Allow for per-widget image-surface backing

This is an intermediate commit, before replacing image surfaces with
cairo pattern groups.

The eventual goal is to reduce flickering and/or use
CPU + bitblt for specific widgets instead of cairo
graphics-cards accel.

This also removes excessive calls to getenv() for every rendering
operation.

2 files changed, 37 insertions, 42 deletions

diff --git a/libs/gtkmm2ext/cairo_widget.cc b/libs/gtkmm2ext/cairo_widget.cc
index 37d7f3806b..b06e443ec0 100644
--- a/libs/gtkmm2ext/cairo_widget.cc
+++ b/libs/gtkmm2ext/cairo_widget.cc
@@ -17,9 +17,6 @@
  * with this program; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
-#if !defined USE_CAIRO_IMAGE_SURFACE && !defined NDEBUG
-#define OPTIONAL_CAIRO_IMAGE_SURFACE
-#endif
 
 #include "gtkmm2ext/cairo_widget.h"
 #include "gtkmm2ext/gui_thread.h"
@@ -60,6 +57,11 @@ CairoWidget::CairoWidget ()
 	, _nsglview (0)
 {
 	_name_proxy.connect (sigc::mem_fun (*this, &CairoWidget::on_name_changed));
+#ifdef USE_CAIRO_IMAGE_SURFACE
+	_use_image_surface = true;
+#else
+	_use_image_surface = NULL != getenv("ARDOUR_IMAGE_SURFACE");
+#endif
 }
 
 CairoWidget::~CairoWidget ()
@@ -67,7 +69,9 @@ CairoWidget::~CairoWidget ()
 	if (_canvas_widget) {
 		gtk_widget_set_realized (GTK_WIDGET(gobj()), false);
 	}
-	if (_parent_style_change) _parent_style_change.disconnect();
+	if (_parent_style_change) {
+		_parent_style_change.disconnect();
+	}
 }
 
 void
@@ -78,6 +82,8 @@ CairoWidget::set_canvas_widget ()
 	ensure_style ();
 	gtk_widget_set_realized (GTK_WIDGET(gobj()), true);
 	_canvas_widget = true;
+	_use_image_surface = false;
+	image_surface.clear ();
 }
 
 void
@@ -91,6 +97,16 @@ CairoWidget::use_nsglview ()
 #endif
 }
 
+void
+CairoWidget::use_image_surface (bool yn)
+{
+	if (_use_image_surface == yn) {
+		return;
+	}
+	image_surface.clear ();
+	_use_image_surface = yn;
+}
+
 int
 CairoWidget::get_width () const
 {
@@ -147,9 +163,8 @@ CairoWidget::on_expose_event (GdkEventExpose *ev)
 		return true;
 	}
 #endif
-#ifdef OPTIONAL_CAIRO_IMAGE_SURFACE
 	Cairo::RefPtr<Cairo::Context> cr;
-	if (getenv("ARDOUR_IMAGE_SURFACE")) {
+	if (_use_image_surface) {
 		if (!image_surface) {
 			image_surface = Cairo::ImageSurface::create (Cairo::FORMAT_ARGB32, get_width(), get_height());
 		}
@@ -157,16 +172,6 @@ CairoWidget::on_expose_event (GdkEventExpose *ev)
 	} else {
 		cr = get_window()->create_cairo_context ();
 	}
-#elif defined USE_CAIRO_IMAGE_SURFACE
-
-	if (!image_surface) {
-		image_surface = Cairo::ImageSurface::create (Cairo::FORMAT_ARGB32, get_width(), get_height());
-	}
-
-	Cairo::RefPtr<Cairo::Context> cr = Cairo::Context::create (image_surface);
-#else
-	Cairo::RefPtr<Cairo::Context> cr = get_window()->create_cairo_context ();
-#endif
 
 	cr->rectangle (ev->area.x, ev->area.y, ev->area.width, ev->area.height);
 
