fdo#74702 New abstract function UsePolyPolygonForComplexGradient()

A new protected abstract function has been introduced only for
complex gradients. As it stands, we currently need to work out if
we should use a PolyPolygon or a Polygon because, as the comments
say:

    // Determine if we output via Polygon or PolyPolygon
    // For all rasteroperations other then Overpaint always use
    // PolyPolygon, as we will get wrong results if we output multiple
    // times on top of each other.
    // Also for printers always use PolyPolygon, as not all printers
    // can print polygons on top of each other.

Interestingly, the next line is either wrong or expressed badly,
because the check uses PolyPolygons when a VirtualDevice is in use:

    // Also virtual devices are excluded, as some drivers are too slow.

Therefore, I've removed that comment as it seems rather misleading.

Change-Id: Ic496284cb2be8e7e2d348eae76aeeec994e1029c
Reviewed-on: https://gerrit.libreoffice.org/8802Reviewed-by: Chris Sherlock <chris.sherlock79@gmail.com>
Tested-by: Chris Sherlock <chris.sherlock79@gmail.com>

include/vcl/outdev.hxx

@@ -805,6 +805,7 @@ protected:
                                                 const Point& rSrcPtPixel, const Size& rSrcSizePixel );
 
     virtual long                ImplGetGradientStepCount( long nMinRect );
+    virtual bool                UsePolyPolygonForComplexGradient() = 0;
 
     /** Transform and draw a bitmap directly
 

include/vcl/print.hxx

@@ -274,6 +274,7 @@ public:
 
 protected:
     long                        ImplGetGradientStepCount( long nMinRect ) SAL_OVERRIDE;
+    virtual bool                UsePolyPolygonForComplexGradient() SAL_OVERRIDE;
     void                        ScaleBitmap ( Bitmap&, SalTwoRect& ) SAL_OVERRIDE { };
 
 public:

include/vcl/virdev.hxx

@@ -140,6 +140,9 @@ public:
 private:
     SAL_DLLPRIVATE void ImplSetReferenceDevice( RefDevMode, sal_Int32 i_nDPIX, sal_Int32 i_nDPIY );
 
+protected:
+    virtual bool                UsePolyPolygonForComplexGradient() SAL_OVERRIDE;
+
 };
 
 #endif // INCLUDED_VCL_VIRDEV_HXX

include/vcl/window.hxx

@@ -579,8 +579,9 @@ protected:
     virtual sal_uInt16 getDefaultAccessibleRole() const;
     virtual OUString getDefaultAccessibleName() const;
 
-    virtual void               CopyAreaFinal( SalTwoRect& aPosAry, sal_uInt32 nFlags) SAL_OVERRIDE;
-    virtual void               ClipToPaintRegion( Rectangle& rDstRect ) SAL_OVERRIDE;
+    virtual void                CopyAreaFinal( SalTwoRect& aPosAry, sal_uInt32 nFlags) SAL_OVERRIDE;
+    virtual void                ClipToPaintRegion( Rectangle& rDstRect ) SAL_OVERRIDE;
+    virtual bool                UsePolyPolygonForComplexGradient() SAL_OVERRIDE;
 
 public:
     bool HasMirroredGraphics() const SAL_OVERRIDE;

vcl/source/gdi/outdev4.cxx

@@ -372,7 +372,6 @@ void OutputDevice::ImplDrawComplexGradient( const Rectangle& rRect,
     // as we will get wrong results if we output multiple times on top of each other.
     // Also for printers always use PolyPolygon, as not all printers
     // can print polygons on top of each other.
-    // Also virtual devices are excluded, as some drivers are too slow.
 
     boost::scoped_ptr<PolyPolygon> pPolyPoly;
     Rectangle       aRect;
@@ -393,7 +392,7 @@ void OutputDevice::ImplDrawComplexGradient( const Rectangle& rRect,
 
     rGradient.GetBoundRect( rRect, aRect, aCenter );
 
-    if( (meRasterOp != ROP_OVERPAINT) || (meOutDevType != OUTDEV_WINDOW) || bMtf )
+    if ( UsePolyPolygonForComplexGradient() || bMtf )
         pPolyPoly.reset(new PolyPolygon( 2 ));
 
     long nMinRect = std::min( aRect.GetWidth(), aRect.GetHeight() );

vcl/source/gdi/print.cxx

@@ -1863,4 +1863,9 @@ void Printer::updatePrinters()
     }
 }
 
+bool Printer::UsePolyPolygonForComplexGradient()
+{
+    return true;
+}
+
 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */

vcl/source/gdi/virdev.cxx

@@ -543,6 +543,11 @@ sal_uInt16 VirtualDevice::GetAlphaBitCount() const
     return 0;
 }
 
+bool VirtualDevice::UsePolyPolygonForComplexGradient()
+{
+    return true;
+}
+
 void VirtualDevice::Compat_ZeroExtleadBug()
 {
     meRefDevMode = (sal_uInt8)meRefDevMode | REFDEV_FORCE_ZERO_EXTLEAD;

vcl/source/window/window.cxx

@@ -9840,4 +9840,12 @@ Selection Window::GetSurroundingTextSelection() const
   return Selection( 0, 0 );
 }
 
+bool Window::UsePolyPolygonForComplexGradient()
+{
+    if ( meRasterOp != ROP_OVERPAINT )
+        return true;
+
+    return false;
+}
+
 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */