Minor structure changes

... to prepare having "valid" icon

src/gui_elements/Atomic.cc

@@ -58,8 +58,6 @@ Atomic::Atomic(QString section, QString key, QWidget *parent)
  */
 void Atomic::setDefaultPanelStyles(const QString &in_value)
 {
-	setPanelStyle(FAULTY, false); //first we disable temporary styles
-	setPanelStyle(VALID, false);
 	const bool is_default = (QString::compare(in_value, this->property("default_value").toString(),
 	    Qt::CaseInsensitive) == 0);
 	setPanelStyle(DEFAULT, is_default && !this->property("default_value").isNull() && !in_value.isNull());
@@ -197,11 +195,8 @@ void Atomic::setPanelStyle(const PanelStyle &style, const bool &set, QWidget *wi
 	case DEFAULT:
 		style_string = "shows_default";
 		break;
-	case FAULTY:
-		style_string = "faulty";
-		break;
-	case VALID:
-		style_string = "valid";
+	case INVALID:
+		style_string = "invalid";
 	}
 	widget_to_set->setProperty(style_string.toLocal8Bit(), set? "true" : "false");
 	this->style()->unpolish(widget_to_set); //if a property is set dynamically, we might have to refresh
@@ -209,13 +204,12 @@ void Atomic::setPanelStyle(const PanelStyle &style, const bool &set, QWidget *wi
 } //https://wiki.qt.io/Technical_FAQ#How_can_my_stylesheet_account_for_custom_properties.3F
 
 /**
- * @brief Switch between "faulty" and "valid" panel styles.
- * @param[in] on True to set "faulty", false to set "valid".
+ * @brief Style a panel to contain invalid values.
+ * @param[in] invalid True to set "invalid", false to disable (= "valid").
  */
-void Atomic::setValidPanelStyle(const bool &on)
+void Atomic::setInvalidStyle(const bool &invalid)
 {
-	setPanelStyle(VALID, on);
-	setPanelStyle(FAULTY, !on);
+	setPanelStyle(INVALID, invalid);
 }
 
 /**

src/gui_elements/Atomic.h

@@ -46,8 +46,7 @@ class Atomic : public QWidget {
 		enum PanelStyle {
 			MANDATORY,
 			DEFAULT,
-			VALID,
-			FAULTY
+			INVALID
 		};
 		Atomic(QString section, QString key, QWidget *parent = nullptr);
 		virtual void setDefaultPanelStyles(const QString &in_value);
@@ -61,7 +60,7 @@ class Atomic : public QWidget {
 		void setEmphasisWidget(QWidget *emphasis_widget, const bool &set_object_name = true);
 		QString getId() const noexcept { return section_ + Cst::sep + key_; }
 		void setPanelStyle(const PanelStyle &style, const bool &set = true, QWidget *widget = nullptr);
-		void setValidPanelStyle(const bool &on);
+		void setInvalidStyle(const bool &on);
 		void substituteKeys(QDomElement &parent_element, const QString &replace,
 		    const QString &replace_with);
 		QSpacerItem * buildSpacer();

src/gui_elements/Number.cc

@@ -167,8 +167,6 @@ Number::~Number()
  */
 void Number::setDefaultPanelStyles(const QString &in_value)
 {
-	setPanelStyle(FAULTY, false); //first we disable temporary styles
-	setPanelStyle(VALID, false);
 	bool is_default = false;
 	bool success_inval, success_default;
 	double inval = in_value.toDouble(&success_inval);
@@ -307,7 +305,7 @@ void Number::setOptions(const QDomNode &options)
 	QString bg_color( colors::getQColor("app_bg").name() );
 	//find font color to use for hidden spinbox text dependent on background color:
 	if (options.toElement().attribute("optional").toLower() == "false")
-		if (!qobject_cast<QLabel*>(getEmphasisWidget())) //the entry widget is used for styling
+		if (!qobject_cast<QLabel *>(getEmphasisWidget())) //the entry widget is used for styling
 			bg_color = colors::getQColor("mandatory").name();
 	number_element_->setStyleSheet("* [empty=\"true\"] {color: " + bg_color + "}");
 
@@ -391,7 +389,7 @@ void Number::checkStrValue(const QString &str_check)
 	setDefaultPanelStyles(str_check);
 
 	if (expr::checkExpression(str_check, evaluation_success, substitutions_) || !evaluation_success)
-		setValidPanelStyle(evaluation_success || str_check.isEmpty());
+		setInvalidStyle(!evaluation_success && !str_check.isEmpty());
 	QTimer::singleShot(1, this, [=]{ setEmpty(false); });
 	setIniValue(str_check); //it is just a hint - save anyway
 }

src/gui_elements/Textfield.cc

@@ -129,11 +129,12 @@ void Textfield::checkValue(const QString &text)
 		if (!validation_regex_.isNull()) { //check against regex specified in XML
 			const QRegularExpression rex_xml(validation_regex_);
 			const QRegularExpressionMatch xml_match(rex_xml.match(text));
-			setValidPanelStyle(xml_match.captured(idx_full) == text && !text.isEmpty());
+			setInvalidStyle(xml_match.captured(idx_full) != text && !text.isEmpty());
 		} else { //check for (arithmetic) expressions
 			bool evaluation_success;
-			if (expr::checkExpression(text, evaluation_success, substitutions_, needs_prefix_for_evaluation_))
-				setValidPanelStyle(evaluation_success);
+			const bool is_expression = expr::checkExpression(text, evaluation_success,
+				substitutions_, needs_prefix_for_evaluation_);
+			setInvalidStyle((is_expression && !evaluation_success) && !text.isEmpty());
 		}
 	}
 	setIniValue(text); //checks are just a hint - set anyway

src/main/colors.cc

@@ -71,10 +71,8 @@ QColor getQColor(const QString &colorname)
 		name = "sl_red";
 	else if (name == "default_values")
 		name = "sl_base00";
-	else if (name == "faulty_values")
+	else if (name == "invalid_values")
 		name = "sl_yellow";
-	else if (name == "valid_values")
-		return (use_darkmode)? QColor("white") : QColor();
 	else if (name == "number")
 		name = "sl_cyan";
 	else if (name == "groupborder")

src/main/main.cc

@@ -189,11 +189,10 @@ void setAppStylesheet(QApplication &app, const command_line_args &cmd_args)
 	 * of our design elements trying to take into account current OS color scheme settings.
 	 */
 	app.setStyleSheet(" \
-	    * [mandatory=\"true\"] {background-color: " + colors::getQColor("mandatory").name() + "; color: " + colors::getQColor("normal").name() + "} \
+	    * [mandatory=\"true\"] {font: bold; color: " + colors::getQColor("mandatory").name() + "} \
 	    * [shows_default=\"true\"] {font-style: italic; color: " + colors::getQColor("default_values").name() + "} \
-	    * [faulty=\"true\"] {color: " + colors::getQColor("faulty_values").name() + "} \
-	    * [valid=\"true\"] {color: " + colors::getQColor("valid_values").name() + "} \
-		* [highlight=\"true\"] {background-color: " + colors::getQColor("sl_yellow").name() + "} \
+	    * [invalid=\"true\"] {color:" + colors::getQColor("invalid_values").name() + ";} \
+	    * [highlight=\"true\"] {background-color: " + colors::getQColor("sl_yellow").name() + "} \
 	    QTabWidget {padding: 0px; font-weight: bold; background-color: " + colors::getQColor("app_bg").name() + "} \
 	    QTabWidget:pane {background-color: " + colors::getQColor("app_bg").name() + "} \
 	    QScrollArea {background-color: " + colors::getQColor("app_bg").name() + "} \