I display text using OpenGL which is aligned with (2D) objects that can have any rotation on display, making the text also appear at any angle on display. So far I've used FreeType to render raster for each supported symbol to file and load the files into OpenGL as textures at application start.
When the text is rotated (other than 90 degree increments) the hinting goes all bad. My plan so far to remedy the situation is to render a few rotated (transformed) variants of each symbol and linearly interpolate between the two closest variants. As an example I may render variants in 15 degree increments between 0-75 degrees inclusive, and if text is rotated by 5 degrees on display I'd take 1/3 from the 0 degree raster and 2/3 from the 15 degree raster.
...but this is only a theory of mine. Should work if having small enough increments, but if there are too many of them I'll run out of memory resources and making the shader awfully inefficient. I imagine the increment count depends on the pixel size of each symbol which could turn problematic...
So I reach out to the expert community: How to render rotated text with proper font hinting in real-time?
Using OpenGL ES 2.0. Font size ~16pix. If you need more info ask away.