Re: [AD] Strange palettes under Windows 7 RTM

[John Murphy <wonsungi@xxxxxxxxxx>]

Update: I have pretty much confirmed it is an issue with Windows 7:

The Win7 taskbar/explorer.exe interferes with many 8-bit color programs (like older DOS games).

I confirmed this work-around works for exflame.exe: kill explorer.exe.

More info: http://windows7forums.com/windows-7-games/1466-games-8-bit-color-modes-palette-issues.html

So is there anything the Allegro library can do to ensure the palette changes correctly in Windows 7?

Also, the issue with palette problems in my asteroids program may be a completely separate issue (loading 8-bit graphics into a different bit depth, perhaps...) It actually works in windowed mode at 8-bits. I think in previous versions of Allegro/Vista instead of presenting weird colors, Allegro calculated the correct colors (at a severe performance cost...)

John

On Mon, Oct 12, 2009 at 7:48 PM, John Murphy <wonsungi@xxxxxxxxxx> wrote:

Hello,

I'd like to report some strangeness with Allegro palettes under Windows 7.

I am fairly certain it is an Allegro/Win7 problem, since it occurs with the example programs from Allegro 4.2.3

Repro steps:

run exflame

Expected:

White text on black; flame colored gradient palette

Actual:

Momentarily white text on maroon; flame colored gradient palette, but unusual purple/yellow outline

After 1 or 2 seconds: Blue text on maroon; entire flame lacks "fire" palette: all purple/yellow

Notes:

Repros with several, but not all of the allegro examples. Mostly limited to 8-bit palette programs, although one of my own programs repros in all color depths.

Environment:

Allegro 4.2.3

Visual Studio Express 2008

Windows 7 RTM
Lenovo Thinkpad X301 (integrated graphics==Intel X4500)

When I used Allegro (4.2.?) under Vista I did not see this problem at all.

I think Windows 7 is preventing Allegro from fully controlling the screen palette.

I did some further experimentation with my own programs:

My own fire program has a graphics mode selection dialog and takes a pcx screen capture.

- It also displays palette problems, but only in 8-bit fullscreen modes. 8-bit windowed/16+bit full screen modes have no problems.

- Even though the screen palette does not look right, the pcx screen capture is good.

- By constantly setting the palette each frame, the problem can be mostly fixed. There are still some artifacts of a bad palette.

Another program, asteroids, displays palette problems in any graphics mode.

- The pcx screen capture also shows a messed up palette

- I double-checked the DAT file, and the palette and graphics look fine in the grabber tool.

- Constantly setting the palette each frame does not help at all in this case

Both these programs worked without palette problems under Vista + Allegro (4.2.?)

Please advise how to debug this type of problem.

I have not been able to test on a non-Windows 7 machine, but I have a feeling it only repros on Windows 7.

- The Allegro example programs have palette problems, which probably would have been noticed by others already

- My own programs started showing palette problems, although the only change was Vista->Win7 (and possibly a minor Allegro version change)

Thanks~

John