automatically select the system monitor profile if the preferences say so

Fix for issue #3821

rtengine/iccstore.cc

@@ -302,6 +302,8 @@ public:
         if (loadAll) {
             loadProfiles(stdProfilesDir, nullptr, nullptr, &fileStdProfilesFileNames, true);
         }
+
+        defaultMonitorProfile = settings->monitorProfile;
     }
 
     cmsHPROFILE workingSpace(const Glib::ustring& name) const
@@ -534,6 +536,16 @@ public:
         return getProofIntents(getProfile(name));
     }
 
+    Glib::ustring getDefaultMonitorProfileName() const
+    {
+        return defaultMonitorProfile;
+    }
+
+    void setDefaultMonitorProfileName(const Glib::ustring &name)
+    {
+        defaultMonitorProfile = name;
+    }
+
 private:
     using ProfileMap = std::map<Glib::ustring, cmsHPROFILE>;
     using MatrixMap = std::map<Glib::ustring, TMatrix>;
@@ -617,6 +629,18 @@ rtengine::ProfileContent rtengine::ICCStore::getContent(const Glib::ustring& nam
     return implementation->getContent(name);
 }
 
+
+Glib::ustring rtengine::ICCStore::getDefaultMonitorProfileName() const
+{
+    return implementation->getDefaultMonitorProfileName();
+}
+
+
+void rtengine::ICCStore::setDefaultMonitorProfileName(const Glib::ustring &name)
+{
+    implementation->setDefaultMonitorProfileName(name);
+}
+
 cmsHPROFILE rtengine::ICCStore::getXYZProfile() const
 {
     return implementation->getXYZProfile();

rtengine/iccstore.h

@@ -78,6 +78,9 @@ public:
     cmsHPROFILE      getStdProfile(const Glib::ustring& name) const;
     ProfileContent   getContent(const Glib::ustring& name) const;
 
+    Glib::ustring getDefaultMonitorProfileName() const;
+    void setDefaultMonitorProfileName(const Glib::ustring &name);
+
     cmsHPROFILE      getXYZProfile() const;
     cmsHPROFILE      getsRGBProfile() const;
 

rtengine/rtthumbnail.cc

@@ -1040,7 +1040,7 @@ IImage8* Thumbnail::processImage (const procparams::ProcParams& params, int rhei
 
     ImProcFunctions ipf (&params, false);
     ipf.setScale (sqrt(double(fw * fw + fh * fh)) / sqrt(double(thumbImg->getWidth() * thumbImg->getWidth() + thumbImg->getHeight() * thumbImg->getHeight()))*scale);
-    ipf.updateColorProfiles (options.rtSettings.monitorProfile, options.rtSettings.monitorIntent, false, false);
+    ipf.updateColorProfiles (ICCStore::getInstance()->getDefaultMonitorProfileName(), options.rtSettings.monitorIntent, false, false);
 
     LUTu hist16 (65536);