From e803505aad864067258ef8d6efd5145a8167a7d0 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Mon, 27 Apr 2020 18:02:53 +0530
Subject: [PATCH] CoreText: When centering glyphs ignore negative origins

This is needed for FiraCode ligatures to line up correctly. See
https://github.com/kovidgoyal/kitty/issues/2591#issuecomment-619937030
---
 kitty/core_text.m | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kitty/core_text.m b/kitty/core_text.m
index 9e25a42da..5da81b2ea 100644
--- a/kitty/core_text.m
+++ b/kitty/core_text.m
@@ -506,8 +506,10 @@ do_render(CTFontRef ct_font, bool bold, bool italic, hb_glyph_info_t *info, hb_g
         render_alpha_mask(render_buf, canvas, &src, &dest, canvas_width, canvas_width);
     }
     if (num_cells && (center_glyph || (num_cells == 2 && *was_colored))) {
-        // center glyphs (two cell emoji and PUA glyphs)
-        CGFloat delta = (((CGFloat)canvas_width - br.size.width) / 2.f) - br.origin.x;
+        // center glyphs (two cell emoji, PUA glyphs, ligatures, etc)
+        CGFloat delta = (((CGFloat)canvas_width - br.size.width) / 2.f);
+        // FiraCode ligatures result in negative origins
+        if (br.origin.x > 0) delta -= br.origin.x;
         if (delta >= 1.f) right_shift_canvas(canvas, canvas_width, cell_height, (unsigned)(delta));
     }
     return true;