scale stroked line properly in cairocanvas

- Line width should be scaled by the scaled vector, not just its X
component (see VclMetafileProcessor2D::getTransformedLineWidth()).
- Lenths of dashes should not be scaled by the scaled line width,
but by the scaling.
Testcase document sd/qa/unit/data/pptx/tdf134053_dashdot.pptx .

Change-Id: I4116f82e91620f5612f5e4e187468508f683b93e
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/115147
Tested-by: Jenkins
Reviewed-by: Luboš Luňák <l.lunak@collabora.com>

1 files changed, 8 insertions, 6 deletions

diff --git a/canvas/source/cairo/cairo_canvashelper.cxx b/canvas/source/cairo/cairo_canvashelper.cxx
index d308961a0865..2711634e9948 100644
--- a/canvas/source/cairo/cairo_canvashelper.cxx
+++ b/canvas/source/cairo/cairo_canvashelper.cxx
@@ -913,10 +913,12 @@ namespace cairocanvas
             useStates( viewState, renderState, true );
 
             cairo_matrix_t aMatrix;
-            double w = strokeAttributes.StrokeWidth, h = 0;
             cairo_get_matrix( mpCairo.get(), &aMatrix );
-            cairo_matrix_transform_distance( &aMatrix, &w, &h );
-            cairo_set_line_width( mpCairo.get(), w );
+            double scaleFactorX = 1;
+            double scaleFactorY = 0;
+            cairo_matrix_transform_distance( &aMatrix, &scaleFactorX, &scaleFactorY );
+            double scaleFactor = basegfx::B2DVector( scaleFactorX, scaleFactorY ).getLength();
+            cairo_set_line_width( mpCairo.get(), strokeAttributes.StrokeWidth * scaleFactor );
 
             cairo_set_miter_limit( mpCairo.get(), strokeAttributes.MiterLimit );
 
@@ -952,14 +954,14 @@ namespace cairocanvas
                     break;
             }
 
-            //tdf#103026 If the w scaling is 0, then all dashes become zero so
+            //tdf#103026 If the scaling is 0, then all dashes become zero so
             //cairo will set the cairo_t status to CAIRO_STATUS_INVALID_DASH
             //and no further drawing will occur
-            if (strokeAttributes.DashArray.hasElements() && w > 0.0)
+            if (strokeAttributes.DashArray.hasElements() && scaleFactor > 0.0)
             {
                 auto aDashArray(comphelper::sequenceToContainer<std::vector<double>>(strokeAttributes.DashArray));
                 for (auto& rDash : aDashArray)
-                    rDash *= w;
+                    rDash *= scaleFactor;
                 cairo_set_dash(mpCairo.get(), aDashArray.data(), aDashArray.size(), 0);
             }