Add wxTransparentColour global pseudo-variable.

Introduce a symbolic name for a fully transparent colour.

See #11897.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@63856 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/changes.txt

@@ -499,6 +499,7 @@ All (GUI):
 - Add "initial selection" parameter to wxGetSingleChoice() (Nikolay Tjushkov).
 - Implement wxDocument::Revert() (troelsk).
 - Allow overriding print preview frame creation in docview (troelsk).
+- Added wxTransparentColour.
 
 GTK:
 

include/wx/colour.h

@@ -43,6 +43,10 @@ class WXDLLIMPEXP_FWD_CORE wxColour;
 const unsigned char wxALPHA_TRANSPARENT = 0;
 const unsigned char wxALPHA_OPAQUE = 0xff;
 
+// a valid but fully transparent colour
+#define wxTransparentColour wxColour(0, 0, 0, wxALPHA_TRANSPARENT)
+#define wxTransparentColor wxTransparentColour
+
 // ----------------------------------------------------------------------------
 // wxVariant support
 // ----------------------------------------------------------------------------
@@ -149,14 +153,14 @@ public:
 
     // manipulation
     // ------------
-    
+
     // These methods are static because they are mostly used
     // within tight loops (where we don't want to instantiate wxColour's)
 
     static void          MakeMono    (unsigned char* r, unsigned char* g, unsigned char* b, bool on);
     static void          MakeDisabled(unsigned char* r, unsigned char* g, unsigned char* b, unsigned char brightness = 255);
     static void          MakeGrey    (unsigned char* r, unsigned char* g, unsigned char* b); // integer version
-    static void          MakeGrey    (unsigned char* r, unsigned char* g, unsigned char* b, 
+    static void          MakeGrey    (unsigned char* r, unsigned char* g, unsigned char* b,
                                       double weight_r, double weight_g, double weight_b); // floating point version
     static unsigned char AlphaBlend  (unsigned char fg, unsigned char bg, double alpha);
     static void          ChangeLightness(unsigned char* r, unsigned char* g, unsigned char* b, int ialpha);

interface/wx/colour.h

@@ -37,6 +37,7 @@
 
     @stdobjects
     - ::wxNullColour - An empty, invalid colour.
+    - ::wxTransparentColour - Valid but fully transparent colour (new in 2.9.1).
     - ::wxBLACK
     - ::wxBLUE
     - ::wxCYAN