From e88380e464d7a0275556f99e38bd0f67358bcd4e Mon Sep 17 00:00:00 2001
From: Andrey Kleshchev <117672381+akleshchev@users.noreply.github.com>
Date: Thu, 21 May 2026 22:50:34 +0300
Subject: #5858 Crash at LLFontFreetype::renderGlyph

---
 indra/llrender/llfontfreetype.cpp | 45 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 44 insertions(+), 1 deletion(-)

diff --git a/indra/llrender/llfontfreetype.cpp b/indra/llrender/llfontfreetype.cpp
index 075c496ec5..3c5682dfc9 100644
--- a/indra/llrender/llfontfreetype.cpp
+++ b/indra/llrender/llfontfreetype.cpp
@@ -720,7 +720,50 @@ void LLFontFreetype::renderGlyph(EFontGlyphType bitmap_type, U32 glyph_index, ll
         llassert_always_msg(FT_Err_Ok == error, message.c_str());
     }
 
-    llassert_always(! FT_Render_Glyph(mFTFace->glyph, gFontRenderMode) );
+    // TODO: Make this more sturdy, make asserts/ll_errs conditional
+    // to non-critical characters.
+    // Temporarily leaving them for data gathering, but unicode chars
+    // like emojis should not cause the app to crash and should either
+    // fallback to some predetermined bitmap or simply return.
+
+    // Verify glyph slot is valid
+    if (!mFTFace->glyph)
+    {
+        LL_ERRS() << "FT_Load_Glyph succeeded but glyph slot is null for wchar " << llformat("U+%xu", U32(wch)) << LL_ENDL;
+        return;
+    }
+
+    // Check if bitmap buffer is already allocated
+    // It can potentially be preallocated for:
+    // 1. SVG/color glyphs rendered by FreeType's SVG_RendererHooks
+    // 2. Embedded bitmap fonts
+    // 3. Some Color emoji that use FT_LOAD_COLOR
+    if (!mFTFace->glyph->bitmap.buffer)
+    {
+        error = FT_Render_Glyph(mFTFace->glyph, gFontRenderMode);
+        if (error != FT_Err_Ok)
+        {
+            std::string render_message = llformat(
+                "Error %d (%s) rendering wchar %u glyph %u: format=%lu, pixel_mode=%d, render_mode=%d",
+                error, FT_Error_String(error), wch, glyph_index,
+                (unsigned long)mFTFace->glyph->format, mFTFace->glyph->bitmap.pixel_mode, gFontRenderMode);
+
+            // Try with FT_RENDER_MODE_NORMAL as fallback
+            if (gFontRenderMode != FT_RENDER_MODE_NORMAL)
+            {
+                LL_WARNS_ONCE() << render_message << LL_ENDL;
+                error = FT_Render_Glyph(mFTFace->glyph, FT_RENDER_MODE_NORMAL);
+                if (error != FT_Err_Ok)
+                {
+                    LL_ERRS() << "Fallback to FT_RENDER_MODE_NORMAL failed. " << render_message << LL_ENDL;
+                }
+            }
+            else
+            {
+                LL_ERRS() << render_message << LL_ENDL;
+            }
+        }
+    }
 
     mRenderGlyphCount++;
 }
-- 
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