Thanks, Dave!

2017-06-13 9:11 GMT-03:00 Dave Crossland <[email protected]>:

> Hi
>
> I thought I would forward on Felipe's request for a convenience method
> below :)
> ---------- Forwarded message ----------
> From: "Felipe Sanches" <[email protected]>
> Date: Jun 2, 2017 9:35 PM
> Subject: Re: [googlefonts-discuss] Re: Variable Fonts support in Inkscape
> To: "googlefonts-discuss" <[email protected]>,
> "Inkscape Devel List" <[email protected]>
> Cc:
>
> Hi there,
>
> These past days I've been adding an experimental UI to Inkscape for
> tweaking parameters in OpenType variable fonts. One major roadblock I
> stumbled upon is requiring me to think more carefully about some
> potentially deeper architectural changes. In the screenshot attached to
> this message you can see some text written with the Decovar variable font.
> The slider labeled "Testing" in the "Text & Font" dialog is wired to invoke
> a callback upon value-change. This callback detects the currently selected
> font based on the canvas text-tool cursor position, retrieves the
> corresponding font_instance object and invokes Freetype's
> FT_Set_Var_Design_Coordinates method with the updated design-space
> coordinates (the slider in this experiment is hardwired to adjust the
> weight axis of Decovar).
>
> (I really miss a Freetype method to alter a single design-space
> coordinate, instead of having to pass the full array, by the way)
>
> The way things work right now, unfortunately, leads to the glyphs not
> changing on-canvas because once they are loaded, they seem to be kept in a
> cache. As you can see in the screenshot, each glyph has a different weigth,
> based on the slider setting when the glyph was loaded for the first time.
> It seems quite obvious that I should do something to invalidate the cache
> upon dragging the slider. But that, on the other hand, should not alter
> glyphs in other places where the same variable font is being used in the
> same document.
>
> Based on all that, I think that the proper implementation would involve
> creating individual font_instance objects for each text chunk where a
> variable-font is used with non-default design-space coordinates so that
> they can be tweaked independently. Achieving that, though, will surely
> involve a bit deeper fiddling with Inkscape's text internals, which is what
> I expect to do in my next few days of work on this.
>
> cheers,
> Felipe Sanches
>
> PS:
> I'm crossposting this to the Inkscape-devel mailing list as the rest of
> the development community may be interested in receiving updates on this
> topic. I may as well move all future updates to the Inkscape mailing list
> directly.
>
> PS2: I heard that there's a GSoC student this year who's going to work on
> Inkscape's text implementation (fixing compliance issues to the SVG spec, I
> think...) It would be really great to keep in contact with him/her and the
> mentor to coordinate efforts.
>
>
> 2017-05-30 7:48 GMT-03:00 Khaled Hosny <[email protected]>:
>
>> On Tue, May 30, 2017 at 12:35:24AM -0300, Felipe Sanches wrote:
>> > The relationship between pango and harfbuzz is still not very clear to
>> me,
>> > as I have the impression that even pango_shape() invokes hb_shape()
>> under
>> > the hood nowadays.
>>
>> It will eventually call HarfBuzz on Linux, but in Windows and Mac it
>> will call Uniscribe and Core Text, respectively. Switching to HarfBuzz
>> on all platforms is kinda on Pango’s TODO list, but I don’t think anyone
>> is working on it currently.
>>
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>
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