[glabels/zint] Improved centering of barcode text.

[Jim Evins <jimevins src gnome org>]

commit b012b9c74def1a87e21e678486eeb4debeaf23be
Author: Jim Evins <evins snaught com>
Date:   Sat Jul 10 01:38:48 2010 -0400

    Improved centering of barcode text.
    
    Don't try to calculate x offset using hardcoded fixed character width, which
    does not work properly for proportional fonts.  Use the origin provided by
    zint (wich is at the horizontal center) and use pango to calculate the offset
    at render time.

 src/bc-zint.c       |    2 +-
 src/bc.h            |    3 ++-
 src/label-barcode.c |   10 ++++++++--
 3 files changed, 11 insertions(+), 4 deletions(-)
---
diff --git a/src/bc-zint.c b/src/bc-zint.c
index fb02b51..ca83f61 100644
--- a/src/bc-zint.c
+++ b/src/bc-zint.c
@@ -213,7 +213,7 @@ static glBarcode *render_zint(struct zint_symbol *symbol, gboolean text_flag)
                 for ( zstring = render->strings; zstring != NULL; zstring = zstring->next )
                 {
                         bstring = gl_barcode_shape_string_new();
-                        bstring->x = (double) zstring->x - (((6.0 / 9.0) * zstring->length * zstring->fsize) / 2);
+                        bstring->x = (double) zstring->x;
                         bstring->y = (double) zstring->y;
                         bstring->fsize = (double) zstring->fsize;
                         bstring->str   = g_strndup (zstring->text, zstring->length);
diff --git a/src/bc.h b/src/bc.h
index 5a0374f..6c7cbcb 100644
--- a/src/bc.h
+++ b/src/bc.h
@@ -151,7 +151,8 @@ typedef struct {
  *         /  /      \  \  | |_)  | |  (__      |
  *        /__/        \__\ |_.___/   \____|     |
  *                                              v
- *       @ --------------------------------------
+ *                           @ ------------------
+ *                           x = horizontal center
  */
 typedef struct {
 
diff --git a/src/label-barcode.c b/src/label-barcode.c
index 6f53818..7f3cf8f 100644
--- a/src/label-barcode.c
+++ b/src/label-barcode.c
@@ -428,7 +428,7 @@ draw_object (glLabelObject *object,
         glBarcodeShapeAlpha  *bchar;
         glBarcodeShapeString *bstring;
         GList                *p;
-        gdouble               y_offset;
+        gdouble               x_offset, y_offset;
         PangoLayout          *layout;
         PangoFontDescription *desc;
         gchar                *text, *cstring;
@@ -440,6 +440,8 @@ draw_object (glLabelObject *object,
         glColorNode          *color_node;
         guint                 format_digits;
         gdouble               w, h;
+        gint                  iw, ih;
+        gdouble               layout_width;
 
 	gl_debug (DEBUG_LABEL, "START");
 
@@ -556,9 +558,13 @@ draw_object (glLabelObject *object,
 
                                 pango_layout_set_text (layout, bstring->str, -1);
 
+                                pango_layout_get_size (layout, &iw, &ih);
+                                layout_width = (gdouble)iw / (gdouble)PANGO_SCALE;
+
+                                x_offset = layout_width / 2.0;
                                 y_offset = 0.2 * bstring->fsize;
 
-                                cairo_move_to (cr, bstring->x, bstring->y-y_offset);
+                                cairo_move_to (cr, (bstring->x - x_offset), (bstring->y - y_offset));
                                 pango_cairo_show_layout (cr, layout);
 
                                 g_object_unref (layout);