[GSoC] Subpixel glyph positioning - Looking for a mentor

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Alexander Farrow Alexander Farrow
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[GSoC] Subpixel glyph positioning - Looking for a mentor

For GSoC 2019 I would love to work on the "Sub-pixel and stable glyph positioning" project from the
list of ideas without a mentor:
https://bugs.documentfoundation.org/show_bug.cgi?id=103322 <https://bugs.documentfoundation.org/show_bug.cgi?id=103322>

I'm particularly interested in this project as I experience poor glyph positioning quite often as a
LibreOffice user.

To achieve the required skills for this project I read the "State of text rendering" paper  by Behdad
Esfahbod to further my understanding of text rendering. I've also followed the HarfBuzz tutorial to
develop a primitive text rendering program.

I've been familiarising myself with the LibreOffice text rendering code particularly CommonSalLayout.
I've written a very small patch for this file, changing a variable from tools::Point to basegfx::B2DPoint
to add support for floating point values.

I've followed the Bugzilla comments and I'm now looking into what changes will need to be made
throughout the code-base to store the glyph positions in a floating point variable. Specifically, I'm
currently looking into how to make the following code changes:

1. DeviceCoordinate -  Change from a long to a double.
2. GlyphItem - Change m_aLinearPos from tools::Point to basegfx::B2DPoint. Change m_nOrigWidth
from an int to a double. Change m_nXOffset from an int to a double.

I am hoping that somebody would like to be my mentor for this project.

With many thanks,
Alexander Farrow (IRC: AlexanderFarrow)
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Jan-Marek Glogowski Jan-Marek Glogowski
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Re: [GSoC] Subpixel glyph positioning - Looking for a mentor

Hi Alexander,

Am 29.03.19 um 17:06 schrieb Alexander Farrow:

> For GSoC 2019 I would love to work on the "Sub-pixel and stable glyph positioning" project from the
> list of ideas without a mentor:
> https://bugs.documentfoundation.org/show_bug.cgi?id=103322
>
> I'm particularly interested in this project as I experience poor glyph positioning quite often as a
> LibreOffice user.
>
> To achieve the required skills for this project I read the "State of text rendering" paper  by Behdad
> Esfahbod to further my understanding of text rendering. I've also followed the HarfBuzz tutorial to
> develop a primitive text rendering program.

This is more then 10 years old. I have no idea how much it represents the
current state.

> I've been familiarising myself with the LibreOffice text rendering code particularly CommonSalLayout.
> I've written a very small patch for this file, changing a variable from tools::Point to basegfx::B2DPoint
> to add support for floating point values.
>
> I've followed the Bugzilla comments and I'm now looking into what changes will need to be made
> throughout the code-base to store the glyph positions in a floating point variable. Specifically, I'm
> currently looking into how to make the following code changes:
>
> 1. DeviceCoordinate -  Change from a long to a double.
> 2. GlyphItem - Change m_aLinearPos from tools::Point to basegfx::B2DPoint. Change m_nOrigWidth
> from an int to a double. Change m_nXOffset from an int to a double.

There is also https://gerrit.libreoffice.org/#/c/62219/

Interesting post for a different problem with the same solution: Getting real
linearly-scalable text
(https://lists.cairographics.org/archives/cairo/2008-May/014149.html)
But it's also 10 years old...

The image link still works and show the (potentially long fixed?) problem
https://www.flickr.com/photos/behdad/2493693932/sizes/o/

Then there is
https://www.unicodeconference.org/presentations/S5T2-R%c3%b6ttsches-Esfahbod.pdf
- that's from 2016.
It's not about positioning, but a nice overview of Chromes text rendering
evolution, as Behdad Esfahbod is working for Google for quite some time.

> I am hoping that somebody would like to be my mentor for this project.

I have added some potential mentors, which are normally also interested in font
rendering. As much as I could potentially do some mentoring, as I know a share
of SalLayout and VCL, I have just minimal idea about text rendering, mainly from
the time writing the Qt5 VCL backend. I'm willing to do some larger share of it.
Someone of you want to share?

