vcl: Improve precision and performance of clipping when region is a RegionBand

Change-Id: I7a481ba86d03b0eb8f4b456e38cfa89b6cbc209d

vcl/inc/openglgdiimpl.hxx

@@ -24,6 +24,7 @@
 #include <vcl/dllapi.h>
 
 #include "opengl/texture.hxx"
+#include "regionband.hxx"
 
 #include <tools/poly.hxx>
 #include <vcl/opengl/OpenGLContext.hxx>
@@ -125,6 +126,7 @@ public:
     void DrawRect( const Rectangle& rRect );
     void DrawPolygon( sal_uInt32 nPoints, const SalPoint* pPtAry );
     void DrawPolyPolygon( const basegfx::B2DPolyPolygon& rPolyPolygon );
+    void DrawRegionBand( const RegionBand& rRegion );
     void DrawTextureRect( OpenGLTexture& rTexture, const SalTwoRect& rPosAry, bool bInverted = false );
     void DrawTexture( OpenGLTexture& rTexture, const SalTwoRect& rPosAry, bool bInverted = false );
     void DrawTransformedTexture( OpenGLTexture& rTexture, OpenGLTexture& rMask, const basegfx::B2DPoint& rNull, const basegfx::B2DPoint& rX, const basegfx::B2DPoint& rY );

vcl/opengl/gdiimpl.cxx

@@ -247,7 +247,10 @@ void OpenGLSalGraphicsImpl::ImplSetClipBit( const vcl::Region& rClip, GLuint nMa
 
     glClear( GL_STENCIL_BUFFER_BIT );
     BeginSolid( MAKE_SALCOLOR( 0xFF, 0xFF, 0xFF ) );
-    DrawPolyPolygon( rClip.GetAsB2DPolyPolygon() );
+    if( rClip.getRegionBand() )
+        DrawRegionBand( *rClip.getRegionBand() );
+    else
+        DrawPolyPolygon( rClip.GetAsB2DPolyPolygon() );
     EndSolid();
 
     glColorMask( GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE );
@@ -793,6 +796,41 @@ void OpenGLSalGraphicsImpl::DrawPolyPolygon( const basegfx::B2DPolyPolygon& rPol
     CHECK_GL_ERROR();
 }
 
+void OpenGLSalGraphicsImpl::DrawRegionBand( const RegionBand& rRegion )
+{
+    RectangleVector aRects;
+    std::vector<GLfloat> aVertices;
+    rRegion.GetRegionRectangles( aRects );
+
+    if( aRects.empty() )
+        return;
+
+#define ADD_VERTICE(pt) \
+    aVertices.push_back( 2 * pt.X() / GetWidth() - 1.0 ); \
+    aVertices.push_back( 1.0 - (2 * pt.Y() / GetHeight()) );
+
+    for( size_t i = 0; i < aRects.size(); ++i )
+    {
+        aRects[i].Bottom() += 1;
+        aRects[i].Right() += 1;
+        ADD_VERTICE( aRects[i].TopLeft() );
+        ADD_VERTICE( aRects[i].TopRight() );
+        ADD_VERTICE( aRects[i].BottomLeft() );
+        ADD_VERTICE( aRects[i].BottomLeft() );
+        ADD_VERTICE( aRects[i].TopRight() );
+        ADD_VERTICE( aRects[i].BottomRight() );
+    }
+
+#undef ADD_VERTICE
+
+    glEnableVertexAttribArray( GL_ATTRIB_POS );
+    glVertexAttribPointer( GL_ATTRIB_POS, 2, GL_FLOAT, GL_FALSE, 0, &aVertices[0] );
+    glDrawArrays( GL_TRIANGLES, 0, aVertices.size() / 2 );
+    glDisableVertexAttribArray( GL_ATTRIB_POS );
+
+    CHECK_GL_ERROR();
+}
+
 void OpenGLSalGraphicsImpl::DrawTextureRect( OpenGLTexture& rTexture, const SalTwoRect& rPosAry, bool bInverted )
 {
     GLfloat aTexCoord[8];