[PATCH 05/13] glamor: Add glamor_program based 0-width dashed lines

[Eric Anholt]

Keith Packard <keithp at keithp.com> writes:

> Markus Wick <markus at selfnet.de> writes:
>
>> Am 2014-05-06 00:02, schrieb Keith Packard:
>>> +static const char on_off_fs_exec[] =
>>> +    "       float pattern = texture2D(dash, vec2(dash_offset, 
>>> 0.5)).w;\n"
>>> +    "       if (pattern == 0.0)\n"
>>> +    "               discard;\n";
>>
>> Did you care about the sampler configuration? eg with linear filtering, 
>> you don't have to get exactly 0.0. Maybe it's better to check in this 
>> way:
>> if (pattern < 0.5)
>
> If the sampler is filtering, then we're going to get the wrong answer. I
> do note that I'm not explicitly setting the filtering for the dash
> texture; do I need to?

You've got this in glamor_create_tex():

        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

So as long as nothing changes that (like, say, glamor_render.c doing
linear filtering from the pixmap), you're safe.
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