Support RTL layout in VCL using Matrices

Did some changes inspired by Noel, corrected the
transformation due to mirroring already applied,
re-added 'mirror this window back'-mode

Change-Id: I21999e59898cf672fd293bc2b11f5d568e6673be
Reviewed-on: https://gerrit.libreoffice.org/59842
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
Tested-by: Jenkins
Reviewed-by: Armin Le Grand <Armin.Le.Grand@cib.de>

1 files changed, 13 insertions, 1 deletions

diff --git a/basegfx/source/matrix/b2dhommatrix.cxx b/basegfx/source/matrix/b2dhommatrix.cxx
index 1e991304a4f0..61178c496011 100644
--- a/basegfx/source/matrix/b2dhommatrix.cxx
+++ b/basegfx/source/matrix/b2dhommatrix.cxx
@@ -148,8 +148,20 @@ namespace basegfx
 
     B2DHomMatrix& B2DHomMatrix::operator*=(const B2DHomMatrix& rMat)
     {
-        if(!rMat.isIdentity())
+        if(rMat.isIdentity())
+        {
+            // multiply with identity, no change -> nothing to do
+        }
+        else if(isIdentity())
+        {
+            // we are identity, result will be rMat -> assign
+            *this = rMat;
+        }
+        else
+        {
+            // multiply
             mpImpl->doMulMatrix(*rMat.mpImpl);
+        }
 
         return *this;
     }