Merge branch 'less-contrast-for-powerline-alt-separator' of https://github.com/chipaca/kitty

docs/changelog.rst

@@ -71,6 +71,8 @@ To update |kitty|, :doc:`follow the instructions <binary>`.
   executing any command specified on the command line via the users' shell
   just as ssh does (:iss:`3638`)
 
+- Tab bar: Use a lower contrast color for tab separators (:pull:`3666`)
+
 
 0.20.3 [2021-05-06]
 ----------------------

kitty/rgb.py

@@ -12,6 +12,16 @@ class Color(NamedTuple):
     green: int
     blue: int
 
+    def luminance(self) -> float:
+        return 0.299 * self.red + 0.587 * self.green + 0.114 * self.blue
+
+    def contrast(self, other: 'Color') -> float:
+        a = self.luminance()
+        b = other.luminance()
+        if a < b:
+            a, b = b, a
+        return (a + 0.05) / (b + 0.05)
+
 
 def alpha_blend_channel(top_color: int, bottom_color: int, alpha: float) -> int:
     return int(alpha * top_color + (1 - alpha) * bottom_color)

kitty/tab_bar.py

@@ -234,7 +234,16 @@ def draw_tab_with_powerline(draw_data: DrawData, screen: Screen, tab: TabBarData
             screen.cursor.bg = inactive_bg
         screen.draw(separator_symbol)
     else:
+        prev_fg = screen.cursor.fg
+        if tab_bg == tab_fg:
+            screen.cursor.fg = default_bg
+        elif tab_bg != default_bg:
+            c1 = draw_data.inactive_bg.contrast(draw_data.default_bg)
+            c2 = draw_data.inactive_bg.contrast(draw_data.inactive_fg)
+            if c1 < c2:
+                screen.cursor.fg = default_bg
         screen.draw(f' {separator_alt_symbol}')
+        screen.cursor.fg = prev_fg
 
     end = screen.cursor.x
     if end < screen.columns: