Allow any symbol to be an animated symbol

Users can now indicate that a symbol should be treated as a animated
symbol, through the new "Animation Settings" option in the symbol
widget's Advanced menu.

This settings panel allows users to enable animation for the symbol
and set a specific frame rate at which the symbol should be redrawn.
When enabled, the @symbol_frame variable can be used in any
symbol data defined property in order to animate that property.

For instance, setting the symbol's rotation to the data defined
expression

    @symbol_frame % 360

will cause the symbol to rotate over time. (with rotation speed
dictated by the symbol's refresh rate)

python/core/auto_generated/symbology/qgssymbol.sip.in

@@ -11,6 +11,58 @@
 
 typedef QList<QgsSymbolLayer *> QgsSymbolLayerList;
 
+class QgsSymbolAnimationSettings
+{
+%Docstring(signature="appended")
+
+Contains settings relating to symbol animation.
+
+.. versionadded:: 3.26
+%End
+
+%TypeHeaderCode
+#include "qgssymbol.h"
+%End
+  public:
+
+    void setIsAnimated( bool animated );
+%Docstring
+Sets whether the symbol is animated.
+
+This is a user-facing setting for symbols, which allows users to define whether a
+symbol is animated, and allows for creation of animated symbols via data
+defined properties.
+
+.. seealso:: :py:func:`isAnimated`
+%End
+
+    bool isAnimated() const;
+%Docstring
+Returns ``True`` if the symbol is animated.
+
+This is a user-facing setting for symbols, which allows users to define whether a
+symbol is animated, and allows for creation of animated symbols via data
+defined properties.
+
+.. seealso:: :py:func:`setIsAnimated`
+%End
+
+    void setFrameRate( double rate );
+%Docstring
+Sets the symbol animation frame ``rate`` (in frames per second).
+
+.. seealso:: :py:func:`frameRate`
+%End
+
+    double frameRate() const;
+%Docstring
+Returns the symbol animation frame rate (in frames per second).
+
+.. seealso:: :py:func:`setFrameRate`
+%End
+
+};
+
 class QgsSymbol
 {
 %Docstring(signature="appended")
@@ -522,6 +574,25 @@ direction.
 .. seealso:: :py:func:`setForceRHR`
 
 .. versionadded:: 3.6
+%End
+
+    QgsSymbolAnimationSettings &animationSettings();
+%Docstring
+Returns a reference to the symbol animation settings.
+
+.. seealso:: :py:func:`setAnimationSettings`
+
+.. versionadded:: 3.26
+%End
+
+
+    void setAnimationSettings( const QgsSymbolAnimationSettings &settings );
+%Docstring
+Sets a the symbol animation ``settings``.
+
+.. seealso:: :py:func:`animationSettings`
+
+.. versionadded:: 3.26
 %End
 
     QSet<QString> usedAttributes( const QgsRenderContext &context ) const;
@@ -704,6 +775,7 @@ Render editing vertex marker at specified point
 
 
 
+
   private:
     QgsSymbol( const QgsSymbol & );
 };

python/gui/auto_generated/symbology/qgssymbolanimationsettingswidget.sip.in

@@ -0,0 +1,89 @@
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/gui/symbology/qgssymbolanimationsettingswidget.h                 *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
+
+
+
+
+
+
+
+class QgsSymbolAnimationSettingsWidget: QgsPanelWidget
+{
+%Docstring(signature="appended")
+A widget for customising animation settings for a symbol.
+
+.. versionadded:: 3.26
+%End
+
+%TypeHeaderCode
+#include "qgssymbolanimationsettingswidget.h"
+%End
+  public:
+
+    QgsSymbolAnimationSettingsWidget( QWidget *parent /TransferThis/ = 0 );
+%Docstring
+Constructor for QgsSymbolAnimationSettingsWidget
+%End
+
+    void setAnimationSettings( const QgsSymbolAnimationSettings &settings );
+%Docstring
+Sets the animation ``settings`` to show in the widget.
+
+.. seealso:: :py:func:`animationSettings`
+%End
+
+    QgsSymbolAnimationSettings animationSettings() const;
+%Docstring
+Returns the animation settings as defined in the widget.
+
+.. seealso:: :py:func:`setAnimationSettings`
+%End
+
+};
+
+class QgsSymbolAnimationSettingsDialog : QDialog
+{
+%Docstring(signature="appended")
+A dialog for customising animation settings for a symbol.
+
+.. versionadded:: 3.26
+%End
+
+%TypeHeaderCode
+#include "qgssymbolanimationsettingswidget.h"
+%End
+  public:
+
+    QgsSymbolAnimationSettingsDialog( QWidget *parent /TransferThis/ = 0, Qt::WindowFlags f = Qt::WindowFlags() );
+%Docstring
+Constructor for QgsSymbolAnimationSettingsDialog
+%End
+
+    void setAnimationSettings( const QgsSymbolAnimationSettings &settings );
+%Docstring
+Sets the animation ``settings`` to show in the dialog.
+
+.. seealso:: :py:func:`animationSettings`
+%End
+
+    QgsSymbolAnimationSettings animationSettings() const;
+%Docstring
+Returns the animation settings as defined in the dialog.
+
+.. seealso:: :py:func:`setAnimationSettings`
+%End
+
+};
+
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/gui/symbology/qgssymbolanimationsettingswidget.h                 *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/

