Hi all,
I'm trying to add support for transformations to OT-SVG glyphs. I've a concern.
For traditional glyphs, transforms are just directly applied to the coordinates of outline points. FreeType understands these outlines thus it can apply the transforms. For SVG glyphs, FreeType doesn't have the ability to manipulate the documents, instead we are gonna rely on the external library to apply the transform. The coordinate system of TTF/CFF outlines is different than the SVG coordinate system in many ways. The y axis is inverted and the relative scale is different too, since the SVG glyph is also free to choose the size of the EM square.
Thus, my point is, if I just directly apply the transform that the user has given, the result may not be the expected one if the user is unaware that the actual glyph that will get loaded is an OT SVG glyph. What's even worse is that, the transform is set before the glyphs are loaded, so the user doesn't know the EM square of the SVG glyph until after the glyph has been loaded.
The solution that I have in mind is, let the user pretend that the glyph is just a traditional one, then we take the transformation that the user has given and convert it to an equivalent one for the SVG coordinate system. The conversion will take into account y-axis inversion as well as the relative scale difference between the two.
I think this solution is good. Let me know your views. :-)
Moazin