1 files changed, 123 insertions, 0 deletions
diff --git a/builtin_vga_demo.asm b/builtin_vga_demo.asm
new file mode 100644
index 0000000..54d4a4f
--- /dev/null
+++ b/builtin_vga_demo.asm
@@ -0,0 +1,123 @@
+%ifndef _VGA_DEMO_ASM
+%define _VGA_DEMO_ASM
+
+VGA_SCREEN_WIDTH equ 320
+VGA_SCREEN_HEIGHT equ 200
+VGA_COLORS equ 0x100
+
+vga_plot:
+	%define .x [bp + 4]
+	%define .y [bp + 6]
+	%define .color [bp + 8]
+	push bp
+	mov bp, sp
+	pusha
+	push es
+	push ds
+	;push ax
+	;push cx
+	;push dx
+	;push di
+;
+	xor ax, ax
+	xor cx, cx
+	xor dx, dx
+	xor di, di
+
+	mov ax, 0A000h
+	mov es, ax			; Store VGA memory segment in ES
+	mov ds, ax
+
+	mov ax, word VGA_SCREEN_WIDTH
+	mov cx, word .y
+	mul cx
+	add ax, word .x
+	mov di, ax
+
+	mov ax, word .color
+	mov [es:di], ax
+
+	.return:
+		;pop di
+		;pop dx
+		;pop cx
+		;pop ax
+		pop ds
+		pop es
+		popa
+		mov sp, bp
+		pop bp
+		ret
+
+
+
+builtin_vga_demo:
+	push bp
+	mov bp, sp
+	sub sp, 2
+
+	;
+	; no arguments for this program
+	;
+
+	.main:
+		mov ah, 0fh		; get current video mode
+		int 10h
+		mov [bp - 2], al	; save current video mode
+
+		mov ah, 00h
+		mov al, 13h		; set 256 color VGA mode
+		int 10h
+
+		mov di, 0ffh
+		.loop:
+			mov si, .data_smiley	; address of smiley face array
+			mov cx, 10	; number of array elements
+		.do_plot:
+			mov ax, [si]	; Load coordinates
+			add si, 2	; Next set
+
+			movzx dx, al	; Store y
+			movzx bx, ah	; Store x
+
+			push di		; color
+			push dx		; y
+			push bx		; x
+			call vga_plot	; write pixel
+			add sp, 2 * 3
+
+			and di, 0ffh	; DI overflows into infinity so
+					; use its low byte instead of resetting to zero
+			dec di		; Next color
+			dec cx		; Next loop
+			jne .do_plot
+
+		xor ax, ax
+		call kbd_read_async	; ZF=1 if no key is pressed
+		je .loop
+
+	.return:
+		mov ah, 00h		; Set video mode
+		mov al, [bp - 2]	; Restore video mode
+		int 10h
+
+		add sp, 2
+		mov sp, bp
+		pop bp
+		ret
+
+	.data_smiley:
+		;  plots a smiley face using coordinates
+		;  row col
+		db 01h,01h	; left eye
+		db 01h,05h	; right eye
+		db 04h,03h	; nose
+		db 06h,00h	; left uptick mouth
+		db 06h,06h	; mouth
+		db 07h,01h	; mouth
+		db 07h,02h	; mouth
+		db 07h,03h	; mouth
+		db 07h,04h	; mouth
+		db 07h,05h	; right uptick mouth
+
+%endif