ATB

Jan-Marek

P.S. this is potentially cross-platform and I just have Linux.
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Alexander Farrow Alexander Farrow
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Re: [GSoC] Subpixel glyph positioning - Looking for a mentor

Hi Jan-Marek,

Thank you for your reply.

        I have added some potential mentors, which are normally also interested in font
        rendering. As much as I could potentially do some mentoring, as I know a share
        of SalLayout and VCL, I have just minimal idea about text rendering, mainly from
        the time writing the Qt5 VCL backend. I'm willing to do some larger share of it.
        Someone of you want to share?

I'm extremely glad to hear that you are happy to be a mentor for this project, as
I am very keen to continue working on this for GSoC. Thank you for CC'ing Mike and
Khaled, hopefully we can find another mentor to join us on this project.

        There is also https://gerrit.libreoffice.org/#/c/62219 <https://gerrit.libreoffice.org/#/c/62219>

        Interesting post for a different problem with the same solution: Getting real
        linearly-scalable text
        (https://lists.cairographics.org/archives/cairo/2008-May/014149.html <https://lists.cairographics.org/archives/cairo/2008-May/014149.html>)
        But it's also 10 years old...

        The image link still works and show the (potentially long fixed?) problem
        https://www.flickr.com/photos/behdad/2493693932/sizes/o <https://www.flickr.com/photos/behdad/2493693932/sizes/o>

        Then there is
        https://www.unicodeconference.org/presentations/S5T2-Röttsches-Esfahbod.pdf <https://www.unicodeconference.org/presentations/S5T2-Röttsches-Esfahbod.pdf>
        - that's from 2016.
        It's not about positioning, but a nice overview of Chromes text rendering
        evolution, as Behdad Esfahbod is working for Google for quite some time.

Thanks for the links, I'll give them a read through. Any resources regarding text
rendering are greatly appreciated.

I've continued familiarising myself with the text layout code and I've got a couple
of simple patches to submit for review. I've finished looking into how to change
GlyphItem to use floating point values for glyph positioning and I'm now looking
into how to change DeviceCoordinate from a long to a double.

I think to move forward with the project the next step is to get the proposal finished
and submitted. I've got the first draft ready and although it is a WIP I was wondering
if I could send it to you for some feedback?

I look forward to working with you on this project.

Thanks,
Alex (IRC: AlexanderFarrow)
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Kaganski Mike Kaganski Mike
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Re: [GSoC] Subpixel glyph positioning - Looking for a mentor

On 04.04.2019 19:56, Alexander Farrow wrote:

> Hi Jan-Marek,
>
> Thank you for your reply.
>
>          I have added some potential mentors, which are normally also interested in font
>          rendering. As much as I could potentially do some mentoring, as I know a share
>          of SalLayout and VCL, I have just minimal idea about text rendering, mainly from
>          the time writing the Qt5 VCL backend. I'm willing to do some larger share of it.
>          Someone of you want to share?
>
> I'm extremely glad to hear that you are happy to be a mentor for this project, as
> I am very keen to continue working on this for GSoC. Thank you for CC'ing Mike and
> Khaled, hopefully we can find another mentor to join us on this project.

Oh! I didn't realize that I was in the explicit CC list; since I never
worked with font rendering stuff closely, I even didn't consider myself
as a potential mentor. Sorry, but I don't have required skills. But of
course, I'm ready to answer any questions in the course of the project
(be it GSoC or otherwise) as much as I have knowledge. I consider this
task an important thins, so it's in my scope of interest.

--
Best regards,
Mike Kaganski
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Alexander Farrow Alexander Farrow
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Re: [GSoC] Subpixel glyph positioning - Looking for a mentor

In reply to this post by Alexander Farrow
Hi Mike,

Kaganski Mike wrote:
>Oh! I didn't realize that I was in the explicit CC list; since I never
>worked with font rendering stuff closely, I even didn't consider myself
>as a potential mentor. Sorry, but I don't have required skills.

Not a problem, apologies for the confusion.


>But of course, I'm ready to answer any questions in the course of the project
>(be it GSoC or otherwise) as much as I have knowledge. I consider this
>task an important thins, so it's in my scope of interest.

Awesome, thanks in advance for your help.

- Alex

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