From bc85d90468f6375d8ee426c9645940f07f8da241 Mon Sep 17 00:00:00 2001
From: mrdudz <mrdudz@users.noreply.github.com>
Date: Mon, 12 Oct 2015 16:15:40 +0200
Subject: [PATCH] check for space bottom up, which is faster for the average
 case

---
 libsrc/c64/soft80_cputc.s | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/libsrc/c64/soft80_cputc.s b/libsrc/c64/soft80_cputc.s
index 4f2eb7ada..9f27f64d7 100644
--- a/libsrc/c64/soft80_cputc.s
+++ b/libsrc/c64/soft80_cputc.s
@@ -482,30 +482,39 @@ soft80_putcolor:
         sta     (CRAM_PTR),y    ; vram
         rts
 
+;
 ; test if there is a space or a character at current position
-; in:  y must be $00
+;
+; in:  x = $34
+;      y must be $00
 ; out: CLC: space        SEC: character
+;      x = $34
 ;      y = $00
 soft80_checkchar:
 
-        ;ldy     #$00            ; is still $00
+        ;ldy     #$00                            ; is still $00
 
         ;lda     CURS_X
         ;and     #$01
         lda     soft80_internal_cursorxlsb
-        jne     @l1a
+        bne     @l1a
+
+        ; check charset data from bottom up, since a lot of eg lowercase chars
+        ; have no data in the top rows, but all of the DO have data in the
+        ; second to bottom row, this will likely be faster in average.
 
+        ldy     #7
         .repeat 8,line
         lda     (SCREEN_PTR),y
         and     #$f0
         cmp     #$f0
         bne     @l2b
         .if (line < 7)
-        iny
+        dey
         .endif
         .endrepeat
 
-        ldy     #$00
+        ;ldy     #$00                            ; is 0
         clc
         rts
 @l2b:
@@ -513,16 +522,17 @@ soft80_checkchar:
         sec
         rts
 @l1a:
+        ldy     #$07
         .repeat 8,line
         lda     (SCREEN_PTR),y
         and     #$0f
         cmp     #$0f
         bne     @l2bb
         .if line < 7
-        iny
+        dey
         .endif
         .endrepeat
-        ldy     #$00
+        ;ldy     #$00                            ; is 0
         clc
         rts
 @l2bb:
-- 
2.39.5