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diff --git a/tex/context/base/mkiv/back-trf.mkiv b/tex/context/base/mkiv/back-trf.mkiv
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+%D \module
+%D   [       file=back-trf,
+%D        version=2019.02.08, % 2009.04.15,
+%D          title=\CONTEXT\ Backend Macros,
+%D       subtitle=Transformations,
+%D         author=Hans Hagen,
+%D           date=\currentdate,
+%D      copyright={PRAGMA ADE \& \CONTEXT\ Development Team}]
+%C
+%C This module is part of the \CONTEXT\ macro||package and is
+%C therefore copyrighted by \PRAGMA. See mreadme.pdf for
+%C details.
+
+\unprotect
+
+\registerctxluafile{back-trf}{}
+
+% rotation
+
+\unexpanded\def\dostartrotation#1%
+  {\forcecolorhack
+   \clf_startrotation#1\relax} % todo: implement without Q q
+
+\unexpanded\def\dostoprotation
+  {\clf_stoprotation
+   \forcecolorhack}
+
+% scaling
+
+\unexpanded\def\dostartscaling#1#2%
+  {\forcecolorhack
+   \clf_startscaling rx #1 ry #2\relax}
+
+\unexpanded\def\dostopscaling
+  {\clf_stopscaling
+   \forcecolorhack}
+
+% mirroring
+
+\unexpanded\def\dostartmirroring
+  {\clf_startmirroring}
+
+\unexpanded\def\dostopmirroring
+  {\clf_stopmirroring}
+
+% transform
+
+\unexpanded\def\dotransformnextbox#1#2#3#4#5#6%
+  {\dowithnextbox{\dodotransformnextbox{#1}{#2}{#3}{#4}{#5}{#6}}}
+
+\unexpanded\def\dodotransformnextbox#1#2#3#4#5#6%
+  {\hpack
+     {\kern #5\onebasepoint
+      \raise#6\onebasepoint
+      \hpack
+        {\clf_startmatrix rx #1 sx #2 sy #3 ry #4\relax
+         \box\nextbox
+         \clf_stopmatrix}}}
+
+%D \macros
+%D   {dostartclipping,dostopclipping}
+%D
+%D Clipping is implemented in such a way that an arbitrary code can be fed.
+%D
+%D \starttyping
+%D \dostartclipping {pathname} {width} {height}
+%D \dostopclipping
+%D \stoptyping
+
+\unexpanded\def\dostartclipping#1#2#3% we can move this to lua and only set a box here
+  {\forcecolorhack
+   \meta_grab_clip_path{#1}{#2}{#3}%
+   \clf_startclipping{\MPclippath}%
+   \glet\MPclippath\empty}
+
+\unexpanded\def\dostopclipping
+  {\clf_stopclipping}
+
+\protect \endinput