[LyX/master] Color Preferences: Disable colors rather than hide them (#10483)

[Guillaume MM]

commit 9bf8ac4432c7e33afc180c2dc7470b53da063206
Author: Daniel Ramöller <d....@web.de>
Date:   Sun Nov 6 08:45:09 2016 +0100

    Color Preferences: Disable colors rather than hide them (#10483)
---
 src/frontends/qt4/GuiPrefs.cpp |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/src/frontends/qt4/GuiPrefs.cpp b/src/frontends/qt4/GuiPrefs.cpp
index 69877e3..bacf17a 100644
--- a/src/frontends/qt4/GuiPrefs.cpp
+++ b/src/frontends/qt4/GuiPrefs.cpp
@@ -1294,12 +1294,17 @@ void PrefColors::changeSysColor()
 {
        for (int row = 0 ; row < lyxObjectsLW->count() ; ++row) {
                // skip colors that are taken from system palette
-               bool const hide = syscolorsCB->isChecked()
+               bool const disable = syscolorsCB->isChecked()
                        && guiApp->colorCache().isSystem(lcolors_[row]);
 
-               lyxObjectsLW->item(row)->setHidden(hide);
-       }
+               QListWidgetItem * const item = lyxObjectsLW->item(row);
+               Qt::ItemFlags const flags = item->flags();
 
+               if (disable)
+                       item->setFlags(flags & ~Qt::ItemIsEnabled);
+               else
+                       item->setFlags(flags | Qt::ItemIsEnabled);
+       }
 }
 
 void PrefColors::changeLyxObjectsSelection()