Surface device scale convenience overloads

3 files changed, 24 insertions, 0 deletions

diff --git a/cairomm/surface.cc b/cairomm/surface.cc
index 8e7d076..9982625 100644
--- a/cairomm/surface.cc
+++ b/cairomm/surface.cc
@@ -173,6 +173,13 @@ void Surface::get_device_scale(double& x_scale, double& y_scale) const
   cairo_surface_get_device_scale(const_cast<cobject*>(cobj()), &x_scale, &y_scale);
 }
 
+double Surface::get_device_scale() const
+{
+  double x_scale = 1, y_scale = 1;
+  get_device_scale(x_scale, y_scale);
+  return (x_scale + y_scale) / 2;
+}
+
 void Surface::set_fallback_resolution(double x_pixels_per_inch, double y_pixels_per_inch)
 {
   cairo_surface_set_fallback_resolution(cobj(), x_pixels_per_inch, y_pixels_per_inch);
diff --git a/cairomm/surface.h b/cairomm/surface.h
index 5d5d5dc..65d7cea 100644
--- a/cairomm/surface.h
+++ b/cairomm/surface.h
@@ -446,10 +446,22 @@ public:
    */
   void set_device_scale(double x_scale, double y_scale);
 
+  /** Sets x and y scale to the same value.
+   * See set_device_scale(double, double) for details.
+   *
+   * @param scale 	a scale factor in the X and Y direction
+   */
+  inline void set_device_scale(double scale) { set_device_scale(scale, scale); }
+
   /** Returns a previous device scale set by set_device_scale().
    */
   void get_device_scale(double& x_scale, double& y_scale) const;
 
+  /** Returns the x and y average of a previous device scale set by
+   * set_device_scale().
+   */
+  double get_device_scale() const;
+
   /**
    * Set the horizontal and vertical resolution for image fallbacks.
    *
diff --git a/tests/test-surface.cc b/tests/test-surface.cc
index fa78048..152787c 100644
--- a/tests/test-surface.cc
+++ b/tests/test-surface.cc
@@ -98,6 +98,11 @@ BOOST_AUTO_TEST_CASE(test_device_scale)
   surface->get_device_scale(x, y);
   BOOST_CHECK_EQUAL(x, new_x);
   BOOST_CHECK_EQUAL(y, new_y);
+  // average x/y scaling
+  BOOST_CHECK_EQUAL(4.0, surface->get_device_scale());
+  // uniform scaling
+  surface->set_device_scale(2);
+  BOOST_CHECK_EQUAL(2.0, surface->get_device_scale());
 }
 
 BOOST_AUTO_TEST_CASE(test_fallback_resolution)