Fix embedding larger files then can fit in a QLineEdit's contents

Fixes #20329

(cherry picked from commit 32dc102)

Author: nyalldawson

src/gui/qgssvgsourcelineedit.cpp

@@ -66,7 +66,7 @@ QgsSvgSourceLineEdit::QgsSvgSourceLineEdit( QWidget *parent )
 
 QString QgsSvgSourceLineEdit::source() const
 {
-  return mFileLineEdit->text();
+  return mBase64.isEmpty() ? mFileLineEdit->text() : mBase64;
 }
 
 void QgsSvgSourceLineEdit::setLastPathSettingsKey( const QString &key )
@@ -76,9 +76,16 @@ void QgsSvgSourceLineEdit::setLastPathSettingsKey( const QString &key )
 
 void QgsSvgSourceLineEdit::setSource( const QString &source )
 {
-  if ( source == mFileLineEdit->text() )
+  const bool isBase64 = source.startsWith( QLatin1String( "base64:" ), Qt::CaseInsensitive );
+
+  if ( ( !isBase64 && source == mFileLineEdit->text() ) || ( isBase64 && source == mBase64 ) )
     return;
 
+  if ( isBase64 )
+    mBase64 = source;
+  else
+    mBase64.clear();
+
   mFileLineEdit->setText( source );
   emit sourceChanged( source );
 }
@@ -95,6 +102,7 @@ void QgsSvgSourceLineEdit::selectFile()
   {
     return;
   }
+  mBase64.clear();
   mFileLineEdit->setText( file );
   s.setValue( settingsKey(), fi.absolutePath() );
   emit sourceChanged( mFileLineEdit->text() );
@@ -106,6 +114,7 @@ void QgsSvgSourceLineEdit::selectUrl()
   const QString path = QInputDialog::getText( this, tr( "SVG From URL" ), tr( "Enter SVG URL" ), QLineEdit::Normal, mFileLineEdit->text(), &ok );
   if ( ok && path != source() )
   {
+    mBase64.clear();
     mFileLineEdit->setText( path );
     emit sourceChanged( mFileLineEdit->text() );
   }
@@ -141,8 +150,9 @@ void QgsSvgSourceLineEdit::embedFile()
   if ( path == source() )
     return;
 
+  mBase64 = path;
   mFileLineEdit->setText( path );
-  emit sourceChanged( mFileLineEdit->text() );
+  emit sourceChanged( path );
 }
 
 void QgsSvgSourceLineEdit::extractFile()
@@ -164,7 +174,7 @@ void QgsSvgSourceLineEdit::extractFile()
   QString path = mFileLineEdit->text().trimmed();
   if ( path.startsWith( QLatin1String( "base64:" ), Qt::CaseInsensitive ) )
   {
-    QByteArray base64 = path.mid( 7 ).toLocal8Bit(); // strip 'base64:' prefix
+    QByteArray base64 = mBase64.mid( 7 ).toLocal8Bit(); // strip 'base64:' prefix
     QByteArray decoded = QByteArray::fromBase64( base64, QByteArray::OmitTrailingEquals );
 
     QFile fileOut( file );

src/gui/qgssvgsourcelineedit.h

@@ -83,6 +83,7 @@ class GUI_EXPORT QgsSvgSourceLineEdit : public QWidget
     QLineEdit *mFileLineEdit = nullptr;
     QToolButton *mFileToolButton = nullptr;
     QString mLastPathKey;
+    QString mBase64;
 
     QString defaultPath() const;
     QString settingsKey() const;

tests/src/python/test_qgssvgsourcelineedit.py

@@ -13,11 +13,12 @@
 __revision__ = '$Format:%H$'
 
 import qgis  # NOQA
-
+import os
 from qgis.gui import QgsSvgSourceLineEdit
 
 from qgis.PyQt.QtTest import QSignalSpy
 from qgis.testing import start_app, unittest
+from utilities import unitTestDataPath
 
 start_app()
 
@@ -44,6 +45,37 @@ def testGettersSetters(self):
         self.assertEqual(len(spy), 2)
         self.assertEqual(spy[1][0], 'another')
 
+    def testEmbedding(self):
+        """Test embedding large SVGs """
+        w = QgsSvgSourceLineEdit()
+        spy = QSignalSpy(w.sourceChanged)
+
+        w.setSource('source')
+        self.assertEqual(w.source(), 'source')
+        self.assertEqual(len(spy), 1)
+        self.assertEqual(spy[0][0], 'source')
+
+        b64 = 'base64:' + ''.join(['x'] * 1000000)
+        w.setSource(b64)
+        self.assertEqual(w.source(), b64)
+        self.assertEqual(len(spy), 2)
+        self.assertEqual(spy[1][0], b64)
+
+        w.setSource(os.path.join(unitTestDataPath(), 'landsat.tif'))
+        self.assertEqual(w.source(), os.path.join(unitTestDataPath(), 'landsat.tif'))
+        self.assertEqual(len(spy), 3)
+        self.assertEqual(spy[2][0], os.path.join(unitTestDataPath(), 'landsat.tif'))
+
+        w.setSource(b64)
+        self.assertEqual(w.source(), b64)
+        self.assertEqual(len(spy), 4)
+        self.assertEqual(spy[3][0], b64)
+
+        w.setSource('')
+        self.assertEqual(w.source(), '')
+        self.assertEqual(len(spy), 5)
+        self.assertEqual(spy[4][0], '')
+
 
 if __name__ == '__main__':
     unittest.main()