diff --git a/src/msw/dc.cpp b/src/msw/dc.cpp index 5079795653..17ffaae9bf 100644 --- a/src/msw/dc.cpp +++ b/src/msw/dc.cpp @@ -1967,11 +1967,39 @@ void wxMSWDCImpl::RealizeScaleAndOrigin() #ifndef __WXWINCE__ ::SetMapMode(GetHdc(), MM_ANISOTROPIC); - int width = DeviceToLogicalXRel(VIEWPORT_EXTENT)*m_signX, - height = DeviceToLogicalYRel(VIEWPORT_EXTENT)*m_signY; + // wxWidgets API assumes that the coordinate space is "infinite" (i.e. only + // limited by 2^32 range of the integer coordinates) but in MSW API we must + // actually specify the extents that we use. So we more or less arbitrarily + // decide to use "base" VIEWPORT_EXTENT and adjust it depending on scale. + // + // To avoid rounding errors we prefer to multiply by the scale if it's > 1 + // and to divide by it if it's < 1. + int devExtX, devExtY, // Viewport, i.e. device space, extents. + logExtX, logExtY; // Window, i.e. logical coordinate space, extents. + if ( m_scaleX >= 1 ) + { + devExtX = VIEWPORT_EXTENT*m_scaleX; + logExtX = m_signX*VIEWPORT_EXTENT; + } + else + { + devExtX = VIEWPORT_EXTENT; + logExtX = m_signX*VIEWPORT_EXTENT/m_scaleX; + } - ::SetViewportExtEx(GetHdc(), VIEWPORT_EXTENT, VIEWPORT_EXTENT, NULL); - ::SetWindowExtEx(GetHdc(), width, height, NULL); + if ( m_scaleY >= 1 ) + { + devExtY = VIEWPORT_EXTENT*m_scaleY; + logExtY = m_signY*VIEWPORT_EXTENT; + } + else + { + devExtY = VIEWPORT_EXTENT; + logExtY = m_signY*VIEWPORT_EXTENT/m_scaleY; + } + + ::SetViewportExtEx(GetHdc(), devExtX, devExtY, NULL); + ::SetWindowExtEx(GetHdc(), logExtX, logExtY, NULL); ::SetViewportOrgEx(GetHdc(), m_deviceOriginX, m_deviceOriginY, NULL); ::SetWindowOrgEx(GetHdc(), m_logicalOriginX, m_logicalOriginY, NULL);