X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?p=ld45_start_nothing;a=blobdiff_plain;f=src%2Fgfx.asm;fp=src%2Fgfx.asm;h=d35213935a64775454a4b5145621837a550a34a2;hp=0000000000000000000000000000000000000000;hb=778d7ca8d282c31b4067f6a6e06df7be72822ea1;hpb=43024162f96501c111a0fb7ff6b14f39d478c1a3

diff --git a/src/gfx.asm b/src/gfx.asm
new file mode 100644
index 0000000..d352139
--- /dev/null
+++ b/src/gfx.asm
@@ -0,0 +1,88 @@
+; vi:filetype=nasm ts=8 sts=8 sw=8:
+;
+; list of functions
+; -----------------
+; init_gfx
+;    initializes the video hardware and graphics routines
+; clear
+;    clears the framebuffer (not vmem)
+;    clobbers: ax, cx, di
+; swap_buffers
+;    copies the framebuffer to video memory
+;    clobbers: ax, cx, di, si
+; wait_vsync
+;    clobbers: al, dx
+; set_palette_entry(idx[al], r[ah], g[bl], b[bh])
+;    colors are 0-255
+
+VIDMEM_SEG	equ 0a000h
+FRAMEBUF_SEG	equ 09000h
+
+REG_CRTC_STATUS	equ 3dah
+CRTC_VBLANK_BIT	equ 08h
+
+REG_DAC_ADDR	equ 3c8h
+REG_DAC_DATA	equ 3c9h
+
+init_gfx:
+	; video mode 13h (320x200 8bpp)
+	mov ax, 13h
+	int 10h
+
+	call clear
+	ret
+
+clear:
+	push es
+	mov ax, FRAMEBUF_SEG
+	mov es, ax
+	xor di, di
+	xor ax, ax
+	mov cx, 16000
+	rep stosd
+	pop es
+	ret
+
+swap_buffers:
+	push ds
+	push es
+	mov ax, FRAMEBUF_SEG
+	mov ds, ax
+	xor si, si
+	mov ax, VIDMEM_SEG
+	mov es, ax
+	xor di, di
+	mov cx, 16000
+	rep movsd
+	pop es
+	pop ds
+	ret
+
+wait_vsync:
+	mov dx, REG_CRTC_STATUS
+.wait_vblank_end:
+	in al, dx
+	and al, CRTC_VBLANK_BIT
+	jnz .wait_vblank_end
+.wait_vblank_start:
+	in al, dx
+	and al, CRTC_VBLANK_BIT
+	jz .wait_vblank_start
+	ret
+
+set_palette_entry:
+	push dx
+	mov dx, REG_DAC_ADDR
+	out dx, al
+	inc dx	; dx <- REG_DAC_DATA
+	mov al, ah
+	shr al, 2
+	out dx, al
+	mov al, bl
+	shr al, 2
+	out dx, al
+	mov al, bh
+	shr al, 2
+	out dx, al
+	pop dx
+	ret