Implement an option to adjust the line height

Fixes #116

kitty/config.py

@@ -198,7 +198,14 @@ def positive_float(x):
     return max(0, float(x))
 
 
+def adjust_line_height(x):
+    if x.endswith('%'):
+        return float(x[:-1]) / 100.0
+    return int(x)
+
+
 type_map = {
+    'adjust_line_height': adjust_line_height,
     'scrollback_lines': positive_int,
     'scrollback_pager': shlex.split,
     'scrollback_in_new_tab': to_bool,

kitty/fonts/core_text.py

@@ -7,7 +7,7 @@
 import sys
 
 from kitty.fast_data_types import CTFace as Face, coretext_all_fonts
-from kitty.utils import ceil_int, get_logical_dpi, safe_print, wcwidth
+from kitty.utils import ceil_int, get_logical_dpi, safe_print, wcwidth, adjust_line_height
 
 main_font = {}
 symbol_map = {}
@@ -93,6 +93,7 @@ def set_font_family(opts, override_font_size=None, ignore_dpi_failure=False):
     install_symbol_map(all_fonts, opts.symbol_map, font_size, dpi)
     mf = main_font[(False, False)]
     cell_width, cell_height = mf.cell_size()
+    cell_height = adjust_line_height(cell_height, opts.adjust_line_height)
     CellTexture = ctypes.c_ubyte * (cell_width * cell_height)
     WideCellTexture = ctypes.c_ubyte * (2 * cell_width * cell_height)
     baseline = int(round(mf.ascent))

kitty/fonts/freetype.py

@@ -12,7 +12,7 @@
 
 from kitty.fast_data_types import FT_PIXEL_MODE_GRAY, Face
 from kitty.fonts.box_drawing import render_missing_glyph
-from kitty.utils import ceil_int, get_logical_dpi, safe_print, wcwidth
+from kitty.utils import ceil_int, get_logical_dpi, safe_print, wcwidth, adjust_line_height
 
 from .fontconfig import (
     FontNotFound, find_font_for_character, font_for_family, get_font_files
@@ -93,6 +93,7 @@ def set_font_family(opts, override_font_size=None):
     cell_height = font_units_to_pixels(
         face.height, face.units_per_EM, size_in_pts, dpi[1]
     )
+    cell_height = adjust_line_height(cell_height, opts.adjust_line_height)
     baseline = font_units_to_pixels(
         face.ascender, face.units_per_EM, size_in_pts, dpi[1]
     )

kitty/kitty.conf

@@ -25,6 +25,14 @@ font_size        11.0
 # the font size in a running terminal.
 font_size_delta 2
 
+
+# Adjust the line height. 
+# You can use either numbers, which are interpreted as pixels or percentages
+# (number followed by %), which are interpreted as percentages of the
+# unmodified line height. You can use negative pixels or percentages less than
+# 100% to reduce line height (but this might cause rendering artifacts).
+adjust_line_height 0
+
 # The foreground color
 foreground       #dddddd
 

kitty/utils.py

@@ -226,3 +226,9 @@ def detach(fork=True, setsid=True, redirect=True):
         os.setsid()
     if redirect:
         redirect_std_streams(os.devnull)
+
+
+def adjust_line_height(cell_height, val):
+    if isinstance(val, int):
+        return cell_height + val
+    return int(cell_height * val)