clear_screen:
	; fill screen with a color
	mov rdi, [visu_surf]
	push rdi
	call SDL_LockSurface

	%ifdef SDL1
		xor rcx, rcx
		MOV_surf_w ecx, visu_surf
		push rcx
		MOV_surf_h ecx, visu_surf
		MOV_surf_pixels rdi, visu_surf
		;mov rax, 0xffcc22ff ; magenta
		;mov rax, 0xffffffff ; white
		dec rcx
		.loop_razh:
			push rcx
			mov rcx, [rsp+8]
			dec rcx
			.loop_razw:
				stosd
				loop .loop_razw
			pop rcx
			loop .loop_razh
		pop rcx
	%endif

	pop rdi ; surface addr
	call SDL_UnlockSurface

	mov rdi, [visu_surf]

blitflip_visu:
	; blit a suface on screen and flip screen
	; with rdi the src surface

	xor rsi, rsi
	mov rdx, [visu_scr]
	xor rcx, rcx
	call SDL_BlitSurface
	test rax, rax
	jnz sdl_error

flip_visu:
	; flip screen

	%ifdef SDL2
		mov rdi, [visu_win]
		call SDL_UpdateWindowSurface
	%endif
	%ifdef SDL1
		mov rdi, [visu_scr]
		call SDL_Flip
	%endif
	
	ret