This was verified by visual comparison with Flash Player; lines of text appear to be shifted by half-pixels, while the script output is always still rounded down.
This is an approximate text with a 1-pixel tolerance because our height is currently off by one and I cannot explain why. Previous attempts to fix the bug have resulted in cascading errors that resulted in off-by-one errors in the opposite direction. This is still better than nothing and I need to check other tests in.
Flash has a weird bug where it will NOT trim trailing spaces off of the metrics reported to users if the text is left-aligned. We replicate this here so that tests pass.
The `Default` bounds are NOT safe to union against if they were uninitialized. Doing so will force any resulting layout box to enclose `(0,0)`, which can throw off certain layout calculations. Instead, we use `None` to signal an uninitialized box.
`EditText` supports two different forms of leading:
1. Font-provided leading, specified relative to the EM square and scaled with font size
2. User-specificed leading, specified in pixels
Notably, the former appears to apply to the first line in the text and pushes it down. This showed up in the `edittext_font_size` test, and according to that test result the leading is rounded *up* to the nearest pixel, plus one.
That last bit seems possibly wrong and is subject to further change, but it matches the tests at multiple scales.
Certain text routines calculate text on the pixel grid, despite the fact that Flash ordinarily works in twips. There is probably a reason for this - my guess is to keep text wrapping stable across multiple pixel densities (e.g. low-res screens plus high-res print).
I don't know why, but this is necessary for the "NEW STUFF" box on homestarrunner.com's toons menu to position correctly. SOMEWHERE, we are performing some kind of operation that adjusts one of the two, but not the other, and I can't find out what.
This fixes spaces at the start of text spans not being rendered, but also breaks center-align.
I also broke the font tests, so I had to rewrite them, which makes me question their value.
Right margins: Simple enough, we just need to subtract the right margin from the bounds when we calculate our alignment adjustment.
Trailing spaces: This is very tricky as we effectively have to remeasure the last box in the line when fixing it up. This also means LayoutContext has to hold the text itself so we can remeasure again...
Lines wider than bounds: If word wrap is disabled it is possible for a line to exceed the bounds of the box. In this case it will be left-aligned. Effectively, the align adjustment is clamped to positive values and we do that here too.
This doesn't work right yet because the resulting width doesn't apply correctly to the field. This is because `EditText`'s `_width` and `_height` change it's intrinsic bounds rather than it's X and Y scale (like it would with a button or a movie clip).
These tests depend on the particulars of our default device font, Noto Sans. If this test proves to be fragile we may need to create a testing font with a locked width and kerning table...
This prevents a bounds-check panic when we inevitably try to slice an array like `[300..2]` or something like that.
We also skip rendering the space that we're turning into a newline to avoid it popping up on the next line by accident.
David Wendt