glScissor must be disabled

[MungoBerry]

Hi,

it seems I must disable glScissor to works properly on AMD Radeon HD 6450 card.
When I drag windows around glScissor fails:

I've solved adding glEnable(GL_SCISSOR_TEST) to r_clear() func and glDisable(GL_SCISSOR_TEST) to r_present() func.
I understand this is a quick demo but a not OpenGL expert like me can need to fix this.

Maybe there's a better workaround ?

Thank you.