Noto Sans Khmer UI variable font has the diacritics shift problem

hrhatada commented 7 years ago

STEPS TO REPRODUCE

On the device A, replace the Noto Sans Khmer font to Noto Sans Khmer variable font and modify the fonts.xml file
On the device B, replace the Noto Sans Khmer fonts to the phase III Noto Sans Khmer fonts
Reboot both devices and compare the UIs

RESULT : Some of the variable font's diacritics position shift is slightly shifted to the left. Please refer to the attached screenshot.

hrhatada commented 7 years ago

The above sample text is below:

នៅពេលដែលមុខងារនេះបើក អ្នកអាចបញ្ជូនមាតិកាកម្មវិធីទៅឧបករណ៍ដែលអាចប្រើ NFC ផ្សេងទៀតដោយដាក់ឧបករណ៍ផ្ទប់គ្នា។ ឧទាហរណ៍៖ អ្នកអាចបញ្ជូនគេហទំព័រ, វីដេអូ YouTube, ទំនាក់ទំនង និងមាតិកាជាច្រើនទៀត។

គ្រាន់តែដាក់ឧបករណ៍ផ្ទប់គ្នា (តាមធម្មតាខ្នងទល់ខ្នង) បន្ទាប់មកប៉ះអេក្រង់របស់អ្នកជាការស្រេច។ កម្មវិធីនេះនឹងកំណត់របស់ដែលត្រូវបញ្ជូន។

punchcutter commented 7 years ago

There's definitely something wrong with the mark positioning on the right side, but the right is the document font and the left is the UI font so this isn't exactly a comparison of static vs variable.

hrhatada commented 7 years ago

Yes, I found the mistake for my fonts.xml, and corrected, but still see the diacritics shift

marekjez86 commented 7 years ago

Summary: while I can see the difference in the images above, my tests on the fonts itself show no difference. Conjecture: the above environment has something that causes the above. This could be the (1) version of fonts itself, (2) fonts.xml, (3) harfbuzz implementation. In other words: not a font, but the execution environment where the font is presented needs debugging and/or fixing.

Test case

<html lang="khm">
    <p style="font-size: 4em; font-weight: 90;"></p>
    <p style="font-size: 4em; font-weight: 90;">នៅពេលដែលមុខងារនេះបើក អ្នកអាចបញ្ជូនមាតិកាកម្មវិធីទៅឧបករណ៍ដែលអាចប្រើ NFC ផ្សេងទៀតដោយដាក់ឧបករណ៍ផ្ទប់គ្នា។ ឧទាហរណ៍៖ អ្នកអាចបញ្ជូនគេហទំព័រ, វីដេអូ YouTube, ទំនាក់ទំនង និងមាតិកាជាច្រើនទៀត។</p>
    <p style="font-size: 4em; font-weight: 90;"></p>
    <p style="font-size: 4em; font-weight: 90;">គ្រាន់តែដាក់ឧបករណ៍ផ្ទប់គ្នា (តាមធម្មតាខ្នងទល់ខ្នង) បន្ទាប់មកប៉ះអេក្រង់របស់អ្នកជាការស្រេច។ កម្មវិធីនេះនឹងកំណត់របស់ដែលត្រូវបញ្ជូន។</p>
    <p style="font-size: 4em; font-weight: 90;"></p>
</html>

static font used: https://github.com/googlei18n/noto-fonts/blob/master/alpha/from-pipeline/unhinted/ttf/sans/NotoSansKhmerUI-Regular.ttf variable font used: https://github.com/googlei18n/noto-fonts/blob/master/alpha/from-pipeline/unhinted/variable-ttf/sans/NotoSansKhmerUI-VF.ttf

I used fontdiff tool from https://github.com/googlei18n/fontdiff to compare the fonts

The results from comparison show that there's no difference between static and variable fonts. For example these two show no shift: no-shift

Full test results for the test text above are located in the following PDF file: khm-shift-test-Khmer-Sans-UIRegular-UIVF.pdf

marekjez86 commented 7 years ago

@hrhatada : did you get the fonts from static font: https://github.com/googlei18n/noto-fonts/blob/master/alpha/from-pipeline/unhinted/ttf/sans/NotoSansKhmerUI-Regular.ttf variable font: https://github.com/googlei18n/noto-fonts/blob/master/alpha/from-pipeline/unhinted/variable-ttf/sans/NotoSansKhmerUI-VF.ttf ? If not then could you test with the above fonts?

hrhatada commented 7 years ago

Hi marekjez86, yes I got the fonts from the location you mentioned above. Also, I didn't see the diacritics shift problem when I tested on OSX with the FontView tool. The shift occurs on the Android device.

marekjez86 commented 7 years ago

@hrhatada : could you try swapping the devices (ie. on device B place the variable fonts and on device A static fonts) and see it the problem described here and in https://github.com/googlei18n/noto-fonts/issues/874 occurs on the device A only? Just trying to find more possibilities.

hrhatada commented 7 years ago

@marekjez86 : I swiped the devices as you requested, and I still see the same result, the variant fonts' diacritics shifting problem.

xiangyexiao commented 7 years ago

@hrhatada you mentioned that the diacritics shifting issue is gone offline. could you confirm and close the bug?

hrhatada commented 7 years ago

Yes, diacritics problem had gone on the different OS.

notofonts / khmer

Noto Sans Khmer UI variable font has the diacritics shift problem #20