Replace the not-enough-precision 32 bit to float impl

keep the proc though to encapsulate it but uses the older
logic of rounding down to 3.13 first

mandel.s

@@ -126,6 +126,10 @@ KEY_7     = 51
 KEY_8     = 53
 KEY_9     = 48
 KEY_0     = 50
+KEY_PERIOD = 34
+KEY_E     = 42
+KEY_X     = 22
+KEY_Y     = 43
 
 .struct float48
     exponent .byte
@@ -403,6 +407,13 @@ elapsed_work:
 elapsed_digit:
     .byte 0
 
+input_col:
+    .byte 0
+input_row:
+    .byte 0
+input_max:
+    .byte 0
+
 ; 2 + 9 * byte cycles
 .macro add bytes, dest, arg1, arg2
     clc ; 2 cyc
@@ -983,6 +994,17 @@ common:
 
 .endproc
 
+; rounds to 16-bit first!
+; input in FR0, 32 bits signed 6.26 fixed
+; output in FR0, Atari float
+; clobbers a, x, y, FR0, FR1
+.proc fixed6_26_to_float
+    shift_round_16 FR0, 3
+    copy16 FR0, FR0 + 2
+    jsr fixed3_13_to_float
+    rts
+.endproc
+
 ; input in FR0, Atari float
 ; output in FR0, 16 bits signed 3.13 fixed
 ; clobbers a, x, y, FR0, FR1
@@ -1603,7 +1625,7 @@ number_keys:
     beq five
     cpy #KEY_6
     beq six
-    jmp skip_char
+    jmp letter_keys
 
 one:
     ldx #0
@@ -1622,7 +1644,21 @@ five:
     jmp load_key_viewport
 six:
     ldx #5
-    ; fall through
+    jmp load_key_viewport
+
+letter_keys:
+    cpy #KEY_X
+    bne not_x
+    jsr input_x
+    jmp load_key_viewport
+not_x:
+    cpy #KEY_Y
+    bne not_y
+    jsr input_y
+    jmp load_key_viewport
+not_y:
+    jmp skip_char
+
 load_key_viewport:
     jsr load_viewport
     ; fall through
@@ -1632,6 +1668,23 @@ done:
 
 .endproc
 
+.proc input_x
+    ldx #col_x
+    ldy #1
+    jsr input_number
+
+
+    rts
+.endproc
+
+.proc input_y
+    rts
+.endproc
+
+.proc input_number
+    rts
+.endproc
+
 .proc clear_screen
     ; zero the range from framebuffer_top to display_list
     lda #.lobyte(framebuffer_top)
@@ -1679,9 +1732,7 @@ zero_byte_loop:
     draw_string_const str_x
 
     copy32 FR0, ox
-    shift_round_16 FR0, 3
+    jsr fixed6_26_to_float
-    copy16 FR0, FR0 + 2
-    jsr fixed3_13_to_float
     jsr FASC
     jsr draw_string
 
@@ -1690,9 +1741,7 @@ zero_byte_loop:
     draw_string_const str_y
 
     copy32 FR0, oy
-    shift_round_16 FR0, 3
+    jsr fixed6_26_to_float
-    copy16 FR0, FR0 + 2
-    jsr fixed3_13_to_float
     jsr FASC
     jsr draw_string