[Qemu-devel] r6349 broke Commander Keen 4 ;-(

[Qemu-devel] r6349 broke Commander Keen 4 ;-(

[Robert Riebisch]

Hi!

When running Commander Keen 4 (<ftp://ftp.3drealms.com/share/4keen.zip>)
in DOS only the left half of the VGA screen is shown on the SDL interface.

By doing lots of builds I narrowed the problem down to
<http://svn.savannah.gnu.org/viewvc?view=rev&root=qemu&revision=6349> by
Stefano Stabellini.

Robert Riebisch
-- 
BTTR Software
http://www.bttr-software.de/

Re: [Qemu-devel] r6349 broke Commander Keen 4 ;-(

[Rick Vernam]

[-- Attachment #1: Type: text/plain, Size: 618 bytes --]

On Monday 16 March 2009 4:57:28 pm Robert Riebisch wrote:
> Hi!
>
> When running Commander Keen 4 (<ftp://ftp.3drealms.com/share/4keen.zip>)
> in DOS only the left half of the VGA screen is shown on the SDL interface.
>
> By doing lots of builds I narrowed the problem down to
> <http://svn.savannah.gnu.org/viewvc?view=rev&root=qemu&revision=6349> by
> Stefano Stabellini.
>
> Robert Riebisch

Tragic!
Okay, I haven't actually played commander keen since my PC had a turbo button, 
but I think when (if?) this gets fixed I will need to start up again...
Thanks for the URL there - I would not have known otherwise...

[-- Attachment #2: Type: text/html, Size: 1212 bytes --]

Re: [Qemu-devel] r6349 broke Commander Keen 4 ;-(

[malc]

On Mon, 16 Mar 2009, Robert Riebisch wrote:

> Hi!
> 
> When running Commander Keen 4 (<ftp://ftp.3drealms.com/share/4keen.zip>)
> in DOS only the left half of the VGA screen is shown on the SDL interface.
> 
> By doing lots of builds I narrowed the problem down to
> <http://svn.savannah.gnu.org/viewvc?view=rev&root=qemu&revision=6349> by
> Stefano Stabellini.

6349 is indeed what broke stuff, the code was moved (why?) and uses
disp_width that could be modified later..

diff --git a/hw/vga.c b/hw/vga.c
index e3d2446..eeb77f1 100644
--- a/hw/vga.c
+++ b/hw/vga.c
@@ -1619,6 +1619,16 @@ static void vga_draw_graphic(VGAState *s, int full_update)
         s->double_scan = double_scan;
     }
 
+    if (shift_control == 0) {
+        if (s->sr[0x01] & 8) {
+            disp_width <<= 1;
+        }
+    } else if (shift_control == 1) {
+        if (s->sr[0x01] & 8) {
+            disp_width <<= 1;
+        }
+    }
+
     depth = s->get_bpp(s);
     if (s->line_offset != s->last_line_offset ||
         disp_width != s->last_width ||
@@ -1660,7 +1670,6 @@ static void vga_draw_graphic(VGAState *s, int full_update)
         full_update |= update_palette16(s);
         if (s->sr[0x01] & 8) {
             v = VGA_DRAW_LINE4D2;
-            disp_width <<= 1;
         } else {
             v = VGA_DRAW_LINE4;
         }
@@ -1669,7 +1678,6 @@ static void vga_draw_graphic(VGAState *s, int full_update)
         full_update |= update_palette16(s);
         if (s->sr[0x01] & 8) {
             v = VGA_DRAW_LINE2D2;
-            disp_width <<= 1;
         } else {
             v = VGA_DRAW_LINE2;
         }


-- 
mailto:av1474@comtv.ru

Re: [Qemu-devel] r6349 broke Commander Keen 4 ;-(

[Stefano Stabellini]

malc wrote:

> On Mon, 16 Mar 2009, Robert Riebisch wrote:
> 
>> Hi!
>>
>> When running Commander Keen 4 (<ftp://ftp.3drealms.com/share/4keen.zip>)
>> in DOS only the left half of the VGA screen is shown on the SDL interface.
>>
>> By doing lots of builds I narrowed the problem down to
>> <http://svn.savannah.gnu.org/viewvc?view=rev&root=qemu&revision=6349> by
>> Stefano Stabellini.
> 
> 6349 is indeed what broke stuff, the code was moved (why?) and uses
> disp_width that could be modified later..

Good catch! Thanks to Robert Riebisch for the extremely good bug report.

The code was moved because the DisplaySurface color depth could change
as a consequence of qemu_create_displaysurface_from or
qemu_console_resize: rgb_to_pixel depends on the DysplaySurface depth
and update_palette[16,256] depends on rgb_to_pixel.
Therefore your patch is fine because fixes the problem keeping the
benefit of the original patch.