@@ -193,24 +198,16 @@ CairoWidget::on_expose_event (GdkEventExpose *ev)
 
 	render (cr, &expose_area);
 
-#ifdef OPTIONAL_CAIRO_IMAGE_SURFACE
-	if (getenv("ARDOUR_IMAGE_SURFACE")) {
-#endif
-#if defined USE_CAIRO_IMAGE_SURFACE || defined OPTIONAL_CAIRO_IMAGE_SURFACE
-	image_surface->flush();
-	/* now blit our private surface back to the GDK one */
-
-	Cairo::RefPtr<Cairo::Context> cairo_context = get_window()->create_cairo_context ();
-
-	cairo_context->rectangle (ev->area.x, ev->area.y, ev->area.width, ev->area.height);
-	cairo_context->clip ();
-	cairo_context->set_source (image_surface, 0, 0);
-	cairo_context->set_operator (Cairo::OPERATOR_SOURCE);
-	cairo_context->paint ();
-#endif
-#ifdef OPTIONAL_CAIRO_IMAGE_SURFACE
+	if (_use_image_surface) {
+		image_surface->flush();
+		/* now blit our private surface back to the GDK one */
+		Cairo::RefPtr<Cairo::Context> window_context = get_window()->create_cairo_context ();
+		window_context->rectangle (ev->area.x, ev->area.y, ev->area.width, ev->area.height);
+		window_context->clip ();
+		window_context->set_source (image_surface, 0, 0);
+		window_context->set_operator (Cairo::OPERATOR_SOURCE);
+		window_context->paint ();
 	}
-#endif
 
 	return true;
 }
@@ -264,19 +261,15 @@ CairoWidget::on_size_allocate (Gtk::Allocation& alloc)
 		memcpy (&_allocation, &alloc, sizeof(Gtk::Allocation));
 	}
 
-#ifdef OPTIONAL_CAIRO_IMAGE_SURFACE
-	if (getenv("ARDOUR_IMAGE_SURFACE")) {
-#endif
-#if defined USE_CAIRO_IMAGE_SURFACE || defined OPTIONAL_CAIRO_IMAGE_SURFACE
-	image_surface = Cairo::ImageSurface::create (Cairo::FORMAT_ARGB32, alloc.get_width(), alloc.get_height());
-#endif
-#ifdef OPTIONAL_CAIRO_IMAGE_SURFACE
+	if (_use_image_surface) {
+		image_surface.clear ();
+		image_surface = Cairo::ImageSurface::create (Cairo::FORMAT_ARGB32, alloc.get_width(), alloc.get_height());
 	}
-#endif
 
 	if (_canvas_widget) {
 		return;
 	}
+
 #ifdef __APPLE__
 	if (_nsglview) {
 		gint xx, yy;
diff --git a/libs/gtkmm2ext/gtkmm2ext/cairo_widget.h b/libs/gtkmm2ext/gtkmm2ext/cairo_widget.h
index cecb2165a1..0dbd8fe8a0 100644
--- a/libs/gtkmm2ext/gtkmm2ext/cairo_widget.h
+++ b/libs/gtkmm2ext/gtkmm2ext/cairo_widget.h
@@ -40,6 +40,7 @@ public:
 
 	void set_canvas_widget ();
 	void use_nsglview ();
+	void use_image_surface (bool yn = true);
 
 	/* swizzle Gtk::Widget methods for Canvas::Widget */
 	void queue_draw ();
@@ -141,13 +142,14 @@ protected:
 
 	static sigc::slot<void,Gtk::Widget*> focus_handler;
 
-  private:
+private:
 	Cairo::RefPtr<Cairo::Surface> image_surface;
 	Glib::SignalProxyProperty _name_proxy;
 	sigc::connection _parent_style_change;
 	Widget * _current_parent;
 	bool _canvas_widget;
 	void* _nsglview;
+	bool _use_image_surface;
 	Gdk::Rectangle _allocation;
 
 };