From 411b0fda72c30e024bfdd17b7ce0afc7b799ada3 Mon Sep 17 00:00:00 2001
From: Joshua Bell <inexorabletash@gmail.com>
Date: Sat, 9 Feb 2019 13:11:12 -0800
Subject: [PATCH] factor out mul/div routines

---
 desktop/desktop_lc.s   | 50 ++++++++++++++++++++++++++++++++++++++++++
 desktop/desktop_main.s | 13 +++++------
 desktop/ovl2.s         | 36 ++++++++++++------------------
 3 files changed, 70 insertions(+), 29 deletions(-)

diff --git a/desktop/desktop_lc.s b/desktop/desktop_lc.s
index 10624f2..8273c44 100644
--- a/desktop/desktop_lc.s
+++ b/desktop/desktop_lc.s
@@ -253,6 +253,56 @@ op:     lda     dummy1234
         rts
 .endproc
 
+;;; ============================================================
+;;; Input: numbers in A,X, Y
+;;; Output: number in A,X
+
+.proc Multiply_16_8_16
+        stax    num16
+        sty     num8
+        copy16  #0, accum
+        ldx     num8
+        beq     done
+
+loop:   add16   num16, accum, accum
+        dex
+        bne     loop
+
+done:   ldax    accum
+        rts
+
+num16:  .word   0
+num8:   .byte   0
+accum:  .word   0
+
+.endproc
+
+;;; ============================================================
+;;; Input: numerator in A,X, divisor in Y
+;;; Output: result in A,X
+
+.proc Divide_16_8_16
+        stax    numerator
+        sty     divisor
+        copy16  #0, result
+
+loop:   sub16_8 numerator, divisor, numerator
+        bmi     done
+        inc16   result
+        jmp     loop
+
+done:   ldax    result
+        rts
+
+numerator:
+        .word   0
+divisor:
+        .byte   0
+
+result: .word   0
+
+.endproc
+
 ;;; ============================================================
 
         PAD_TO $D200
diff --git a/desktop/desktop_main.s b/desktop/desktop_main.s
index a3f68e2..1b778d9 100644
--- a/desktop/desktop_main.s
+++ b/desktop/desktop_main.s
@@ -14102,7 +14102,7 @@ done:   jmp     reset_grafport3a
         jmp     skip
 
         ;; Compute text width and center it
-:       tya
+:       and     #$7F            ; strip "center?" flag
         pha
         add16   ptr, #1, textptr
         jsr     load_aux_from_ptr
@@ -14111,14 +14111,13 @@ done:   jmp     reset_grafport3a
         lsr16   result
         sub16   #200, result, dialog_label_pos
         pla
-        and     #$7F            ; strip "center?" flag
-        tay
 
         ;; y = base + desktop_aux::dialog_label_height * line
-skip:   copy16  dialog_label_base_pos::ycoord, dialog_label_pos::ycoord
-:       add16   dialog_label_pos::ycoord, #desktop_aux::dialog_label_height, dialog_label_pos::ycoord
-        dey
-        bne     :-
+skip:   ldx     #0
+        ldy     #desktop_aux::dialog_label_height
+        jsr     Multiply_16_8_16
+        stax    dialog_label_pos::ycoord
+        add16   dialog_label_pos::ycoord, dialog_label_base_pos::ycoord, dialog_label_pos::ycoord
         MGTK_RELAY_CALL MGTK::MoveTo, dialog_label_pos
         addr_call_indirect draw_text1, ptr
         ldx     dialog_label_pos
diff --git a/desktop/ovl2.s b/desktop/ovl2.s
index 119bfa0..775336d 100644
--- a/desktop/ovl2.s
+++ b/desktop/ovl2.s
@@ -255,7 +255,7 @@ L0B47:  .byte   0
 
 ;;; ============================================================
 
-        labels_voffset = 40
+        labels_voffset = 49
 
 L0B48:  cmp16   screentowindow_windowx, #40
         bpl     :+
@@ -265,7 +265,7 @@ L0B48:  cmp16   screentowindow_windowx, #40
         return  #$FF
 :       lda     screentowindow_windowy
         sec
-        sbc     #labels_voffset+desktop_aux::dialog_label_height
+        sbc     #labels_voffset
         sta     screentowindow_windowy
         lda     screentowindow_windowy+1
         sbc     #0
@@ -274,17 +274,12 @@ L0B48:  cmp16   screentowindow_windowx, #40
 :       sta     screentowindow_windowy+1
 
         ;; Divide by desktop_aux::dialog_label_height
-        ldx     #0
-        lda     screentowindow_windowy
-:       sec
-        sbc     #desktop_aux::dialog_label_height
-        bmi     :+
-        inx
-        bne     :-              ; always
+        ldax    screentowindow_windowy
+        ldy     #desktop_aux::dialog_label_height
+        jsr     Divide_16_8_16
+        stax    screentowindow_windowy
 
-:       stx     screentowindow_windowy
-        lda     screentowindow_windowy
-        cmp     #$04
+        cmp     #4
         bcc     L0B98
         return  #$FF
 
@@ -359,16 +354,13 @@ L0C20:  ldy     #39
         txa
         sec
         sbc     L0CA9           ; entry % 4
-        tax
-        lda     #0
-:       clc
-        adc     #desktop_aux::dialog_label_height
-        dex
-        bpl     :-
-        adc     #labels_voffset
-        sta     select_volume_rect::y1
-        lda     #0
-        sta     select_volume_rect::y1+1
+        ldx     #0
+
+        ldy     #desktop_aux::dialog_label_height
+        jsr     Multiply_16_8_16
+        stax    select_volume_rect::y1
+        add16_8 select_volume_rect::y1, #labels_voffset, select_volume_rect::y1
+
         add16   select_volume_rect::x1, #label_width-1, select_volume_rect::x2
         add16   select_volume_rect::y1, #desktop_aux::dialog_label_height-1, select_volume_rect::y2
         MGTK_RELAY_CALL MGTK::SetPenMode, penXOR