support generic flag for pixel offsetting, see #11853

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67502 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/graphics.h

@@ -643,6 +643,13 @@ public:
     // helper to determine if a 0.5 offset should be applied for the drawing operation
     virtual bool ShouldOffset() const { return false; }
     
+    // indicates whether the context should try to offset for pixel boundaries, this only makes sense on 
+    // bitmap devices like screen, by default this is turned off
+    virtual void EnableOffset(bool enable = true);
+    
+    void DisableOffset() { EnableOffset(false); }
+    bool OffsetEnabled() { return m_enableOffset; }
+    
 protected:
     // These fields must be initialized in the derived class ctors.
     wxDouble m_width,
@@ -653,6 +660,7 @@ protected:
     wxGraphicsFont m_font;
     wxAntialiasMode m_antialias;
     wxCompositionMode m_composition;
+    bool m_enableOffset;
 
 protected:
     // implementations of overloaded public functions: we use different names

src/common/graphcmn.cpp

@@ -534,7 +534,8 @@ IMPLEMENT_ABSTRACT_CLASS(wxGraphicsContext, wxObject)
 wxGraphicsContext::wxGraphicsContext(wxGraphicsRenderer* renderer) :
     wxGraphicsObject(renderer),
       m_antialias(wxANTIALIAS_DEFAULT),
-      m_composition(wxCOMPOSITION_OVER)
+      m_composition(wxCOMPOSITION_OVER),
+      m_enableOffset(false)
 {
 }
 
@@ -564,6 +565,11 @@ void wxGraphicsContext::Flush()
 {
 }
 
+void wxGraphicsContext::EnableOffset(bool enable) 
+{ 
+    m_enableOffset = enable; 
+}
+
 #if 0
 void wxGraphicsContext::SetAlpha( wxDouble WXUNUSED(alpha) )
 {