Check for NULL before dereferencing

[wxWidgets.git] / src / msw / dcmemory.cpp

diff --git a/src/msw/dcmemory.cpp b/src/msw/dcmemory.cpp
index f79d33b26eb8bc25392064b5aa6c78fd639c8b82..744f2ae65a3c46dd335ca597a6d719713d508258 100644 (file)
--- a/src/msw/dcmemory.cpp
+++ b/src/msw/dcmemory.cpp
@@ -41,7 +41,7 @@
 // wxWin macros
 // ----------------------------------------------------------------------------
 
-    IMPLEMENT_DYNAMIC_CLASS(wxMemoryDC, wxDC)
+IMPLEMENT_DYNAMIC_CLASS(wxMemoryDC, wxDC)
 
 // ============================================================================
 // implementation
@@ -53,37 +53,47 @@
 
 wxMemoryDC::wxMemoryDC()
 {
-    m_hDC = (WXHDC) ::CreateCompatibleDC((HDC) NULL);
-    m_ok = (m_hDC != 0);
-    m_bOwnsDC = TRUE;
-
-    SetBrush(*wxWHITE_BRUSH);
-    SetPen(*wxBLACK_PEN);
+    CreateCompatible(NULL);
 
-    // the background mode is only used for text background and is set in
-    // DrawText() to OPAQUE as required, otherwise always TRANSPARENT
-    ::SetBkMode( GetHdc(), TRANSPARENT );
+    Init();
 }
 
-wxMemoryDC::wxMemoryDC(wxDC *old_dc)
+wxMemoryDC::wxMemoryDC(wxDC *dc)
 {
-    old_dc->BeginDrawing();
+    wxCHECK_RET( dc, _T("NULL dc in wxMemoryDC ctor") );
 
-    m_hDC = (WXHDC) ::CreateCompatibleDC(GetHdcOf(*old_dc));
-    m_ok = (m_hDC != 0);
+    dc->BeginDrawing();
 
-    old_dc->EndDrawing();
+    CreateCompatible(dc);
 
-    SetBrush(*wxWHITE_BRUSH);
-    SetPen(*wxBLACK_PEN);
+    dc->EndDrawing();
 
-    // the background mode is only used for text background and is set in
-    // DrawText() to OPAQUE as required, otherwise always TRANSPARENT
-    ::SetBkMode( GetHdc(), TRANSPARENT );
+    Init();
 }
 
-wxMemoryDC::~wxMemoryDC()
+void wxMemoryDC::Init()
 {
+    if ( m_ok )
+    {
+        SetBrush(*wxWHITE_BRUSH);
+        SetPen(*wxBLACK_PEN);
+
+        // the background mode is only used for text background and is set in
+        // DrawText() to OPAQUE as required, otherwise always TRANSPARENT
+        ::SetBkMode( GetHdc(), TRANSPARENT );
+    }
+}
+
+bool wxMemoryDC::CreateCompatible(wxDC *dc)
+{
+    m_hDC = (WXHDC)::CreateCompatibleDC(dc ? GetHdcOf(*dc) : NULL);
+
+    // as we created the DC, we must delete it in the dtor
+    m_bOwnsDC = TRUE;
+
+    m_ok = m_hDC != 0;
+
+    return m_ok;
 }
 
 void wxMemoryDC::SelectObject(const wxBitmap& bitmap)
@@ -102,8 +112,7 @@ void wxMemoryDC::SelectObject(const wxBitmap& bitmap)
     // check for whether the bitmap is already selected into a device context
     wxCHECK_RET( !bitmap.GetSelectedInto() ||
                  (bitmap.GetSelectedInto() == this),
-                 wxT("Bitmap is selected in another wxMemoryDC, delete the "
-                     "first wxMemoryDC or use SelectObject(NULL)") );
+                 wxT("Bitmap is selected in another wxMemoryDC, delete the first wxMemoryDC or use SelectObject(NULL)") );
 
     m_selectedBitmap = bitmap;
     WXHBITMAP hBmp = m_selectedBitmap.GetHBITMAP();
@@ -115,7 +124,7 @@ void wxMemoryDC::SelectObject(const wxBitmap& bitmap)
 
     if ( !hBmp )
     {
-        wxLogLastError("SelectObject(memDC, bitmap)");
+        wxLogLastError(wxT("SelectObject(memDC, bitmap)"));
 
         wxFAIL_MSG(wxT("Couldn't select a bitmap into wxMemoryDC"));
     }
@@ -139,6 +148,13 @@ void wxMemoryDC::DoGetSize(int *width, int *height) const
     }
 }
 
+// the rest of this file deals with drawing rectangles workaround, disabled by
+// default
+
+#define wxUSE_MEMORY_DC_DRAW_RECTANGLE 0
+
+#if wxUSE_MEMORY_DC_DRAW_RECTANGLE
+
 // For some reason, drawing a rectangle on a memory DC has problems.
 // Use this substitute if we can.
 static void wxDrawRectangle(wxDC& dc, wxCoord x, wxCoord y, wxCoord width, wxCoord height)
@@ -167,11 +183,13 @@ static void wxDrawRectangle(wxDC& dc, wxCoord x, wxCoord y, wxCoord width, wxCoo
     }
 }
 
+#endif // wxUSE_MEMORY_DC_DRAW_RECTANGLE
+
 void wxMemoryDC::DoDrawRectangle(wxCoord x, wxCoord y, wxCoord width, wxCoord height)
 {
     // Set this to 1 to work around an apparent video driver bug
     // (visible with e.g. 70x70 rectangle on a memory DC; see Drawing sample)
-#if 0
+#if wxUSE_MEMORY_DC_DRAW_RECTANGLE
     if (m_brush.Ok() && m_pen.Ok() &&
         (m_brush.GetStyle() == wxSOLID || m_brush.GetStyle() == wxTRANSPARENT) &&
         (m_pen.GetStyle() == wxSOLID || m_pen.GetStyle() == wxTRANSPARENT) &&
@@ -180,11 +198,9 @@ void wxMemoryDC::DoDrawRectangle(wxCoord x, wxCoord y, wxCoord width, wxCoord he
         wxDrawRectangle(* this, x, y, width, height);
     }
     else
+#endif // wxUSE_MEMORY_DC_DRAW_RECTANGLE
     {
         wxDC::DoDrawRectangle(x, y, width, height);
     }
-#else
-    wxDC::DoDrawRectangle(x, y, width, height);
-#endif
 }