Using character-by-character value of font-selection-strategy attribute
Often you need to compose text blocks whith several language mixed together or with use of special characters.
It these cases there might be necesary to render such a block using multiple different fonts since
neither of them have all required glyphs. XSL FO provides special property font-selection-strategy
that targets this problem togher with font-family property.
XSL FO Recommendation, Chapter 7.8.2 "font-family"
XSL FO Recommendation, Chapter 7.8.3 "font-selection-strategy"
The font-family property allows you to specify several font families (separated by comma)
and font-selection-strategy defines how these fonts will by applied by rendering engine.
When font-selection-strategy is set to character-by-character,
formatter will trigger font selection process for every character rendered.
Consider following example:
<fo:block font-size="24pt"
font-family="Courier, ArialMT"
font-selection-strategy="character-by-character">
абABCв
</fo:block>
First, second and sixth characters are Russian, the rest are basic Latin characters.
Font Courier has glyps only for Latin characters, while ArialMT covers both Latin and Russian.
In this example formatter will look through all fonts in order to find one that has appropriate glyph.
This process will be repeated for every character no metter which font was selected on previous step.
Thus characters 3, 4 and 5 will be rendered using Courier and characters 1, 2 and 6 will be
rendered using ArialMT:
абABCв
If we replace font-selection-strategy="character-by-character" with
font-selection-strategy="auto" in the example above,
formatter will restart font selecting process only when previously selected font has no required glyph.
In such a case all six characters will be rendered using ArialMT font as shown below:
абABCв