add an alternate viewport (compile-time currently)

zoomed to max

mandel.s

@@ -246,6 +246,18 @@ fill_masks:
     .byte %00000001
     .byte %00000000
 
+viewport_zoom:
+    .byte 1
+    .byte 8
+
+viewport_ox:
+    .word $0000
+    .word $f110
+
+viewport_oy:
+    .word $0000
+    .word $fbe0
+
 ; 2 + 9 * byte cycles
 .macro add bytes, dest, arg1, arg2
     clc ; 2 cyc
@@ -1213,13 +1225,27 @@ zero_byte_loop:
 
     jsr imul8xe_init
 
-    ; ox = 0; oy = 0
+    ; initialize viewport
+    ;ldx #0 ; overview
+    ldx #1 ; closeup
+    lda viewport_zoom,x
+    sta zoom
+
+    txa
+    asl a
+    tax
+    lda viewport_ox,x
+    sta ox
+    lda viewport_oy,x
+    sta oy
+    inx
+    lda viewport_ox,x
+    sta ox + 1
+    lda viewport_oy,x
+    sta oy + 1
+
     ; count_frames = 0; count_pixels = 0
     lda #0
-    sta ox
-    sta ox + 1
-    sta oy
-    sta oy + 1
     sta count_frames
     sta count_pixels
 
@@ -1229,10 +1255,6 @@ zero_byte_loop:
     ldx #total_pixels
     jsr ZF1
 
-    ; zoom = 2x
-    lda #1
-    sta zoom
-
     ; Disable display DMA
     lda #0
     sta DMACTL