Working on the TGI library

git-svn-id: svn://svn.cc65.org/cc65/trunk@1323 b7a2c559-68d2-44c3-8de9-860c34a00d81
2002-06-22 21:40:24 +00:00
parent 897c1d8523
commit bf944755dd
16 changed files with 202 additions and 50 deletions
--- a/libsrc/tgi/tgi_getset.s
+++ b/libsrc/tgi/tgi_getset.s
@@ -0,0 +1,44 @@
+;
+; Ullrich von Bassewitz, 22.06.2002
+;
+; Helper function for getpixel/setpixel. Load X/Y from stack and check if
+; the coordinates are valid. Return carry clear if so.
+;
+
+        .include        "tgi-kernel.inc"
+
+        .import         popax
+        .importzp       ptr1, ptr2
+
+
+tgi_getset:
+        sta     ptr2            ; Y
+        stx     ptr2+1
+        jsr     popax
+        sta     ptr1            ; X
+        stx     ptr1+1
+
+; Are the coordinates are out of range? First check if any ccord is negative.
+
+        txa
+        ora     ptr2+1
+        asl     a
+        bcs     @L9             ; Bail out if negative
+
+; Check if X is larger than the maximum x coord. If so, bail out
+
+        lda     ptr1
+        cmp     _tgi_xres
+        txa
+        sbc     _tgi_xres+1
+        bcs     @L9
+
+; Check if Y is larger than the maximum y coord.
+
+        lda     ptr2
+        cmp     _tgi_yres
+        lda     ptr2+1
+        sbc     _tgi_yres+1
+@L9:    rts
+
+