tdf#144073 and tdf#147645: use bounds and angle for gradient

Passing an expanded, rotated polygon noticeably modifies the
drawing of the gradient in a slideshow due to moving of the
starting and ending colors far off the edges of the drawing
surface. So try another way and set the angle of the
gradient and draw only the unadjusted bounds.

Change-Id: I95441dfa3215396d5bc7edfa9f985335480b37de
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/155729
Tested-by: Jenkins
Reviewed-by: Patrick Luby <plubius@neooffice.org>

1 files changed, 20 insertions, 34 deletions

diff --git a/canvas/source/vcl/canvashelper_texturefill.cxx b/canvas/source/vcl/canvashelper_texturefill.cxx
index 13778b990b61..5e9399f56841 100644
--- a/canvas/source/vcl/canvashelper_texturefill.cxx
+++ b/canvas/source/vcl/canvashelper_texturefill.cxx
@@ -154,24 +154,17 @@ namespace vclcanvas
             // 2 colors and 2 stops (at 0 and 1) is a linear gradient:
             if( rColors.size() == 2 && rValues.maStops.size() == 2 && rValues.maStops[0] == 0 && rValues.maStops[1] == 1)
             {
-                // tdf#144073: Note that the code below adjusts the gradient area this way.
-                // No, I have no idea why.
-                aLeftTop -= 2.0*nDiagonalLength*aDirection;
-                aLeftBottom -= 2.0*nDiagonalLength*aDirection;
-                aRightTop += 2.0*nDiagonalLength*aDirection;
-                aRightBottom += 2.0*nDiagonalLength*aDirection;
+                // tdf#144073 and tdf#147645: use bounds and angle for gradient
+                // Passing an expanded, rotated polygon noticeably modifies the
+                // drawing of the gradient in a slideshow due to moving of the
+                // starting and ending colors far off the edges of the drawing
+                // surface. So try another way and set the angle of the
+                // gradient and draw only the unadjusted bounds.
                 Gradient vclGradient( css::awt::GradientStyle_LINEAR, rColors[ 0 ], rColors[ 1 ] );
-                ::tools::Polygon aTempPoly( static_cast<sal_uInt16>(5) );
-                aTempPoly[0] = ::Point( ::basegfx::fround( aLeftTop.getX() ),
-                                        ::basegfx::fround( aLeftTop.getY() ) );
-                aTempPoly[1] = ::Point( ::basegfx::fround( aRightTop.getX() ),
-                                        ::basegfx::fround( aRightTop.getY() ) );
-                aTempPoly[2] = ::Point( ::basegfx::fround( aRightBottom.getX() ),
-                                        ::basegfx::fround( aRightBottom.getY() ) );
-                aTempPoly[3] = ::Point( ::basegfx::fround( aLeftBottom.getX() ),
-                                        ::basegfx::fround( aLeftBottom.getY() ) );
-                aTempPoly[4] = aTempPoly[0];
-                rOutDev.DrawGradient( ::tools::PolyPolygon(aTempPoly), vclGradient );
+                double fRotate = atan2( aDirection.getY(), aDirection.getX() );
+                const double nAngleInTenthOfDegrees = 3600.0 - basegfx::rad2deg<10>( fRotate ) + 900.0;
+                vclGradient.SetAngle( Degree10( ::basegfx::fround( nAngleInTenthOfDegrees ) ) );
+                rOutDev.DrawGradient( rBounds, vclGradient );
                 return;
             }
             // 3 colors with first and last being equal and 3 stops (at 0, 0.5 and 1) is an axial gradient:
@@ -179,24 +172,17 @@ namespace vclcanvas
                 && rValues.maStops.size() == 3 && rValues.maStops[0] == 0
                 && rValues.maStops[1] == 0.5 && rValues.maStops[2] == 1)
             {
-                // tdf#144073: Note that the code below adjusts the gradient area this way.
-                // No, I have no idea why.
-                aLeftTop -= 2.0*nDiagonalLength*aDirection;
-                aLeftBottom -= 2.0*nDiagonalLength*aDirection;
-                aRightTop += 2.0*nDiagonalLength*aDirection;
-                aRightBottom += 2.0*nDiagonalLength*aDirection;
+                // tdf#144073 and tdf#147645: use bounds and angle for gradient
+                // Passing an expanded, rotated polygon noticeably modifies the
+                // drawing of the gradient in a slideshow due to moving of the
+                // starting and ending colors far off the edges of the drawing
+                // surface. So try another way and set the angle of the
+                // gradient and draw only the unadjusted bounds.
                 Gradient vclGradient( css::awt::GradientStyle_AXIAL, rColors[ 1 ], rColors[ 0 ] );
-                ::tools::Polygon aTempPoly( static_cast<sal_uInt16>(5) );
-                aTempPoly[0] = ::Point( ::basegfx::fround( aLeftTop.getX() ),
-                                        ::basegfx::fround( aLeftTop.getY() ) );
-                aTempPoly[1] = ::Point( ::basegfx::fround( aRightTop.getX() ),
-                                        ::basegfx::fround( aRightTop.getY() ) );
-                aTempPoly[2] = ::Point( ::basegfx::fround( aRightBottom.getX() ),
-                                        ::basegfx::fround( aRightBottom.getY() ) );
-                aTempPoly[3] = ::Point( ::basegfx::fround( aLeftBottom.getX() ),
-                                        ::basegfx::fround( aLeftBottom.getY() ) );
-                aTempPoly[4] = aTempPoly[0];
-                rOutDev.DrawGradient( ::tools::PolyPolygon(aTempPoly), vclGradient );
+                double fRotate = atan2( aDirection.getY(), aDirection.getX() );
+                const double nAngleInTenthOfDegrees = 3600.0 - basegfx::rad2deg<10>( fRotate ) + 900.0;
+                vclGradient.SetAngle( Degree10( ::basegfx::fround( nAngleInTenthOfDegrees ) ) );
+                rOutDev.DrawGradient( rBounds, vclGradient );
                 return;
             }