python/gui/gui_auto.sip

@@ -447,6 +447,7 @@
 %Include auto_generated/symbology/qgsstylemanagerdialog.sip
 %Include auto_generated/symbology/qgsstylesavedialog.sip
 %Include auto_generated/symbology/qgssvgselectorwidget.sip
+%Include auto_generated/symbology/qgssymbolanimationsettingswidget.sip
 %Include auto_generated/symbology/qgssymbollayerwidget.sip
 %Include auto_generated/symbology/qgssymbollevelsdialog.sip
 %Include auto_generated/symbology/qgssymbolselectordialog.sip

src/core/expression/qgsexpression.cpp

@@ -854,6 +854,7 @@ void QgsExpression::initVariableHelp()
   sVariableHelpTexts()->insert( QStringLiteral( "symbol_layer_index" ), QCoreApplication::translate( "symbol_layer_index", "Current symbol layer index." ) );
   sVariableHelpTexts()->insert( QStringLiteral( "symbol_marker_row" ), QCoreApplication::translate( "symbol_marker_row", "Row number for marker (valid for point pattern fills only)." ) );
   sVariableHelpTexts()->insert( QStringLiteral( "symbol_marker_column" ), QCoreApplication::translate( "symbol_marker_column", "Column number for marker (valid for point pattern fills only)." ) );
+  sVariableHelpTexts()->insert( QStringLiteral( "symbol_frame" ), QCoreApplication::translate( "symbol_frame", "Frame number (for animated symbols only)." ) );
 
   sVariableHelpTexts()->insert( QStringLiteral( "symbol_label" ), QCoreApplication::translate( "symbol_label", "Label for the symbol (either a user defined label or the default autogenerated label)." ) );
   sVariableHelpTexts()->insert( QStringLiteral( "symbol_id" ), QCoreApplication::translate( "symbol_id", "Internal ID of the symbol." ) );

src/core/symbology/qgsfillsymbol.cpp

@@ -152,6 +152,7 @@ QgsFillSymbol *QgsFillSymbol::clone() const
   cloneSymbol->setForceRHR( mForceRHR );
   cloneSymbol->setDataDefinedProperties( dataDefinedProperties() );
   cloneSymbol->setFlags( mSymbolFlags );
+  cloneSymbol->setAnimationSettings( mAnimationSettings );
   return cloneSymbol;
 }
 

src/core/symbology/qgslinesymbol.cpp

@@ -283,5 +283,6 @@ QgsLineSymbol *QgsLineSymbol::clone() const
   cloneSymbol->setForceRHR( mForceRHR );
   cloneSymbol->setDataDefinedProperties( dataDefinedProperties() );
   cloneSymbol->setFlags( mSymbolFlags );
+  cloneSymbol->setAnimationSettings( mAnimationSettings );
   return cloneSymbol;
 }

src/core/symbology/qgsmarkersymbol.cpp

@@ -498,6 +498,7 @@ QgsMarkerSymbol *QgsMarkerSymbol::clone() const
   cloneSymbol->setForceRHR( mForceRHR );
   cloneSymbol->setDataDefinedProperties( dataDefinedProperties() );
   cloneSymbol->setFlags( mSymbolFlags );
+  cloneSymbol->setAnimationSettings( mAnimationSettings );
   return cloneSymbol;
 }
 

src/core/symbology/qgssymbol.cpp

@@ -352,6 +352,21 @@ void QgsSymbol::setMapUnitScale( const QgsMapUnitScale &scale )
   }
 }
 
+QgsSymbolAnimationSettings &QgsSymbol::animationSettings()
+{
+  return mAnimationSettings;
+}
+
+const QgsSymbolAnimationSettings &QgsSymbol::animationSettings() const
+{
+  return mAnimationSettings;
+}
+
+void QgsSymbol::setAnimationSettings( const QgsSymbolAnimationSettings &settings )
+{
+  mAnimationSettings = settings;
+}
+
 QgsSymbol *QgsSymbol::defaultSymbol( QgsWkbTypes::GeometryType geomType )
 {
   std::unique_ptr< QgsSymbol > s;
@@ -498,6 +513,26 @@ void QgsSymbol::startRender( QgsRenderContext &context, const QgsFields &fields
   QgsSymbolRenderContext symbolContext( context, QgsUnitTypes::RenderUnknownUnit, mOpacity, false, mRenderHints, nullptr, fields );
 
