fonts: improve font_rules behavior

We now always append the synthetic rules to the those in the config,
and include rules for generating half-bright font selection.

config/src/font.rs

@@ -129,6 +129,10 @@ impl FontWeight {
         }
     }
 
+    pub fn lighter(self) -> Self {
+        Self::from_opentype_weight(self.to_opentype_weight().saturating_sub(200))
+    }
+
     pub fn bolder(self) -> Self {
         Self::from_opentype_weight(self.to_opentype_weight() + 200)
     }
@@ -412,6 +416,22 @@ impl TextStyle {
         }
     }
 
+    pub fn make_half_bright(&self) -> Self {
+        Self {
+            foreground: self.foreground,
+            font: self
+                .font
+                .iter()
+                .map(|attr| {
+                    let mut attr = attr.clone();
+                    attr.weight = attr.weight.lighter();
+                    attr.is_synthetic = true;
+                    attr
+                })
+                .collect(),
+        }
+    }
+
     /// Make a version of this style with italic enabled.
     pub fn make_italic(&self) -> Self {
         Self {

config/src/lib.rs

@@ -1385,40 +1385,51 @@ impl Config {
             }
         }
 
-        if cfg.font_rules.is_empty() {
-            // Expand out some reasonable default font rules
-            let reduced = self.font.reduce_first_font_to_family();
-            let mut bold = reduced.make_bold();
-            let mut italic = reduced.make_italic();
-            let mut bold_italic = bold.make_italic();
+        // Add some reasonable default font rules
+        let reduced = self.font.reduce_first_font_to_family();
 
-            // add the reduced version of the font as a fallback right after
-            // the bold/italic variants.  Some users have installed just the
-            // regular weight variant of a font and we'd like to fall back
-            // to that weight in that case, rather than show them an error
-            bold.font.insert(1, reduced.font[0].clone());
-            italic.font.insert(1, reduced.font[0].clone());
-            bold_italic.font.insert(1, reduced.font[0].clone());
+        let italic = reduced.make_italic();
 
-            cfg.font_rules.push(StyleRule {
-                italic: Some(true),
-                font: italic,
-                ..Default::default()
-            });
+        let bold = reduced.make_bold();
+        let bold_italic = bold.make_italic();
 
-            cfg.font_rules.push(StyleRule {
-                intensity: Some(wezterm_term::Intensity::Bold),
-                font: bold,
-                ..Default::default()
-            });
+        let half_bright = reduced.make_half_bright();
+        let half_bright_italic = half_bright.make_italic();
 
-            cfg.font_rules.push(StyleRule {
-                italic: Some(true),
-                intensity: Some(wezterm_term::Intensity::Bold),
-                font: bold_italic,
-                ..Default::default()
-            });
-        }
+        cfg.font_rules.push(StyleRule {
+            italic: Some(true),
+            intensity: Some(wezterm_term::Intensity::Half),
+            font: half_bright_italic,
+            ..Default::default()
+        });
+
+        cfg.font_rules.push(StyleRule {
+            italic: Some(false),
+            intensity: Some(wezterm_term::Intensity::Half),
+            font: half_bright,
+            ..Default::default()
+        });
+
+        cfg.font_rules.push(StyleRule {
+            italic: Some(false),
+            intensity: Some(wezterm_term::Intensity::Bold),
+            font: bold,
+            ..Default::default()
+        });
+
+        cfg.font_rules.push(StyleRule {
+            italic: Some(true),
+            intensity: Some(wezterm_term::Intensity::Bold),
+            font: bold_italic,
+            ..Default::default()
+        });
+
+        cfg.font_rules.push(StyleRule {
+            italic: Some(true),
+            intensity: Some(wezterm_term::Intensity::Normal),
+            font: italic,
+            ..Default::default()
+        });
 
         // Load any additional color schemes into the color_schemes map
         cfg.load_color_schemes(&cfg.compute_color_scheme_dirs())

docs/changelog.md

@@ -26,6 +26,7 @@ As features stabilize some brief notes about them will accumulate here.
 * Fixed: half-pixel gaps in ligatured/double-wide glyphs depending on the font size [#614](https://github.com/wez/wezterm/issues/614)
 * Fixed: Window could vanish if a tab closed while the rightmost tab was active(!) [#690](https://github.com/wez/wezterm/issues/690)
 * Fixed: macOS: mouse cursor could get stuck in the hidden state. [#618](https://github.com/wez/wezterm/issues/618)
+* Improved: [font_rules](config/lua/config/font_rules.md) behavior to always append reasonable default `font_rules` to those that you may have specified in your config.  `font_rules` now also include defaults for half-bright text styles.
 
 ### 20210405-110924-a5bb5be8
 

docs/config/lua/config/font_rules.md

@@ -86,3 +86,118 @@ return {
   },
 }
 ```
+
+*Since: nightly builds only*
+
+The default `font_rules` generated by wezterm are now always appended to the
+rules that you've supplied (rather than used only if you didn't specify any),
+and now also include rules for selecting lighter weight fonts when half-bright
+text is rendered to the terminal.
+
+That means that you shouldn't need to specify as many rules as in previously
+releases.
+
+You can run `wezterm ls-fonts` to summarize the font rules and the fonts that
+match them:
+
+```bash
+$ wezterm ls-fonts
+Primary font:
+wezterm.font_with_fallback({
+  -- <built-in>, BuiltIn
+  "JetBrains Mono",
+
+  -- /home/wez/.fonts/NotoColorEmoji.ttf, FontConfig
+  "Noto Color Emoji",
+
+  -- <built-in>, BuiltIn
+  "Last Resort High-Efficiency",
+
+})
+
+
+When Intensity=Half Italic=true:
+wezterm.font_with_fallback({
+  -- <built-in>, BuiltIn
+  {family="JetBrains Mono", weight="ExtraLight", italic=true},
+
+  -- /home/wez/.fonts/NotoColorEmoji.ttf, FontConfig
+  "Noto Color Emoji",
+
+  -- <built-in>, BuiltIn
+  "JetBrains Mono",
+
+  -- <built-in>, BuiltIn
+  "Last Resort High-Efficiency",
+
+})
+
+
+When Intensity=Half Italic=false:
+wezterm.font_with_fallback({
+  -- <built-in>, BuiltIn
+  {family="JetBrains Mono", weight="ExtraLight"},
+
+  -- /home/wez/.fonts/NotoColorEmoji.ttf, FontConfig
+  "Noto Color Emoji",
+
+  -- <built-in>, BuiltIn
+  "JetBrains Mono",
+
+  -- <built-in>, BuiltIn
+  "Last Resort High-Efficiency",
+
+})
+
+
+When Intensity=Bold Italic=false:
+wezterm.font_with_fallback({
+  -- <built-in>, BuiltIn
+  {family="JetBrains Mono", weight="Bold"},
+
+  -- /home/wez/.fonts/NotoColorEmoji.ttf, FontConfig
+  "Noto Color Emoji",
+
+  -- <built-in>, BuiltIn
+  "JetBrains Mono",
+
+  -- <built-in>, BuiltIn
+  "Last Resort High-Efficiency",
+
+})
+
+
+When Intensity=Bold Italic=true:
+wezterm.font_with_fallback({
+  -- <built-in>, BuiltIn
+  {family="JetBrains Mono", weight="Bold", italic=true},
+
+  -- /home/wez/.fonts/NotoColorEmoji.ttf, FontConfig
+  "Noto Color Emoji",
+
+  -- <built-in>, BuiltIn
+  "JetBrains Mono",
+
+  -- <built-in>, BuiltIn
+  "Last Resort High-Efficiency",
+
+})
+
+
+When Intensity=Normal Italic=true:
+wezterm.font_with_fallback({
+  -- <built-in>, BuiltIn
+  {family="JetBrains Mono", italic=true},
+
+  -- /home/wez/.fonts/NotoColorEmoji.ttf, FontConfig
+  "Noto Color Emoji",
+
+  -- <built-in>, BuiltIn
+  "JetBrains Mono",
+
+  -- <built-in>, BuiltIn
+  "Last Resort High-Efficiency",
+
+})
+```
+

test-data/styles.txt

@@ -0,0 +1,8 @@
+
+Regular
+Bold
+Italic
+Bold Italic
+Half Bright
+Half Bright Italic
+