Truncate filter from middle of string

python/core/auto_generated/qgsstringutils.sip.in

@@ -325,6 +325,17 @@ Returns an escaped string matching the behavior of QRegExp.escape.
 
 :return: Escaped string
 
+.. versionadded:: 3.22
+%End
+
+    static QString truncateMiddleOfString( const QString &string, int maxLength );
+%Docstring
+Truncates a ``string`` to the specified maximum character length.
+
+If the ``string`` exceeds the maximum character length, then the string
+will be truncated by removing characters from the middle of the string
+and replacing them with a horizontal ellipsis character.
+
 .. versionadded:: 3.22
 %End
 

src/app/qgslayertreeviewfilterindicator.cpp

@@ -23,7 +23,7 @@
 #include "qgsvectorlayer.h"
 #include "qgsrasterlayer.h"
 #include "qgisapp.h"
-
+#include "qgsstringutils.h"
 
 QgsLayerTreeViewFilterIndicatorProvider::QgsLayerTreeViewFilterIndicatorProvider( QgsLayerTreeView *view )
   : QgsLayerTreeViewIndicatorProvider( view )
@@ -63,7 +63,7 @@ QString QgsLayerTreeViewFilterIndicatorProvider::tooltipText( QgsMapLayer *layer
 
   if ( filter.size() > 1024 )
   {
-    filter = filter.left( 1023 ) + QString( QChar( 0x2026 ) );
+    filter = QgsStringUtils::truncateMiddleOfString( filter, 1024 );
   }
 
   return QStringLiteral( "<b>%1:</b><br>%2" ).arg( tr( "Filter" ), filter.toHtmlEscaped() );

src/core/qgsstringutils.cpp

@@ -721,6 +721,18 @@ QString QgsStringUtils::qRegExpEscape( const QString &string )
   return escaped;
 }
 
+QString QgsStringUtils::truncateMiddleOfString( const QString &string, int maxLength )
+{
+  const int charactersToTruncate = string.length() - maxLength;
+  if ( charactersToTruncate <= 0 )
+    return string;
+
+  // note we actually truncate an extra character, as we'll be replacing it with the ... character
+  const int truncateFrom = string.length() / 2 - ( charactersToTruncate + 1 ) / 2;
+
+  return string.leftRef( truncateFrom ) + QString( QChar( 0x2026 ) ) + string.midRef( truncateFrom + charactersToTruncate + 1 );
+}
+
 QgsStringReplacement::QgsStringReplacement( const QString &match, const QString &replacement, bool caseSensitive, bool wholeWordOnly )
   : mMatch( match )
   , mReplacement( replacement )

src/core/qgsstringutils.h

@@ -315,6 +315,17 @@ class CORE_EXPORT QgsStringUtils
      */
     static QString qRegExpEscape( const QString &string );
 
+    /**
+     * Truncates a \a string to the specified maximum character length.
+     *
+     * If the \a string exceeds the maximum character length, then the string
+     * will be truncated by removing characters from the middle of the string
+     * and replacing them with a horizontal ellipsis character.
+     *
+     * \since QGIS 3.22
+     */
+    static QString truncateMiddleOfString( const QString &string, int maxLength );
+
 };
 
 #endif //QGSSTRINGUTILS_H

tests/src/python/test_qgsstringutils.py

@@ -220,6 +220,23 @@ class PyQgsStringUtils(unittest.TestCase):
             QgsStringUtils.fuzzyScore('abcd efg hig', 'abcd e hi')
         )
 
+    def test_truncate_from_middle(self):
+        """
+        Test QgsStringUtils.truncateMiddleOfString
+        """
+        self.assertEqual(QgsStringUtils.truncateMiddleOfString('', 0), '')
+        self.assertEqual(QgsStringUtils.truncateMiddleOfString('', 10), '')
+        self.assertEqual(QgsStringUtils.truncateMiddleOfString('abcdef', 10), 'abcdef')
+        self.assertEqual(QgsStringUtils.truncateMiddleOfString('abcdefghij', 10), 'abcdefghij')
+        self.assertEqual(QgsStringUtils.truncateMiddleOfString('abcdefghijk', 10), 'abcd…ghijk')
+        self.assertEqual(QgsStringUtils.truncateMiddleOfString('abcdefghijkl', 10), 'abcde…ijkl')
+        self.assertEqual(QgsStringUtils.truncateMiddleOfString('abcdefghijklmnop', 10), 'abcde…mnop')
+        self.assertEqual(QgsStringUtils.truncateMiddleOfString('this is a test', 11), 'this … test')
+        self.assertEqual(QgsStringUtils.truncateMiddleOfString('this is a test', 1), '…')
+        self.assertEqual(QgsStringUtils.truncateMiddleOfString('this is a test', 2), 't…')
+        self.assertEqual(QgsStringUtils.truncateMiddleOfString('this is a test', 3), 't…t')
+        self.assertEqual(QgsStringUtils.truncateMiddleOfString('this is a test', 0), '…')
+
 
 if __name__ == '__main__':
     unittest.main()