Fix imports and work on drawing

Author: commonkestrel

examples/box.asm

@@ -1,3 +1,4 @@
+@define TEXT_BUFFER 0xF800
 @define SCREEN_WIDTH 80
 @define SCREEN_HEIGHT 25
 @define BOX_WIDTH (SCREEN_WIDTH - 2)
@@ -10,6 +11,7 @@
 @define WALL 0xBA
 @define DASH 0xCD
 
+@org 0x0000
 jmp [_start]
 
 /// math = ./math
@@ -23,8 +25,23 @@ _start:
     halt
 
 draw_top:
-    mv A, 1
+    mv A, 1 ; A contains the X coordinate
+    push A, 1, TL_CORNER ; x, y, character
+    call [draw_character]
+    halt
+    mv B, (BOX_WIDTH - 2)
+.loop:
+    inc A
+
+    push A, 1, DASH
+    call [draw_character]
 
+    dec B
+    jnz B, [.loop]
+
+    inc A
+    push A, 1, TR_CORNER
+    call [draw_character]
 
     ret
 
@@ -36,3 +53,16 @@ draw_left:
 
 draw_right:
     ret
+
+draw_character:
+    pop C, B, A ; character, y, x
+    push B, 0, SCREEN_WIDTH, 0
+    call [mul16] ; get Y offset
+    pop H, L
+
+    add16 H, L, (TEXT_BUFFER >> 8), (TEXT_BUFFER & 0xFF) ; Shift address to text-buffer space
+    add16 H, L, 0, SCREEN_WIDTH ; add X to address
+
+    st C
+
+    ret

math/mul.asm

@@ -0,0 +1,35 @@
+@ifndef MUL_ASM
+@define MUL_ASM
+
+/// Multiplies the most recent numbers on the stack, pushing the result back to the stack
+mul:
+    mv A, 0
+    pop C
+    pop B
+.loop:
+    add A, C
+    dec B
+    jnz B, [.loop]
+    push A
+    ret
+
+/// Multiples the top 16-bit integers on the stack, pushing the result back to the stack,
+/// with high at the top of the stack
+mul16:
+    mv A, 0
+    mv B, 0
+    pop E ; H0
+    pop F ; L0
+    pop C ; H1
+    pop D ; L1
+.loop:
+    add16 A, B, E, F
+    dec C, D
+    mv H, C
+    or H, D
+    jnz H, [.loop]
+    push B, A ; LO, HO
+    
+    ret
+
+@endif

src/assembler/macros.asm

@@ -1,28 +1,28 @@
 // All pre-built macros
 
 @macro push {
-    ; push two registers
-    (%r0:reg, %r1:reg) {
+    ; push two values
+    (%r0:reg|imm, %r1:reg|imm) {
         push %r0
         push %r1
     }
-    ; push three registers
-    (%r0:reg, %r1:reg, %r2:reg) {
+    ; push three values
+    (%r0:reg|imm, %r1:reg|imm, %r2:reg|imm) {
         push %r0
         push %r1, %r2
     }
-    ; push four registers
-    (%r0:reg, %r1:reg, %r2:reg, %r3:reg) {
+    ; push four values
+    (%r0:reg|imm, %r1:reg|imm, %r2:reg|imm, %r3:reg|imm) {
         push %r0
         push %r1, %r2, %r3
     }
-    ; push five registers
-    (%r0:reg, %r1:reg, %r2:reg, %r3:reg, %r4:reg) {
+    ; push five values
+    (%r0:reg|imm, %r1:reg|imm, %r2:reg|imm, %r3:reg|imm, %r4:reg|imm) {
         push %r0
         push %r1, %r2, %r3, %r4
     }
-    ; push six registers
-    (%r0:reg, %r1:reg, %r2:reg, %r3:reg, %r4:reg, %r5:reg) {
+    ; push six values
+    (%r0:reg|imm, %r1:reg|imm, %r2:reg|imm, %r3:reg|imm, %r4:reg|imm, %r5:reg|imm) {
         push %r0
         push %r1, %r2, %r3, %r4, %r5
     }