From dac25b8db9686f4a6dd03fcc2d616004b1c1dd44 Mon Sep 17 00:00:00 2001
From: Tim Mayberry <mojofunk@gmail.com>
Date: Mon, 13 Mar 2017 20:45:13 +1000
Subject: [PATCH] Add PreRender signal to the canvas

Emitted by the canvas immediately before rendering.
---
 libs/canvas/canvas.cc       | 2 ++
 libs/canvas/canvas/canvas.h | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/libs/canvas/canvas.cc b/libs/canvas/canvas.cc
index fb06b06b97..be61b6cb84 100644
--- a/libs/canvas/canvas.cc
+++ b/libs/canvas/canvas.cc
@@ -101,6 +101,8 @@ Canvas::zoomed ()
 void
 Canvas::render (Rect const & area, Cairo::RefPtr<Cairo::Context> const & context) const
 {
+	PreRender (); // emit signal
+
 #ifdef CANVAS_DEBUG
 	if (DEBUG_ENABLED(PBD::DEBUG::CanvasRender)) {
 		cerr << this << " RENDER: " << area << endl;
diff --git a/libs/canvas/canvas/canvas.h b/libs/canvas/canvas/canvas.h
index 934f1fe08e..2f506fc3c0 100644
--- a/libs/canvas/canvas/canvas.h
+++ b/libs/canvas/canvas/canvas.h
@@ -135,6 +135,8 @@ public:
 	*/
 	sigc::signal<void,Duple const&> MouseMotion;
 
+	sigc::signal<void> PreRender;
+
 	/** Ensures that the position given by @param winpos (in window
 	    coordinates) is within the current window area, possibly reduced by
 	    @param border.