Support for all BMFont output file types in FlxBitmapFont

[UncertainProd]

FlxBitmapFont.fromAngelCode used to work only with XML files generated by BMFont, but BMFont can also generate text or binary file descriptors. This pr should add support for all BMFont output format types. It also deprecates FlxAngelCodeXmlAsset which is now renamed to FlxAngelCodeAsset since it can also support strings and bytes

[Geokureli]

are there additional features we could gain from these other file formats, or is this just for variety?

[UncertainProd]

It's mainly to support all the 3 types of font descriptors that BMFont provides. The binary format, for example usually takes up less space than the text and xml format

[Geokureli]

whoops, got distracted, got any sample files I can use to test this, preferably 3 different files formats made from the same font

[UncertainProd]

Sure, I used this font: https://emhuo.itch.io/nico-pixel-fonts-pack
Test_Font_DigitalPup.zip

Source code that I used:

package;

import flixel.FlxG;
import flixel.FlxState;
import flixel.graphics.frames.FlxBitmapFont;
import flixel.text.FlxBitmapText;

class PlayState extends FlxState
{
	var bmText:FlxBitmapText;
	var curIndex = 0;

	var tests:Array<{ font: FlxBitmapFont, text: String }>;
	override public function create()
	{
		super.create();
		var testXMLFont:FlxBitmapFont = FlxBitmapFont.fromAngelCode('assets/images/DigitalPup.png', 'assets/images/BMFont XML/DigitalPup.fnt');
		var testtxtFont:FlxBitmapFont = FlxBitmapFont.fromAngelCode('assets/images/DigitalPup.png', 'assets/images/BMFont Text/DigitalPup.fnt');
		var testBinaryFont:FlxBitmapFont = FlxBitmapFont.fromAngelCode('assets/images/DigitalPup.png', 'assets/images/BMFont Binary/DigitalPup.fnt');

		tests = [
			{
				font: testXMLFont,
				text: 'This font uses XML'
			},
			{
				font: testtxtFont,
				text: 'This font uses Text'
			},
			{
				font: testBinaryFont,
				text: 'This font uses Binary'
			},
		];

		bmText = new FlxBitmapText(0, 0, tests[curIndex].text, tests[curIndex].font);
		bmText.scale.scale(2.0);
		bmText.screenCenter();
		add(bmText);
	}

	function changeFontTo(index: Int)
	{
		bmText.text = tests[index].text;
		bmText.font = tests[index].font;
	}

	override public function update(elapsed:Float)
	{
		super.update(elapsed);
		if(FlxG.keys.justPressed.LEFT)
		{
			curIndex--;
			if(curIndex < 0)
				curIndex = 2;
			changeFontTo(curIndex);
		}

		if(FlxG.keys.justPressed.RIGHT)
		{
			curIndex = (curIndex + 1) % 3;
			changeFontTo(curIndex);
		}
	}
}

[Geokureli]

Made some changes:

1. the typedefs are now classes that use @:structInit
2. Changed FlxAngelCodeAsset from a typedef to an abstract, with a parse() function
3. the parsing of the BMFont object are now moved to their respective classes.
4. made a generic BMFontUtil.forEachAttribute to iterate the key-value pairs of BMFont's text format, rather than using the ad-hoc per-char parser you made (I was actually getting infinite loops on some of my tests, and this prevents it)
5. renamed the classes
6. moved to the bmfont package
7. added an optional letter field to BMFontChar, using id everwhere. Note: binary only has id, where .xml and and .txt seem to sometimes have a letter field, but ALWAYS have a an id in my tests, if you saw a case where id was missing, let me know
8. renamed some class fields to more closely match the source data's field names

re - 1, 2, 3 and 4:
this should make it easier to make changes to individual classes across all parsers, it should improve some performance on desktop targets and is typically how I prefer to organize file data objects. this opens up the floor for more features inside these classes down the road, like the ability to merge font instances and use multi-atlas tools. and once code-climate is fixed to allow final vars we can make many these class fields final and get more perf benefits of having immutable kernings, chars and whatnot

What's left

• I think this needs a unit test that loads a minimal font example in all three formats and verifies that the data in these files are being parsed and used correctly, even the optional kerning stuff

• Some minimal docs explaining how to use these classes via FlxBitmapFont.fromAngelCode, and @since tags

[UncertainProd]

I tested this on a few fonts I had and it seems to work (although I haven't tested with any fonts having kerning pairs yet).

binary only has id, where .xml and and .txt seem to sometimes have a letter field, but ALWAYS have a an id

Yeah I haven't seen any fonts without an id field so far
Edit: I tried using this font which had kerning pairs (after manually converting it using bmfont) and it seems to work too.

[MondayHopscotch]

Overall this looks like a great addition. I had a couple comments around cleanup and one potential bug.

This also looks like a good place for a couple unit tests to get some coverage of the code.

[MondayHopscotch]

These don't appear to be part of the spec, but I've seen tools like Hiero put these lines in. Do you know where they come from / why they are here? Maybe just so human eyes can spot check the file for accuracy?

[Geokureli]

I don't know who Hiero is, but I assume the count is either to make sure you parsed correctly, or to aid in the parsing in some way

[MondayHopscotch]

Oops. Mean to add link, but obviously didn't. Hiero is a libGDX font tool that I've used before.

[UncertainProd]

I had generated a few fonts using BMFont and I saw these tags there. It doesn't seem to be part of the binary file spec but I did see them in the text and xml outputs

[MondayHopscotch]

Might be worth adding a comment to call out that this isn't part of the spec and is here for debug purposes, if needed. (at least that's what I've gathered from this PR)

[Geokureli]

this isn't part of the spec

what does "this" refer to?

[MondayHopscotch]

https://www.angelcode.com/products/bmfont/doc/file_format.html

Didn't realize this wasn't already in the PR description or something like that

[MondayHopscotch]

And I was specifically calling out that letter isn't in the spec, in case that's what you were asking.

[UncertainProd]

Yeah I found that the letter field gets generated sometimes for the text/xml outputs (despite not being part of the spec) so I thought of adding it here just in case

[Geokureli]

I'm not sure why and when letter appears in bmfont files, but it does, sometimes, so I figured it should be in the type as an optional field

[MondayHopscotch]

@UncertainProd, I'm throwing together some unit tests for this that I'll put a PR against your branch hopefully later today along with a couple other changes related to my other comments.

[Geokureli]

Thanks @UncertainProd and @MondayHopscotch !