MultiLineTextWidget : Add "activation hint" overlay

This hopefully makes the <kbd>Ctrl</kbd>+<kbd>Return</kbd> much more discoverable. I've deliberately not added methods to enable/disable this functionality as I think it is best applied consistently throughout the entire UI. As soon as you show it in one place and not another, it implies that the shortcut doesn't exist in both.

Changes.md

@@ -5,6 +5,7 @@ Improvements
 ------------
 
 - SetFilter, StandardAttributes, StandardOptions : Added syntax highlighting and auto-complete for set expressions.
+- NodeEditor, UIEditor, PythonEditor : Added popup hint for the <kbd>Ctrl</kbd>+<kbd>Return</kbd> shortcut.
 - CodeWidget : Added highlighting of braces and operators.
 
 Fixes

python/GafferUI/MultiLineTextWidget.py

@@ -327,6 +327,8 @@ def dropTextSignal( self ) :
 	def _emitEditingFinished( self ) :
 
 		self.editingFinishedSignal()( self )
+		# Hide our activation hint
+		self._qtWidget().document().setModified( False )
 
 	def __textChanged( self ) :
 
@@ -407,9 +409,12 @@ def __drop( self, widget, event ) :
 class _PlainTextEdit( QtWidgets.QPlainTextEdit ) :
 
 	def __init__( self, parent = None ) :
+
 		QtWidgets.QPlainTextEdit.__init__( self, parent )
 		self.__fixedLineHeight = None
 
+		self.document().modificationChanged.connect( self.update )
+
 	def setFixedLineHeight( self, fixedLineHeight ) :
 
 		self.__fixedLineHeight = fixedLineHeight
@@ -480,15 +485,31 @@ def paintEvent( self, event ) :
 
 		QtWidgets.QPlainTextEdit.paintEvent( self, event )
 
+		painter = QtGui.QPainter( self.viewport() )
+
 		if self.isEnabled() :
+			self.__paintActivationHint( painter )
 			return
 
 		# Disabled. We want the text to use faded colours but we can't
 		# do that with a stylesheet because we may have embedded HTML
 		# colours and/or a highlighter. So instead we draw a semi-transparent
 		# overlay the same colour as our background.
 
-		painter = QtGui.QPainter( self.viewport() )
 		color = self.palette().base().color()
 		color.setAlpha( 128 )
 		painter.fillRect( 0, 0, self.width(), self.height(), color )
+
+	def __paintActivationHint( self, painter ) :
+
+		if self.isReadOnly() or not self.document().isModified() :
+			return
+
+		widget = GafferUI.Widget._owner( self )
+		if widget is None or ( widget.activatedSignal().numSlots() + widget.editingFinishedSignal().numSlots() ) == 0 :
+			return
+
+		viewport = self.viewport()
+		pixmap = GafferUI.Image._qtPixmapFromFile( "ctrlEnter.png" )
+		painter.setOpacity( 0.75 )
+		painter.drawPixmap( viewport.width() - ( pixmap.width() + 4 ), viewport.height() - ( pixmap.height() + 4 ), pixmap )

resources/graphics.py

@@ -334,6 +334,7 @@
 			"ids" : [
 				"colorPlugValueWidgetSlidersOff",
 				"colorPlugValueWidgetSlidersOn",
+				"ctrlEnter",
 			]
 
 		},