reduce some include dependencies

rtengine/curves.h

@@ -22,12 +22,9 @@
 #include <string>
 #include <vector>
 
-#include <glibmm/ustring.h>
-
 #include "rt_math.h"
 #include "flatcurvetypes.h"
 #include "diagonalcurvetypes.h"
-#include "pipettebuffer.h"
 #include "noncopyable.h"
 #include "LUT.h"
 #include "sleef.h"
@@ -37,6 +34,13 @@
 
 #define CLIPI(a) ((a)>0?((a)<65534?(a):65534):0)
 
+namespace Glib
+{
+
+class ustring;
+
+}
+
 using namespace std;
 
 namespace rtengine
@@ -940,7 +944,7 @@ private:
     float calculateToneCurveContrastValue() const;
 public:
     static void init();
-    void initApplyState(PerceptualToneCurveState & state, Glib::ustring workingSpace) const;
+    void initApplyState(PerceptualToneCurveState & state, const Glib::ustring& workingSpace) const;
     void BatchApply(const size_t start, const size_t end, float *r, float *g, float *b, const PerceptualToneCurveState &state) const;
 };