wezterm: make the split color configurable and darker

This makes the color of the split divider darker by default,
and configurable via the color scheme configuration file.

refs: #297

config/src/color.rs

@@ -26,6 +26,8 @@ pub struct Palette {
     /// The color of the "thumb" of the scrollbar; the segment that
     /// represents the current viewable area
     pub scrollbar_thumb: Option<RgbColor>,
+    /// The color of the split line between panes
+    pub split: Option<RgbColor>,
 }
 impl_lua_conversion!(Palette);
 
@@ -47,6 +49,7 @@ impl From<Palette> for wezterm_term::color::ColorPalette {
         apply_color!(selection_fg);
         apply_color!(selection_bg);
         apply_color!(scrollbar_thumb);
+        apply_color!(split);
 
         if let Some(ansi) = cfg.ansi {
             for (idx, col) in ansi.iter().enumerate() {

docs/config/appearance.markdown

@@ -47,6 +47,9 @@ return {
       -- The color of the scrollbar "thumb"; the portion that represents the current viewport
       scrollbar_thumb = "#222222",
 
+      -- The color of the split lines between panes
+      split = "#444444",
+
       ansi = {"black", "maroon", "green", "olive", "navy", "purple", "teal", "silver"},
       brights = {"grey", "red", "lime", "yellow", "blue", "fuchsia", "aqua", "white"},
   }

term/src/color.rs

@@ -28,6 +28,7 @@ pub struct ColorPalette {
     pub selection_fg: RgbColor,
     pub selection_bg: RgbColor,
     pub scrollbar_thumb: RgbColor,
+    pub split: RgbColor,
 }
 
 /// Adjust the color to make it appear disabled.
@@ -88,6 +89,7 @@ impl ColorPalette {
             selection_fg: grey_out(self.selection_fg),
             selection_bg: grey_out(self.selection_bg),
             scrollbar_thumb: grey_out(self.scrollbar_thumb),
+            split: grey_out(self.split),
         }
     }
 }
@@ -232,6 +234,7 @@ impl Default for ColorPalette {
         let selection_bg = RgbColor::new(0xff, 0xfa, 0xcd);
 
         let scrollbar_thumb = RgbColor::new(0x22, 0x22, 0x22);
+        let split = RgbColor::new(0x44, 0x44, 0x44);
 
         ColorPalette {
             colors: Palette256(colors),
@@ -243,6 +246,7 @@ impl Default for ColorPalette {
             selection_fg,
             selection_bg,
             scrollbar_thumb,
+            split,
         }
     }
 }

wezterm/src/gui/termwindow.rs

@@ -2255,7 +2255,7 @@ impl TermWindow {
             "─"
         };
         let palette = pane.palette();
-        let foreground = rgbcolor_to_window_color(palette.foreground);
+        let foreground = rgbcolor_to_window_color(palette.split);
         let background = rgbcolor_alpha_to_window_color(
             palette.background,
             if self.window_background.is_none() && config.window_background_opacity == 1.0 {