fixing overrelease and out-of-bounds write, fixes #13725

[wxWidgets.git] / src / common / dcbufcmn.cpp

diff --git a/src/common/dcbufcmn.cpp b/src/common/dcbufcmn.cpp
index d76a8a545e81138b7edf648f4367f8ef954544a5..d625c72f8fd288e7928d9cb1e5275410928b3619 100644 (file)
--- a/src/common/dcbufcmn.cpp
+++ b/src/common/dcbufcmn.cpp
@@ -24,17 +24,143 @@
     #pragma hdrstop
 #endif
 
+#include "wx/dcbuffer.h"
+
 #ifndef WX_PRECOMP
+    #include "wx/module.h"
 #endif
 
-#include "wx/dcbuffer.h"
+// ============================================================================
+// implementation
+// ============================================================================
+
+IMPLEMENT_DYNAMIC_CLASS(wxBufferedDC,wxMemoryDC)
+IMPLEMENT_ABSTRACT_CLASS(wxBufferedPaintDC,wxBufferedDC)
+
+// ----------------------------------------------------------------------------
+// wxSharedDCBufferManager: helper class maintaining backing store bitmap
+// ----------------------------------------------------------------------------
+
+class wxSharedDCBufferManager : public wxModule
+{
+public:
+    wxSharedDCBufferManager() { }
+
+    virtual bool OnInit() { return true; }
+    virtual void OnExit() { wxDELETE(ms_buffer); }
+
+    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() )
+        {
+            delete ms_buffer;
+
+            // we must always return a valid bitmap but creating a bitmap of
+            // size 0 would fail, so create a 1*1 bitmap in this case
+            if ( !w )
+                w = 1;
+            if ( !h )
+                h = 1;
+
+            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)
 
 // ============================================================================
-// implementation
+// wxBufferedDC
 // ============================================================================
 
-// This file is intentionally empty.  It has not been removed in case another
-// wxBufferedDC reimplementation is attempted in the near future.  If not then
-// this file can be removed and the bakefiles updated.
+void wxBufferedDC::UseBuffer(wxCoord w, wxCoord h)
+{
+    wxCHECK_RET( w >= -1 && h >= -1, "Invalid buffer size" );
+
+    if ( !m_buffer || !m_buffer->IsOk() )
+    {
+        if ( w == -1 || h == -1 )
+            m_dc->GetSize(&w, &h);
+
+        m_buffer = wxSharedDCBufferManager::GetBuffer(w, h);
+        m_style |= wxBUFFER_USES_SHARED_BUFFER;
+        m_area.Set(w,h);
+    }
+    else
+        m_area = m_buffer->GetSize();
+
+    SelectObject(*m_buffer);
+
+    // now that the DC is valid we can inherit the attributes (fonts, colours,
+    // layout direction, ...) from the original DC
+    if ( m_dc && m_dc->IsOk() )
+        CopyAttributes(*m_dc);
+}
+
+void wxBufferedDC::UnMask()
+{
+    wxCHECK_RET( m_dc, wxT("no underlying wxDC?") );
+    wxASSERT_MSG( m_buffer && m_buffer->IsOk(), wxT("invalid backing store") );
+
+    wxCoord x = 0,
+            y = 0;
+
+    // Ensure the scale matches the device
+    SetUserScale(1.0, 1.0);
+
+    if ( m_style & wxBUFFER_CLIENT_AREA )
+        GetDeviceOrigin(&x, &y);
+
+    // It's possible that the buffer may be bigger than the area that needs to
+    // be drawn (the client size of the window is smaller than the bitmap, or
+    // a shared bitmap has been reused for a smaller area, etc.) so avoid
+    // blitting too much if possible, but only use the real DC size if the
+    // wxBUFFER_VIRTUAL_AREA style is not set.
+    int width = m_area.GetWidth(),
+        height = m_area.GetHeight();
+
+    if (! m_style & wxBUFFER_VIRTUAL_AREA)
+    {
+        int widthDC,
+            heightDC;
+        m_dc->GetSize(&widthDC, &heightDC);
+        width = wxMin(width, widthDC);
+        height = wxMin(height, heightDC);
+    }
+
+    m_dc->Blit(0, 0, width, height, this, -x, -y);
+    m_dc = NULL;
 
+    if ( m_style & wxBUFFER_USES_SHARED_BUFFER )
+        wxSharedDCBufferManager::ReleaseBuffer(m_buffer);
+}