From a4350b41ae8922d7d4f09c84511ab2043b6a7d7c Mon Sep 17 00:00:00 2001
From: Karl Zylinski <karl@zylinski.se>
Date: Fri, 10 Oct 2025 23:40:29 +0200
Subject: [PATCH] Add fontIndex parameter to fontstash that controls which font
 in a TTC to load

---
 vendor/fontstash/fontstash.odin       | 12 ++++++++----
 vendor/fontstash/fontstash_os.odin    |  5 ++++-
 vendor/fontstash/fontstash_other.odin |  1 +
 3 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/vendor/fontstash/fontstash.odin b/vendor/fontstash/fontstash.odin
index b3000de70..30e42be86 100644
--- a/vendor/fontstash/fontstash.odin
+++ b/vendor/fontstash/fontstash.odin
@@ -323,11 +323,15 @@ __AtlasAddWhiteRect :: proc(ctx: ^FontContext, w, h: int) -> bool {
 
 // push a font to the font stack
 // optionally init with ascii characters at a wanted size
+//
+// 'fontIndex' controls which font you want to load within a multi-font format such
+// as TTC. Leave it as zero if you are loading a single-font format such as TTF.
 AddFontMem :: proc(
 	ctx:            ^FontContext,
 	name:           string,
 	data:           []u8,
 	freeLoadedData: bool,
+	fontIndex:      int = 0,
 ) -> int {
 	append(&ctx.fonts, Font{})
 	res := &ctx.fonts[len(ctx.fonts) - 1]
@@ -335,10 +339,10 @@ AddFontMem :: proc(
 	res.freeLoadedData = freeLoadedData
 	res.name           = strings.clone(name)
 
-	// Get offset of first font (if the font is a TTC then it can contain multiple fonts)
-	// Note: There is currently no support for specifying any other font than first one.
-	font_offset := stbtt.GetFontOffsetForIndex(raw_data(res.loadedData), 0)
-	stbtt.InitFont(&res.info, raw_data(res.loadedData), font_offset)
+	num_fonts := stbtt.GetNumberOfFonts(raw_data(data))
+	font_index_clamped := num_fonts > 0 ? clamp(i32(fontIndex), 0, num_fonts-1) : 0
+	font_offset := stbtt.GetFontOffsetForIndex(raw_data(data), font_index_clamped)
+	stbtt.InitFont(&res.info, raw_data(data), font_offset)
 	ascent, descent, line_gap: i32
 
 	stbtt.GetFontVMetrics(&res.info, &ascent, &descent, &line_gap)
diff --git a/vendor/fontstash/fontstash_os.odin b/vendor/fontstash/fontstash_os.odin
index ed453926f..e510a4834 100644
--- a/vendor/fontstash/fontstash_os.odin
+++ b/vendor/fontstash/fontstash_os.odin
@@ -4,10 +4,13 @@ package fontstash
 import "core:log"
 import "core:os"
 
+// 'fontIndex' controls which font you want to load within a multi-font format such
+// as TTC. Leave it as zero if you are loading a single-font format such as TTF.
 AddFontPath :: proc(
 	ctx: ^FontContext,
 	name: string,
 	path: string,
+	fontIndex: int = 0,
 ) -> int {
 	data, ok := os.read_entire_file(path)
 
@@ -15,6 +18,6 @@ AddFontPath :: proc(
 		log.panicf("FONT: failed to read font at %s", path)
 	}
 
-	return AddFontMem(ctx, name, data, true)
+	return AddFontMem(ctx, name, data, true, fontIndex)
 }
 
diff --git a/vendor/fontstash/fontstash_other.odin b/vendor/fontstash/fontstash_other.odin
index edb76d9db..b0a0e2ab9 100644
--- a/vendor/fontstash/fontstash_other.odin
+++ b/vendor/fontstash/fontstash_other.odin
@@ -5,6 +5,7 @@ AddFontPath :: proc(
 	ctx: ^FontContext,
 	name: string,
 	path: string,
+	fontIndex: int = 0,
 ) -> int {
 	panic("fontstash.AddFontPath is unsupported on the JS target")
 }