disallow creation of wxDC objects and made wxDC an ABC; use wxDCTemp instead of wxDC in wx code; fixed WinCE bug with deleting a DC which should be released in wxListBox::MSWOnMeasure()

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@36564 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/dc.h

@@ -9,8 +9,8 @@
 // Licence:     wxWindows licence
 /////////////////////////////////////////////////////////////////////////////
 
-#ifndef _WX_DC_H_
-#define _WX_DC_H_
+#ifndef _WX_MSW_DC_H_
+#define _WX_MSW_DC_H_
 
 #include "wx/defs.h"
 
@@ -40,10 +40,12 @@ public:
 };
 #endif
 
+// this is an ABC: use one of the derived classes to create a DC associated
+// with a window, screen, printer and so on
 class WXDLLEXPORT wxDC : public wxDCBase
 {
 public:
-    wxDC();
+    wxDC(WXHDC hDC) { Init(); m_hDC = hDC; }
     ~wxDC();
 
     // implement base class pure virtuals
@@ -138,6 +140,26 @@ public:
 #endif
 
 protected:
+    void Init()
+    {
+        m_canvas = NULL;
+        m_bOwnsDC = false;
+        m_hDC = NULL;
+
+        m_oldBitmap = NULL;
+        m_oldPen = NULL;
+        m_oldBrush = NULL;
+        m_oldFont = NULL;
+
+#if wxUSE_PALETTE
+        m_oldPalette = NULL;
+#endif // wxUSE_PALETTE
+    }
+
+    // create an uninitialized DC: this should be only used by the derived
+    // classes
+    wxDC() { Init(); }
+
     virtual bool DoFloodFill(wxCoord x, wxCoord y, const wxColour& col,
                              int style = wxFLOOD_SURFACE);
 
@@ -186,7 +208,6 @@ protected:
     virtual void DoGetClippingBox(wxCoord *x, wxCoord *y,
                                   wxCoord *w, wxCoord *h) const;
 
-    virtual void DoGetSize(int *width, int *height) const;
     virtual void DoGetSizeMM(int* width, int* height) const;
 
     virtual void DoDrawLines(int n, wxPoint points[],
@@ -216,6 +237,17 @@ protected:
     // common part of DoSetClippingRegion() and DoSetClippingRegionAsRegion()
     void SetClippingHrgn(WXHRGN hrgn);
 
+    // implementation of DoGetSize() for wxScreen/PrinterDC: this simply
+    // returns the size of the entire device this DC is associated with
+    //
+    // notice that we intentionally put it in a separate function instead of
+    // DoGetSize() itself because we want it to remain pure virtual both
+    // because each derived class should take care to define it as needed (this
+    // implementation is not at all always appropriate) and because we want
+    // wxDC to be an ABC to prevent it from being created directly
+    void GetDeviceSize(int *width, int *height) const;
+
+
     // MSW-specific member variables
     // -----------------------------
 
@@ -259,12 +291,29 @@ protected:
 class WXDLLEXPORT wxDCTemp : public wxDC
 {
 public:
-    wxDCTemp(WXHDC hdc) { SetHDC(hdc); }
-    virtual ~wxDCTemp() { SetHDC((WXHDC)NULL); }
+    wxDCTemp(WXHDC hdc) : wxDC(hdc)
+    {
+    }
+
+    virtual ~wxDCTemp()
+    {
+        // prevent base class dtor from freeing it
+        SetHDC((WXHDC)NULL);
+    }
+
+    virtual void DoGetSize(int *w, int *h) const
+    {
+        wxFAIL_MSG( _T("no way to retrieve the size of generic DC") );
+
+        if ( w )
+            *w = 0;
+        if ( h )
+            *h = 0;
+    }
 
 private:
     DECLARE_NO_COPY_CLASS(wxDCTemp)
 };
 
-#endif
-    // _WX_DC_H_
+#endif // _WX_MSW_DC_H_
+