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List: cairo
Subject: Re: [cairo] rounding glyph positions
From: Matthias Clasen <matthias.clasen () gmail ! com>
Date: 2019-08-02 15:24:18
Message-ID: CAFwd_vBQ6q-DZCmz-ezXTiiasm1aHtsPZcEcK8kg_tO1JyY_Ug () mail ! gmail ! com
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On Fri, Aug 2, 2019 at 10:21 AM Uli Schlachter <psychon@znc.in> wrote:
> Hi,
>
> On 01.08.19 23:00, Matthias Clasen wrote:
> > But I'd still like to understand what the rationale is for a) this being
> > separate from hint metrics
> > and b) this not being settable.
>
> the rationale basically is "the test suite's reference images are
> correct by definition, so how can we make cairo generate this output"?
> According to "git blame", I introduced this option back when I still
> tried to sort out the mess that is the test suite:
>
> commit cee1dadc66107e1cc6bcac7718e0b67969141876
> Author: Uli Schlachter <psychon@znc.in>
> Date: Thu Oct 21 22:14:57 2010 +0200
>
> Other backends: Set round_glyph_positions to OFF
>
> This sets CAIRO_ROUND_GLYPH_POS_OFF in all surface backends that
> didn't use
> CAIRO_ROUND_GLYPH_POS_ON.
>
> Signed-off-by: Uli Schlachter <psychon@znc.in>
>
> commit d24e9881de7b392cfce1d82c9861553ece558aaf
> Author: Uli Schlachter <psychon@znc.in>
> Date: Thu Oct 21 14:03:38 2010 +0200
>
> raster backends: Set round_glpyh_positions to ON
>
> This fixes "text-rotate" in the test suite for the image backend and
> "overlapping-glyphs" for the xcb backend.
>
> Signed-off-by: Uli Schlachter <psychon@znc.in>
>
> commit b514863a0ee8e6c4f0a994f6f5e7db18ce290e79
> Author: Uli Schlachter <psychon@znc.in>
> Date: Thu Oct 21 13:59:25 2010 +0200
>
> Actually implement round_glpyh_positions
>
> The previous commit only added this option and made sure it gets
> set, but it
> didn't actually have any effect. This commit now implements this
> option.
>
> Signed-off-by: Uli Schlachter <psychon@znc.in>
>
> commit 6bfe71124b56b496056b77b3b51eef4d656ccf54
> Author: Uli Schlachter <psychon@znc.in>
> Date: Thu Oct 21 13:52:33 2010 +0200
>
> font options: Add private round_glpyh_positions field
>
> Signed-off-by: Uli Schlachter <psychon@znc.in>
>
> Looking at the git history for the reference images... I am not quite
> sure where it came from. Back in 2010, I was assuming that the reference
> images are correct, I guess. Since then, I saw others fixing test
> failures by just declaring the current cairo output as the reference. I
> never tried to do that since I do not what each test actually really
> tests and if the difference that makes the test fail is a bug or not.
>
> What to do with this information... well, I do not know. If you want,
> you can revert the above four commits, but I would hope that this does
> not regress the test suite (= some higher power has to declare that the
> current reference images are wrong and the new output is correct and
> should be the new reference image).
>
>
>
I might suggest to simply reuse hint-metrics for this purpose, based
on the theory that if you don't want hinted metrics, you probably don't
want rounded glyph positions either.
[Attachment #5 (text/html)]
<div dir="ltr"><div dir="ltr"><br></div><br><div class="gmail_quote"><div dir="ltr" \
class="gmail_attr">On Fri, Aug 2, 2019 at 10:21 AM Uli Schlachter <<a \
href="mailto:psychon@znc.in">psychon@znc.in</a>> wrote:<br></div><blockquote \
class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid \
rgb(204,204,204);padding-left:1ex">Hi,<br> <br>
On 01.08.19 23:00, Matthias Clasen wrote:<br>
> But I'd still like to understand what the rationale is for a) this being<br>
> separate from hint metrics<br>
> and b) this not being settable.<br>
<br>
the rationale basically is "the test suite's reference images are<br>
correct by definition, so how can we make cairo generate this output"?<br>
According to "git blame", I introduced this option back when I still<br>
tried to sort out the mess that is the test suite:<br>
<br>
commit cee1dadc66107e1cc6bcac7718e0b67969141876<br>
Author: Uli Schlachter <<a href="mailto:psychon@znc.in" \
target="_blank">psychon@znc.in</a>><br>
Date: Thu Oct 21 22:14:57 2010 +0200<br>
<br>
Other backends: Set round_glyph_positions to OFF<br>
<br>
This sets CAIRO_ROUND_GLYPH_POS_OFF in all surface backends that<br>
didn't use<br>
CAIRO_ROUND_GLYPH_POS_ON.<br>
<br>
Signed-off-by: Uli Schlachter <<a href="mailto:psychon@znc.in" \
target="_blank">psychon@znc.in</a>><br> <br>
commit d24e9881de7b392cfce1d82c9861553ece558aaf<br>
Author: Uli Schlachter <<a href="mailto:psychon@znc.in" \
target="_blank">psychon@znc.in</a>><br>
Date: Thu Oct 21 14:03:38 2010 +0200<br>
<br>
raster backends: Set round_glpyh_positions to ON<br>
<br>
This fixes "text-rotate" in the test suite for the image backend \
and<br> "overlapping-glyphs" for the xcb backend.<br>
<br>
Signed-off-by: Uli Schlachter <<a href="mailto:psychon@znc.in" \
target="_blank">psychon@znc.in</a>><br> <br>
commit b514863a0ee8e6c4f0a994f6f5e7db18ce290e79<br>
Author: Uli Schlachter <<a href="mailto:psychon@znc.in" \
target="_blank">psychon@znc.in</a>><br>
Date: Thu Oct 21 13:59:25 2010 +0200<br>
<br>
Actually implement round_glpyh_positions<br>
<br>
The previous commit only added this option and made sure it gets<br>
set, but it<br>
didn't actually have any effect. This commit now implements this \
option.<br> <br>
Signed-off-by: Uli Schlachter <<a href="mailto:psychon@znc.in" \
target="_blank">psychon@znc.in</a>><br> <br>
commit 6bfe71124b56b496056b77b3b51eef4d656ccf54<br>
Author: Uli Schlachter <<a href="mailto:psychon@znc.in" \
target="_blank">psychon@znc.in</a>><br>
Date: Thu Oct 21 13:52:33 2010 +0200<br>
<br>
font options: Add private round_glpyh_positions field<br>
<br>
Signed-off-by: Uli Schlachter <<a href="mailto:psychon@znc.in" \
target="_blank">psychon@znc.in</a>><br> <br>
Looking at the git history for the reference images... I am not quite<br>
sure where it came from. Back in 2010, I was assuming that the reference<br>
images are correct, I guess. Since then, I saw others fixing test<br>
failures by just declaring the current cairo output as the reference. I<br>
never tried to do that since I do not what each test actually really<br>
tests and if the difference that makes the test fail is a bug or not.<br>
<br>
What to do with this information... well, I do not know. If you want,<br>
you can revert the above four commits, but I would hope that this does<br>
not regress the test suite (= some higher power has to declare that the<br>
current reference images are wrong and the new output is correct and<br>
should be the new reference image).<br>
<br><br></blockquote><div><br></div><div>I might suggest to simply reuse hint-metrics \
for this purpose, based</div><div>on the theory that if you don't want hinted \
metrics, you probably don't</div><div>want rounded glyph positions \
either.<br></div></div></div>
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