fdo#63786 rhbz#1081968: fix PDF export of cropped SVG

When a META_FLOATTRANSPARENT_ACTION is exported, the
beginTransparencyGroup()/endTransparencyGroup() will write something
like "Q 0 0 0 rg" where the Q clears the previously set clipping region,
which is then not restored.

bdf75c7d9bce985ed10a9c41d03420f33ce82142 appears to be a fix for a
previous related problem; this essentially reverts it since it
introduced the current cropping problem.  (Particularly funny is the
comment "force reemitting clip region" since the commit does the
opposite.)

It does not really make sense to me to write something to the page
content stream from beginRedirect()/endRedirect(), because that does not
actually have any effect on the _content_ of the substream, because the
referencing of the substream is only written _after_ endRedirect()
returns, so basically what is written can in the best case cancel itself
out and in the worst case introduce bugs; the state manipulations there
are just to modify the m_aCurrentPDFState following the push()/pop() (it
is necessary to clear the clip region before starting the substream to
avoid spurious "Q" at the beginning of the stream).

Change-Id: I4a5f57b784068bd7d3ba187115444574f7418195
(cherry picked from commit e8062623355fcf3e65beae7f8f5e4d46384141f2)
Reviewed-on: https://gerrit.libreoffice.org/8813
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

2 files changed, 13 insertions, 10 deletions

diff --git a/vcl/source/gdi/pdfwriter_impl.cxx b/vcl/source/gdi/pdfwriter_impl.cxx
index 8f86255a7027..89355ad6422d 100644
--- a/vcl/source/gdi/pdfwriter_impl.cxx
+++ b/vcl/source/gdi/pdfwriter_impl.cxx
@@ -8662,9 +8662,12 @@ void PDFWriterImpl::beginRedirect( SvStream* pStream, const Rectangle& rTargetRe
 {
     push( PUSH_ALL );
 
-    // force reemitting clip region
+    // force reemitting clip region inside the new stream, and
+    // prevent emitting an unbalanced "Q" at the start
     clearClipRegion();
-    updateGraphicsState();
+    // this is needed to point m_aCurrentPDFState at the pushed state
+    // ... but it's pointless to actually write into the "outer" stream here!
+    updateGraphicsState(NOWRITE);
 
     m_aOutputStreams.push_front( StreamRedirect() );
     m_aOutputStreams.front().m_pStream = pStream;
@@ -8701,14 +8704,12 @@ SvStream* PDFWriterImpl::endRedirect()
     }
 
     pop();
-    // force reemitting colors and clip region
-    clearClipRegion();
-    m_aCurrentPDFState.m_bClipRegion = m_aGraphicsStack.front().m_bClipRegion;
-    m_aCurrentPDFState.m_aClipRegion = m_aGraphicsStack.front().m_aClipRegion;
+
     m_aCurrentPDFState.m_aLineColor = Color( COL_TRANSPARENT );
     m_aCurrentPDFState.m_aFillColor = Color( COL_TRANSPARENT );
 
-    updateGraphicsState();
+    // needed after pop() to set m_aCurrentPDFState
+    updateGraphicsState(NOWRITE);
 
     return pStream;
 }
@@ -10497,7 +10498,7 @@ void PDFWriterImpl::drawWallpaper( const Rectangle& rRect, const Wallpaper& rWal
     }
 }
 
-void PDFWriterImpl::updateGraphicsState()
+void PDFWriterImpl::updateGraphicsState(Mode const mode)
 {
     OStringBuffer aLine( 256 );
     GraphicsState& rNewState = m_aGraphicsStack.front();
@@ -10593,7 +10594,7 @@ void PDFWriterImpl::updateGraphicsState()
 
     // everything is up to date now
     m_aCurrentPDFState = m_aGraphicsStack.front();
-    if( !aLine.isEmpty() )
+    if ((mode != NOWRITE) &&  !aLine.isEmpty())
         writeBuffer( aLine.getStr(), aLine.getLength() );
 }
 
diff --git a/vcl/source/gdi/pdfwriter_impl.hxx b/vcl/source/gdi/pdfwriter_impl.hxx
index 46020446fd48..8e622faf4b90 100644
--- a/vcl/source/gdi/pdfwriter_impl.hxx
+++ b/vcl/source/gdi/pdfwriter_impl.hxx
@@ -840,10 +840,12 @@ i12626
     void drawRelief( SalLayout& rLayout, const OUString& rText, bool bTextLines );
     void drawShadow( SalLayout& rLayout, const OUString& rText, bool bTextLines );
 
+    enum Mode { DEFAULT, NOWRITE };
+
     /*  writes differences between graphics stack and current real PDF
      *   state to the file
      */
-    void updateGraphicsState();
+    void updateGraphicsState(Mode mode = DEFAULT);
 
     /* writes a transparency group object */
     bool writeTransparentObject( TransparencyEmit& rObject );