Hello again,
I have some questions stacked so I think I'll ask them in a bunch(except for one).

1. I've noticed quite a slow performance of the CL_Font rendering. In my game I have one particular effect - a floating score points when player pick ups a bonus, and I use sprite font for this. I got a noticeable performance drop when I encountered situation with about a half thousand of such floating scores had to be rendered on screen. Profiling pinpointed me that this performance drop happened in draw_text function of CL_Font and half of it consist of vector's allocations. I'll rewrite score effect with my own renderer, I think, but it would be nice to have CL_Font to perform better anyway.

2. I am not very familiar with OpenGL and modern graphics rendering algorithms generally, to my own shame. So I whould be very grateful if you could give me some overall guidance about how ClanLib works in general overview and how I can improve it's performance from my side.
For example, am I correct that using one big sprite sheet image for ten sprites is better than using ten different images with spritesheets for each sprite?
It is possible to create different sprites using one source image but will it image be stored as one texture or each sprite object will create it's own texture nonetheless?
Should I assume that OpenGL rendering pass can take up to three textures at once and if there are more textures to render it will require another pass? How to correctly take rendering sequence into consideration when constructing rendering cycle? For example, if I have some small image used in rendering both in the lower background layer and in the topmost effects layer with about ten layers of game objects between them - wouldn't it be better not to use separate sprite for this image but to include it to background and effects spritesheets twice?
What are optimal sizes for textures to use? Or should I ask better what are texture sizes that would choke graphic performance being too small or too big or something else?

Well, that will do for now

P.S.: I'm using ClanLib 2.2 currently. Maybe there is already improvement with CL_Font in 2.3 I just don't know about?