[Glamor] [PATCH 4/7] Fix the problem of set the same stop several times

[Zhigang Gong]

On Tue, May 08, 2012 at 08:44:54AM +0800, junyan.he at linux.intel.com wrote:
> From: Junyan He <junyan.he at linux.intel.com>
> 
>  Some gradient set the stops at the same position, for
>  example: firstly 0.5 to red color and then set 0.5 to
>  blue. This kind of setting will cause the shader work
>  not correctly because the percentage caculating need to
>  use the stop[i] - stop[i-1] as dividend. The previous
>  patch we just kill some stop if the distance between
>  them is 0. But this cause the problem that the color
>  for next stop is wrong. We now modify to handle it in
>  the shader to avoid the 0 as dividend.
> 
> 
> Signed-off-by: Junyan He <junyan.he at linux.intel.com>
> ---
>  src/glamor_gradient.c |   25 ++++++++-----------------
>  1 files changed, 8 insertions(+), 17 deletions(-)
> 
> diff --git a/src/glamor_gradient.c b/src/glamor_gradient.c
> index a519b34..7263c2b 100644
> --- a/src/glamor_gradient.c
> +++ b/src/glamor_gradient.c
> @@ -67,9 +67,12 @@ _glamor_create_getcolor_fs_program(ScreenPtr screen, int stops_count, int use_ar
>  	    "            break; \n"
>  	    "    }\n"
>  	    "    \n"
> -	    "    percentage = (stop_len - stops[i-1])/(stops[i] - stops[i-1]);\n"
>  	    "    if(stops[i] - stops[i-1] > 2.0)\n"
>  	    "        percentage = 0.0;\n" //For comply with pixman, walker->stepper overflow.
> +	    "    else if(stops[i] - stops[i-1] < 0.000001)\n"
> +	    "        percentage = 0.0;\n"
> +	    "    else \n"
> +	    "        percentage = (stop_len - stops[i-1])/(stops[i] - stops[i-1]);\n"
>  	    "    new_alpha = percentage * stop_colors[i].a + \n"
>  	    "                       (1.0-percentage) * stop_colors[i-1].a; \n"
>  	    "    gradient_color = vec4((percentage * stop_colors[i].rgb \n"
> @@ -116,58 +119,53 @@ _glamor_create_getcolor_fs_program(ScreenPtr screen, int stops_count, int use_ar
>  	    "        stop_color_after = stop_color0;\n"
>  	    "        stop_after = stop0;\n"
>  	    "        stop_before = stop0;\n"
> -	    "        percentage = 0.0;\n"
>  	    "    } else if((stop_len < stop1) && (n_stop >= 2)) {\n"
>  	    "        stop_color_before = stop_color0;\n"
>  	    "        stop_color_after = stop_color1;\n"
>  	    "        stop_after = stop1;\n"
>  	    "        stop_before = stop0;\n"
> -	    "        percentage = (stop_len - stop0)/(stop1 - stop0);\n"
>  	    "    } else if((stop_len < stop2) && (n_stop >= 3)) {\n"
>  	    "        stop_color_before = stop_color1;\n"
>  	    "        stop_color_after = stop_color2;\n"
>  	    "        stop_after = stop2;\n"
>  	    "        stop_before = stop1;\n"
> -	    "        percentage = (stop_len - stop1)/(stop2 - stop1);\n"
>  	    "    } else if((stop_len < stop3) && (n_stop >= 4)){\n"
>  	    "        stop_color_before = stop_color2;\n"
>  	    "        stop_color_after = stop_color3;\n"
>  	    "        stop_after = stop3;\n"
>  	    "        stop_before = stop2;\n"
> -	    "        percentage = (stop_len - stop2)/(stop3 - stop2);\n"
>  	    "    } else if((stop_len < stop4) && (n_stop >= 5)){\n"
>  	    "        stop_color_before = stop_color3;\n"
>  	    "        stop_color_after = stop_color4;\n"
>  	    "        stop_after = stop4;\n"
>  	    "        stop_before = stop3;\n"
> -	    "        percentage = (stop_len - stop3)/(stop4 - stop3);\n"
>  	    "    } else if((stop_len < stop5) && (n_stop >= 6)){\n"
>  	    "        stop_color_before = stop_color4;\n"
>  	    "        stop_color_after = stop_color5;\n"
>  	    "        stop_after = stop5;\n"
>  	    "        stop_before = stop4;\n"
> -	    "        percentage = (stop_len - stop4)/(stop5 - stop4);\n"
>  	    "    } else if((stop_len < stop6) && (n_stop >= 7)){\n"
>  	    "        stop_color_before = stop_color5;\n"
>  	    "        stop_color_after = stop_color6;\n"
>  	    "        stop_after = stop6;\n"
>  	    "        stop_before = stop5;\n"
> -	    "        percentage = (stop_len - stop5)/(stop6 - stop5);\n"
>  	    "    } else if((stop_len < stop7) && (n_stop >= 8)){\n"
>  	    "        stop_color_before = stop_color6;\n"
>  	    "        stop_color_after = stop_color7;\n"
>  	    "        stop_after = stop7;\n"
>  	    "        stop_before = stop6;\n"
> -	    "        percentage = (stop_len - stop6)/(stop7 - stop6);\n"
>  	    "    } else {\n"
>  	    "        stop_color_before = stop_color7;\n"
>  	    "        stop_color_after = stop_color7;\n"
>  	    "        stop_after = stop7;\n"
>  	    "        stop_before = stop7;\n"
> -	    "        percentage = 0.0;\n"
>  	    "    }\n"
>  	    "    if(stop_after - stop_before > 2.0)\n"
>  	    "        percentage = 0.0;\n"//For comply with pixman, walker->stepper overflow.
> +	    "    else if(stop_after - stop_before < 0.000001)\n"
> +	    "        percentage = 0.0;\n"
> +	    "    else \n"
> +	    "        percentage = (stop_len - stop_before)/(stop_after - stop_before);\n"
>  	    "    new_alpha = percentage * stop_color_after.a + \n"
>  	    "                       (1.0-percentage) * stop_color_before.a; \n"
>  	    "    gradient_color = vec4((percentage * stop_color_after.rgb \n"
> @@ -883,13 +881,6 @@ _glamor_gradient_set_stops(PicturePtr src_picture, PictGradient * pgradient,
>  	int count = 1;
>  
>  	for (i = 0; i < pgradient->nstops; i++) {
> -		/* We find some gradient picture set the stops at the same percentage, which
> -		   will cause the shader problem because the (stops[i] - stops[i-1]) will
> -		   be used as divisor. We just keep the later one if stops[i] == stops[i-1] */
> -		if (i < pgradient->nstops - 1
> -		         && pgradient->stops[i].x == pgradient->stops[i+1].x)
> -			continue;
> -
>  		stop_colors[count*4] = pixman_fixed_to_double(
>  		                                pgradient->stops[i].color.red);
>  		stop_colors[count*4+1] = pixman_fixed_to_double(
> -- 
> 1.7.7.6
> 

Reviewed-by: Zhigang Gong <zhigang.gong at linux.intel.com>