allow using multiple wxBufferedDCs at once (patch 1589441)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@44736 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/dcbuffer.h

@@ -37,6 +37,10 @@
 // does not prepare the window DC
 #define wxBUFFER_CLIENT_AREA        0x02
 
+// Set when not using specific buffer bitmap. Note that this
+// is private style and not returned by GetStyle.
+#define wxBUFFER_USES_SHARED_BUFFER 0x04
+
 class WXDLLEXPORT wxBufferedDC : public wxMemoryDC
 {
 public:
@@ -98,25 +102,11 @@ public:
     // Usually called in the dtor or by the dtor of derived classes if the
     // BufferedDC must blit before the derived class (which may own the dc it's
     // blitting to) is destroyed.
-    void UnMask()
-    {
-        wxCHECK_RET( m_dc, _T("no underlying wxDC?") );
-        wxASSERT_MSG( m_buffer && m_buffer->IsOk(), _T("invalid backing store") );
-
-        wxCoord x = 0,
-                y = 0;
-
-        if ( m_style & wxBUFFER_CLIENT_AREA )
-            GetDeviceOrigin(&x, &y);
-
-        m_dc->Blit(0, 0, m_buffer->GetWidth(), m_buffer->GetHeight(),
-                   this, -x, -y );
-        m_dc = NULL;
-    }
+    void UnMask();
 
     // Set and get the style
     void SetStyle(int style) { m_style = style; }
-    int GetStyle() const { return m_style; }
+    int GetStyle() const { return m_style & ~wxBUFFER_USES_SHARED_BUFFER; }
 
 private:
     // common part of Init()s

src/common/dcbufcmn.cpp

@@ -48,6 +48,9 @@ public:
 
     static wxBitmap* GetBuffer(int w, int h)
     {
+        if ( ms_usingSharedBuffer )
+            return new wxBitmap(w, h);
+
         if ( !ms_buffer ||
                 w > ms_buffer->GetWidth() ||
                     h > ms_buffer->GetHeight() )
@@ -55,16 +58,33 @@ public:
             delete ms_buffer;
             ms_buffer = new wxBitmap(w, h);
         }
+
+        ms_usingSharedBuffer = true;
         return ms_buffer;
     }
 
+    static void ReleaseBuffer(wxBitmap* buffer)
+    {
+        if ( buffer == ms_buffer )
+        {
+            wxASSERT_MSG( ms_usingSharedBuffer, wxT("shared buffer already released") );
+            ms_usingSharedBuffer = false;
+        }
+        else
+        {
+            delete buffer;
+        }
+    }
+
 private:
     static wxBitmap *ms_buffer;
+    static bool ms_usingSharedBuffer;
 
     DECLARE_DYNAMIC_CLASS(wxSharedDCBufferManager)
 };
 
 wxBitmap* wxSharedDCBufferManager::ms_buffer = NULL;
+bool wxSharedDCBufferManager::ms_usingSharedBuffer = false;
 
 IMPLEMENT_DYNAMIC_CLASS(wxSharedDCBufferManager, wxModule)
 
@@ -80,8 +100,27 @@ void wxBufferedDC::UseBuffer(wxCoord w, wxCoord h)
             m_dc->GetSize(&w, &h);
 
         m_buffer = wxSharedDCBufferManager::GetBuffer(w, h);
+        m_style |= wxBUFFER_USES_SHARED_BUFFER;
     }
 
     SelectObject(*m_buffer);
 }
 
+void wxBufferedDC::UnMask()
+{
+    wxCHECK_RET( m_dc, _T("no underlying wxDC?") );
+    wxASSERT_MSG( m_buffer && m_buffer->IsOk(), _T("invalid backing store") );
+
+    wxCoord x = 0,
+            y = 0;
+
+    if ( m_style & wxBUFFER_CLIENT_AREA )
+        GetDeviceOrigin(&x, &y);
+
+    m_dc->Blit(0, 0, m_buffer->GetWidth(), m_buffer->GetHeight(),
+               this, -x, -y );
+    m_dc = NULL;
+
+    if ( m_style & wxBUFFER_USES_SHARED_BUFFER )
+        wxSharedDCBufferManager::ReleaseBuffer(m_buffer);
+}