From 3fc85286928d677f70de1986f6e6020d92e44934 Mon Sep 17 00:00:00 2001
From: David Carter <dcarter@davidcarter.ca>
Date: Wed, 29 Oct 2025 17:46:23 -0400
Subject: [PATCH] Materials: Assigning material without appearance

Assigning a material without an appearance reset the appearance to the
default appearance.

There were two main problems. One was the comparison function for
App::Material objects. It would return false when the UUID or MatType
values were different although there are many circumstances where this
could be true and the appearance be the same. It also incorrectly
compared the imagePath.

The second problem was the logic for detecting if an object has already
been assigned an appearance by assigning a material or manually setting
the appearance. If assigned a material, the appearance should update but
not if it has been set manually. This logic has been corrected.

(cherry picked from commit f4e78e316394b07695cbbb933100da44948df434)
---
 src/App/Material.h                     | 9 +++++----
 src/Gui/ViewProviderGeometryObject.cpp | 6 ++++--
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/src/App/Material.h b/src/App/Material.h
index 9a6bcad85e..e3f169c6f5 100644
--- a/src/App/Material.h
+++ b/src/App/Material.h
@@ -140,16 +140,17 @@ public:
     bool operator==(const Material& m) const
     {
         // clang-format off
-        return _matType == m._matType
-            && shininess == m.shininess
+        if (!uuid.empty() && uuid == m.uuid) {
+            return true;
+        }
+        return shininess == m.shininess
             && transparency == m.transparency
             && ambientColor == m.ambientColor
             && diffuseColor == m.diffuseColor
             && specularColor == m.specularColor
             && emissiveColor == m.emissiveColor
             && image == m.image
-            && image == m.imagePath
-            && uuid == m.uuid;
+            && imagePath == m.imagePath;
         // clang-format on
     }
     bool operator!=(const Material& m) const
diff --git a/src/Gui/ViewProviderGeometryObject.cpp b/src/Gui/ViewProviderGeometryObject.cpp
index 5ecba8fbd8..1ef6938154 100644
--- a/src/Gui/ViewProviderGeometryObject.cpp
+++ b/src/Gui/ViewProviderGeometryObject.cpp
@@ -195,8 +195,10 @@ void ViewProviderGeometryObject::updateData(const App::Property* prop)
              */
             App::Material defaultMaterial;
             auto material = geometry->getMaterialAppearance();
-            if ((materialAppearance == defaultMaterial)
-                || (ShapeAppearance.getSize() == 1 && ShapeAppearance[0] == materialAppearance)) {
+            if ((ShapeAppearance.getSize() == 1)
+                && (ShapeAppearance[0] == defaultMaterial
+                    || ShapeAppearance[0] == materialAppearance)
+                && (material != defaultMaterial)) {
                 ShapeAppearance.setValue(material);
             }
             materialAppearance = material;