PathColumn : Add contextMenuSignal()

This allows columns to contribute to their own context menu, combined with the menu items defined by `PathListingWidget.columnContextMenuSignal()`.

Changes.md

@@ -48,6 +48,7 @@ API
   - A `DeprecationWarning` is now emitted by `_plugConnections()`. Use `_blockedUpdateFromValues()` instead.
 - NodeGadget, ConnectionGadget : Added `updateFromContextTracker()` virtual methods.
 - Path : Added `inspectionContext()` virtual method.
+- PathColumn : Added `contextMenuSignal()`, allowing the creation of custom context menus.
 
 Breaking Changes
 ----------------

include/GafferUI/PathColumn.h

@@ -50,6 +50,7 @@
 namespace GafferUI
 {
 
+class MenuDefinition;
 class PathListingWidget;
 
 /// Abstract class for extracting properties from a Path in a form
@@ -162,13 +163,17 @@ class GAFFERUI_API PathColumn : public IECore::RefCounted, public Gaffer::Signal
 		ButtonSignal &buttonReleaseSignal();
 		ButtonSignal &buttonDoubleClickSignal();
 
+		using ContextMenuSignal = Gaffer::Signals::Signal<void ( PathColumn &column, PathListingWidget &widget, MenuDefinition &menuDefinition ), Gaffer::Signals::CatchingCombiner<void>>;
+		ContextMenuSignal &contextMenuSignal();
+
 	private :
 
 		PathColumnSignal m_changedSignal;
 
 		ButtonSignal m_buttonPressSignal;
 		ButtonSignal m_buttonReleaseSignal;
 		ButtonSignal m_buttonDoubleClickSignal;
+		ContextMenuSignal m_contextMenuSignal;
 
 		SizeMode m_sizeMode;
 
@@ -274,4 +279,27 @@ class PathListingWidget
 
 };
 
+/// C++ interface for the `IECore.MenuDefinition` Python class. Provided for use
+/// in `PathColumn::contextMenuSignal()`, so that event handling may be
+/// implemented from C++ if desired.
+class MenuDefinition
+{
+
+	public :
+
+		struct MenuItem
+		{
+			using Command = std::function<void ()>;
+			Command command;
+			std::string description;
+			std::string icon;
+			std::string shortCut;
+			bool divider = false;
+			bool active = true;
+		};
+
+		virtual void append( const std::string &path, const MenuItem &item ) = 0;
+
+};
+
 } // namespace GafferUI

python/GafferUI/PathListingWidget.py

@@ -766,17 +766,16 @@ def __dragEnd( self, widget, event ) :
 
 	def __contextMenu( self, widget ) :
 
-		if not self.columnContextMenuSignal().numSlots() :
+		mousePosition = GafferUI.Widget.mousePosition( relativeTo = self )
+		column = self.columnAt( mousePosition )
+		if not column.contextMenuSignal().numSlots() and not self.columnContextMenuSignal().numSlots() :
 			# Allow legacy clients connected to `Widget.contextMenuSignal()` to
 			# do their own thing instead.
 			return False
 
 		# Select the path under the mouse, if it's not already selected.
 		# The user will expect to be operating on the thing under the mouse.
 
-		mousePosition = GafferUI.Widget.mousePosition( relativeTo = self )
-		column = self.columnAt( mousePosition )
-
 		path = self.pathAt( mousePosition )
 		if path is not None :
 			path = str( path )
@@ -797,6 +796,7 @@ def __contextMenu( self, widget ) :
 		# Use signals to build menu and display it.
 
 		menuDefinition = IECore.MenuDefinition()
+		column.contextMenuSignal()( column, self, menuDefinition )
 		self.columnContextMenuSignal()( column, self, menuDefinition )
 
 		if menuDefinition.size() :

src/GafferUI/PathColumn.cpp

@@ -110,6 +110,11 @@ PathColumn::ButtonSignal &PathColumn::buttonDoubleClickSignal()
 	return m_buttonDoubleClickSignal;
 }
 
+PathColumn::ContextMenuSignal &PathColumn::contextMenuSignal()
+{
+	return m_contextMenuSignal;
+}
+
 //////////////////////////////////////////////////////////////////////////
 // StandardPathColumn
 //////////////////////////////////////////////////////////////////////////

src/GafferUIModule/PathColumnBinding.cpp

@@ -47,6 +47,7 @@
 #include "IECorePython/RefCountedBinding.h"
 #include "IECorePython/ScopedGILLock.h"
 
+#include "boost/mpl/vector.hpp"
 #include "boost/python/suite/indexing/container_utils.hpp"
 
 using namespace boost::python;
@@ -147,6 +148,83 @@ class PathListingWidgetAccessor : public GafferUI::PathListingWidget
 
 } // namespace
 
+//////////////////////////////////////////////////////////////////////////
+// MenuDefinitionAccessor class
+//////////////////////////////////////////////////////////////////////////
+
+namespace
+{
+
+struct GILReleaseMenuCommand
+{
+
+	GILReleaseMenuCommand( MenuDefinition::MenuItem::Command command )
+		:	m_command( command )
+	{
+	}
+
+	void operator()()
+	{
+		IECorePython::ScopedGILRelease gilRelease;
+		m_command();
+	}
+
+	private :
+
+		MenuDefinition::MenuItem::Command m_command;
+
+};
+
+// Provides a C++ interface to the functionality implemented in the Python
+// MenuDefinition class.
+class MenuDefinitionAccessor : public GafferUI::MenuDefinition
+{
+
+	public :
+
+		MenuDefinitionAccessor( object menuDefinition )
+			:	m_menuDefinition( menuDefinition )
+		{
+		}
+
+		object menuDefinition()
+		{
+			return m_menuDefinition;
+		}
+
+		void append( const std::string &path, const MenuItem &item ) override
+		{
+			IECorePython::ScopedGILLock gilLock;
+
+			dict pythonItem;
+
+			if( item.command != nullptr )
+			{
+				pythonItem["command"] = make_function(
+					GILReleaseMenuCommand( item.command ),
+					boost::python::default_call_policies(),
+					boost::mpl::vector<void>()
+				);
+			}
+
+			pythonItem["description"] = item.description;
+			pythonItem["icon"] = item.icon;
+			pythonItem["shortCut"] = item.shortCut;
+			pythonItem["divider"] = item.divider;
+			pythonItem["active"] = item.active;
+
+			m_menuDefinition.attr( "append" )( path, pythonItem );
+		}
+
+	private :
+
+		// The Python MenuDefinition object.
+		object m_menuDefinition;
+
+};
+
+} // namespace
+
 //////////////////////////////////////////////////////////////////////////
 // Bindings
 //////////////////////////////////////////////////////////////////////////
@@ -330,6 +408,37 @@ struct ButtonSignalSlotCaller
 	}
 };
 
+struct ContextMenuSignalCaller
+{
+	static void call( PathColumn::ContextMenuSignal &s, PathColumn &column, object pathListingWidget, object menuDefinition )
+	{
+		PathListingWidgetAccessor pathListingWidgetAccessor( pathListingWidget );
+		MenuDefinitionAccessor menuDefinitionAccessor( menuDefinition );
+		IECorePython::ScopedGILRelease gilRelease;
+		s( column, pathListingWidgetAccessor, menuDefinitionAccessor );
+	}
+};
+
+struct ContextMenuSignalSlotCaller
+{
+	void operator()( boost::python::object slot, PathColumn &column, PathListingWidget &pathListingWidget, MenuDefinition &menuDefinition )
+	{
+		try
+		{
+			slot(
+				PathColumnPtr( &column ),
+				static_cast<PathListingWidgetAccessor &>( pathListingWidget ).widget(),
+				static_cast<MenuDefinitionAccessor &>( menuDefinition ).menuDefinition()
+
+			);
+		}
+		catch( const error_already_set & )
+		{
+			IECorePython::ExceptionAlgo::translatePythonException();
+		}
+	}
+};
+
 template<typename T>
 const char *pathColumnProperty( const T &column )
 {
@@ -384,6 +493,7 @@ void GafferUIModule::bindPathColumn()
 
 		SignalClass<PathColumn::PathColumnSignal, DefaultSignalCaller<PathColumn::PathColumnSignal>, ChangedSignalSlotCaller>( "PathColumnSignal" );
 		SignalClass<PathColumn::ButtonSignal, ButtonSignalCaller, ButtonSignalSlotCaller>( "ButtonSignal" );
+		SignalClass<PathColumn::ContextMenuSignal, ContextMenuSignalCaller, ContextMenuSignalSlotCaller>( "ContextMenuSignal" );
 	}
 
 	pathColumnClass.def( init<PathColumn::SizeMode>( arg( "sizeMode" ) = PathColumn::SizeMode::Default ) )
@@ -393,6 +503,7 @@ void GafferUIModule::bindPathColumn()
 		.def( "buttonPressSignal", &PathColumn::buttonPressSignal, return_internal_reference<1>() )
 		.def( "buttonReleaseSignal", &PathColumn::buttonReleaseSignal, return_internal_reference<1>() )
 		.def( "buttonDoubleClickSignal", &PathColumn::buttonDoubleClickSignal, return_internal_reference<1>() )
+		.def( "contextMenuSignal", &PathColumn::contextMenuSignal, return_internal_reference<1>() )
 		.def( "getSizeMode", (PathColumn::SizeMode (PathColumn::*)() const )&PathColumn::getSizeMode )
 		.def( "setSizeMode", &PathColumn::setSizeMode, ( arg( "sizeMode" ) ) )
 	;