From 07db3d00d7ff36afe331c6adbeae2398a53c8173 Mon Sep 17 00:00:00 2001
From: Brooke Vibber <bvibber@pobox.com>
Date: Sat, 22 Feb 2025 11:23:13 -0800
Subject: [PATCH] second status bar display with coords/zoom

currently using 3.13 precision to output to floats for formatting
---
 mandel.s | 162 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 160 insertions(+), 2 deletions(-)

diff --git a/mandel.s b/mandel.s
index 81ee0eb..a89be85 100644
--- a/mandel.s
+++ b/mandel.s
@@ -169,6 +169,27 @@ str_padding_len = str_padding_end - str_padding
 
 speed_start = 40 - str_done_len - str_speed_len - str_padding_len - 1
 
+col_x = 1
+str_x:
+    .byte "X:"
+    .byte 0
+str_x_len = 2
+str_x_space = 12
+str_x_padding = 2
+
+col_y = str_x_len + str_x_space + str_x_padding
+str_y:
+    .byte "Y:"
+    .byte 0
+str_y_len = 2
+str_y_space = 12
+str_y_padding = 2
+
+col_zoom = col_y + str_y_len + str_y_space + str_y_padding
+str_zoom:
+    .byte "ZOOM:"
+    .byte 0
+str_zoom_len = 5
 
 char_map:
     ; Map ATASCII string values to framebuffer font entries
@@ -205,6 +226,17 @@ aspect_x: ; fixed3.13 5/4
 aspect_y: ; fixed3.13 3/4
     .word 3 << (13 - 2)
 
+fixed3_13_as_float: ; float48
+    ; 1 << 13
+    ; 8192
+    ; 81 92 . 00 00 00
+    .byte 65 ; exponent/sign - +1 byte
+    .byte $81
+    .byte $92
+    .byte $00
+    .byte $00
+    .byte $00
+
 sec_per_frame: ; float48 00 . 01 66 66 66 67
     .byte 63  ; exponent/sign - -1 bytes
     .byte $01 ; BCD digits
@@ -895,6 +927,68 @@ next:
 
 .endmacro
 
+; input in FR0, 16 bits signed 3.13 fixed
+; output in FR0, Atari float
+; clobbers a, x, y, FR0, FR1
+.proc fixed3_13_to_float
+    ldx #.lobyte(fixed3_13_as_float)
+    ldy #.hibyte(fixed3_13_as_float)
+    jsr FLD1R
+
+    ; check sign bit! conversion routine is for unsigned
+    lda FR0 + 1
+    bpl positive
+
+negative:
+    neg16 FR0
+    jsr IFP
+
+    ; set float sign bit
+    lda FR0
+    ora #$80
+    sta FR0
+    jmp common
+
+positive:
+    jsr IFP
+
+common:
+    jsr FDIV
+    rts
+
+.endproc
+
+; input in FR0, Atari float
+; output in FR0, 16 bits signed 3.13 fixed
+; clobbers a, x, y, FR0, FR1
+.proc float_to_fixed3_13
+    ldx #.lobyte(fixed3_13_as_float)
+    ldy #.hibyte(fixed3_13_as_float)
+    jsr FLD1R
+    jsr FMUL
+
+    ; check sign bit! conversion routine is for unsigned
+    lda FR0
+    bcc positive
+
+negative:
+    ; clearfloat sign bit
+    lda FR0
+    eor #$80
+    sta FR0
+
+    jsr FPI
+    neg16 FR0
+    jmp common
+
+positive:
+    jsr FPI
+
+common:
+    rts
+
+.endproc
+
 .proc mandelbrot
     ; input:
     ; cx: position scaled to 6.26 fixed point - -32..+31.9
@@ -1254,7 +1348,7 @@ done:
 .endproc
 
 ; in/out: column in text_col
-; in: row in text_row @fixme implement
+; in: row in text_row
 ; in: pointer to string in INBUFF
 ; clobbers x/y/a/temp
 .proc draw_string
@@ -1269,6 +1363,21 @@ done:
     adc #0
     sta temp + 1
 
+    ldx text_row
+    beq done_rows
+continue_rows:
+    clc
+    lda temp
+    adc #40
+    sta temp
+    lda temp + 1
+    adc #0
+    sta temp + 1
+    dex
+    bne continue_rows
+
+done_rows:
+
     ldy #0
 loop:
     lda (strptr),y
@@ -1429,7 +1538,7 @@ skip_char:
 
 plus:
     lda zoom
-    cmp #7
+    cmp #8
     bpl skip_char
     inc zoom
     jmp done
@@ -1441,15 +1550,19 @@ minus:
     jmp done
 up:
     sub32 oy, oy, temp
+    jsr display_coords
     jmp done
 down:
     add32 oy, oy, temp
+    jsr display_coords
     jmp done
 left:
     sub32 ox, ox, temp
+    jsr display_coords
     jmp done
 right:
     add32 ox, ox, temp
+    jsr display_coords
     jmp done
 
 number_keys:
@@ -1533,6 +1646,49 @@ zero_byte_loop:
     rts
 .endproc
 
+.proc display_coords
+    lda #1
+    sta text_row
+    lda #col_x
+    sta text_col
+    draw_string_const str_x
+
+    copy32 FR0, ox
+    shift_round_16 FR0, 3
+    copy16 FR0, FR0 + 2
+    jsr fixed3_13_to_float
+    jsr FASC
+    jsr draw_string
+
+    lda #col_y
+    sta text_col
+    draw_string_const str_y
+
+    copy32 FR0, oy
+    shift_round_16 FR0, 3
+    copy16 FR0, FR0 + 2
+    jsr fixed3_13_to_float
+    jsr FASC
+    jsr draw_string
+
+    lda #col_zoom
+    sta text_col
+    draw_string_const str_zoom
+
+    lda zoom
+    clc
+    adc #0
+    sta FR0
+    lda #0
+    sta FR0 + 1
+    jsr IFP
+    jsr FASC
+    jsr draw_string
+
+    rts
+
+.endproc
+
 ; input: viewport selector in x
 ; clobbers: a, x
 .proc load_viewport
@@ -1584,6 +1740,7 @@ zero_byte_loop:
     sta DMACTL
 
     jsr clear_screen
+    jsr display_coords
 
     ; Copy the display list into properly aligned memory
     ; Can't cross 1024-byte boundaries :D
@@ -1639,6 +1796,7 @@ main_loop:
 
     jsr clear_screen
     jsr status_bar
+    jsr display_coords
 
     lda #0
     sta fill_level