[css-fonts-4] Clarified that font variations do not count as font synthesis, #9391

Author: svgeesus

css-fonts-4/Overview.bs

@@ -1957,6 +1957,31 @@ Shorthand font property: the 'font' property</h3>
 <h3 id="font-synthesis-intro">
 Controlling synthetic faces</h3>
 
+Synthetic font faces are a fallback strategy
+to provide an approximation to the requested font
+when a font family lacks a suitable face.
+
+<div class="example" id="ex-synthesis-types">
+	For example, a user agent might:
+
+	* synthesize a bold face by drawing a thin stroke around each glyph
+	* synthesize small-caps, superscripts, or subscripts by 
+		rendering regular glyphs at a smaller size and positioning them appropriately
+	* syntesize an oblique face by geometrical shearing of each glyph
+</div>
+
+Synthesis is a fallback strategy
+because the end result,
+while perhaps better than nothing at all,
+does not meet the level of quality
+of a face designed for the purpose.
+
+Variable fonts,
+where the font designer has provided
+one or more axes of variation
+do <em>not</em> count as font synthesis
+and their use is not affected by the 'font-synthesis' property.
+
 <h4 id="font-synthesis-weight">
 Controlling synthesized bold: The 'font-synthesis-weight' property</h4>