From 240b1475c7dac9d6cd722ca7237dc771037f5491 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Mon, 5 Feb 2018 00:04:05 +0530
Subject: [PATCH] Fix regression that caused a few ligatures to not render
 correctly in rare circumstances

This was caused by cache corruption. is_special_glyph() and
is_empty_glyph() were treading over each other if called in
the right sequence. Fixes #303
---
 kitty/fonts.c        | 9 +++++----
 kitty_tests/fonts.py | 1 +
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/kitty/fonts.c b/kitty/fonts.c
index 31cccea8f..3e61a6507 100644
--- a/kitty/fonts.c
+++ b/kitty/fonts.c
@@ -156,15 +156,16 @@ sprite_position_for(Font *font, glyph_index glyph, ExtraGlyphs *extra_glyphs, ui
 }
 
 static inline SpecialGlyphCache*
-special_glyph_cache_for(Font *font, glyph_index glyph, uint8_t mask) {
+special_glyph_cache_for(Font *font, glyph_index glyph, uint8_t filled_mask) {
     SpecialGlyphCache *s = font->special_glyph_cache + (glyph & 0x3ff);
     // Optimize for the common case of glyph under 1024 already in the cache
-    if (LIKELY(s->glyph == glyph && s->data & mask)) return s;  // Cache hit
+    if (LIKELY(s->glyph == glyph && s->data & filled_mask)) return s;  // Cache hit
     while(true) {
-        if (s->data & mask) {
+        if (s->data & filled_mask) {
             if (s->glyph == glyph) return s;  // Cache hit
         } else {
-            break;
+            if (!s->glyph) break;  // Empty cache slot
+            else if (s->glyph == glyph) return s;  // Cache slot that contains other data than the data indicated by filled_mask
         }
         if (!s->next) {
             s->next = calloc(1, sizeof(SpecialGlyphCache));
diff --git a/kitty_tests/fonts.py b/kitty_tests/fonts.py
index 662b496db..3d27b4e9d 100644
--- a/kitty_tests/fonts.py
+++ b/kitty_tests/fonts.py
@@ -78,6 +78,7 @@ class Rendering(BaseTest):
 
         self.ae(groups('abcd'), [(1, 1) for i in range(4)])
         self.ae(groups('A=>>B!=C', path='kitty_tests/FiraCode-Medium.otf'), [(1, 1), (3, 3), (1, 1), (2, 2), (1, 1)])
+        self.ae(groups('F--a--', path='kitty_tests/FiraCode-Medium.otf'), [(1, 1), (2, 2), (1, 1), (2, 2)])
         self.ae(groups('==!=<>==<><><>', path='kitty_tests/FiraCode-Medium.otf'), [(2, 2), (2, 2), (2, 2), (2, 2), (2, 2), (2, 2), (2, 2)])
         colon_glyph = shape_string('9:30', path='kitty_tests/FiraCode-Medium.otf')[1][2]
         self.assertNotEqual(colon_glyph, shape_string(':', path='kitty_tests/FiraCode-Medium.otf')[0][2])