From 60072360e1e01ac0134def097f606c528c4f8e49 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Tue, 21 Apr 2026 16:05:48 +0300
Subject: [PATCH] sokol: fix gg.draw_text text corruption with font size and
 long string on mac (fixes #20457)

---
 vlib/gg/text_rendering.c.v    | 40 +++++++++++++++++++++++++++--------
 vlib/gg/text_rendering_test.v | 24 +++++++++++++++++++--
 2 files changed, 53 insertions(+), 11 deletions(-)

diff --git a/vlib/gg/text_rendering.c.v b/vlib/gg/text_rendering.c.v
index f77b9cbb6..98ba6aab2 100644
--- a/vlib/gg/text_rendering.c.v
+++ b/vlib/gg/text_rendering.c.v
@@ -33,19 +33,41 @@ pub enum VerticalAlign {
 	baseline = C.FONS_ALIGN_BASELINE
 }
 
-const buff_size = int($d('gg_text_buff_size', 2048))
+const initial_text_atlas_size = int($d('gg_text_buff_size', 2048))
+const max_text_atlas_size = 8192
 
-fn clear_atlas_callback(uptr voidptr, error int, _val int) {
-	if error == 1 { // atlas overflow error code
-		fons := unsafe { &fontstash.Context(uptr) }
-		fons.reset_atlas(buff_size, buff_size)
+fn expand_atlas_callback(uptr voidptr, error int, _val int) {
+	if error != C.FONS_ATLAS_FULL {
+		return
+	}
+	fons := unsafe { &fontstash.Context(uptr) }
+	width, height := fons.get_atlas_size()
+	mut next_width := if width > 0 { width } else { initial_text_atlas_size }
+	mut next_height := if height > 0 { height } else { initial_text_atlas_size }
+	if next_width < max_text_atlas_size {
+		next_width = if next_width * 2 > max_text_atlas_size {
+			max_text_atlas_size
+		} else {
+			next_width * 2
+		}
+	}
+	if next_height < max_text_atlas_size {
+		next_height = if next_height * 2 > max_text_atlas_size {
+			max_text_atlas_size
+		} else {
+			next_height * 2
+		}
+	}
+	if next_width == width && next_height == height {
+		return
 	}
+	fons.expand_atlas(next_width, next_height)
 }
 
 fn new_ft(c FTConfig) ?&FT {
 	if c.font_path == '' {
 		if c.bytes_normal.len > 0 {
-			fons := sfons.create(buff_size, buff_size, 1)
+			fons := sfons.create(initial_text_atlas_size, initial_text_atlas_size, 1)
 			bytes_normal := c.bytes_normal
 			bytes_bold := if c.bytes_bold.len > 0 {
 				c.bytes_bold
@@ -65,7 +87,7 @@ fn new_ft(c FTConfig) ?&FT {
 				debug_font_println('setting italic variant to normal')
 				bytes_normal
 			}
-			fons.set_error_callback(clear_atlas_callback, fons)
+			fons.set_error_callback(expand_atlas_callback, fons)
 			return &FT{
 				fons:        fons
 				font_normal: fons.add_font_mem('sans', bytes_normal.clone(), true)
@@ -126,12 +148,12 @@ fn new_ft(c FTConfig) ?&FT {
 		italic_path = c.font_path
 		bytes
 	}
-	fons := sfons.create(buff_size, buff_size, 1)
+	fons := sfons.create(initial_text_atlas_size, initial_text_atlas_size, 1)
 	debug_font_println('Font used for font_normal : ${normal_path}')
 	debug_font_println('Font used for font_bold   : ${bold_path}')
 	debug_font_println('Font used for font_mono   : ${mono_path}')
 	debug_font_println('Font used for font_italic : ${italic_path}')
-	fons.set_error_callback(clear_atlas_callback, fons)
+	fons.set_error_callback(expand_atlas_callback, fons)
 	return &FT{
 		fons:        fons
 		font_normal: fons.add_font_mem('sans', bytes.clone(), true)
diff --git a/vlib/gg/text_rendering_test.v b/vlib/gg/text_rendering_test.v
index ab841162a..8ae348cfa 100644
--- a/vlib/gg/text_rendering_test.v
+++ b/vlib/gg/text_rendering_test.v
@@ -5,9 +5,13 @@ import fontstash
 const embedded_test_mono_font = $embed_file('@VEXEROOT/examples/assets/fonts/RobotoMono-Regular.ttf')
 
 fn new_test_text_context() (&Context, &fontstash.Context) {
+	return new_test_text_context_with_atlas(512, 512)
+}
+
+fn new_test_text_context_with_atlas(width int, height int) (&Context, &fontstash.Context) {
 	mut fons := fontstash.create_internal(&C.FONSparams{
-		width:  512
-		height: 512
+		width:  width
+		height: height
 		flags:  0
 	})
 	assert fons != unsafe { nil }
@@ -15,6 +19,7 @@ fn new_test_text_context() (&Context, &fontstash.Context) {
 	assert font_id != fontstash.invalid
 	fons.set_font(font_id)
 	fons.set_size(16)
+	fons.set_error_callback(expand_atlas_callback, fons)
 	return &Context{
 		ft:          &FT{
 			fons: fons
@@ -57,3 +62,18 @@ fn test_text_width_counts_trailing_space_advance() {
 	width, _ := ctx.text_size('a ')
 	assert width == int(advance / ctx.scale)
 }
+
+fn test_text_atlas_expands_on_overflow() {
+	_, fons := new_test_text_context_with_atlas(64, 64)
+	defer {
+		fontstash.delete_internal(fons)
+	}
+	before_width, before_height := fons.get_atlas_size()
+	mut bounds := [4]f32{}
+	for size in [48, 64, 80] {
+		fons.set_size(size)
+		_ = fons.text_bounds(0, 0, 'Some very long text here 0123456789', &bounds[0])
+	}
+	after_width, after_height := fons.get_atlas_size()
+	assert after_width > before_width || after_height > before_height
+}
-- 
2.39.5