Fix retrieving clipping box after changing wxDC coordinates (MSW)

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 HDC is associated with wxDC using SetHDC() or when wxDC coordinates are transformed with SetDeviceOrigin(), SetLogicalOrigin(), SetUserScale(), SetLogicalScale(), SetTransformMatrix() or ResetTransformMatrix().
When any of these functions is called then clipping box data are marked as invalid and updated using GetClipBox() Win API at nearest call to GetClippingBox().

See #17646.

docs/changes.txt

@@ -124,6 +124,7 @@ wxMSW:
 - Restore dispatching wxThreadEvent while resizing the window broken in 3.1.0.
 - Fix wxGraphicsMatrix::TransformDistance for Direct2D renderer.
 - Fix wxDC::Clear() for rotated DC.
+- Fix wxDC::GetClippingBox() for transformed wxDC.
 
 wxOSX:
 

include/wx/msw/dc.h

@@ -121,8 +121,7 @@ public:
         // return it if asked -- but avoid calling ::GetClipBox() right now as
         // it could be unnecessary wasteful
         m_clipping = true;
-        m_clipX1 =
+        m_isClipBoxValid = false;
-        m_clipX2 = 0;
     }
 
     void* GetHandle() const { return (void*)GetHDC(); }
@@ -164,6 +163,7 @@ protected:
 #if wxUSE_PALETTE
         m_oldPalette = NULL;
 #endif // wxUSE_PALETTE
+        m_isClipBoxValid = false;
     }
 
     // create an uninitialized DC: this should be only used by the derived
@@ -323,6 +323,8 @@ protected:
     static wxObjectList     sm_dcCache;
 #endif
 
+    bool m_isClipBoxValid;
+
     wxDECLARE_CLASS(wxMSWDCImpl);
     wxDECLARE_NO_COPY_CLASS(wxMSWDCImpl);
 };

src/msw/dc.cpp

@@ -579,21 +579,32 @@ void wxMSWDCImpl::UpdateClipBox()
     m_clipY1 = (wxCoord) YDEV2LOG(rect.top);
     m_clipX2 = (wxCoord) XDEV2LOG(rect.right);
     m_clipY2 = (wxCoord) YDEV2LOG(rect.bottom);
+    m_isClipBoxValid = true;
 }
 
 void
 wxMSWDCImpl::DoGetClippingBox(wxCoord *x, wxCoord *y, wxCoord *w, wxCoord *h) const
 {
     // check if we should try to retrieve the clipping region possibly not set
-    // by our SetClippingRegion() but preset by Windows:this can only happen
+    // by our SetClippingRegion() but preset or modified by Windows: this
-    // when we're associated with an existing HDC usign SetHDC(), see there
+    // can happen when we're associated with an existing HDC using SetHDC() or
-    if ( m_clipping && !m_clipX1 && !m_clipX2 )
+    // when wxDC logical coordinates are transformed with SetDeviceOrigin(),
+    // SetLogicalOrigin(), SetUserScale(), SetLogicalScale(),
+    // SetTransformMatrix(), ResetTransformMatrix().
+    if ( !m_isClipBoxValid )
     {
         wxMSWDCImpl *self = wxConstCast(this, wxMSWDCImpl);
         self->UpdateClipBox();
     }
 
-    wxDCImpl::DoGetClippingBox(x, y, w, h);
+    if ( x )
+        *x = m_clipX1;
+    if ( y )
+        *y = m_clipY1;
+    if ( w )
+        *w = m_clipX2 - m_clipX1;
+    if ( h )
+        *h = m_clipY2 - m_clipY1;
 }
 
 // common part of DoSetClippingRegion() and DoSetDeviceClippingRegion()
@@ -679,6 +690,7 @@ void wxMSWDCImpl::DestroyClippingRegion()
     }
 
     wxDCImpl::DestroyClippingRegion();
+    m_isClipBoxValid = false;
 }
 
 // ---------------------------------------------------------------------------
@@ -1868,6 +1880,8 @@ void wxMSWDCImpl::RealizeScaleAndOrigin()
 
     ::SetViewportOrgEx(GetHdc(), m_deviceOriginX, m_deviceOriginY, NULL);
     ::SetWindowOrgEx(GetHdc(), m_logicalOriginX, m_logicalOriginY, NULL);
+
+    m_isClipBoxValid = false;
 }
 
 void wxMSWDCImpl::SetMapMode(wxMappingMode mode)
@@ -1977,6 +1991,8 @@ void wxMSWDCImpl::SetDeviceOrigin(wxCoord x, wxCoord y)
     wxDCImpl::SetDeviceOrigin( x, y );
 
     ::SetViewportOrgEx(GetHdc(), (int)m_deviceOriginX, (int)m_deviceOriginY, NULL);
+
+    m_isClipBoxValid = false;
 }
 
 // ----------------------------------------------------------------------------
@@ -2022,6 +2038,7 @@ bool wxMSWDCImpl::SetTransformMatrix(const wxAffineMatrix2D &matrix)
         return false;
     }
 
+    m_isClipBoxValid = false;
     return true;
 }
 
@@ -2047,6 +2064,7 @@ void wxMSWDCImpl::ResetTransformMatrix()
 {
     ::ModifyWorldTransform(GetHdc(), NULL, MWT_IDENTITY);
     ::SetGraphicsMode(GetHdc(), GM_COMPATIBLE);
+    m_isClipBoxValid = false;
 }
 
 #endif // wxUSE_DC_TRANSFORM_MATRIX