Skia Issue with rendering some Emoticons

[Neeraj garg]

I am trying to some emoticons like   ♠️ .  But i am getting an empty box after the emoticon.

Does anyone have any idea, is it related to surrogate pair or unicode 9 introduced in android 7?

[Cary Clark]

Drawing a spade with fiddle works fine: https://fiddle.skia.org/c/@spade

What code are you using to draw (which font, encoding, glyph, ...), Which Android SDK are you building against?

On Sat, Apr 14, 2018 at 3:28 AM, Neeraj garg <neera...@gmail.com> wrote:

I am trying to some emoticons like   ♠️ .  But i am getting an empty box after the emoticon.

Does anyone have any idea, is it related to surrogate pair or unicode 9 introduced in android 7?

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[Neeraj garg]

I am currently using skia library which is  android 5 source code based . But my current Android SDK version is 27.

You can find the attached source code and the output i am getting.

I am dumping the skia output raw data in a file to visualize it with some external tool.

On Saturday, April 14, 2018 at 4:15:34 PM UTC+5:30, Cary Clark wrote:

Drawing a spade with fiddle works fine: https://fiddle.skia.org/c/@spade

What code are you using to draw (which font, encoding, glyph, ...), Which Android SDK are you building against?

On Sat, Apr 14, 2018 at 3:28 AM, Neeraj garg <neera...@gmail.com> wrote:

I am trying to some emoticons like   ♠️ .  But i am getting an empty box after the emoticon.

Does anyone have any idea, is it related to surrogate pair or unicode 9 introduced in android 7?

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[Hal Canary]

On Sat, Apr 14, 2018, 9:37 AM Neeraj garg <neera...@gmail.com> wrote:

I am currently using skia library which is  android 5 source code based .

That is a very old version of Skia. Try the most recent stable branch:

git clone https://skia.googlesource.com/skia.git

cd skia

git checkout origin/chrome/m67

[Neeraj garg]

I am using a legacy code base so upgrading the entire source code giving me lots of issues. Major one is default  font fallback feature which is no longer present with latest skia version.

Can you help me with the source code that i have attached with earlier post.

[Cary Clark]

If you are relying on font fallback, you'll need to do additional diagnostic work to figure out why it is failing. I would try turning the text into glyphs when drawing only the spade to see why it is generating both a spade and a missing character. I would also try setting the font explicitly rather than relying on font fallback, just to understand it better.

To directly answer your question, there's no support for older versions of Skia.

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[Cary Clark]

I have managed to reproduce your bug using modern Skia: https://fiddle.skia.org/c/@spademono

I wrote up a bug to track this here: skbug.com/7811

[Neeraj garg]

Thanks a lot Cary.

What do you think? Is this some encoding issue. I see the same issue with some other emoticons but not all. 

On Saturday, April 14, 2018 at 8:29:38 PM UTC+5:30, Cary Clark wrote:

I have managed to reproduce your bug using modern Skia: https://fiddle.skia.org/c/@spademono

I wrote up a bug to track this here: skbug.com/7811

On Sat, Apr 14, 2018 at 10:46 AM, Cary Clark <cary...@google.com> wrote:

If you are relying on font fallback, you'll need to do additional diagnostic work to figure out why it is failing. I would try turning the text into glyphs when drawing only the spade to see why it is generating both a spade and a missing character. I would also try setting the font explicitly rather than relying on font fallback, just to understand it better.

To directly answer your question, there's no support for older versions of Skia.

On Sat, Apr 14, 2018 at 10:21 AM, Neeraj garg <neera...@gmail.com> wrote:

I am using a legacy code base so upgrading the entire source code giving me lots of issues. Major one is default  font fallback feature which is no longer present with latest skia version.

Can you help me with the source code that i have attached with earlier post.

On Saturday, April 14, 2018 at 7:44:11 PM UTC+5:30, Hal Canary wrote:

On Sat, Apr 14, 2018, 9:37 AM Neeraj garg <neera...@gmail.com> wrote:

I am currently using skia library which is  android 5 source code based .

That is a very old version of Skia. Try the most recent stable branch:

git clone https://skia.googlesource.com/skia.git

cd skia

git checkout origin/chrome/m67

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[Cary Clark]

If I did my analysis right, when you paste the spade character in, your text editor is inserting U+2660 (the spade character) followed by U+FE0F, a variation selector. I'm guessing the variation selector is there to allow the preceding character to be drawn in color, as would be the case for red hearts or diamonds. The fallback font chosen for you has the spade code point, but not the variation selector, so it draws the spade and a missing character symbol.

You can fix this by either describing your spade with  "\xE2" "\x99" "\xA0", or by selecting a font that includes U+FE0F as one of its code points.

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[Neeraj Garg]

The same thing is happening when I take a input text field and and then I enter some emoticons I get this empty box. How do I handle this at runtime?

I am using skia calls behind  input text.

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[Neeraj garg]

Do you have any idea which handles variation character(U+FE0F) ? 

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[Neeraj garg]

Sorry for the typo.

I meant to say which font family handles the variation character?

[Cary Clark]

I don't know if Skia has a way to iterate through all of the fonts it can see, or if it can determine if a particular Unicode value is present in the font. I'll consult with our local font expert and find out. 

But do you need this at all? For your purposes, can you remove U+FE0F from the text stream before drawing to fix the bug?

[Neeraj Garg]

What I read about variation selector on internet, it provides the color, animation,size etc. meta data to the precedding character which in our case is spade emoticon. 

If I remove it from the stream.... won't it affect the emoticon appearance on the screen while drawing?

I just debug my app....I didn't find the unicode (U+FE0F) . I just could see some extra characters (\x0F\xFE). I am trying with  alteing/removing these characters. But I guess there should be some better solution for this problem with no side affects(appearance).

Sorry for the typo.

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[Neeraj garg]

Cary, did you get any help from your local font team? 

Sorry for the typo.

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[Cary Clark]

Yes, thanks to Hal. 

"Take a look at

https://fiddle.skia.org/c/@SkFontMgr_example

Also, SkFontMgr::matchFamilyStyleCharacter(...)"

[Neeraj garg]

As per my understanding, this is sort of font fallback which is by default handled in android 5  source code(my code version). 

Below snippet of code use matchFamilyStyleCharacter internally:

ANPPaint* paint = new ANPPaint();
SkPaintOptionsAndroid paintOptions;
paintOptions.setUseFontFallbacks(true);
paint->setPaintOptionsAndroid(paintOptions);

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[Neeraj garg]

Cary , i am trying to understand why skia font fallback is choosing a font for me which does not have codepoint of variation selector?

What is default typeface skia uses while drawing any text?

[Neeraj garg]

I am getting attached output for below snippet of code on mac device :

   canvas->clear(SK_ColorWHITE);

   SkPaint paint;

   paint.setTextEncoding(SkPaint::kUTF8_TextEncoding);

   paint.setSubpixelText(true);

   paint.setColor(SK_ColorBLACK);

   paint.setTextSize(30);

   paint.setAntiAlias(true);

   paint.setTypeface(SkTypeface::MakeFromName("Apple Color Emoji", SkFontStyle()) );

   static const char message[] = "❤️";

   canvas->drawText(message, sizeof (message) , fWindow->width()/2, fWindow->height()/2, paint);

[Neeraj garg]

Cary, I am still stuck with this issue and need your help. Please respond.

[Cary Clark]

Skia is designed to operate at a low level, and draws the glyphs requested. Because of the complexity of converting Unicode to font glyphs, Skia has been deprecating font fallback and relegates font shaping to dedicated packages like harfbuzz. You may want to pursue your issue at that level.

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