   std::unique_ptr< QgsExpressionContextScope > scope( QgsExpressionContextUtils::updateSymbolScope( this, new QgsExpressionContextScope() ) );
+
+  if ( mAnimationSettings.isAnimated() )
+  {
+    const long long mapFrameNumber = context.currentFrame();
+    double animationTimeSeconds = 0;
+    if ( mapFrameNumber >= 0 && context.frameRate() > 0 )
+    {
+      // render is part of an animation, so we base the calculated frame on that
+      animationTimeSeconds = mapFrameNumber / context.frameRate();
+    }
+    else
+    {
+      // render is outside of animation, so base the calculated frame on the current epoch
+      animationTimeSeconds = QDateTime::currentMSecsSinceEpoch() / 1000.0;
+    }
+
+    const long long symbolFrame = static_cast< long long >( std::floor( animationTimeSeconds * mAnimationSettings.frameRate() ) );
+    scope->setVariable( QStringLiteral( "symbol_frame" ), symbolFrame, true );
+  }
+
   mSymbolRenderContext->setExpressionContextScope( scope.release() );
 
   mDataDefinedProperties.prepare( context.expressionContext() );

src/core/symbology/qgssymbol.h

@@ -28,6 +28,61 @@ class QgsLineSymbolLayer;
 
 typedef QList<QgsSymbolLayer *> QgsSymbolLayerList;
 
+/**
+ * \ingroup core
+ * \class QgsSymbol
+ *
+ * \brief Contains settings relating to symbol animation.
+ *
+ * \since QGIS 3.26
+ */
+class CORE_EXPORT QgsSymbolAnimationSettings
+{
+  public:
+
+    /**
+     * Sets whether the symbol is animated.
+     *
+     * This is a user-facing setting for symbols, which allows users to define whether a
+     * symbol is animated, and allows for creation of animated symbols via data
+     * defined properties.
+     *
+     * \see isAnimated()
+     */
+    void setIsAnimated( bool animated ) { mIsAnimated = animated; }
+
+    /**
+     * Returns TRUE if the symbol is animated.
+     *
+     * This is a user-facing setting for symbols, which allows users to define whether a
+     * symbol is animated, and allows for creation of animated symbols via data
+     * defined properties.
+     *
+     * \see setIsAnimated()
+     */
+    bool isAnimated() const { return mIsAnimated; }
+
+    /**
+     * Sets the symbol animation frame \a rate (in frames per second).
+     *
+     * \see frameRate()
+     */
+    void setFrameRate( double rate ) { mFrameRate = rate; }
+
+    /**
+     * Returns the symbol animation frame rate (in frames per second).
+     *
+     * \see setFrameRate()
+     */
+    double frameRate() const { return mFrameRate; }
+
+  private:
+
+    bool mIsAnimated = false;
+    double mFrameRate = 10;
+
+};
+
 /**
  * \ingroup core
  * \class QgsSymbol
@@ -518,6 +573,30 @@ class CORE_EXPORT QgsSymbol
      */
     bool forceRHR() const { return mForceRHR; }
 
+    /**
+     * Returns a reference to the symbol animation settings.
+     *
+     * \see setAnimationSettings()
+     * \since QGIS 3.26
+     */
+    QgsSymbolAnimationSettings &animationSettings();
+
+    /**
+     * Returns a reference to the symbol animation settings.
+     *
+     * \see setAnimationSettings()
+     * \since QGIS 3.26
+     */
+    const QgsSymbolAnimationSettings &animationSettings() const SIP_SKIP;
+
+    /**
+     * Sets a the symbol animation \a settings.
+     *
+     * \see animationSettings()
+     * \since QGIS 3.26
+     */
+    void setAnimationSettings( const QgsSymbolAnimationSettings &settings );
+
     /**
      * Returns a list of attributes required to render this feature.
      * This should include any attributes required by the symbology including
@@ -721,6 +800,8 @@ class CORE_EXPORT QgsSymbol
     bool mClipFeaturesToExtent = true;
     bool mForceRHR = false;
 
+    QgsSymbolAnimationSettings mAnimationSettings;
+
     Q_DECL_DEPRECATED const QgsVectorLayer *mLayer = nullptr; //current vectorlayer
 
   private:

src/core/symbology/qgssymbollayerutils.cpp

@@ -1308,6 +1308,9 @@ QgsSymbol *QgsSymbolLayerUtils::loadSymbol( const QDomElement &element, const Qg
     flags |= Qgis::SymbolFlag::RendererShouldUseSymbolLevels;
   symbol->setFlags( flags );
 
+  symbol->animationSettings().setIsAnimated( element.attribute( QStringLiteral( "is_animated" ), QStringLiteral( "0" ) ).toInt() );
+  symbol->animationSettings().setFrameRate( element.attribute( QStringLiteral( "frame_rate" ), QStringLiteral( "10" ) ).toDouble() );
+
   const QDomElement ddProps = element.firstChildElement( QStringLiteral( "data_defined_properties" ) );
   if ( !ddProps.isNull() )
   {
@@ -1402,6 +1405,9 @@ QDomElement QgsSymbolLayerUtils::saveSymbol( const QString &name, const QgsSymbo
   if ( symbol->flags() & Qgis::SymbolFlag::RendererShouldUseSymbolLevels )
     symEl.setAttribute( QStringLiteral( "renderer_should_use_levels" ), QStringLiteral( "1" ) );
 
