[reactos] 03/06: [BOOTVID] Fix BitBlt behavior (#2936)

[Dmitry Borisov]

https://git.reactos.org/?p=reactos.git;a=commitdiff;h=5d40981efa6160eac3472…

commit 5d40981efa6160eac3472d815c6bec6464736c27
Author:     Dmitry Borisov <di.sean(a)protonmail.com>
AuthorDate: Sun Jun 21 19:21:46 2020 +0600
Commit:     Stanislav Motylkov <x86corez(a)gmail.com>
CommitDate: Wed Jul 29 19:10:38 2020 +0300

    [BOOTVID] Fix BitBlt behavior (#2936)
---
 drivers/base/bootvid/common.c | 38 +++++++++++++++++++++-----------------
 1 file changed, 21 insertions(+), 17 deletions(-)

diff --git a/drivers/base/bootvid/common.c b/drivers/base/bootvid/common.c
index 87257167ec0..9f4dda4de23 100644
--- a/drivers/base/bootvid/common.c
+++ b/drivers/base/bootvid/common.c
@@ -55,9 +55,9 @@ BitBlt(
     _In_ ULONG BitsPerPixel,
     _In_ ULONG Delta)
 {
-    ULONG sx, dx, dy;
-    UCHAR color;
-    ULONG offset = 0;
+    ULONG X, Y, Pixel;
+    UCHAR Colors;
+    PUCHAR InputBuffer;
     const ULONG Bottom = Top + Height;
     const ULONG Right = Left + Width;
 
@@ -82,24 +82,28 @@ BitBlt(
     PrepareForSetPixel();
 
     /* 4bpp blitting */
-    for (dy = Top; dy < Bottom; ++dy)
+    for (Y = Top; Y < Bottom; ++Y)
     {
-        sx = 0;
-        do
-        {
-            /* Extract color */
-            color = Buffer[offset + sx];
+        InputBuffer = Buffer;
 
-            /* Calc destination x */
-            dx = Left + (sx << 1);
+        for (X = Left, Pixel = 0;
+             X < Right;
+             ++X, ++Pixel)
+        {
+            if (Pixel % 2 == 0)
+            {
+                /* Extract colors at every two pixels */
+                Colors = *InputBuffer++;
 
-            /* Set two pixels */
-            SetPixel(dx, dy, color >> 4);
-            SetPixel(dx + 1, dy, color & 0x0F);
+                SetPixel(X, Y, Colors >> 4);
+            }
+            else
+            {
+                SetPixel(X, Y, Colors & 0x0F);
+            }
+        }
 
-            sx++;
-        } while (dx < Right);
-        offset += Delta;
+        Buffer += Delta;
     }
 }