Add a config option to control the line thickness for box drawing characters

Fixes #183

kitty/config.py

@@ -220,6 +220,13 @@ def adjust_line_height(x):
     return int(x)
 
 
+def box_drawing_scale(x):
+    ans = tuple(float(x.strip()) for x in x.split(','))
+    if len(ans) != 4:
+        raise ValueError('Invalid box_drawing scale, must have four entries')
+    return ans
+
+
 type_map = {
     'adjust_line_height': adjust_line_height,
     'scrollback_lines': positive_int,
@@ -249,6 +256,7 @@ type_map = {
     'use_system_wcwidth': to_bool,
     'macos_hide_titlebar': to_bool,
     'macos_option_as_alt': to_bool,
+    'box_drawing_scale': box_drawing_scale,
 }
 
 for name in (

kitty/fonts/box_drawing.py

@@ -9,9 +9,17 @@ from itertools import repeat
 from kitty.utils import get_logical_dpi
 
 
+scale = (0.001, 1, 1.5, 2)
+
+
+def set_scale(new_scale):
+    global scale
+    scale = tuple(new_scale)
+
+
 def thickness(level=1, horizontal=True):
     dpi = get_logical_dpi()[0 if horizontal else 1]
-    pts = (0.001, 1, 1.5, 2)[level]
+    pts = scale[level]
     return int(math.ceil(pts * dpi / 72.0))
 
 

kitty/kitty.conf

@@ -31,6 +31,12 @@ font_size_delta 2
 # 100% to reduce line height (but this might cause rendering artifacts).
 adjust_line_height 0
 
+# Change the sizes of the lines used for the box drawing unicode characters
+# These values are in pts. They will be scaled by the monitor DPI to arrive at 
+# a pixel value. There must be four values corresponding to thin, normal, thick,
+# and very thick lines;
+box_drawing_scale 0.001, 1, 1.5, 2
+
 # The foreground color
 foreground       #dddddd
 

kitty/main.py

@@ -26,6 +26,7 @@ from .fast_data_types import (
     glfw_init, glfw_init_hint_string, glfw_swap_interval, glfw_terminate,
     glfw_window_hint, install_sigchld_handler, set_logical_dpi, set_options
 )
+from .fonts.box_drawing import set_scale
 from .layout import all_layouts
 from .utils import (
     color_as_int, detach, end_startup_notification, get_logical_dpi,
@@ -170,6 +171,7 @@ def initialize_window(window, opts, debug_gl=False):
 def run_app(opts, args):
     set_options(opts)
     setup_opengl(opts)
+    set_scale(opts.box_drawing_scale)
     load_cached_values()
     if 'window-size' in cached_values and opts.remember_window_size:
         ws = cached_values['window-size']