From a2109c90b2304f022d8db74210f1400512e9d4f9 Mon Sep 17 00:00:00 2001
From: "Marat Zakiyanov (Mario79)" <mario79@bk.ru>
Date: Sat, 18 Feb 2012 17:56:20 +0000
Subject: [PATCH] Fix for f38 - correction for the remainder of the division

git-svn-id: svn://kolibrios.org@2353 a494cfbc-eb01-0410-851d-a64ba20cac60
---
 kernel/trunk/video/vesa20.inc | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/kernel/trunk/video/vesa20.inc b/kernel/trunk/video/vesa20.inc
index 368ce3fbd6..019f3345c0 100644
--- a/kernel/trunk/video/vesa20.inc
+++ b/kernel/trunk/video/vesa20.inc
@@ -445,6 +445,14 @@ dl_dy equ esp+0
         cdq                 ; extend eax sing to edx
         shl     eax, 16     ; using 16bit fix-point maths
         idiv    ebp         ; eax = ((x2-x1)*65536)/(y2-y1)
+;--------------------------------------
+; correction for the remainder of the division
+        shl     edx, 1
+        cmp     ebp, edx
+        jb      @f
+        inc     eax
+@@:
+;--------------------------------------
         mov     edx, ebp    ; edx = counter (number of pixels to draw)
         mov     ebp, 1 *65536; <<16   ; ebp = dy = 1.0
         mov     esi, eax    ; esi = dx
@@ -466,6 +474,14 @@ dl_dy equ esp+0
         cdq                 ; extend eax sing to edx
         shl     eax, 16     ; using 16bit fix-point maths
         idiv    esi         ; eax = ((y2-y1)*65536)/(x2-x1)
+;--------------------------------------
+; correction for the remainder of the division
+        shl     edx, 1
+        cmp     esi, edx
+        jb      @f
+        inc     eax
+@@:
+;--------------------------------------
         mov     edx, esi    ; edx = counter (number of pixels to draw)
         mov     esi, 1 *65536;<< 16   ; esi = dx = 1.0
         mov     ebp, eax    ; ebp = dy
@@ -474,10 +490,25 @@ dl_dy equ esp+0
         mov     ebx, [dl_y1]
         shl     eax, 16
         shl     ebx, 16
+;-----------------------------------------------------------------------------
 align 4
 .draw:
         push    eax ebx
+;--------------------------------------
+; correction for the remainder of the division
+        test    ah, 0x80
+        jz      @f
+        add     eax, 1 shl 16
+@@:
+;--------------------------------------
         shr     eax, 16
+;--------------------------------------
+; correction for the remainder of the division
+        test    bh, 0x80
+        jz      @f
+        add     ebx, 1 shl 16
+@@:
+;--------------------------------------
         shr     ebx, 16
         call    [putpixel]
         pop     ebx eax