extend vcl backendtest to more backends

At least the KF5/Qt5 VCL plugins passes fine.

Change-Id: I033ddf6ae9cc663729ca459cdc514dc0fa51ddc2

11 files changed, 67 insertions, 34 deletions

diff --git a/vcl/inc/headless/svpgdi.hxx b/vcl/inc/headless/svpgdi.hxx
index 5dc136f6058c..444169009e5e 100644
--- a/vcl/inc/headless/svpgdi.hxx
+++ b/vcl/inc/headless/svpgdi.hxx
@@ -261,6 +261,7 @@ public:
 
     virtual SystemGraphicsData GetGraphicsData() const override;
 
+    virtual OUString getRenderBackendName() const override { return "svp"; }
 
 #if ENABLE_CAIRO_CANVAS
     virtual bool            SupportsCairo() const override;
diff --git a/vcl/inc/opengl/gdiimpl.hxx b/vcl/inc/opengl/gdiimpl.hxx
index 95e3aa261472..2deba40eba53 100644
--- a/vcl/inc/opengl/gdiimpl.hxx
+++ b/vcl/inc/opengl/gdiimpl.hxx
@@ -198,6 +198,8 @@ public:
 
     virtual void freeResources() override;
 
+    virtual OUString getRenderBackendName() const override { return "opengl"; }
+
     const vcl::Region& getClipRegion() const;
     virtual bool setClipRegion( const vcl::Region& ) override;
 
diff --git a/vcl/inc/qt5/Qt5Graphics.hxx b/vcl/inc/qt5/Qt5Graphics.hxx
index a7c7aaa727ac..d11297bf335e 100644
--- a/vcl/inc/qt5/Qt5Graphics.hxx
+++ b/vcl/inc/qt5/Qt5Graphics.hxx
@@ -80,6 +80,7 @@ public:
     virtual SalGraphicsImpl* GetImpl() const override;
     virtual SystemGraphicsData GetGraphicsData() const override;
     virtual bool supportsOperation(OutDevSupportType) const override;
+    virtual OUString getRenderBackendName() const override { return "qt5"; }
 
 #if ENABLE_CAIRO_CANVAS
     virtual bool SupportsCairo() const override;
diff --git a/vcl/inc/qt5/Qt5SvpGraphics.hxx b/vcl/inc/qt5/Qt5SvpGraphics.hxx
index 0c2485f2a7ed..895023033468 100644
--- a/vcl/inc/qt5/Qt5SvpGraphics.hxx
+++ b/vcl/inc/qt5/Qt5SvpGraphics.hxx
@@ -46,6 +46,8 @@ public:
 #endif // ENABLE_CAIRO_CANVAS
 
     virtual void GetResolution(sal_Int32& rDPIX, sal_Int32& rDPIY) override;
+
+    virtual OUString getRenderBackendName() const override { return "qt5svp"; }
 };
 
 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/vcl/inc/quartz/salgdi.h b/vcl/inc/quartz/salgdi.h
index 338878e79529..48ae50e2c68c 100644
--- a/vcl/inc/quartz/salgdi.h
+++ b/vcl/inc/quartz/salgdi.h
@@ -387,6 +387,7 @@ public:
                             GetTextLayout(int nFallbackLevel) override;
     virtual void            DrawTextLayout( const GenericSalLayout& ) override;
     virtual bool            supportsOperation( OutDevSupportType ) const override;
+    virtual OUString getRenderBackendName() const override { return "aqua"; }
 
     virtual SystemGraphicsData
                             GetGraphicsData() const override;
diff --git a/vcl/inc/salgdiimpl.hxx b/vcl/inc/salgdiimpl.hxx
index 2a314ed207c1..432dbdb7ec0d 100644
--- a/vcl/inc/salgdiimpl.hxx
+++ b/vcl/inc/salgdiimpl.hxx
@@ -50,7 +50,7 @@ public:
 
     virtual void freeResources() = 0;
 
