Currently, if the rect packer is unable to fit all of the text glyphs into a single atlas texture, then text rendering will fail.

This is normally not a problem when targeting modern mobile devices with huge texture size limits, but Impeller may be used with embedded systems that are much more restrictive. For example, QNX with a 2048x2048 OpenGL texture size limit. To make Impeller text rendering safer, we should overflow atlas glyphs into multiple packed textures when the max texture size has been reached.