[glabels/vala] Workaround for pango kerning bug.

[Jim Evins <jimevins src gnome org>]

commit 0de454afee7a9f9da423c4af4b0ffe63974eb12d
Author: Jim Evins <evins snaught com>
Date:   Wed May 21 22:33:20 2014 -0400

    Workaround for pango kerning bug.
    
    Fixes bug #698777.  This is a workaround for pango-cairo bug #700592, which is
    a regression of bug #341481 which was originally fixed back in 2009.  This
    workaround works by rendering the font at device scale rather than world scale.
    To make this work the actual font size is manually scaled appropriately to
    compensate for this.

 glabels/label_object_text.vala |   38 ++++++++++++++++++++++++++++++--------
 1 files changed, 30 insertions(+), 8 deletions(-)
---
diff --git a/glabels/label_object_text.vala b/glabels/label_object_text.vala
index a27af10..99fa03e 100644
--- a/glabels/label_object_text.vala
+++ b/glabels/label_object_text.vala
@@ -436,7 +436,18 @@ namespace glabels
 
                private void set_text_path( Cairo.Context cr, bool in_editor, MergeRecord? record )
                {
+                       /*
+                        * Workaround for pango Bug#700592, which is a regression of Bug#341481.
+                        * Render font at device scale and scale font size accordingly.
+                        */
+                       double scale_x = 1.0;
+                       double scale_y = 1.0;
+                       cr.device_to_user_distance( ref scale_x, ref scale_y );
+                       scale_x = Math.fabs( scale_x );
+                       scale_y = Math.fabs( scale_y );
+
                        cr.save();
+                       cr.scale( scale_x, scale_y );
 
                        TextLines lines = get_lines();
                        string    text = lines.expand( record );
@@ -463,13 +474,13 @@ namespace glabels
                        Pango.FontDescription desc = new Pango.FontDescription();
                        desc.set_family( font_family );
                        desc.set_weight( font_weight );
-                       desc.set_size( (int)(scaled_font_size * Pango.SCALE + 0.5) );
+                       desc.set_size( (int)(scaled_font_size * Pango.SCALE/scale_x + 0.5) );
                        desc.set_style( style );
                        layout.set_font_description( desc );
 
                        layout.set_text( text, -1 );
-                       layout.set_spacing( (int)(scaled_font_size * (text_line_spacing-1) * Pango.SCALE + 
0.5) );
-                       layout.set_width( (int)(w * Pango.SCALE + 0.5) );
+                       layout.set_spacing( (int)(scaled_font_size * (text_line_spacing-1) * 
Pango.SCALE/scale_x + 0.5) );
+                       layout.set_width( (int)(w * Pango.SCALE/scale_x + 0.5) );
                        layout.set_wrap( Pango.WrapMode.WORD );
                        layout.set_alignment( text_alignment );
 
@@ -480,17 +491,17 @@ namespace glabels
                        switch (text_valignment)
                        {
                        case ValignType.CENTER:
-                               y = (h - ih) / 2;
+                               y = (h/scale_x - ih) / 2;
                                break;
                        case ValignType.BOTTOM:
-                               y = h - ih;
+                               y = h/scale_x - ih;
                                break;
                        default:
                                y = 0;
                                break;
                        }
 
-                       cr.move_to( TEXT_MARGIN, y );
+                       cr.move_to( TEXT_MARGIN/scale_x, y );
                        Pango.cairo_layout_path( cr, layout );
 
                        cr.restore();
@@ -499,7 +510,18 @@ namespace glabels
 
                private void set_empty_text_path( Cairo.Context cr )
                {
+                       /*
+                        * Workaround for pango Bug#700592, which is a regression of Bug#341481.
+                        * Render font at device scale and scale font size accordingly.
+                        */
+                       double scale_x = 1.0;
+                       double scale_y = 1.0;
+                       cr.device_to_user_distance( ref scale_x, ref scale_y );
+                       scale_x = Math.fabs( scale_x );
+                       scale_y = Math.fabs( scale_y );
+
                        cr.save();
+                       cr.scale( scale_x, scale_y );
 
                        Pango.Layout layout = Pango.cairo_create_layout( cr );
 
@@ -511,13 +533,13 @@ namespace glabels
                        Pango.FontDescription desc = new Pango.FontDescription();
                        desc.set_family( "Sans" );
                        desc.set_weight( Pango.Weight.NORMAL );
-                       desc.set_size( (int)(12 * FONT_SCALE * Pango.SCALE) );
+                       desc.set_size( (int)(12 * FONT_SCALE * Pango.SCALE/scale_x + 0.5) );
                        desc.set_style( Pango.Style.NORMAL );
                        layout.set_font_description( desc );
 
                        layout.set_text( _("Text"), -1 );
 
-                       cr.move_to( TEXT_MARGIN, 0 );
+                       cr.move_to( TEXT_MARGIN/scale_x, 0 );
                        Pango.cairo_layout_path( cr, layout );
 
                        cr.restore();