+  symEl.setAttribute( QStringLiteral( "is_animated" ), symbol->animationSettings().isAnimated() ? QStringLiteral( "1" ) : QStringLiteral( "0" ) );
+  symEl.setAttribute( QStringLiteral( "frame_rate" ), qgsDoubleToString( symbol->animationSettings().frameRate() ) );
+
   //QgsDebugMsg( "num layers " + QString::number( symbol->symbolLayerCount() ) );
 
   QDomElement ddProps = doc.createElement( QStringLiteral( "data_defined_properties" ) );
@@ -4966,6 +4972,13 @@ double QgsSymbolLayerUtils::rendererFrameRate( const QgsFeatureRenderer *rendere
 
       void visitSymbol( const QgsSymbol *symbol )
       {
+        // symbol may be marked as animated on a symbol level (e.g. when it implements animation
+        // via data defined properties)
+        if ( symbol->animationSettings().isAnimated() )
+        {
+          if ( symbol->animationSettings().frameRate() > refreshRate )
+            refreshRate = symbol->animationSettings().frameRate();
+        }
         for ( int idx = 0; idx < symbol->symbolLayerCount(); idx++ )
         {
           const QgsSymbolLayer *sl = symbol->symbolLayer( idx );

src/gui/CMakeLists.txt

@@ -61,6 +61,7 @@ set(QGIS_GUI_SRCS
   symbology/qgsstylemanagerdialog.cpp
   symbology/qgsstylesavedialog.cpp
   symbology/qgssvgselectorwidget.cpp
+  symbology/qgssymbolanimationsettingswidget.cpp
   symbology/qgssymbollayerwidget.cpp
   symbology/qgssymbollevelsdialog.cpp
   symbology/qgssymbolslistwidget.cpp
@@ -1316,6 +1317,7 @@ set(QGIS_GUI_HDRS
   symbology/qgsstylemanagerdialog.h
   symbology/qgsstylesavedialog.h
   symbology/qgssvgselectorwidget.h
+  symbology/qgssymbolanimationsettingswidget.h
   symbology/qgssymbollayerwidget.h
   symbology/qgssymbollevelsdialog.h
   symbology/qgssymbolselectordialog.h

src/gui/symbology/qgslayerpropertieswidget.cpp

@@ -281,6 +281,7 @@ QgsExpressionContext QgsLayerPropertiesWidget::createExpressionContext() const
   expContext.lastScope()->addVariable( QgsExpressionContextScope::StaticVariable( QStringLiteral( "symbol_layer_index" ), 1, true ) );
   expContext.lastScope()->addVariable( QgsExpressionContextScope::StaticVariable( QStringLiteral( "symbol_marker_row" ), 1, true ) );
   expContext.lastScope()->addVariable( QgsExpressionContextScope::StaticVariable( QStringLiteral( "symbol_marker_column" ), 1, true ) );
+  expContext.lastScope()->addVariable( QgsExpressionContextScope::StaticVariable( QStringLiteral( "symbol_frame" ), 1, true ) );
 
   // additional scopes
   const auto constAdditionalExpressionContextScopes = mContext.additionalExpressionContextScopes();
@@ -297,7 +298,8 @@ QgsExpressionContext QgsLayerPropertiesWidget::createExpressionContext() const
                                       << QgsExpressionContext::EXPR_GEOMETRY_RING_NUM
                                       << QgsExpressionContext::EXPR_GEOMETRY_POINT_COUNT << QgsExpressionContext::EXPR_GEOMETRY_POINT_NUM
                                       << QgsExpressionContext::EXPR_CLUSTER_COLOR << QgsExpressionContext::EXPR_CLUSTER_SIZE
-                                      << QStringLiteral( "symbol_layer_count" ) << QStringLiteral( "symbol_layer_index" ) );
+                                      << QStringLiteral( "symbol_layer_count" ) << QStringLiteral( "symbol_layer_index" )
+                                      << QStringLiteral( "symbol_frame" ) );
 
   return expContext;
 }

src/gui/symbology/qgssymbolanimationsettingswidget.cpp

@@ -0,0 +1,85 @@
+/***************************************************************************
+    qgssymbolanimationsettingswidget.cpp
+    ---------------------
+    begin                : April 2022
+    copyright            : (C) 2022 by Nyall Dawson
+    email                : nyall dot dawson at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgssymbolanimationsettingswidget.h"
+#include "qgssymbol.h"
+
+#include <QDialogButtonBox>
+
+QgsSymbolAnimationSettingsWidget::QgsSymbolAnimationSettingsWidget( QWidget *parent )
+  : QgsPanelWidget( parent )
+{
+  setupUi( this );
+
+  mFrameRateSpin->setClearValue( 10 );
+  mFrameRateSpin->setShowClearButton( true );
+
+  connect( mFrameRateSpin, qOverload< double >( &QDoubleSpinBox::valueChanged ), this, [ this ]
+  {
+    if ( !mBlockUpdates )
+      emit widgetChanged();
+  } );
+  connect( mIsAnimatedGroup, &QGroupBox::toggled, this, [ this ]
+  {
+    if ( !mBlockUpdates )
+      emit widgetChanged();
+  } );
+}
+
+void QgsSymbolAnimationSettingsWidget::setAnimationSettings( const QgsSymbolAnimationSettings &settings )
+{
+  mBlockUpdates = true;
+  mIsAnimatedGroup->setChecked( settings.isAnimated() );
+  mFrameRateSpin->setValue( settings.frameRate() );
+  mBlockUpdates = false;
+}
+
+QgsSymbolAnimationSettings QgsSymbolAnimationSettingsWidget::animationSettings() const
+{
+  QgsSymbolAnimationSettings settings;
+  settings.setIsAnimated( mIsAnimatedGroup->isChecked() );
+  settings.setFrameRate( mFrameRateSpin->value() );
+  return settings;
+}
+
+
+//
+// QgsSymbolAnimationSettingsDialog
+//
+
+QgsSymbolAnimationSettingsDialog::QgsSymbolAnimationSettingsDialog( QWidget *parent, Qt::WindowFlags f )
+  : QDialog( parent, f )
+{
+  QVBoxLayout *vLayout = new QVBoxLayout();
+  mWidget = new QgsSymbolAnimationSettingsWidget( );
+  vLayout->addWidget( mWidget );
+  QDialogButtonBox *bbox = new QDialogButtonBox( QDialogButtonBox::Ok | QDialogButtonBox::Cancel, Qt::Horizontal );
+  connect( bbox, &QDialogButtonBox::accepted, this, &QgsSymbolAnimationSettingsDialog::accept );
+  connect( bbox, &QDialogButtonBox::rejected, this, &QgsSymbolAnimationSettingsDialog::reject );
+  vLayout->addWidget( bbox );
+  setLayout( vLayout );
+  setWindowTitle( tr( "Animation Settings" ) );
+}
+
+void QgsSymbolAnimationSettingsDialog::setAnimationSettings( const QgsSymbolAnimationSettings &settings )
+{
+  mWidget->setAnimationSettings( settings );
+}
+
+QgsSymbolAnimationSettings QgsSymbolAnimationSettingsDialog::animationSettings() const
+{
+  return mWidget->animationSettings();
+}
+

src/gui/symbology/qgssymbolanimationsettingswidget.h

@@ -0,0 +1,96 @@
+/***************************************************************************
+    qgssymbolanimationsettingswidget.h
+    ---------------------
+    begin                : April 2022
+    copyright            : (C) 2022 by Nyall Dawson
+    email                : nyall dot dawson at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSSYMBOLANIMATIONSETTINGSWIDGET_H
+#define QGSSYMBOLANIMATIONSETTINGSWIDGET_H
+
+#include "ui_qgssymbolanimationsettingswidgetbase.h"
+
+#include "qgis_gui.h"
+#include "qgis_sip.h"
+#include "qgspanelwidget.h"
+
+#include <QDialog>
+
+class QgsSymbolAnimationSettings;
+
+
+/**
+ * \ingroup gui
+ * \brief A widget for customising animation settings for a symbol.
+ * \since QGIS 3.26
+*/
+class GUI_EXPORT QgsSymbolAnimationSettingsWidget: public QgsPanelWidget, private Ui::QgsSymbolAnimationSettingsWidgetBase
+{
+    Q_OBJECT
+  public:
+
+    //! Constructor for QgsSymbolAnimationSettingsWidget
+    QgsSymbolAnimationSettingsWidget( QWidget *parent SIP_TRANSFERTHIS = nullptr );
+
+    /**
+     * Sets the animation \a settings to show in the widget.
+     *
+     * \see animationSettings()
+     */
+    void setAnimationSettings( const QgsSymbolAnimationSettings &settings );
+
+    /**
+     * Returns the animation settings as defined in the widget.
+     *
+     * \see setAnimationSettings()
+     */
+    QgsSymbolAnimationSettings animationSettings() const;
+
+  private:
+
+    bool mBlockUpdates = false;
+
+};
+
+/**
+ * \ingroup gui
+ * \brief A dialog for customising animation settings for a symbol.
+ * \since QGIS 3.26
+*/
+class GUI_EXPORT QgsSymbolAnimationSettingsDialog : public QDialog
+{
+    Q_OBJECT
+  public:
+
+    //! Constructor for QgsSymbolAnimationSettingsDialog
+    QgsSymbolAnimationSettingsDialog( QWidget *parent SIP_TRANSFERTHIS = nullptr, Qt::WindowFlags f = Qt::WindowFlags() );
+
+    /**
+     * Sets the animation \a settings to show in the dialog.
+     *
+     * \see animationSettings()
+     */
+    void setAnimationSettings( const QgsSymbolAnimationSettings &settings );
+
+    /**
+     * Returns the animation settings as defined in the dialog.
+     *
+     * \see setAnimationSettings()
+     */
+    QgsSymbolAnimationSettings animationSettings() const;
+
+  private:
+
+    QgsSymbolAnimationSettingsWidget *mWidget = nullptr;
+
+};
+
+#endif // QGSSYMBOLANIMATIONSETTINGSWIDGET_H

