From 494e9dc5f9fde5794d582b38633c6e0d1d404f3f Mon Sep 17 00:00:00 2001
From: hugova <hugova@kth.se>
Date: Tue, 4 Mar 2025 21:00:21 +0100
Subject: [PATCH] A fix of line_up_inv such that X_pos < X_end like all other
 line_* implementations.

---
 wip-hugo/routines/memory/line/line_up_inv.s | 28 +++++++--------------
 1 file changed, 9 insertions(+), 19 deletions(-)

diff --git a/wip-hugo/routines/memory/line/line_up_inv.s b/wip-hugo/routines/memory/line/line_up_inv.s
index cf2aa19..57deeff 100644
--- a/wip-hugo/routines/memory/line/line_up_inv.s
+++ b/wip-hugo/routines/memory/line/line_up_inv.s
@@ -1,11 +1,11 @@
 ;drawing line from 2 cordinates
 .proc line_up_inv
-    ;;#                                      (X_pos, Y_pos) #
+    ;;#                                      (X_end, Y_end) #
     ;;#                                   *                 #
     ;;#                         *                           #
     ;;#                *                                    #
-    ;;# (X_end, Y_end)                                      #
-   ;;NOTE THAT Y_pos <= Y_end, X_pos >= X_end. Min 45deg!
+    ;;# (X_pos, Y_pos)                                      #
+   ;;NOTE THAT Y_pos >) Y_end, X_pos <= X_end. Min 45deg!
 
     ;;Not values but register position in memory
     X_end = $04
@@ -17,16 +17,6 @@
     V = $0809
     D = $0a0b
 
-    ;example values ~~~~~ SHOULD BE PRECOMPILED
-    ;LDA #$60
-    ;STA X_pos
-    ;STA Y_pos
-    ;LDA #$50
-    ;STA X_end
-    ;LDA #$90
-    ;STA Y_end
-    ;;~~~~~~~~~~
-
     ;We need to clear this memory
     LDA #$00
     STA <V
@@ -35,14 +25,14 @@
 
     ;; V = 2*(dy -dx)
     ;; where: dy = Y_pos - Y_end, dx = X_end - X_start
-    LDA X_pos
+    LDA X_end
     SEC
-    SBC X_end
+    SBC X_pos
     STA >V
     STA >dx_2;  >dy_2 = dy. Needed for dy_2 (not for V)
-    LDA Y_end
+    LDA Y_pos
     SEC
-    SBC Y_pos
+    SBC Y_end
     STA dy
     SEC
     SBC >V
@@ -63,7 +53,7 @@
 for_y:
     jsr pixel_draw
     ;;Increment Y until Y_pos = Y_end and X_pos = X_end
-    INC Y_pos
+    DEC Y_pos
     LDY Y_pos
     CPY Y_end
     BEQ end
@@ -72,7 +62,7 @@ for_y:
     ;;else case 1.
     Lag_16 >D, <D, #$00, #$02, case_2
 case_1:
-    DEC X_pos
+    INC X_pos
     Sub_16 >D, <D, >V, <V; D = D - V
     JMP for_y
 case_2: