Add bold_brightens_ansi_colors configuration option

refs: #244

docs/changelog.markdown

@@ -14,6 +14,8 @@ brief notes about them may accumulate here.
   (not multiplexer) terminal sessions.
 * Added support for SGR 53/55 which enable/disable Overline style.
   `printf "\x1b[53moverline\x1b[0m\n"`
+* Added `bold_brightens_ansi_colors` option to allow disabling the automatic
+  brightening of bold text.
 
 ### 20200620-160318-e00b076c
 

docs/config/fonts.markdown

@@ -27,6 +27,20 @@ return {
   -- or notice slight differences when comparing with other terminal
   -- emulators, you may wish to tune this value!
   dpi = 96.0,
+
+  -- When true (the default), text that is set to ANSI color
+  -- indices 0-7 will be shifted to the corresponding brighter
+  -- color index (8-15) when the intensity is set to Bold.
+  --
+  -- This brightening effect doesn't occur when the text is set
+  -- to the default foreground color!
+  --
+  -- This defaults to true for better compatibility with a wide
+  -- range of mature software; for instance, a lot of software
+  -- assumes that Black+Bold renders as a Dark Grey which is
+  -- legible on a Black background, but if this option is set to
+  -- true, it would render as Black on Black.
+  bold_brightens_ansi_colors = true,
 }
 ```
 

src/config/mod.rs

@@ -283,6 +283,12 @@ pub struct Config {
     #[serde(default)]
     pub font_rules: Vec<StyleRule>,
 
+    /// When true (the default), PaletteIndex 0-7 are shifted to
+    /// bright when the font intensity is bold.  The brightening
+    /// doesn't apply to text that is the default color.
+    #[serde(default = "default_true")]
+    pub bold_brightens_ansi_colors: bool,
+
     /// The color palette
     pub colors: Option<Palette>,
 

src/frontend/gui/termwindow.rs

@@ -2312,7 +2312,9 @@ impl TermWindow {
                         params.palette.resolve_fg(attrs.foreground)
                     }
                 }
-                wezterm_term::color::ColorAttribute::PaletteIndex(idx) if idx < 8 => {
+                wezterm_term::color::ColorAttribute::PaletteIndex(idx)
+                    if idx < 8 && params.config.bold_brightens_ansi_colors =>
+                {
                     // For compatibility purposes, switch to a brighter version
                     // of one of the standard ANSI colors when Bold is enabled.
                     // This lifts black to dark grey.
@@ -2599,7 +2601,9 @@ impl TermWindow {
                         palette.resolve_fg(attrs.foreground)
                     }
                 }
-                wezterm_term::color::ColorAttribute::PaletteIndex(idx) if idx < 8 => {
+                wezterm_term::color::ColorAttribute::PaletteIndex(idx)
+                    if idx < 8 && config.bold_brightens_ansi_colors =>
+                {
                     // For compatibility purposes, switch to a brighter version
                     // of one of the standard ANSI colors when Bold is enabled.
                     // This lifts black to dark grey.