AttributedString will only draw Japanese characters if all the fonts used have Japanese characters

General JUCE discussion
1 
	auto canBeRepresented = []( juce::StringRef text )
	{
		for ( auto t = text.text; ! t.isEmpty(); )
		{
			auto c = t.getAndAdvance();
			// latin char and punctuation
			if ( ! ( c < 0x024f || ( c >= 0x2000 && c < 0x20d0 ) ) ) 
			{
				return false;
			}
		}
		return true;
	};

	juce::AttributedString	s;
	auto	font = defaultFontWithHeight ( tooltipFontSize );
	auto	unicodeFont = juce::Font ( "Arial", font.getHeight (), 0 );

	const auto	col = findColour ( juce::TooltipWindow::textColourId );

	s.setJustification ( juce::Justification::centredLeft );

	auto	arr = juce::StringArray::fromLines ( text );
	for ( auto& str : arr )
		s.append ( str + "\n", canBeRepresented ( str ) ? font : unicodeFont, col );

	juce::TextLayout	tl;
	tl.createLayoutWithBalancedLineLengths ( s, 600.0f );
	return tl;

On Windows, the following code draws boxes for the Japanese characters. However, if I use unicodeFont for every line, then it works.

2

try to enable JUCE_USE_DIRECTWRITE=1