kcms/effects: Fix effect loading/unloading order

There are effects that are mutually exclusive, e.g. magnifier and zoom.
They both use the same global shortcuts.

When switching from zoom to magnifier, the zoom effect must be unloaded
first, then the magnifier effect can be loaded. Doing so in the opposite
order will break global shortcuts in the magnifier effect because
zooming shortcuts are still bound by the zoom effect.

BUG: 457800

src/kcms/common/effectsmodel.cpp

@@ -536,12 +536,18 @@ void EffectsModel::save()
         return;
     }
 
-    for (const EffectData &effect : dirtyEffects) {
-        if (effect.status != Status::Disabled) {
-            interface.loadEffect(effect.serviceName);
-        } else {
-            interface.unloadEffect(effect.serviceName);
-        }
+    // Unload effects first, it's need to ensure that switching between mutually exclusive
+    // effects works as expected, for example so global shortcuts are handed over, etc.
+    auto split = std::partition(dirtyEffects.begin(), dirtyEffects.end(), [](const EffectData &data) {
+        return data.status == Status::Disabled;
+    });
+
+    for (auto it = dirtyEffects.begin(); it != split; ++it) {
+        interface.unloadEffect(it->serviceName);
+    }
+
+    for (auto it = split; it != dirtyEffects.end(); ++it) {
+        interface.loadEffect(it->serviceName);
     }
 }