bugfix: more QT checking

- check for QT_QPA_PLATFORMTHEME=qt6ct
    - make plasma-changeicons optional

common/night-theme-switcher.in

@@ -51,6 +51,28 @@ readonly all_off bold blue green red yellow
 ### End insert of Arch script
 
 # dependency checks probably not needed but they do not hurt
+if [ ! "$QT_QPA_PLATFORMTHEME" == "qt6ct" ]; then
+    notify-send \
+        'Wrong environment variable' \
+        'Please set QT_QPA_PLATFORMTHEME=qt6ct.' \
+        -h string:x-canonical-private-synchronous:sys-notify \
+        -u critical \
+        -i dialog-error
+    mesg="environment variable QT_QPA_PLATFORMTHEME=qt6ct is not set."
+    echo -e "${red}==> ERROR:${all_off}${bold} ${mesg}${all_off}"
+    exit 1
+fi
+if ! command -v breeze-settings6 >/dev/null 2>&1; then
+    notify-send \
+        'Missing dependency' \
+        'Please install breeze.' \
+        -h string:x-canonical-private-synchronous:sys-notify \
+        -u critical \
+        -i dialog-error
+    mesg="breeze is required to use this script."
+    echo -e "${red}==> ERROR:${all_off}${bold} ${mesg}${all_off}"
+    exit 1
+fi
 if ! command -v qt6ct >/dev/null 2>&1; then
     notify-send \
         'Missing dependency' \
@@ -74,17 +96,6 @@ if ! command -v gsettings >/dev/null 2>&1; then
     echo -e "${red}==> ERROR:${all_off}${bold} ${mesg}${all_off}"
     exit 1
 fi
-if ! command -v /usr/lib/plasma-changeicons >/dev/null 2>&1; then
-    notify-send \
-        'Missing dependency' \
-        'plasma-changeicons not found.\nPlease install plasma-workspace.' \
-        -h string:x-canonical-private-synchronous:sys-notify \
-        -u critical \
-        -i dialog-error
-    mesg="plasma-workspace is required to use this script."
-    echo -e "${red}==> ERROR:${all_off}${bold} ${mesg}${all_off}"
-    exit 1
-fi
 
 check_config() {
     if [[ ! -f $default_config_file ]]; then
@@ -167,7 +178,9 @@ _set_theme() {
     gsettings set org.gnome.desktop.interface icon-theme "$icon_theme"
 
     ## QT
-    /usr/lib/plasma-changeicons "$icon_theme" >/dev/null 2>&1
+    if [[ -x /usr/lib/plasma-changeicons ]]; then
+        /usr/lib/plasma-changeicons "$icon_theme" >/dev/null 2>&1
+    fi
     if [[ -w "$HOME/.config/qt5ct/qt5ct.conf" ]]; then
         sed -i "s/icon_theme=.*/icon_theme=$icon_theme/g" \
             "$HOME/.config/qt5ct/qt5ct.conf"