src/gui/symbology/qgssymbollayerwidget.cpp

@@ -90,6 +90,7 @@ QgsExpressionContext QgsSymbolLayerWidget::createExpressionContext() const
   expContext.lastScope()->addVariable( QgsExpressionContextScope::StaticVariable( QStringLiteral( "symbol_layer_index" ), 1, true ) );
   expContext.lastScope()->addVariable( QgsExpressionContextScope::StaticVariable( QStringLiteral( "symbol_marker_row" ), 1, true ) );
   expContext.lastScope()->addVariable( QgsExpressionContextScope::StaticVariable( QStringLiteral( "symbol_marker_column" ), 1, true ) );
+  expContext.lastScope()->addVariable( QgsExpressionContextScope::StaticVariable( QStringLiteral( "symbol_frame" ), 1, true ) );
 
   // additional scopes
   const auto constAdditionalExpressionContextScopes = mContext.additionalExpressionContextScopes();
@@ -107,7 +108,7 @@ QgsExpressionContext QgsSymbolLayerWidget::createExpressionContext() const
              << QgsExpressionContext::EXPR_GEOMETRY_RING_NUM
              << QgsExpressionContext::EXPR_GEOMETRY_POINT_COUNT << QgsExpressionContext::EXPR_GEOMETRY_POINT_NUM
              << QgsExpressionContext::EXPR_CLUSTER_COLOR << QgsExpressionContext::EXPR_CLUSTER_SIZE
-             << QStringLiteral( "symbol_layer_count" ) << QStringLiteral( "symbol_layer_index" );
+             << QStringLiteral( "symbol_layer_count" ) << QStringLiteral( "symbol_layer_index" ) << QStringLiteral( "symbol_frame" );
 
 
   if ( expContext.hasVariable( QStringLiteral( "zoom_level" ) ) )

src/gui/symbology/qgssymbolslistwidget.cpp

@@ -25,6 +25,7 @@
 #include "qgsmarkersymbol.h"
 #include "qgslinesymbol.h"
 #include "qgsfillsymbol.h"
+#include "qgssymbolanimationsettingswidget.h"
 
 #include <QMessageBox>
 
@@ -50,7 +51,8 @@ QgsSymbolsListWidget::QgsSymbolsListWidget( QgsSymbol *symbol, QgsStyle *style,
   mStandardizeRingsAction = new QAction( tr( "Force Right-Hand-Rule Orientation" ), this );
   mStandardizeRingsAction->setCheckable( true );
   connect( mStandardizeRingsAction, &QAction::toggled, this, &QgsSymbolsListWidget::forceRHRToggled );
-
+  mAnimationSettingsAction = new QAction( tr( "Animation Settings…" ), this );
+  connect( mAnimationSettingsAction, &QAction::triggered, this, &QgsSymbolsListWidget::showAnimationSettings );
 
   // select correct page in stacked widget
   QgsPropertyOverrideButton *opacityDDBtn = nullptr;
@@ -136,6 +138,7 @@ QgsSymbolsListWidget::~QgsSymbolsListWidget()
   // The menu can be passed in the constructor, so may live longer than this widget
   mStyleItemsListWidget->advancedMenu()->removeAction( mClipFeaturesAction );
   mStyleItemsListWidget->advancedMenu()->removeAction( mStandardizeRingsAction );
+  mStyleItemsListWidget->advancedMenu()->removeAction( mAnimationSettingsAction );
 }
 
 void QgsSymbolsListWidget::registerDataDefinedButton( QgsPropertyOverrideButton *button, QgsSymbolLayer::Property key )
@@ -260,6 +263,32 @@ void QgsSymbolsListWidget::forceRHRToggled( bool checked )
   emit changed();
 }
 
+void QgsSymbolsListWidget::showAnimationSettings()
+{
+  QgsPanelWidget *panel = QgsPanelWidget::findParentPanel( this );
+  if ( panel && panel->dockMode() )
+  {
+    QgsSymbolAnimationSettingsWidget *widget = new QgsSymbolAnimationSettingsWidget( panel );
+    widget->setPanelTitle( tr( "Animation Settings" ) );
+    widget->setAnimationSettings( mSymbol->animationSettings() );
+    connect( widget, &QgsPanelWidget::widgetChanged, this, [ this, widget ]()
+    {
+      mSymbol->setAnimationSettings( widget->animationSettings() );
+      emit changed();
+    } );
+    panel->openPanel( widget );
+    return;
+  }
+
+  QgsSymbolAnimationSettingsDialog d( this );
+  d.setAnimationSettings( mSymbol->animationSettings() );
+  if ( d.exec() == QDialog::Accepted )
+  {
+    mSymbol->setAnimationSettings( d.animationSettings() );
+    emit changed();
+  }
+}
+
 void QgsSymbolsListWidget::saveSymbol()
 {
   if ( !mStyle )
@@ -474,7 +503,8 @@ QgsExpressionContext QgsSymbolsListWidget::createExpressionContext() const
                                       << QgsExpressionContext::EXPR_GEOMETRY_RING_NUM
                                       << QgsExpressionContext::EXPR_GEOMETRY_POINT_COUNT << QgsExpressionContext::EXPR_GEOMETRY_POINT_NUM
                                       << QgsExpressionContext::EXPR_CLUSTER_COLOR << QgsExpressionContext::EXPR_CLUSTER_SIZE
-                                      << QStringLiteral( "symbol_layer_count" ) << QStringLiteral( "symbol_layer_index" ) );
+                                      << QStringLiteral( "symbol_layer_count" ) << QStringLiteral( "symbol_layer_index" )
+                                      << QStringLiteral( "symbol_frame" ) );
 