-    virtual OUString getRenderBackendName() const { return OUString(); }
+    virtual OUString getRenderBackendName() const = 0;
 
     virtual bool setClipRegion( const vcl::Region& ) = 0;
     //
diff --git a/vcl/inc/unx/genpspgraphics.h b/vcl/inc/unx/genpspgraphics.h
index ed735474d443..b820c43a2772 100644
--- a/vcl/inc/unx/genpspgraphics.h
+++ b/vcl/inc/unx/genpspgraphics.h
@@ -193,6 +193,8 @@ public:
 
     virtual SystemGraphicsData GetGraphicsData() const override;
 
+    virtual OUString getRenderBackendName() const override { return "genpsp"; }
+
 #if ENABLE_CAIRO_CANVAS
     virtual bool            SupportsCairo() const override;
     virtual cairo::SurfaceSharedPtr CreateSurface(const cairo::CairoSurfaceSharedPtr& rSurface) const override;
diff --git a/vcl/inc/unx/gtk/gtkgdi.hxx b/vcl/inc/unx/gtk/gtkgdi.hxx
index cd9cf4c5b562..022a72321873 100644
--- a/vcl/inc/unx/gtk/gtkgdi.hxx
+++ b/vcl/inc/unx/gtk/gtkgdi.hxx
@@ -131,6 +131,8 @@ public:
 
     virtual void GetResolution(sal_Int32& rDPIX, sal_Int32& rDPIY) override;
 
+    virtual OUString getRenderBackendName() const override { return "gtk3svp"; }
+
     GtkStyleContext* createStyleContext(gtk_widget_path_iter_set_object_nameFunc set_object_name, GtkControlPart ePart);
     GtkStyleContext* createNewContext(GtkControlPart ePart, gtk_widget_path_iter_set_object_nameFunc set_object_name);
     GtkStyleContext* createOldContext(GtkControlPart ePart);
@@ -293,6 +295,8 @@ public:
     virtual void            copyBits( const SalTwoRect& rPosAry,
                                       SalGraphics* pSrcGraphics ) override;
 
+    virtual OUString getRenderBackendName() const override { return "gtk3"; }
+
 protected:
 
     std::unique_ptr<GdkX11Pixmap> NWGetPixmapFromScreen( tools::Rectangle srcRect, int nBgColor = 0 );
diff --git a/vcl/qa/cppunit/BackendTest.cxx b/vcl/qa/cppunit/BackendTest.cxx
index 928d7746827b..a36c0faa5568 100644
--- a/vcl/qa/cppunit/BackendTest.cxx
+++ b/vcl/qa/cppunit/BackendTest.cxx
@@ -55,6 +55,22 @@ public:
     // exist and we need to fix them. Consistent behaviour of our backends
     // is of highest priority.
 
+    static bool assertBackendNameNotEmpty(const OUString& name)
+    {
+        // This ensures that all backends return a valid name.
+        assert(!name.isEmpty());
+        return false;
+    }
+
+// Check whether tests should fail depending on which backend is used
+// (not all work). If you want to disable just a specific test
+// for a specific backend, use something like
+// 'if(SHOULD_ASSERT && aOutDevTest.getRenderBackendName() != "skia")'.
+#define SHOULD_ASSERT                                                                              \
+    (assertBackendNameNotEmpty(aOutDevTest.getRenderBackendName())                                 \
+     || aOutDevTest.getRenderBackendName() == "skia"                                               \
+     || aOutDevTest.getRenderBackendName() == "qt5svp")
+
     void testDrawRectWithRectangle()
     {
         vcl::test::OutputDeviceTestRect aOutDevTest;
@@ -62,7 +78,7 @@ public:
         auto eResult = vcl::test::OutputDeviceTestCommon::checkRectangle(aBitmap);
         exportImage("01-01_rectangle_test-rectangle.png", aBitmap);
 
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -73,7 +89,7 @@ public:
         auto eResult = vcl::test::OutputDeviceTestCommon::checkRectangle(aBitmap);
         exportImage("01-02_rectangle_test-pixel.png", aBitmap);
 
