Fix retrieving clipping box after changing wxGCDC coordinates (MSW, GTK)

Member data containing clipping box have to be updated not only when the clipping region is explicitly changed by SetClippingRegion()/DestroyClippingRegion() but also when existing wxGraphicsContext is associated with wxGCDC using SetGraphicsContext() or when wxGCDC coordinates are transformed with SetDeviceOrigin(), SetLogicalOrigin(), SetUserScale() or SetLogicalScale().
When any of these functions is called then clipping box data are marked as invalid and retrieved from underlying graphics context using wxGraphicsContext::GetClipBox() at nearest call to GetClippingBox().

See #17646.

docs/changes.txt

@@ -100,6 +100,7 @@ All (GUI):
 - Add wxSYS_CARET_{ON,OFF,TIMEOUT}_MSEC system settings (brawer).
 - Add wxGraphicsContext::GetClipBox().
 - Fix wxGCDC::Clear() for rotated graphics context.
+- Fix wxGCDC::GetClippingBox() for transformed wxDC (MSW, GTK+).
 
 wxGTK:
 

include/wx/dcgraph.h

@@ -185,6 +185,8 @@ public:
     virtual void DoSetDeviceClippingRegion(const wxRegion& region) wxOVERRIDE;
     virtual void DoSetClippingRegion(wxCoord x, wxCoord y,
         wxCoord width, wxCoord height) wxOVERRIDE;
+    virtual void DoGetClippingBox(wxCoord *x, wxCoord *y,
+                                  wxCoord *w, wxCoord *h) const wxOVERRIDE;
 
     virtual void DoGetTextExtent(const wxString& string,
         wxCoord *x, wxCoord *y,
@@ -198,6 +200,9 @@ public:
     virtual wxRect MSWApplyGDIPlusTransform(const wxRect& r) const;
 #endif // __WXMSW__
 
+    // update the internal clip box variables
+    void UpdateClipBox();
+
 protected:
     // unused int parameter distinguishes this version, which does not create a
     // wxGraphicsContext, in the expectation that the derived class will do it
@@ -212,6 +217,8 @@ protected:
 
     wxGraphicsContext* m_graphicContext;
 
+    bool m_isClipBoxValid;
+
 private:
     void Init(wxGraphicsContext*);
 

src/common/dcgraph.cpp

@@ -191,6 +191,8 @@ void wxGCDCImpl::Init(wxGraphicsContext* ctx)
     m_font = *wxNORMAL_FONT;
     m_brush = *wxWHITE_BRUSH;
 
+    m_isClipBoxValid = false;
+
     m_graphicContext = NULL;
     if (ctx)
         SetGraphicsContext(ctx);
@@ -275,6 +277,51 @@ void wxGCDCImpl::Flush()
     m_graphicContext->Flush();
 }
 
+void wxGCDCImpl::UpdateClipBox()
+{
+    double x, y, w, h;
+    m_graphicContext->GetClipBox(&x, &y, &w, &h);
+
+    m_clipX1 = wxRound(x);
+    m_clipY1 = wxRound(y);
+    m_clipX2 = wxRound(x+w);
+    m_clipY2 = wxRound(y+h);
+    m_isClipBoxValid = true;
+}
+
+void wxGCDCImpl::DoGetClippingBox(wxCoord *x, wxCoord *y, wxCoord *w, wxCoord *h) const
+{
+    wxCHECK_RET( IsOk(), wxS("wxGCDC::DoGetClippingRegion - invalid GC") );
+#ifdef __WXOSX__
+    // This is a legacy implementation which doesn't
+    // return proper values if graphics context coordinates
+    // were transformed after the call to SetClippingRegion().
+    // TODO: Check wxMacCoreGraphics::GetClipBox()
+    // and switch to the code used by other ports (below).
+    wxDCImpl::DoGetClippingBox(x, y, w, h);
+#else
+    // Check if we should retrieve the clipping region possibly not set
+    // by SetClippingRegion() but modified by application: this can
+    // happen when we're associated with an existing graphics context using
+    // SetGraphicsContext() or when wxGCDC logical coordinates are transformed
+    // with SetDeviceOrigin(), SetLogicalOrigin(), SetUserScale(), SetLogicalScale().
+    if ( !m_isClipBoxValid )
+    {
+        wxGCDCImpl *self = wxConstCast(this, wxGCDCImpl);
+        self->UpdateClipBox();
+    }
+
+    if ( x )
+        *x = m_clipX1;
+    if ( y )
+        *y = m_clipY1;
+    if ( w )
+        *w = m_clipX2 - m_clipX1;
+    if ( h )
+        *h = m_clipY2 - m_clipY1;
+#endif // __WXOSX__ / !__WXOSX__
+}
+
 void wxGCDCImpl::DoSetClippingRegion( wxCoord x, wxCoord y, wxCoord w, wxCoord h )
 {
     wxCHECK_RET( IsOk(), wxT("wxGCDC(cg)::DoSetClippingRegion - invalid DC") );
@@ -295,7 +342,16 @@ void wxGCDCImpl::DoSetClippingRegion( wxCoord x, wxCoord y, wxCoord w, wxCoord h
     }
     m_graphicContext->Clip( x, y, w, h );
 
