setting font attributes will still work, they are now marked as [Obsoleted]. You should use Font = new FontUsage(size: 200) going forward. For convenience, you can adjust existing fonts like so:

var font = new FontUsage(family: "SourceCodePro");

var fontWithSize = font.With(size: 24);

[smoogipoo]

I'm not sure we want to complicate this by having events and mutability. How about making FontUsage a readonly struct?

[FreezyLemon]

Good point, I'll change it to something simpler as soon as I find the time

[smoogipoo]

After discussing with @peppy , it seems we want to have the following sort of structure, similar to that of OsuColour:

OsuFont:
    FontUsage Header1 = ...;
    FontUsage Header2 = ...;
    FontUsage Monospace = ...;

For this to work FontUsage should also contain TextSize and FixedSize as in the issue description.

[FreezyLemon]

Sure! But this would mean (with a readonly struct) that for every change in text size, a new FontUsage struct would have to be created. I guess that's fine? Just want you to be aware that this changes the usage from

sprite1.TextSize = 150

to

sprite1.Font = new FontUsage("OpenSans", 150).

[luaneko]

You could make TextSize a helper property which reconstructs FontUsage with a new size.

[FreezyLemon]

Good idea! Maybe I should do the same for FixedWidth too.

That way, it's still easy to change these properties but they're both contained in the new struct so the approach (Header1 = ...; Header2 = ...) outlined by smoogi above still works.

[FreezyLemon]

Something I forgot about in this...
With this approach, if someone uses something like

new SpriteText
{
    Font = new FontUsage("OpenSans"),
    TextSize = 100,
};

there is a possibility of the text size being reset/ignored if the line with "Font = ..." is executed after the TextSize setter. No real way around it unless you just don't use TextSize in a FontUsage initializer.

Might just revert this change to completely work around the issue.

[luaneko]

I think it's fine. TextSize is just a helper property for Font. It's the same concept as Size, which is just a helper property for Width and Height. Same goes for Position, and probably many others. Doing something like

new Container
{
    Width = 100,
    Size = new Vector2(200)
}

renders the width initialiser completely redundant. You might as get rid of every helper property if you're worried.

[FreezyLemon]

While it is true that there are other properties that are somewhat redundant, I think there is a difference here:

When you see an initializer like the one you posted, it seems obvious that one of these properties overrides the other (a Size includes a width and a height).
With my example, it doesn't seem as obvious (associating "font" with text height is not usual imho, most people would probably associate font family and maybe weight with the term "font"), especially considering that you currently need to use the TextSize in conjunction with Font AND that the text size does not have to be explicitly specified since there is a default value.

In addition, with what smoogi mentioned above (using pre-defined FontUsages), I don't think this is such a big issue.

[FreezyLemon]

Keeping the comment directly above in mind, how should I handle this now?

There are a lot (~55) simple sprite.TextSize = X initializers / statements just in the framework.
To get this into a compiling state without the TextSize property, I'd either have to replace all these manually with Font = new FontUsage("OpenSans", X) (too verbose?) or maybe start adding some pre-defined usages already. Not sure how to proceed.

[peppy]

I think it's fine to update these existing usages, yes. Do note that you will need to make family optional (default null) so you don't need to specify the fallback (in the framework's case, OpenSans).

[FreezyLemon]

Quick note that with the family being null, italics and font weight don't work. This is due to how the fallback font is "selected". I am not sure if it's viable to change the whole texture routine to fix this... especially performance-wise

[smoogipoo]

I've adjusted this PR with what I see are required changes to get things working nicely. Of note:

1. Old members have been added back temporarily, which throw build-time + resharper warnings.
2. FontUsage has a new .With() method allows adjustment of fonts while preserving other untouched members.

I want to keep the obsolete members in for a month or two or so, just to give people enough time to migrate away from it (it's a pretty intrusive change).

I believe this PR is ready now, @peppy requesting review.