2 files changed, 29 insertions, 10 deletions
diff --git a/src/display/nr-filter.cpp b/src/display/nr-filter.cpp
index 73a3df415..47b05d0b8 100644
--- a/src/display/nr-filter.cpp
+++ b/src/display/nr-filter.cpp
@@ -406,27 +406,46 @@ void Filter::clear_primitives()
     _primitive_count = 0;
 }
 
-void Filter::set_x(SVGLength &length)
+void Filter::set_x(SVGLength const &length)
 { 
   if (length._set)
       _region_x = length;
 }
-void Filter::set_y(SVGLength &length)
+void Filter::set_y(SVGLength const &length)
 {
   if (length._set)
       _region_y = length;
 }
-void Filter::set_width(SVGLength &length)
+void Filter::set_width(SVGLength const &length)
 {
   if (length._set)
       _region_width = length;
 }
-void Filter::set_height(SVGLength &length)
+void Filter::set_height(SVGLength const &length)
 { 
   if (length._set)
       _region_height = length;
 }
 
+void Filter::set_resolution(double const pixels) {
+    if (pixels > 0) {
+        _x_pixels = pixels;
+        _y_pixels = pixels;
+    }
+}
+
+void Filter::set_resolution(double const x_pixels, double const y_pixels) {
+    if (x_pixels >= 0 && y_pixels >= 0) {
+        _x_pixels = x_pixels;
+        _y_pixels = y_pixels;
+    }
+}
+
+void Filter::reset_resolution() {
+    _x_pixels = -1;
+    _y_pixels = -1;
+}
+
 } /* namespace NR */
 
 /*
diff --git a/src/display/nr-filter.h b/src/display/nr-filter.h
index baf23886e..835266e73 100644
--- a/src/display/nr-filter.h
+++ b/src/display/nr-filter.h
@@ -77,10 +77,10 @@ public:
      */
     void set_output(int slot);
 
-    void set_x(SVGLength &lenght);
-    void set_y(SVGLength &length);
-    void set_width(SVGLength &length);
-    void set_height(SVGLength &length);
+    void set_x(SVGLength const &lenght);
+    void set_y(SVGLength const &length);
+    void set_width(SVGLength const &length);
+    void set_height(SVGLength const &length);
 
     /**
      * Sets the filter effects region.
@@ -105,7 +105,7 @@ public:
      * resolution is determined automatically. If x_pixels is less than zero,
      * calling this function results in no changes to filter state.
      */
-    void set_resolution(double x_pixels);
+    void set_resolution(double const x_pixels);
 
     /**
      * Sets the width and height of intermediate images in pixels. If not set,
@@ -113,7 +113,7 @@ public:
      * less than zero, calling this function results in no changes to filter
      * state.
      */
-    void set_resolution(double x_pixels, double y_pixels);
+    void set_resolution(double const x_pixels, double const y_pixels);
 
     /**
      * Resets the filter resolution to its default value, i.e. automatically