Desktop: Rework Setting of Custom Date / Time Formats.

Rework the setting of custom date / time format preferences:
- fix bug causing case changes if custom format case insensitively
  matches a drop down entry;
- fix invalid format examples in tooltip;
- update URL for the format documentation;
- add support for quoted literals to the format validity warning.
From discussion in
https://github.com/subsurface/subsurface/issues/3849#issuecomment-1481239270.

Signed-off-by: Michael Keller <github@ike.ch>

desktop-widgets/preferences/preferences_language.cpp

@@ -7,6 +7,7 @@
 #include <QDir>
 #include <QMessageBox>
 #include <QSortFilterProxyModel>
+#include <QCompleter>
 
 #include "qt-models/models.h"
 
@@ -28,12 +29,14 @@ PreferencesLanguage::PreferencesLanguage() : AbstractPreferencesWidget(tr("Langu
 	dateFormatShortMap.insert("yyyy-MM-dd", "yy-M-d");
 	foreach (QString format, dateFormatShortMap.keys())
 		ui->dateFormatEntry->addItem(format);
+	ui->dateFormatEntry->completer()->setCaseSensitivity(Qt::CaseSensitive);
 	connect(ui->dateFormatEntry, SIGNAL(currentIndexChanged(const QString&)),
 		this, SLOT(dateFormatChanged(const QString&)));
 
 	ui->timeFormatEntry->addItem("hh:mm");
 	ui->timeFormatEntry->addItem("h:mm AP");
 	ui->timeFormatEntry->addItem("hh:mm AP");
+	ui->timeFormatEntry->completer()->setCaseSensitivity(Qt::CaseSensitive);
 }
 
 PreferencesLanguage::~PreferencesLanguage()
@@ -94,15 +97,15 @@ void PreferencesLanguage::syncSettings()
 	// Therefore, refresh the UI fields to give the user a visual feedback of the new formats.
 	refreshSettings();
 
-	QString qDateTimeWeb = tr("These will be used as is. This might not be what you intended.\nSee http://doc.qt.io/qt-5/qdatetime.html#toString");
-	QRegularExpression tfillegalchars("[^hHmszaApPt\\s:;\\.,]");
-	if (tfillegalchars.match(ui->timeFormatEntry->currentText()).hasMatch())
+	QString qDateTimeWeb = tr("These will be used as is. This might not be what you intended. To avoid this warning wrap the literal parts in quotes (').\nSee https://doc.qt.io/archives/qt-4.8/qdatetime.html#fromString");
+	QRegularExpression timeStandardFormat("^([hHmszaApP\\s:\\.]|'[^']*')*$");
+	if (!timeStandardFormat.match(ui->timeFormatEntry->currentText()).hasMatch())
 		QMessageBox::warning(this, tr("Literal characters"),
-			tr("Non-special character(s) in time format.\n") + qDateTimeWeb);
+			tr("Non-standard character(s) in time format.\n") + qDateTimeWeb);
 
-	QRegularExpression dfillegalchars("[^dMy/\\s:;\\.,\\-]");
-	if (dfillegalchars.match(ui->dateFormatEntry->currentText()).hasMatch() ||
-	    dfillegalchars.match(ui->shortDateFormatEntry->text()).hasMatch())
+	QRegularExpression dateStandardFormat("^([dMy\\s/\\.,\\-]|'[^']*')*$");
+	if (!dateStandardFormat.match(ui->dateFormatEntry->currentText()).hasMatch() ||
+	    !dateStandardFormat.match(ui->shortDateFormatEntry->text()).hasMatch())
 		QMessageBox::warning(this, tr("Literal characters"),
-			tr("Non-special character(s) in date format.\n") + qDateTimeWeb);
+			tr("Non-standard character(s) in date format.\n") + qDateTimeWeb);
 }

desktop-widgets/preferences/preferences_language.ui

@@ -110,7 +110,7 @@
       <item row="0" column="1">
        <widget class="QComboBox" name="dateFormatEntry">
         <property name="toolTip">
-         <string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;Preferred date format. Commonly used fields are&lt;/p&gt;&lt;p&gt;d (day of month)&lt;/p&gt;&lt;p&gt;ddd (abbr. day name)&lt;/p&gt;&lt;p&gt;M (month number)&lt;/p&gt;&lt;p&gt;MMM (abbr. month name)&lt;/p&gt;&lt;p&gt;yy/yyyy (2/4 digit year)&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
+         <string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;Preferred date format. Commonly used fields are&lt;/p&gt;&lt;p&gt;d (day of month)&lt;/p&gt;&lt;p&gt;ddd (abbreviated day name)&lt;/p&gt;&lt;p&gt;M (month number)&lt;/p&gt;&lt;p&gt;MMM (abbreviated month name)&lt;/p&gt;&lt;p&gt;yy/yyyy (2/4 digit year)&lt;/p&gt;&lt;p&gt;See https://doc.qt.io/archives/qt-4.8/qdatetime.html#fromString for full list.&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
         </property>
         <property name="editable">
          <bool>true</bool>
@@ -148,7 +148,7 @@
          </sizepolicy>
         </property>
         <property name="toolTip">
-         <string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;Preferred time format&lt;/p&gt;&lt;p&gt;Commonly used format specifiers are&lt;/p&gt;&lt;p&gt;h (hours in 12h format)&lt;/p&gt;&lt;p&gt;H (hours in 24h format)&lt;/p&gt;&lt;p&gt;mm (2 digit minutes)&lt;/p&gt;&lt;p&gt;ss (2 digit seconds)&lt;/p&gt;&lt;p&gt;t/tt (a/p or am/pm)&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
+		<string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;Preferred time format&lt;/p&gt;&lt;p&gt;Commonly used format specifiers are&lt;/p&gt;&lt;p&gt;h (hours)&lt;/p&gt;&lt;p&gt;hh (2 digit hours)&lt;/p&gt;&lt;p&gt;mm (2 digit minutes)&lt;/p&gt;&lt;p&gt;ss (2 digit seconds)&lt;/p&gt;&lt;p&gt;AP or ap (AM/PM or am/pm)&lt;/p&gt;&lt;p&gt;See https://doc.qt.io/archives/qt-4.8/qdatetime.html#fromString for full list.&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
         </property>
         <property name="editable">
          <bool>true</bool>