   return expContext;
 }
@@ -546,6 +576,10 @@ void QgsSymbolsListWidget::updateSymbolInfo()
     {
       mStyleItemsListWidget->advancedMenu()->removeAction( action );
     }
+    else if ( mAnimationSettingsAction->text() == action->text() )
+    {
+      mStyleItemsListWidget->advancedMenu()->removeAction( action );
+    }
   }
 
   if ( mSymbol->type() == Qgis::SymbolType::Line || mSymbol->type() == Qgis::SymbolType::Fill )
@@ -557,6 +591,7 @@ void QgsSymbolsListWidget::updateSymbolInfo()
   {
     mStyleItemsListWidget->advancedMenu()->addAction( mStandardizeRingsAction );
   }
+  mStyleItemsListWidget->advancedMenu()->addAction( mAnimationSettingsAction );
 
   mStyleItemsListWidget->showAdvancedButton( mAdvancedMenu || !mStyleItemsListWidget->advancedMenu()->isEmpty() );
 

src/gui/symbology/qgssymbolslistwidget.h

@@ -96,6 +96,7 @@ class GUI_EXPORT QgsSymbolsListWidget : public QWidget, private Ui::SymbolsListW
     void createAuxiliaryField();
     void createSymbolAuxiliaryField();
     void forceRHRToggled( bool checked );
+    void showAnimationSettings();
     void saveSymbol();
     void updateSymbolDataDefinedProperty();
 
@@ -109,6 +110,7 @@ class GUI_EXPORT QgsSymbolsListWidget : public QWidget, private Ui::SymbolsListW
     QMenu *mAdvancedMenu = nullptr;
     QAction *mClipFeaturesAction = nullptr;
     QAction *mStandardizeRingsAction = nullptr;
+    QAction *mAnimationSettingsAction = nullptr;
     QgsVectorLayer *mLayer = nullptr;
     QgsMapCanvas *mMapCanvas = nullptr;
 

src/ui/symbollayer/qgssymbolanimationsettingswidgetbase.ui

@@ -0,0 +1,92 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ui version="4.0">
+ <class>QgsSymbolAnimationSettingsWidgetBase</class>
+ <widget class="QgsPanelWidget" name="QgsSymbolAnimationSettingsWidgetBase">
+  <property name="geometry">
+   <rect>
+    <x>0</x>
+    <y>0</y>
+    <width>343</width>
+    <height>300</height>
+   </rect>
+  </property>
+  <property name="windowTitle">
+   <string>Dash Space Pattern</string>
+  </property>
+  <layout class="QGridLayout" name="gridLayout">
+   <item row="0" column="0" colspan="2">
+    <widget class="QGroupBox" name="mIsAnimatedGroup">
+     <property name="title">
+      <string>Is Animated</string>
+     </property>
+     <property name="checkable">
+      <bool>true</bool>
+     </property>
+     <layout class="QGridLayout" name="gridLayout_2" columnstretch="1,2">
+      <item row="1" column="0">
+       <widget class="QLabel" name="label_2">
+        <property name="text">
+         <string>Frame rate</string>
+        </property>
+       </widget>
+      </item>
+      <item row="1" column="1">
+       <widget class="QgsDoubleSpinBox" name="mFrameRateSpin">
+        <property name="suffix">
+         <string> fps</string>
+        </property>
+        <property name="minimum">
+         <double>0.010000000000000</double>
+        </property>
+        <property name="maximum">
+         <double>1000.000000000000000</double>
+        </property>
+        <property name="value">
+         <double>10.000000000000000</double>
+        </property>
+       </widget>
+      </item>
+      <item row="0" column="0" colspan="2">
+       <widget class="QLabel" name="label">
+        <property name="text">
+         <string>The symbol will be animated using the specified frame rate. The &lt;code&gt;@symbol_frame&lt;/code&gt; variable can be used in symbol property expressions in order to dynamically alter the symbol's appearance over time.</string>
+        </property>
+        <property name="wordWrap">
+         <bool>true</bool>
+        </property>
+       </widget>
+      </item>
+     </layout>
+    </widget>
+   </item>
+   <item row="1" column="0">
+    <spacer name="verticalSpacer">
+     <property name="orientation">
+      <enum>Qt::Vertical</enum>
+     </property>
+     <property name="sizeHint" stdset="0">
+      <size>
+       <width>20</width>
+       <height>40</height>
+      </size>
+     </property>
+    </spacer>
+   </item>
+  </layout>
+ </widget>
+ <customwidgets>
+  <customwidget>
+   <class>QgsPanelWidget</class>
+   <extends>QWidget</extends>
+   <header>qgspanelwidget.h</header>
+   <container>1</container>
+  </customwidget>
+  <customwidget>
+   <class>QgsDoubleSpinBox</class>
+   <extends>QDoubleSpinBox</extends>
+   <header>qgsdoublespinbox.h</header>
+  </customwidget>
+ </customwidgets>
+ <resources/>
+ <connections/>
+</ui>

tests/src/python/test_qgssymbol.py

@@ -636,6 +636,28 @@ class TestQgsSymbol(unittest.TestCase):
 
         assert self.imageCheck('Reprojection errors linestring', 'reprojection_errors_linestring', image)
 
