[gtk-engines] support: Add ge_cairo_transform_for_layout()

[Benjamin Otte <otte src gnome org>]

commit 7b5801707ce5494f7b244da902c75b22b773f1c3
Author: Benjamin Otte <otte redhat com>
Date:   Thu Aug 12 19:52:24 2010 +0200

    support: Add ge_cairo_transform_for_layout()
    
    This function does the voodoo that is required to get a rotated
    PangoLayout to show up just like the GTK2 drawing code expects it. You
    can use the "rotating label" example in GTK source's tests/testgtk to
    reproduce it.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=626678

 engines/support/cairo-support.c |   32 ++++++++++++++++++++++++++++++++
 engines/support/cairo-support.h |    2 ++
 2 files changed, 34 insertions(+), 0 deletions(-)
---
diff --git a/engines/support/cairo-support.c b/engines/support/cairo-support.c
index d20896b..4344a72 100644
--- a/engines/support/cairo-support.c
+++ b/engines/support/cairo-support.c
@@ -875,6 +875,38 @@ ge_cairo_pattern_destroy(CairoPattern *pattern)
 	}
 }
 
+void
+ge_cairo_transform_for_layout (cairo_t *cr,
+                               PangoLayout *layout,
+                               int x,
+                               int y)
+{
+        const PangoMatrix *matrix;
+
+        matrix = pango_context_get_matrix (pango_layout_get_context (layout));
+        if (matrix)
+        {
+                cairo_matrix_t cairo_matrix;
+                PangoRectangle rect;
+                
+                cairo_matrix_init (&cairo_matrix,
+                                   matrix->xx, matrix->yx,
+                                   matrix->xy, matrix->yy,
+                                   matrix->x0, matrix->y0);
+
+                pango_layout_get_extents (layout, NULL, &rect);
+                pango_matrix_transform_rectangle (matrix, &rect);
+                pango_extents_to_pixels (&rect, NULL);
+                                                    
+                cairo_matrix.x0 += x - rect.x;
+                cairo_matrix.y0 += y - rect.y;
+
+                cairo_set_matrix (cr, &cairo_matrix);
+        }
+        else
+                cairo_translate (cr, x, y);
+}
+
 /* 
  * The following function will be called by GTK+ when the module
  * is loaded and checks to see if we are compatible with the
diff --git a/engines/support/cairo-support.h b/engines/support/cairo-support.h
index 60cce1d..4e15c40 100644
--- a/engines/support/cairo-support.h
+++ b/engines/support/cairo-support.h
@@ -147,3 +147,5 @@ GE_INTERNAL CairoPattern *ge_cairo_pixbuf_pattern(GdkPixbuf *pixbuf);
 GE_INTERNAL CairoPattern *ge_cairo_pixmap_pattern(GdkPixmap *pixmap);
 GE_INTERNAL CairoPattern *ge_cairo_linear_shade_gradient_pattern(CairoColor *base, gdouble shade1, gdouble shade2, gboolean vertical);
 GE_INTERNAL void ge_cairo_pattern_destroy(CairoPattern *pattern);
+
+GE_INTERNAL void ge_cairo_transform_for_layout (cairo_t *cr, PangoLayout *layout, int x, int y);