fonts: fix automatic bold synthesis

For fonts like Lucida Console on Windows which do not have a bold
variant, we were not synthesizing bold.

The reason was that the config-level "make bold" logic works by adding
200 to the weight which takes normal -> demibold, but the bold synthesis
logic is enabled only for bold and higher.

This commit changes the threshold for synthesis to demibold or higher.

refs: https://github.com/wez/wezterm/issues/2074

docs/changelog.md

@@ -77,6 +77,7 @@ As features stabilize some brief notes about them will accumulate here.
 * Wayland: panic when display scaling is enabled. [#1727](https://github.com/wez/wezterm/issues/1727)
 * `Dark+` color scheme background color [#2013](https://github.com/wez/wezterm/pull/2013)
 * Avoid fragmenting XTVERSION, DA2, DA3 query responses [#2060](https://github.com/wez/wezterm/issues/2060)
+* Synthesized bold didn't kick in for automatically computed `font_rules`. [#2074](https://github.com/wez/wezterm/issues/2074)
 
 ### 20220408-101518-b908e2dd
 

wezterm-font/src/parser.rs

@@ -656,7 +656,7 @@ impl ParsedFont {
         self.scale = attr.scale.map(|f| *f);
 
         self.synthesize_italic = self.style == FontStyle::Normal && attr.style != FontStyle::Normal;
-        self.synthesize_bold = attr.weight >= FontWeight::BOLD
+        self.synthesize_bold = attr.weight >= FontWeight::DEMIBOLD
             && attr.weight > self.weight
             && self.weight <= FontWeight::REGULAR;
         self.synthesize_dim = attr.weight < FontWeight::REGULAR