The scope of tests corresponds to the scope of existing wxDC/wxGCDC tests. Additionally, newly introduced wxGraphicsContext::GetClipBox() function is tested too.
1. Under GTK+ 3 wxDC is implemented as wxGCDC (with underlying Cairo renderer) and hence there is no need to test wxDC individually.
2. wxRegion is implemented under GTK+ 2 using GdkRegion but under GTK+ 3 it is implemented using cairo_region_t so some region attributes can be slightly different in some circumstances for both ports. This happens e.g. for non-rectangular regions which can have slightly different clip extents for GTK+ 2 and 3. We have to take this into account in the tests of non-rectangular clipping region and accept that actual clipping box position can differ of few pixels from expected position (so comparing clipping box positions shouldn't be exact but with some error tolerance).
Some coordinates of clipping regions given in device coordinates has to be slightly modified to avoid rounding errors in conversions from device to logical coordinates.
Tests of setting clipping region(s) with wxDC::SetDeviceClippingRegion() for transformed wxDC/wxGCDC (with changed device origin, logical origin and scale and with various renderers for wxGCDC) to check if all transformations are taken into account in the clipping box calculations.
See #17596
In these tests clipping region is set for transformed wxDC/wxGCDC (with changed device origin, logical origin and scale) to check if all these transformations are taken into account in the clipping box calculations.
Flushing native Direct2D renderer (invoking wxGCDC::Flush() -> wxGraphicsContext::Flush() -> ID2D1RenderTarget::Flush()) is apparently not enough to update underlying DC (with selected in bitmap) and therefore we have to destroy the renderer (which in turn invokes ID2D1RenderTarget::EndDraw()) to do so.
1. Added checking if actual drawing output is really clipped at the edge of the clipping box.
2. Added tests for wxGCDC with GDI+, Direct2D, Cairo renderers under wxMSW.
3. Added new test to check calculations for bounding box set entirely outside DC area.
