glyph_brush_layout line metrics

[cjhowedev]

It would be nice to be able to retrieve something similar to DirectWrite's DWRITE_LINE_METRICS from glyph_brush_layout in addition to the actual glyph positions. This would allow us to more easily position inline content within the text, for example, a cursor for a text entry box. Right now, any inline content requires modifying the returned layout to make room for your cursor, and positioning the cursor for text input vertically is impossible.

[alexheretic]

With the returned Vec<SectionGlyph> you have positions of each glyph & the section-byte index for the char.

So if you know your cursor's section-byte index you can find a position to draw it. You can also infer various line metrics from same-y glyphs.

I wouldn't normally imagine moving the layout around to make room for a cursor, don't they usually just go between the glyphs? Custom inline non-glyph content, like a arbitrary rect, is not currently supported but I imagine could be added.

[cjhowedev]

I guess this is just aggregating glyph metrics like ascent and descent across SectionGlyphs for each line. ab_glyph's ScaleFont has the metrics I was looking for, which I should be able to combine with SectionGlyph to calculate the line metrics on my own.