ImFontAtlas::Build() does a sanity memset on glyph rectangles.
diff --git a/imgui.cpp b/imgui.cpp
index a8b8d4b..f3b23c4 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -6602,6 +6602,7 @@
stbrp_rect* buf_rects = (stbrp_rect*)ImGui::MemAlloc(total_glyph_count * sizeof(stbrp_rect));
stbtt_pack_range* buf_ranges = (stbtt_pack_range*)ImGui::MemAlloc(total_glyph_range_count * sizeof(stbtt_pack_range));
memset(buf_packedchars, 0, total_glyph_count * sizeof(stbtt_packedchar));
+ memset(buf_rects, 0, total_glyph_count * sizeof(stbrp_rect)); // Unnessary but let's clear this for the sake of sanity.
memset(buf_ranges, 0, total_glyph_range_count * sizeof(stbtt_pack_range));
// First pass: pack all glyphs (no rendering at this point, we are working with glyph sizes only)
