[PATCH] xrandr: fix brightness to prevent gamma to overflow and to allow 0

[Mikhail Gusarov]

Twas brillig at 00:25:34 10.01.2010 UTC+01 when E.A.B.Piel at tudelft.nl did gyre and gimble:

 EP> Hello,
 EP> This fix the behaviour of brightness for 0 and values above 1. You can
 EP> still can funky display with negative values so all is safe ;-)

 EP> Cheers,
 EP> Eric

 EP> From 2d8896857441a51b9ac14c76a39662c9ee08d566 Mon Sep 17 00:00:00 2001
 EP> From: =?UTF-8?q?=C3=89ric=20Piel?= <eric.piel at tremplin-utc.net>
 EP> Date: Wed, 6 Jan 2010 14:42:15 +0100
 EP> Subject: [PATCH] xrandr: fix brightness to prevent gamma to overflow and to allow 0
 EP> MIME-Version: 1.0
 EP> Content-Type: text/plain; charset=UTF-8
 EP> Content-Transfer-Encoding: 8bit

 EP> With the new brightness option, gamma would overflow with values > 1,
 EP> leading to rainbow looking screen.

 EP> In addition, have the brightness by default to 1, so that specifying 0
 EP> actually does the expected behaviour of leading to a black screen.

 EP> Signed-off-by: Éric Piel <eric.piel at tremplin-utc.net>
 EP> ---
 EP>  xrandr.c |   16 +++++++---------
 EP>  1 files changed, 7 insertions(+), 9 deletions(-)

 EP> diff --git a/xrandr.c b/xrandr.c
 EP> index 2fc0b81..17715ae 100644
 EP> --- a/xrandr.c
 EP> +++ b/xrandr.c
 EP> @@ -626,6 +626,7 @@ add_output (void)
 EP>          fatal ("out of memory\n");
 EP>      output->next = NULL;
 EP>      output->found = False;
 EP> +    output->brightness = 1.0;
 EP>      *outputs_tail = output;
 EP>      outputs_tail = &output->next;
 EP>      return output;
 EP> @@ -1216,30 +1217,27 @@ set_gamma(void)
 EP>          if(output->gamma.red == 0.0 && output->gamma.green == 0.0 && output->gamma.blue == 0.0)
 EP>              output->gamma.red = output->gamma.green = output->gamma.blue = 1.0;
 EP>  
 EP> -        if (output->brightness == 0.0)
 EP> -            output->brightness = 1.0;
 EP> -
 EP>          for (i = 0; i < size; i++) {
 EP>              if (output->gamma.red == 1.0 && output->brightness == 1.0)
 EP>                  gamma->red[i] = i << 8;
 EP>              else
 EP> -                gamma->red[i] = (CARD16)(pow((double)i/(double)(size - 1),
 EP> +                gamma->red[i] = (CARD16)(fmin(pow((double)i/(double)(size - 1),
 EP>                              (double)output->gamma.red) * (double)(size - 1)
 EP> -                            * (double)output->brightness * 256);
 EP> +                            * (double)output->brightness * 256, 65535));
 EP>  
 EP>              if (output->gamma.green == 1.0 && output->brightness == 1.0)
 EP>                  gamma->green[i] = i << 8;
 EP>              else
 EP> -                gamma->green[i] = (CARD16)(pow((double)i/(double)(size - 1),
 EP> +                gamma->green[i] = (CARD16)(fmin(pow((double)i/(double)(size - 1),
 EP>                              (double)output->gamma.green) * (double)(size - 1)
 EP> -                            * (double)output->brightness * 256);
 EP> +                            * (double)output->brightness * 256, 65535));
 EP>  
 EP>              if (output->gamma.blue == 1.0 && output->brightness == 1.0)
 EP>                  gamma->blue[i] = i << 8;
 EP>              else
 EP> -                gamma->blue[i] = (CARD16)(pow((double)i/(double)(size - 1),
 EP> +                gamma->blue[i] = (CARD16)(fmin(pow((double)i/(double)(size - 1),
 EP>                              (double)output->gamma.blue) * (double)(size - 1)
 EP> -                            * (double)output->brightness * 256);
 EP> +                            * (double)output->brightness * 256, 65535));
 EP>          }
 EP>  
 EP>          XRRSetCrtcGamma(dpy, crtc->crtc.xid, gamma);
 EP> -- 
 EP> 1.6.6

Reviewed-by: Mikhail Gusarov <dottedmag at dottedmag.net>

-- 
  http://fossarchy.blogspot.com/
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