pre-render text canvas items so that ::render() is just a blit from an image surface

1 files changed, 42 insertions, 27 deletions

diff --git a/libs/canvas/text.cc b/libs/canvas/text.cc
index feb88e1996..6333d7fae7 100644
--- a/libs/canvas/text.cc
+++ b/libs/canvas/text.cc
@@ -1,5 +1,8 @@
+#include <cairomm/cairomm.h>
 #include <gtkmm/label.h>
+
 #include "pbd/xml++.h"
+
 #include "canvas/text.h"
 #include "canvas/canvas.h"
 #include "canvas/utils.h"
@@ -9,9 +12,12 @@ using namespace ArdourCanvas;
 
 Text::Text (Group* parent)
 	: Item (parent)
-	, _font_description (0)
+	, _image (0)
 	, _color (0x000000ff)
+	, _font_description (0)
 	, _alignment (Pango::ALIGN_LEFT)
+	, _width (0)
+	, _height (0)
 {
 
 }
@@ -27,49 +33,56 @@ Text::set (string const & text)
 	begin_change ();
 	
 	_text = text;
-	
+
+	redraw ();
+
 	_bounding_box_dirty = true;
 	end_change ();
 }
 
 void
-Text::compute_bounding_box () const
+Text::redraw ()
 {
-	if (!_canvas || !_canvas->context ()) {
-		_bounding_box = boost::optional<Rect> ();
-		_bounding_box_dirty = false;
-		return;
-	}
-	
-	Pango::Rectangle const r = layout (_canvas->context())->get_ink_extents ();
-	
-	_bounding_box = Rect (
-		r.get_x() / Pango::SCALE,
-		r.get_y() / Pango::SCALE,
-		(r.get_x() + r.get_width()) / Pango::SCALE,
-		(r.get_y() + r.get_height()) / Pango::SCALE
-		);
-	
-	_bounding_box_dirty = false;
-}
+	_image = Cairo::ImageSurface::create (Cairo::FORMAT_ARGB32, _width, _height);
 
-Glib::RefPtr<Pango::Layout>
-Text::layout (Cairo::RefPtr<Cairo::Context> context) const
-{
+	Cairo::RefPtr<Cairo::Context> context = Cairo::Context::create (_image);
 	Glib::RefPtr<Pango::Layout> layout = Pango::Layout::create (context);
+
 	layout->set_text (_text);
+
 	if (_font_description) {
 		layout->set_font_description (*_font_description);
 	}
+
 	layout->set_alignment (_alignment);
-	return layout;
+	
+	Pango::Rectangle ink_rect = layout->get_ink_extents();
+	
+	_origin.x = ink_rect.get_x() / Pango::SCALE;
+	_origin.y = ink_rect.get_y() / Pango::SCALE;
+	_width = (ink_rect.get_width() + Pango::SCALE / 2) / Pango::SCALE;
+	_height = (ink_rect.get_height() + Pango::SCALE / 2) / Pango::SCALE;
+	
+	set_source_rgba (context, _color);
+
+	layout->show_in_cairo_context (context);
+
+	/* text has now been rendered */
+}
+
+void
+Text::compute_bounding_box () const
+{
+	_bounding_box = Rect (_origin.x, _origin.y, _origin.x + _width, _origin.y + _height);
+	_bounding_box_dirty = false;
 }
 
 void
 Text::render (Rect const & /*area*/, Cairo::RefPtr<Cairo::Context> context) const
 {
-	set_source_rgba (context, _color);
-	layout (context)->show_in_cairo_context (context);
+	context->set_source (_image, 0, 0);
+	context->rectangle (0, 0, _width, _height);
+	context->fill ();
 }
 
 XMLNode *
@@ -96,7 +109,7 @@ Text::set_alignment (Pango::Alignment alignment)
 	begin_change ();
 	
 	_alignment = alignment;
-
+	redraw ();
 	_bounding_box_dirty = true;
 	end_change ();
 }
@@ -107,6 +120,7 @@ Text::set_font_description (Pango::FontDescription font_description)
 	begin_change ();
 	
 	_font_description = new Pango::FontDescription (font_description);
+	redraw ();
 
 	_bounding_box_dirty = true;
 	end_change ();
@@ -118,6 +132,7 @@ Text::set_color (Color color)
 	begin_change ();
 
 	_color = color;
+	redraw ();
 
 	end_change ();
 }