[cairo] Color fonts

Wed Aug 9 22:43:51 UTC 2017

On Sun, Jul 30, 2017 at 12:20 AM, Adrian Johnson <ajohnson at redneon.com>
wrote:

> Does it work with user fonts?
>

Not yet.  There's a comment in cairo-user-font.c:

        /* TODO
         * extend the glyph cache to support argb glyphs.
         * need to figure out the semantics and interaction with subpixel
         * rendering first.
         */

We now have the argb glyph cache.  We have to do some tricks to identify
color glyphs.  Still, interaction with subpixel rendering remains ambiguous.

When we do fix the above, I like to make cairo-surface.c wrap OpenType
color glyphs into a user-font before drawing.  This way we can still get
original text to be embedded in PDF whereas current implementation just
draws them as images and loses text.

> On 30/07/17 01:00, Behdad Esfahbod wrote:
> > On Sat, Jul 29, 2017 at 11:58 AM, Uli Schlachter <psychon at znc.in
> > <mailto:psychon at znc.in>> wrote:
> >
> >     Hi Behdad
> >
> >     I don't think that is my decision to make. When thinking about
> "fonts in
> >     cairo", I'm thinking "Behdad". I'm just asking weird questions from
> the
> >     sideline. :-)
> >
> >
> > Thanks. :-)  Pushed!!!!  At least ten people already asked me "what's up
> > with emoji" at GUADEC...
> >
> >
> >     Uli
> >
> >     P.S.: How relevant and up to date is the CC list here? I always get a
> >     "your message to gtk-devel-list awaits moderator approval"-mail when
> >     replying to this thread...
> >
> >
> > My messages go through, yours probably don't because you are not a
> > member.  It's valuable still.
> >
> > Cheers,
> > b
> >
> >
> >     On 28.07.2017 16:38, Behdad Esfahbod wrote:
> >     > Uli,
> >     >
> >     > Can we commit this?  I don't think waiting another few years will
> >     result in
> >     > a superior patchset. :)
> >     >
> >     > Cheers,
> >     >
> >     > behdad
> >     >
> >     > On Wed, Jul 19, 2017 at 1:53 AM, Behdad Esfahbod
> >     <behdad at behdad.org <mailto:behdad at behdad.org>> wrote:
> >     >
> >     >> Right.  In the future we would want to make it show glyphs in the
> >     input
> >     >> order, ie. not separate color vs non-color.  That's the order
> >     required by
> >     >> CSS for example.  In a show-text-glyphs call with
> >     CAIRO_TEXT_CLUSTER_FLAG_BACKWARD,
> >     >> it might be desirable to show back-to-front.
> >     >>
> >     >> On Tue, Jul 18, 2017 at 1:59 PM, Matthias Clasen <
> >     >> matthias.clasen at gmail.com <mailto:matthias.clasen at gmail.com>>
> wrote:
> >     >>
> >     >>> On Sat, Jul 15, 2017 at 4:05 AM, Uli Schlachter <psychon at znc.in
> >     <mailto:psychon at znc.in>> wrote:
> >     >>>
> >     >>>> On 07.07.2017 15:23, Matthias Clasen wrote:
> >     >>>>> On Sat, Jul 1, 2017 at 2:25 AM, Uli Schlachter <psychon at znc.in
> >     <mailto:psychon at znc.in>> wrote:
> >     >>>>>> On 30.06.2017 17:29, Behdad Esfahbod wrote:
> >     >>>>>>> On Jun 30, 2017 7:51 PM, "Matthias Clasen"
> >     <mclasen at redhat.com <mailto:mclasen at redhat.com>>
> >     >>>> wrote:
> >     >>>>>>> On Fri, 2017-06-30 at 17:02 +0200, Uli Schlachter wrote:
> >     >>>>>>>> On 28.06.2017 14:23, Behdad Esfahbod wrote:
> >     >>>>>>>>> All of you have asked me about the status of color fonts in
> >     >>>>>>>>> cairo.  There's
> >     >>>>>>>>> some discussion here:
> >     >>>>>>>>
> >     >>>>>>>> what was the solution to make this fit into cairo's drawing
> >     model?
> >     >>>>>>>> Text
> >     >>>>>>>> / glyphs are used as a mask and a mask does not have colors.
> >     >>>>>>>>
> >     >>>>>>>
> >     >>>>>>> There is no solution to that. The assumption in cairo's
> >     drawing model
> >     >>>>>>> about glyphs/fonts has simply been invalidated by reality.
> >     >>>>>>>
> >     >>>>>>>
> >     >>>>>>> Correct.
> >     >>>>>>
> >     >>>>>> Okay... so what is the new model? What happens when I draw a
> >     color
> >     >>>> glyph
> >     >>>>>> with operator XOR and a red source?
> >     >>>>>
> >     >>>>>
> >     >>>>> The red source is ignored for color glyphs because they are
> >     used as the
> >     >>>>> source.
> >     >>>>
> >     >>>> Hi again,
> >     >>>>
> >     >>>> I just came up with another question: How are overlapping
> >     glyphs handled?
> >     >>>>
> >     >>>> Let's say I have a red glyph and a blue glyph and I draw them
> >     in such a
> >     >>>> way that they overlap. Let's say this additionally overlaps
> with a
> >     >>>> non-colored glyph in the same position and I use a green source
> >     with 50%
> >     >>>> alpha (cairo_set_source_rgba(cr, 0, 1, 0, 0.5)).
> >     >>>>
> >     >>>> What's the visible result?
> >     >>>>
> >     >>>>
> >     >>> Here is what my implementation does: It renders the color
> glyphs, in
> >     >>> order, followed by the non-color glyphs.
> >     >>>
> >     >>> In practice, I don't think the case of mixed color and non-color
> >     glyphs
> >     >>> in the same call will be all that common.
> >     >>> Most apps will explicitly set a color font just for the emoji
> >     and they
> >     >>> won't render regular text with an emoji font,
> >     >>> with the result that runs of color glyphs and non-color glyphs
> will
> >     >>> typically be in separate calls.
> >     >>>
> >     >>
> >     >>
> >     >>
> >     >> --
> >     >> behdad
> >     >> http://behdad.org/
> >     >>
> >     >
> >     >
> >     >
> >
> >
> >     --
> >     "Why make things difficult, when it is possible to make them cryptic
> >     and totally illogical, with just a little bit more effort?" -- A. P.
> J.
> >
> >
> >
> >
> > --
> > behdad
> > http://behdad.org/
> >
> >
>
>

-- 
behdad
http://behdad.org/
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