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -84,7 +100,7 @@ public:
         auto eResult = vcl::test::OutputDeviceTestCommon::checkRectangle(aBitmap);
         exportImage("01-03_rectangle_test-line.png", aBitmap);
 
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -94,7 +110,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupRectangle(false);
         auto eResult = vcl::test::OutputDeviceTestCommon::checkRectangle(aBitmap);
         exportImage("01-04_rectangle_test-polygon.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -104,7 +120,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupRectangle(false);
         auto eResult = vcl::test::OutputDeviceTestCommon::checkRectangle(aBitmap);
         exportImage("01-05_rectangle_test-polyline.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -114,7 +130,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupRectangle(false);
         auto eResult = vcl::test::OutputDeviceTestCommon::checkRectangle(aBitmap);
         exportImage("01-06_rectangle_test-polyline_b2d.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -124,7 +140,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupRectangle(false);
         auto eResult = vcl::test::OutputDeviceTestCommon::checkRectangle(aBitmap);
         exportImage("01-07_rectangle_test-polypolygon.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -134,7 +150,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupRectangle(false);
         auto eResult = vcl::test::OutputDeviceTestCommon::checkRectangle(aBitmap);
         exportImage("01-08_rectangle_test-polypolygon_b2d.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -144,7 +160,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupRectangle(true);
         auto eResult = vcl::test::OutputDeviceTestCommon::checkRectangleAA(aBitmap);
         exportImage("02-01_rectangle_AA_test-rectangle.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -154,7 +170,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupRectangle(true);
         auto eResult = vcl::test::OutputDeviceTestCommon::checkRectangleAA(aBitmap);
         exportImage("02-02_rectangle_AA_test-pixel.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -164,7 +180,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupRectangle(true);
         auto eResult = vcl::test::OutputDeviceTestCommon::checkRectangleAA(aBitmap);
         exportImage("02-03_rectangle_AA_test-line.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -174,7 +190,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupRectangle(true);
         auto eResult = vcl::test::OutputDeviceTestCommon::checkRectangleAA(aBitmap);
         exportImage("02-04_rectangle_AA_test-polygon.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -184,7 +200,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupRectangle(true);
         auto eResult = vcl::test::OutputDeviceTestCommon::checkRectangleAA(aBitmap);
         exportImage("02-05_rectangle_AA_test-polyline.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -194,7 +210,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupRectangle(true);
         auto eResult = vcl::test::OutputDeviceTestCommon::checkRectangleAA(aBitmap);
         exportImage("02-06_rectangle_AA_test-polyline_b2d.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -204,7 +220,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupRectangle(true);
         auto eResult = vcl::test::OutputDeviceTestCommon::checkRectangleAA(aBitmap);
         exportImage("02-07_rectangle_AA_test-polypolygon.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -214,7 +230,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupRectangle(true);
         auto eResult = vcl::test::OutputDeviceTestCommon::checkRectangleAA(aBitmap);
         exportImage("02-08_rectangle_AA_test-polypolygon_b2d.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -224,7 +240,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupFilledRectangle();
         auto eResult = vcl::test::OutputDeviceTestCommon::checkFilledRectangle(aBitmap);
         exportImage("03-01_filled_rectangle_test-rectangle.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -234,7 +250,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupFilledRectangle();
         auto eResult = vcl::test::OutputDeviceTestCommon::checkFilledRectangle(aBitmap);
         exportImage("03-02_filled_rectangle_test-polygon.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -244,7 +260,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupFilledRectangle();
         auto eResult = vcl::test::OutputDeviceTestCommon::checkFilledRectangle(aBitmap);
         exportImage("03-03_filled_rectangle_test-polypolygon.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -254,7 +270,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupFilledRectangle();
