If dingbats font isn't installed on system, find a good candidate

nyalldawson · nyalldawson · commit 251ba5a0a336 · 2021-11-29T16:15:02.000+10:00
symbol font from the available installed fonts Fixes #46206
diff --git a/src/gui/symbology/qgslayerpropertieswidget.cpp b/src/gui/symbology/qgslayerpropertieswidget.cpp
@@ -47,6 +47,7 @@
 #include "qgsmarkersymbol.h"
 #include "qgslinesymbol.h"
 #include "qgsfillsymbol.h"
+#include "qgsmarkersymbollayer.h"
 
 static bool _initWidgetFunction( const QString &name, QgsSymbolLayerWidgetFunc f )
 {
@@ -389,6 +390,48 @@ void QgsLayerPropertiesWidget::layerTypeChanged()
     }
   }
 
+  // special logic for when NEW symbol layers are created from GUI only...
+  // TODO: find a nicer generic way to handle this!
+  if ( QgsFontMarkerSymbolLayer *fontMarker = dynamic_cast< QgsFontMarkerSymbolLayer * >( newLayer ) )
+  {
+    const QString defaultFont = fontMarker->fontFamily();
+    const QFontDatabase fontDb;
+    if ( !fontDb.hasFamily( defaultFont ) )
+    {
+      // default font marker font choice doesn't exist on system, so just use first available symbol font
+      const QStringList candidates = fontDb.families( QFontDatabase::WritingSystem::Symbol );
+      bool foundGoodCandidate = false;
+      for ( const QString &candidate : candidates )
+      {
+        if ( fontDb.writingSystems( candidate ).size() == 1 )
+        {
+          // family ONLY offers symbol writing systems, so it's a good candidate!
+          fontMarker->setFontFamily( candidate );
+          foundGoodCandidate = true;
+          break;
+        }
+      }
+      if ( !foundGoodCandidate && !candidates.empty() )
+      {
+        // fallback to first available family which advertises symbol writing system
+        QString candidate = candidates.at( 0 );
+        fontMarker->setFontFamily( candidate );
+      }
+    }
+
+    // search (briefly!!) for a unicode character which actually exists in the font
+    const QFontMetrics fontMetrics( fontMarker->fontFamily() );
+    ushort character = fontMarker->character().at( 0 ).unicode();
+    for ( ; character < 1000; ++character )
+    {
+      if ( fontMetrics.inFont( QChar( character ) ) )
+      {
+        fontMarker->setCharacter( QChar( character ) );
+        break;
+      }
+    }
+  }
+
   updateSymbolLayerWidget( newLayer );
   emit changeLayer( newLayer );
 }
