Add QgsGuiUtils::iconSize to get user-prefered toolbar icon size

src/app/qgisapp.cpp

@@ -2052,24 +2052,6 @@ int QgisApp::chooseReasonableDefaultIconSize() const
 
 }
 
-int QgisApp::dockedToolbarIconSize( int standardToolbarIconSize ) const
-{
-  int dockSize;
-  if ( standardToolbarIconSize > 32 )
-  {
-    dockSize = standardToolbarIconSize - 16;
-  }
-  else if ( standardToolbarIconSize == 32 )
-  {
-    dockSize = 24;
-  }
-  else
-  {
-    dockSize = 16;
-  }
-  return dockSize;
-}
-
 void QgisApp::readSettings()
 {
   QgsSettings settings;
@@ -3244,10 +3226,11 @@ void QgisApp::createStatusBar()
 
 void QgisApp::setIconSizes( int size )
 {
-  int dockSize = dockedToolbarIconSize( size );
+  QSize iconSize = QSize( size, size );
+  QSize panelIconSize = QgsGuiUtils::panelIconSize( iconSize );
 
   //Set the icon size of for all the toolbars created in the future.
-  setIconSize( QSize( size, size ) );
+  setIconSize( iconSize );
 
   //Change all current icon sizes.
   QList<QToolBar *> toolbars = findChildren<QToolBar *>();
@@ -3257,11 +3240,11 @@ void QgisApp::setIconSizes( int size )
     QString className = toolbar->parent()->metaObject()->className();
     if ( className == QLatin1String( "QgisApp" ) )
     {
-      toolbar->setIconSize( QSize( size, size ) );
+      toolbar->setIconSize( iconSize );
     }
     else
     {
-      toolbar->setIconSize( QSize( dockSize, dockSize ) );
+      toolbar->setIconSize( panelIconSize );
     }
   }
 
@@ -11050,15 +11033,7 @@ QgsMapLayer *QgisApp::activeLayer()
 
 QSize QgisApp::iconSize( bool dockedToolbar ) const
 {
-  QgsSettings s;
-  int size = s.value( QStringLiteral( "/qgis/iconSize" ), 32 ).toInt();
-
-  if ( dockedToolbar )
-  {
-    size = dockedToolbarIconSize( size );
-  }
-
-  return QSize( size, size );
+  return QgsGuiUtils::iconSize( dockedToolbar );
 }
 
 bool QgisApp::setActiveLayer( QgsMapLayer *layer )

src/app/qgisapp.h

@@ -1979,11 +1979,6 @@ class APP_EXPORT QgisApp : public QMainWindow, private Ui::MainWindow
     //! Attempts to choose a reasonable default icon size based on the window's screen DPI
     int chooseReasonableDefaultIconSize() const;
 
-    /**
-     * Returns the size of docked toolbars for a given standard (non-docked) toolbar icon size.
-     */
-    int dockedToolbarIconSize( int standardToolbarIconSize ) const;
-
     //! Populates project "load from" / "save to" menu based on project storages (when the menu is about to be shown)
     void populateProjectStorageMenu( QMenu *menu, bool saving );
 

src/gui/qgsguiutils.cpp

@@ -248,6 +248,33 @@ namespace QgsGuiUtils
     return static_cast< int >( std::floor( std::max( Qgis::UI_SCALE_FACTOR * fm.height() * scale, static_cast< double >( standardSize ) ) ) );
   }
 
+  QSize iconSize( bool dockableToolbar )
+  {
+    QgsSettings s;
+    int w = s.value( QStringLiteral( "/qgis/iconSize" ), 32 ).toInt();
+    QSize size( w, w );
+
+    if ( dockableToolbar )
+    {
+      size = panelIconSize( size );
+    }
+
+    return size;
+  }
+
+  QSize panelIconSize( QSize size )
+  {
+    int adjustedSize = 16;
+    if ( size.width() > 32 )
+    {
+      adjustedSize = size.width() - 16;
+    }
+    else if ( size.width() == 32 )
+    {
+      adjustedSize = 24;
+    }
+    return QSize( adjustedSize, adjustedSize );
+  }
 }
 
 //

src/gui/qgsguiutils.h

@@ -173,6 +173,22 @@ namespace QgsGuiUtils
    * \since QGIS 3.6
    */
   int GUI_EXPORT scaleIconSize( int standardSize );
+
+  /**
+   * Returns the user-preferred size of a window's toolbar icons.
+   * \param dockableToolbar If set to true, the icon size will be returned for dockable window panel's toolbars.
+   * \returns a QSize object representing an icon's width and height.
+   * \since QGIS 3.8
+   */
+  QSize GUI_EXPORT iconSize( bool dockableToolbar = false );
+
+  /**
+   * Returns dockable panel toolbar icon width based on the provided window toolbar width.
+   * \param size Icon size from which the output size will be derived from.
+   * \returns a QSize object representing an icon's width and height.
+   * \since QGIS 3.8
+   */
+  QSize GUI_EXPORT panelIconSize( QSize size );
 }
 
 /**