         auto eResult = vcl::test::OutputDeviceTestCommon::checkFilledRectangle(aBitmap);
         exportImage("03-04_filled_rectangle_test-polypolygon_b2d.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -264,7 +280,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupDiamond();
         auto eResult = vcl::test::OutputDeviceTestCommon::checkDiamond(aBitmap);
         exportImage("04-01_diamond_test-polygon.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -274,7 +290,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupDiamond();
         auto eResult = vcl::test::OutputDeviceTestCommon::checkDiamond(aBitmap);
         exportImage("04-02_diamond_test-line.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -284,7 +300,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupDiamond();
         auto eResult = vcl::test::OutputDeviceTestCommon::checkDiamond(aBitmap);
         exportImage("04-03_diamond_test-polyline.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -294,7 +310,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupDiamond();
         auto eResult = vcl::test::OutputDeviceTestCommon::checkDiamond(aBitmap);
         exportImage("04-04_diamond_test-polyline_b2d.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -304,7 +320,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupInvert_NONE();
         auto eResult = vcl::test::OutputDeviceTestCommon::checkInvertRectangle(aBitmap);
         exportImage("05-01_invert_test-rectangle.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -314,7 +330,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupInvert_N50();
         auto eResult = vcl::test::OutputDeviceTestCommon::checkInvertN50Rectangle(aBitmap);
         exportImage("05-02_invert_N50_test-rectangle.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -324,7 +340,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupInvert_TrackFrame();
         auto eResult = vcl::test::OutputDeviceTestCommon::checkInvertTrackFrameRectangle(aBitmap);
         exportImage("05-03_invert_TrackFrame_test-rectangle.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -334,7 +350,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupBezier();
         auto eResult = vcl::test::OutputDeviceTestCommon::checkBezier(aBitmap);
         exportImage("06-01_bezier_test-polyline_b2d.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -344,7 +360,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupAABezier();
         auto eResult = vcl::test::OutputDeviceTestCommon::checkBezier(aBitmap);
         exportImage("07-01_bezier_AA_test-polyline_b2d.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -354,7 +370,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupDrawBitmap();
         exportImage("08-01_bitmap_test.png", aBitmap);
         auto eResult = vcl::test::OutputDeviceTestBitmap::checkTransformedBitmap(aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -364,7 +380,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupDrawTransformedBitmap();
         auto eResult = vcl::test::OutputDeviceTestBitmap::checkTransformedBitmap(aBitmap);
         exportImage("08-02_transformed_bitmap_test.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -374,7 +390,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupDrawBitmapExWithAlpha();
         auto eResult = vcl::test::OutputDeviceTestBitmap::checkBitmapExWithAlpha(aBitmap);
         exportImage("08-03_bitmapex_with_alpha_test.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
@@ -384,7 +400,7 @@ public:
         Bitmap aBitmap = aOutDevTest.setupDrawMask();
         auto eResult = vcl::test::OutputDeviceTestBitmap::checkMask(aBitmap);
         exportImage("08-04_mask_test.png", aBitmap);
-        if (aOutDevTest.getRenderBackendName() == "skia")
+        if (SHOULD_ASSERT)
             CPPUNIT_ASSERT(eResult != vcl::test::TestResult::Failed);
     }
 
diff --git a/vcl/unx/generic/gdi/gdiimpl.hxx b/vcl/unx/generic/gdi/gdiimpl.hxx
index d40c31692ea9..6660e191342d 100644
--- a/vcl/unx/generic/gdi/gdiimpl.hxx
+++ b/vcl/unx/generic/gdi/gdiimpl.hxx
@@ -112,6 +112,8 @@ public:
 
     virtual ~X11SalGraphicsImpl() override;
 
+    virtual OUString getRenderBackendName() const override { return "gen"; }
+
     virtual bool setClipRegion( const vcl::Region& ) override;
     //
     // get the depth of the device
diff --git a/vcl/win/gdi/gdiimpl.hxx b/vcl/win/gdi/gdiimpl.hxx
index 53fc4224f69d..3b3b1837b930 100644
--- a/vcl/win/gdi/gdiimpl.hxx
+++ b/vcl/win/gdi/gdiimpl.hxx
@@ -70,6 +70,8 @@ public:
 
     virtual void freeResources() override;
 
+    virtual OUString getRenderBackendName() const override { return "gdi"; }
+
     virtual bool setClipRegion( const vcl::Region& ) override;
     //
     // get the depth of the device