+#ifdef __WXOSX__
+    // This is a legacy implementation which has to be used
+    // because wxMacCoreGraphics::GetClipBox() is not yet tested.
+    // TODO: Check wxMacCoreGraphics::GetClipBox()
+    // and switch to the code used by other ports (below).
     wxDCImpl::DoSetClippingRegion(x, y, w, h);
+#else
+    m_clipping = true;
+    UpdateClipBox();
+#endif // __WXOSX__ / !__WXOSX__
 }
 
 void wxGCDCImpl::DoSetDeviceClippingRegion( const wxRegion &region )
@@ -309,12 +365,15 @@ void wxGCDCImpl::DoSetDeviceClippingRegion( const wxRegion &region )
     // (only offset of the origin is taken into account,
     // but e.g. scale is not).
     // Solution with full conversion doesn't seem to work under WXOSX.
-    // TODO: check wxMacCoreGraphics
+    // TODO: Check wxMacCoreGraphics::Clip() and GetClipBox()
+    // and switch to the code used by other renderers (below).
     wxRegion logRegion(region);
 
     logRegion.Offset(DeviceToLogicalX(0), DeviceToLogicalY(0));
     m_graphicContext->Clip(logRegion);
     wxRect newRegion = logRegion.GetBox();
+    wxDCImpl::DoSetClippingRegion(newRegion.GetLeft(), newRegion.GetTop(),
+                                  newRegion.GetWidth(), newRegion.GetHeight());
 #else
     // Because graphics context works with logical coordinates
     // and clipping region is given in device coordinates
@@ -334,49 +393,9 @@ void wxGCDCImpl::DoSetDeviceClippingRegion( const wxRegion &region )
     // Restore original transformation settings.
     m_graphicContext->SetTransform(currTransform);
 
-    // Convert bounding box of the region to logical coordinates
-    // for further use.
-    wxRect newRegion = region.GetBox();
-    wxPoint logPos = wxPoint(DeviceToLogicalX(newRegion.GetLeft()),
-                             DeviceToLogicalY(newRegion.GetTop()));
-    wxSize logSize = wxSize(DeviceToLogicalXRel(newRegion.GetWidth()),
-                            DeviceToLogicalYRel(newRegion.GetHeight()));
-    newRegion.SetPosition(logPos);
-    newRegion.SetSize(logSize);
+    m_clipping = true;
+    UpdateClipBox();
 #endif // __WXOSX__ / !__WXOSX__
-
-    wxRect clipRegion;
-    if ( m_clipping )
-    {
-        // New clipping box is an intersection
-        // of required clipping box and the current one.
-        wxRect curRegion(m_clipX1, m_clipY1, m_clipX2 - m_clipX1, m_clipY2 - m_clipY1);
-        clipRegion = curRegion.Intersect(newRegion);
-    }
-    else
-    {
-        // Effective clipping box is an intersection
-        // of required clipping box and DC surface.
-        int dcWidth, dcHeight;
-        DoGetSize(&dcWidth, &dcHeight);
-        wxRect dcRect(DeviceToLogicalX(0), DeviceToLogicalY(0),
-                      DeviceToLogicalXRel(dcWidth), DeviceToLogicalYRel(dcHeight));
-        clipRegion = dcRect.Intersect(newRegion);
-
-        m_clipping = true;
-    }
-
-    if ( clipRegion.IsEmpty() )
-    {
-        m_clipX1 = m_clipY1 = m_clipX2 = m_clipY2 = 0;
-    }
-    else
-    {
-        m_clipX1 = clipRegion.GetLeft();
-        m_clipY1 = clipRegion.GetTop();
-        m_clipX2 = clipRegion.GetRight() + 1;
-        m_clipY2 = clipRegion.GetBottom() + 1;
-    }
 }
 
 void wxGCDCImpl::DestroyClippingRegion()
@@ -392,6 +411,7 @@ void wxGCDCImpl::DestroyClippingRegion()
     m_graphicContext->SetBrush( m_brush );
 
     ResetClipping();
+    m_isClipBoxValid = false;
 }
 
 void wxGCDCImpl::DoGetSizeMM( int* width, int* height ) const
@@ -452,6 +472,7 @@ void wxGCDCImpl::ComputeScaleAndOrigin()
 
         m_graphicContext->SetTransform( m_matrixOriginal );
         m_graphicContext->ConcatTransform( m_matrixCurrent );
+        m_isClipBoxValid = false;
     }
 }