From 2b6800b026d9f36f9ad6434aabc3962ce0236db4 Mon Sep 17 00:00:00 2001
From: Leland Lucius <github@homerow.net>
Date: Fri, 5 Jan 2024 22:36:18 -0600
Subject: [PATCH] Only use modified scaling on Windows

And only if the system's scaling factor is greater than 300%.
---
 src/slic3r/GUI/GLCanvas3D.cpp   | 12 +++++++++++-
 src/slic3r/GUI/ImGuiWrapper.cpp | 11 +++++++++--
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/src/slic3r/GUI/GLCanvas3D.cpp b/src/slic3r/GUI/GLCanvas3D.cpp
index 81f6acc22..313c87afb 100644
--- a/src/slic3r/GUI/GLCanvas3D.cpp
+++ b/src/slic3r/GUI/GLCanvas3D.cpp
@@ -6428,7 +6428,17 @@ void GLCanvas3D::_resize(unsigned int w, unsigned int h)
     m_last_w = w;
     m_last_h = h;
 
-    const float font_size = 1.0f * wxGetApp().em_unit();
+    float font_size = wxGetApp().em_unit();
+
+#ifdef _WIN32
+    // On Windows, if manually scaled here, rendering issues can occur when the system's Display
+    // scaling is greater than 300% as the font's size gets to be to large. So, use imgui font
+    // scaling instead (see: ImGuiWrapper::init_font() and issue #3401)
+    font_size *= (font_size > 30.0f) ? 1.0f : 1.5f;
+#else
+    font_size *= 1.5f;
+#endif
+
 #if ENABLE_RETINA_GL
     imgui->set_scaling(font_size, 1.0f, m_retina_helper->get_scale_factor());
 #else
diff --git a/src/slic3r/GUI/ImGuiWrapper.cpp b/src/slic3r/GUI/ImGuiWrapper.cpp
index 416d3365e..aafc93f1b 100644
--- a/src/slic3r/GUI/ImGuiWrapper.cpp
+++ b/src/slic3r/GUI/ImGuiWrapper.cpp
@@ -2110,7 +2110,6 @@ void ImGuiWrapper::init_font(bool compress)
             throw Slic3r::RuntimeError("ImGui: Could not load deafult font");
         }
     }
-    default_font->Scale = 1.5f;
 
     if (m_is_korean)
         bold_font = io.Fonts->AddFontFromFileTTF((Slic3r::resources_dir() + "/fonts/" + "NotoSansKR-Bold.ttf").c_str(), m_font_size, &cfg, ranges.Data);
@@ -2120,7 +2119,15 @@ void ImGuiWrapper::init_font(bool compress)
         bold_font = io.Fonts->AddFontDefault();
         if (bold_font == nullptr) { throw Slic3r::RuntimeError("ImGui: Could not load deafult font"); }
     }
-    bold_font->Scale = 1.5f;
+
+#ifdef _WIN32
+    // Render the text a bit larger (see GLCanvas3D::_resize() and issue #3401), but only if the scale factor
+    // for the Display is greater than 300%.
+    if (wxGetApp().em_unit() > 30) {
+        default_font->Scale = 1.5f;
+        bold_font->Scale    = 1.5f;
+    }
+#endif
 
 #ifdef __APPLE__
     ImFontConfig config;