From 117ed0060d5ba6327cc993c9dcdd40de4b6c24a2 Mon Sep 17 00:00:00 2001
From: Kiss Lorand <50251547+kisslorand@users.noreply.github.com>
Date: Tue, 11 Aug 2026 22:25:09 +0300
Subject: [PATCH] Fix Celsius symbol rendering in Preview (#15202)

---
 deps_src/imgui/imgui_draw.cpp   |  1 +
 src/slic3r/GUI/ImGuiWrapper.cpp | 14 ++++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/deps_src/imgui/imgui_draw.cpp b/deps_src/imgui/imgui_draw.cpp
index 913a551fa0..d88bc79904 100644
--- a/deps_src/imgui/imgui_draw.cpp
+++ b/deps_src/imgui/imgui_draw.cpp
@@ -2856,6 +2856,7 @@ const ImWchar*   ImFontAtlas::GetGlyphRangesDefault()
     {
         0x0020, 0x00FF, // Basic Latin + Latin Supplement
         0x2000, 0x206F, // General Punctuation
+        0x2103, 0x2103, // ℃ Celsius symbol
         0x3000, 0x30FF, // CJK Symbols and Punctuations, Hiragana, Katakana
         0x31F0, 0x31FF, // Katakana Phonetic Extensions
         0xFF00, 0xFFEF, // Half-width characters
diff --git a/src/slic3r/GUI/ImGuiWrapper.cpp b/src/slic3r/GUI/ImGuiWrapper.cpp
index 8974a169d1..d46e8ed31b 100644
--- a/src/slic3r/GUI/ImGuiWrapper.cpp
+++ b/src/slic3r/GUI/ImGuiWrapper.cpp
@@ -2809,12 +2809,26 @@ void ImGuiWrapper::init_font(bool compress)
         }
     }
 
+    if (m_glyph_ranges == ImGui::GetIO().Fonts->GetGlyphRangesThai()) {
+        ImFontConfig fallback_cfg = cfg;
+        fallback_cfg.MergeMode = true;
+        static constexpr ImWchar celsius_range[] = { 0x2103, 0x2103, 0 };
+        io.Fonts->AddFontFromFileTTF((Slic3r::resources_dir() + "/fonts/HarmonyOS_Sans_SC_Regular.ttf").c_str(), m_font_size, &fallback_cfg, celsius_range);
+    }
+
     bold_font        = io.Fonts->AddFontFromFileTTF((Slic3r::resources_dir() + "/fonts/" + font_name_bold).c_str(), m_font_size, &cfg, ranges.Data);
     if (bold_font == nullptr) {
         bold_font = io.Fonts->AddFontDefault();
         if (bold_font == nullptr) { throw Slic3r::RuntimeError("ImGui: Could not load deafult font"); }
     }
 
+    if (m_glyph_ranges == ImGui::GetIO().Fonts->GetGlyphRangesThai()) {
+        ImFontConfig fallback_cfg = cfg;
+        fallback_cfg.MergeMode = true;
+        static constexpr ImWchar celsius_range[] = { 0x2103, 0x2103, 0 };
+        io.Fonts->AddFontFromFileTTF((Slic3r::resources_dir() + "/fonts/HarmonyOS_Sans_SC_Bold.ttf").c_str(), m_font_size, &fallback_cfg, celsius_range);
+    }
+
     if (m_glyph_ranges == ImGui::GetIO().Fonts->GetGlyphRangesThai()) {
         default_font->Scale *= 1.25f;
         bold_font->Scale *= 1.25f;