The blue square.... IT LIVESSSgit add .!

gfx_util.asm

@@ -1,21 +1,70 @@
 VMEM equ 0xA000
 
-; di = y*320+x
-; ah = reserved
-; al = color
-; bx = width
-; cx = height
-gfx_rect:
+; di = y*32+x
+; ax = width
+; bl = height
+; bh = color
+
+; ax/bl = 0 is undefined behavior. Don't do it.
+; (To be clear, in the current implementation it just halts)
+
+_gfx_rect0:
     pusha
 
-    ; Set es to VMEM
     push VMEM
     pop es
 
-    .loop:
-        mov [es:di], al
+    mov dl, 0 ; row counter
 
-        jmp .loop
+    .row:
+        add dl, 1
+
+        mov cx, 0 ; col counter
+
+        .col:
+            add cx, 1
+
+            mov [es:di], bh
+            add di, 1
+
+            cmp cx, ax
+            jnz .col
+        
+        sub di, ax ; di - width + 320. == x=x1; y++
+        add di, 320
+
+        cmp dl, bl
+        jnz .row
+
+    popa
+    ret
+
+
+; cx = x
+; al = y
+; dx = width
+; bl = height
+; bh = color
+gfx_rect:
+    pusha
+
+    ; Set di to y*320+x
+    push bx
+    push dx ; Don't forget, mul clobbers dx!
+
+    mov ah, 0
+    mov bx, 320
+    mul bx
+    add ax, cx
+    mov di, ax
+
+    pop dx
+    pop bx
+
+    ; AX CLOBBERED
+    mov ax, dx
+
+    call _gfx_rect0
 
     popa
     ret

main.asm

@@ -21,31 +21,20 @@ main:
     mov ax, 0x0013
     int 0x10
 
-    push es
-    push 0xa000
-    pop es
+    mov cx, 50 ; x
+    mov al, 50 ; y
+    mov dx, 100 ; w
+    mov bl, 100 ; h
+    mov bh, 0x01 ; color = Dark blue
 
-    mov di, 0
-
-    mov bx, 0
-    .r:
-        add bx, 1
-        .f:
-            mov byte [es:di], bl
-            add di, 1
-            mod di, 320
-            cmp dx, 0
-            jnz .f
-        cmp bx, 200
-        jnz .r
-
-    pop es
+    call gfx_rect
 
 jmp $ ; Halt
     
 ; Libs
 %include "print_util.asm"
 %include "time_util.asm"
+%include "gfx_util.asm"
     
 ; Data
 HELLO_WORLD: