If a border width in pts is non-zero have it result in a minimum 1px border

Change the default to 0.5pt instead of 1px

docs/changelog.rst

@@ -11,7 +11,7 @@ To update |kitty|, :doc:`follow the instructions <binary>`.
   does not display a box around active windows.
 
 - Allow specifying border sizes in either pts or pixels. Change the default to
-  1px borders as this works best with the new minimal border style.
+  0.5pt borders as this works best with the new minimal border style.
 
 - Add support for displaying correct colors with non-sRGB PNG files (Adds a
   dependency on liblcms2)

kitty/config_data.py

@@ -683,7 +683,7 @@ def window_border_width(x: Union[str, int, float]) -> Tuple[float, str]:
     return max(0, val), unit
 
 
-o('window_border_width', '1px', option_type=window_border_width, long_text=_('''
+o('window_border_width', '0.5pt', option_type=window_border_width, long_text=_('''
 The width of window borders. Can be either in pixels (px) or pts (pt). Values
 in pts will be rounded to the nearest number of pixels based on screen
 resolution. If not specified the unit is assumed to be pts.

kitty/window.py

@@ -332,7 +332,7 @@ class Window:
     def effective_border(self) -> int:
         val, unit = self.opts.window_border_width
         if unit == 'pt':
-            val = pt_to_px(val, self.os_window_id)
+            val = max(1 if val > 0 else 0, pt_to_px(val, self.os_window_id))
         else:
             val = round(val)
         return int(val)