SDL is not too slow, its the reason that today no programmer code for a 50 MHZ CPU.
you can use the netsurf or other game ports for linux on a X86 with 50 MHZ.
You see all crawl.the programs are too complex, and they use more bustransfer speed as a slow mediator can offer.thats all.
If you put a 68060 CPU and have a fast GFX Card interface, you can see SDL fly.
too bad that the natami is still not here and show this.
and if you use a native GUI or not doesnt matter for netsurf speed.
problem of netsurf is too, that it can only support 1 pixelformat per bit depth.
I have done the convert routines to use rgb32, or rgb16, but this work not good on voodoo boards and some other cards, but SDL offer to support all cards and can swap data, and with a fast bustransfer speed this cost not so much noticable time in scrolling speed.
so there need another netsurf build do, that support bgr32 and rgb16 PC.
then need release 2 versions, and i am too lazy to add the pixelformant converter for another pixelformat again.
but if somebody add the code in netsurf framebuffer to support rgb16PC, then scroll can work faster on Voodoo 3 cards.
but on page create time it speed up nothing. css is too complex and need so much FPU calcs that a 50 MHZ CPU give no better results.