From 75a150ecc0672bc04c2db428ffbc7fdf7926e74a Mon Sep 17 00:00:00 2001
From: Paul Davis <paul@linuxaudiosystems.com>
Date: Fri, 19 Sep 2014 13:17:45 -0400
Subject: [PATCH] make computation of OS X pango text width correction less
 intrusive/more efficient.

Compute the correction only once after each font specification setting.
---
 libs/canvas/canvas/text.h |  3 +--
 libs/canvas/text.cc       | 48 +++++++++++++++++++++------------------
 2 files changed, 27 insertions(+), 24 deletions(-)

diff --git a/libs/canvas/canvas/text.h b/libs/canvas/canvas/text.h
index d4dacbfa4f..3c0f7ab147 100644
--- a/libs/canvas/canvas/text.h
+++ b/libs/canvas/canvas/text.h
@@ -52,8 +52,6 @@ public:
     double text_width() const { return _width; }
 
 private:
-    double _width_correction;
-    
 	std::string      _text;
 	uint32_t         _color;
 	Pango::FontDescription* _font_description;
@@ -63,6 +61,7 @@ private:
         mutable double _width;
         mutable double _height;
         mutable bool _need_redraw;
+        mutable double _width_correction;
         double _clamped_width;
 
         void redraw (Cairo::RefPtr<Cairo::Context>) const;
diff --git a/libs/canvas/text.cc b/libs/canvas/text.cc
index 0ce3f1d737..7cfdf9422b 100644
--- a/libs/canvas/text.cc
+++ b/libs/canvas/text.cc
@@ -35,13 +35,13 @@ using namespace ArdourCanvas;
 
 Text::Text (Canvas* c)
 	: Item (c)
-    , _width_correction (0)
 	, _color (0x000000ff)
 	, _font_description (0)
 	, _alignment (Pango::ALIGN_LEFT)
 	, _width (0)
 	, _height (0)
 	, _need_redraw (false)
+        , _width_correction (-1)
 	, _clamped_width (COORD_MAX)
 {
 	_outline = false;
@@ -49,13 +49,13 @@ Text::Text (Canvas* c)
 
 Text::Text (Item* parent)
 	: Item (parent)
-    , _width_correction (0)
 	, _color (0x000000ff)
 	, _font_description (0)
 	, _alignment (Pango::ALIGN_LEFT)
 	, _width (0)
 	, _height (0)
 	, _need_redraw (false)
+        , _width_correction (-1)
 	, _clamped_width (COORD_MAX)
 {
 	_outline = false;
@@ -105,6 +105,29 @@ Text::redraw (Glib::RefPtr<Pango::Context> context) const
 void
 Text::_redraw (Glib::RefPtr<Pango::Layout> layout) const
 {
+#ifdef __APPLE__
+        if (_width_correction < 0.0) {
+                // Pango returns incorrect text width on some OS X
+                // So we have to make a correction
+                // To determine the correct indent take the largest symbol for which the width is correct
+                // and make the calculation
+                Gtk::Window win;
+                Gtk::Label foo;
+                win.add (foo);
+                
+                int width = 0;
+                int height = 0;
+                Glib::RefPtr<Pango::Layout> test_layout = foo.create_pango_layout ("H");
+                test_layout->set_font_description (*_font_description);
+                test_layout->get_pixel_size (width, height);
+                
+                _width_correction = width*1.5;
+        }
+#else
+        /* don't bother with a conditional here */
+        _width_correction = 0.0;
+#endif
+
 	layout->set_text (_text);
 
 	if (_font_description) {
@@ -112,26 +135,6 @@ Text::_redraw (Glib::RefPtr<Pango::Layout> layout) const
 	}
 
 	layout->set_alignment (_alignment);
-
-    // Pango returns incorrect text width on some platforms
-    // So we have to make a correction
-    // To determine the correct indent take the largest symbol for which the width is correct
-    // and make the calculation
-    Gtk::Window win;
-    Gtk::Label foo;
-    win.add (foo);
-    
-    int width = 0;
-    int height = 0;
-    Glib::RefPtr<Pango::Layout> test_layout = foo.create_pango_layout ("H");
-    test_layout->set_font_description (*_font_description);
-    test_layout->get_pixel_size (width, height);
-    
-#ifdef __APPLE__
-    double _width_correction = width*1.5;
-#else if
-    double _width_correction = 0;
-#endif
     
 	int w;
 	int h;
@@ -234,6 +237,7 @@ Text::set_font_description (Pango::FontDescription font_description)
 	
 	_font_description = new Pango::FontDescription (font_description);
 	_need_redraw = true;
+        _width_correction = -1.0;
 
 	_bounding_box_dirty = true;
 	end_change ();