+    def test_animation_settings(self):
+        s = QgsFillSymbol()
+        self.assertFalse(s.animationSettings().isAnimated())
+        s.animationSettings().setIsAnimated(True)
+        self.assertTrue(s.animationSettings().isAnimated())
+
+        s.animationSettings().setFrameRate(30)
+        self.assertEqual(s.animationSettings().frameRate(), 30)
+
+        s.setForceRHR(True)
+        doc = QDomDocument()
+        context = QgsReadWriteContext()
+        element = QgsSymbolLayerUtils.saveSymbol('test', s, doc, context)
+
+        s2 = QgsSymbolLayerUtils.loadSymbol(element, context)
+        self.assertTrue(s2.animationSettings().isAnimated())
+        self.assertEqual(s2.animationSettings().frameRate(), 30)
+
+        s3 = s2.clone()
+        self.assertTrue(s3.animationSettings().isAnimated())
+        self.assertEqual(s3.animationSettings().frameRate(), 30)
+
     def renderCollection(self, geom, symbol):
         f = QgsFeature()
         f.setGeometry(geom)
@@ -926,7 +948,24 @@ class TestQgsMarkerSymbol(unittest.TestCase):
         rendered_image = self.renderGeometry(s, g, QgsMapSettings.DrawSymbolBounds)
         self.assertTrue(self.imageCheck('marker_bounds_layer_disabled', 'marker_bounds_layer_disabled', rendered_image))
 
-    def renderGeometry(self, symbol, geom, flags=QgsMapSettings.Flags()):
+    def test_animation(self):
+        markerSymbol = QgsMarkerSymbol()
+        markerSymbol.deleteSymbolLayer(0)
+        markerSymbol.appendSymbolLayer(
+            QgsSimpleMarkerSymbolLayer(QgsSimpleMarkerSymbolLayerBase.Triangle, color=QColor(255, 0, 0),
+                                       strokeColor=QColor(0, 255, 0), size=10, angle=0))
+        markerSymbol[0].setStrokeStyle(Qt.NoPen)
+
+        markerSymbol.animationSettings().setIsAnimated(True)
+
+        markerSymbol[0].setDataDefinedProperty(QgsSymbolLayer.PropertyAngle, QgsProperty.fromExpression('@symbol_frame * 90'))
+        g = QgsGeometry.fromWkt('Point(1 1)')
+        rendered_image = self.renderGeometry(markerSymbol, g, frame=0)
+        self.assertTrue(self.imageCheck('animated_frame1', 'animated_frame1', rendered_image))
+        rendered_image = self.renderGeometry(markerSymbol, g, frame=1)
+        self.assertTrue(self.imageCheck('animated_frame2', 'animated_frame2', rendered_image))
+
+    def renderGeometry(self, symbol, geom, flags=QgsMapSettings.Flags(), frame=None):
         f = QgsFeature()
         f.setGeometry(geom)
 
@@ -945,6 +984,9 @@ class TestQgsMarkerSymbol(unittest.TestCase):
 
         ms.setExtent(extent)
         ms.setOutputSize(image.size())
+        if frame is not None:
+            ms.setFrameRate(10)
+            ms.setCurrentFrame(frame)
         context = QgsRenderContext.fromMapSettings(ms)
         context.setPainter(painter)
         context.setScaleFactor(96 / 25.4)  # 96 DPI

tests/src/python/test_qgssymbollayerutils.py

@@ -635,6 +635,14 @@ class PyQgsSymbolLayerUtils(unittest.TestCase):
         renderer = QgsSingleSymbolRenderer(marker_symbol)
         self.assertEqual(QgsSymbolLayerUtils.rendererFrameRate(renderer), 60)
 
+        s = QgsMarkerSymbol()
+        renderer = QgsSingleSymbolRenderer(s.clone())
+        self.assertEqual(QgsSymbolLayerUtils.rendererFrameRate(renderer), -1)
+        s.animationSettings().setIsAnimated(True)
+        s.animationSettings().setFrameRate(30)
+        renderer = QgsSingleSymbolRenderer(s.clone())
+        self.assertEqual(QgsSymbolLayerUtils.rendererFrameRate(renderer), 30)
+
     def imageCheck(self, name, reference_image, image):
         self.report += "<h2>Render {}</h2>\n".format(name)
         temp_dir = QDir.tempPath() + '/'