Related: tdf#131725 match the basegfx translation to the mirror logic

that is used in the traditional code path, this will fix vcl RTL
scrollbars in otherwise LTR UI

Change-Id: I1451f7e17b93b0339ded6d33147df6415274ebfc
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/133780
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>

2 files changed, 82 insertions, 35 deletions

diff --git a/vcl/inc/salgdi.hxx b/vcl/inc/salgdi.hxx
index eed8ab7160ac..75938afecece 100644
--- a/vcl/inc/salgdi.hxx
+++ b/vcl/inc/salgdi.hxx
@@ -638,10 +638,18 @@ private:
     SalLayoutFlags              m_nLayout; //< 0: mirroring off, 1: mirror x-axis
 
     // for buffering the Mirror-Matrix, see ::getMirror
+    enum class MirrorMode
+    {
+        NONE,
+        Antiparallel,
+        AntiparallelBiDi,
+        BiDi
+    };
+    MirrorMode                  m_eLastMirrorMode;
+    tools::Long                 m_nLastMirrorTranslation;
     basegfx::B2DHomMatrix       m_aLastMirror;
-    tools::Long                 m_aLastMirrorW;
-    tools::Long                 m_nLastMirrorDeviceLTRButBiDiRtlTranslate;
-    bool                        m_bLastMirrorDeviceLTRButBiDiRtlSet;
+
+    MirrorMode GetMirrorMode(const OutputDevice& rOutDev) const;
 
 protected:
     /// flags which hold the SetAntialiasing() value from OutputDevice
diff --git a/vcl/source/gdi/salgdilayout.cxx b/vcl/source/gdi/salgdilayout.cxx
index 89f9d0321daf..a998a7483df8 100644
--- a/vcl/source/gdi/salgdilayout.cxx
+++ b/vcl/source/gdi/salgdilayout.cxx
@@ -53,9 +53,8 @@ SalFrameGeometry SalFrame::GetGeometry() const
 
 SalGraphics::SalGraphics()
 :   m_nLayout( SalLayoutFlags::NONE ),
-    m_aLastMirrorW(0),
-    m_nLastMirrorDeviceLTRButBiDiRtlTranslate(0),
-    m_bLastMirrorDeviceLTRButBiDiRtlSet(false),
+    m_eLastMirrorMode(MirrorMode::NONE),
+    m_nLastMirrorTranslation(0),
     m_bAntiAlias(false),
     m_bTextRenderModeForResolutionIndependentLayout(false)
 {
@@ -271,50 +270,90 @@ basegfx::B2DPolyPolygon SalGraphics::mirror( const basegfx::B2DPolyPolygon& i_rP
     }
 }
 
+SalGraphics::MirrorMode SalGraphics::GetMirrorMode(const OutputDevice& rOutDev) const
+{
+    if (rOutDev.ImplIsAntiparallel())
+    {
+        if (m_nLayout & SalLayoutFlags::BiDiRtl)
+            return MirrorMode::AntiparallelBiDi;
+        else
+            return MirrorMode::Antiparallel;
+    }
+    else if (m_nLayout & SalLayoutFlags::BiDiRtl)
+        return MirrorMode::BiDi;
+    return MirrorMode::NONE;
+}
+
 const basegfx::B2DHomMatrix& SalGraphics::getMirror( const OutputDevice& i_rOutDev ) const
 {
     // get mirroring transformation
-    const tools::Long w = GetDeviceWidth(i_rOutDev);
-    SAL_WARN_IF( !w, "vcl", "missing graphics width" );
-
-    const bool bMirrorDeviceLTRButBiDiRtlSet = !i_rOutDev.IsRTLEnabled();
-    tools::Long nMirrorDeviceLTRButBiDiRtlTranslate(0);
-    if (bMirrorDeviceLTRButBiDiRtlSet)
-        nMirrorDeviceLTRButBiDiRtlTranslate = w - i_rOutDev.GetOutputWidthPixel() - (2 * i_rOutDev.GetOutOffXPixel());
+    MirrorMode eNewMirrorMode = GetMirrorMode(i_rOutDev);
+    tools::Long nTranslate(0);
 
-    // if the device width, or mirror state of the device changed, then m_aLastMirror is invalid
-    bool bLastMirrorValid = w == m_aLastMirrorW && bMirrorDeviceLTRButBiDiRtlSet == m_bLastMirrorDeviceLTRButBiDiRtlSet;
-    if (bLastMirrorValid && bMirrorDeviceLTRButBiDiRtlSet)
+    switch (eNewMirrorMode)
     {
-        // if the device is in the unusual mode of a LTR device, but layout flags of SalLayoutFlags::BiDiRtl are
-        // in use, then the m_aLastMirror is invalid if the distance it should translate has changed
-        bLastMirrorValid = nMirrorDeviceLTRButBiDiRtlTranslate == m_nLastMirrorDeviceLTRButBiDiRtlTranslate;
+        case MirrorMode::AntiparallelBiDi:
+        {
+            const tools::Long w = GetDeviceWidth(i_rOutDev);
+            SAL_WARN_IF(!w, "vcl", "missing graphics width");
+            nTranslate = w - i_rOutDev.GetOutputWidthPixel() - (2 * i_rOutDev.GetOutOffXPixel());
+            break;
+        }
+        case MirrorMode::Antiparallel:
+        {
+            nTranslate = i_rOutDev.GetOutputWidthPixel() + (2 * i_rOutDev.GetOutOffXPixel()) - 1;
+            break;
+        }
+        case MirrorMode::BiDi:
+        {
+            const tools::Long w = GetDeviceWidth(i_rOutDev);
+            SAL_WARN_IF(!w, "vcl", "missing graphics width");
+            nTranslate = w - 1;
+            break;
+        }
+        case MirrorMode::NONE:
+            break;
     }
 
+    // if the translation (due to device width), or mirror state of the device changed, then m_aLastMirror is invalid
+    bool bLastMirrorValid = eNewMirrorMode == m_eLastMirrorMode && nTranslate == m_nLastMirrorTranslation;
     if (!bLastMirrorValid)
     {
-        const_cast<SalGraphics*>(this)->m_aLastMirrorW = w;
-        const_cast<SalGraphics*>(this)->m_bLastMirrorDeviceLTRButBiDiRtlSet = bMirrorDeviceLTRButBiDiRtlSet;
-        const_cast<SalGraphics*>(this)->m_nLastMirrorDeviceLTRButBiDiRtlTranslate = nMirrorDeviceLTRButBiDiRtlTranslate;
+        const_cast<SalGraphics*>(this)->m_nLastMirrorTranslation = nTranslate;
+        const_cast<SalGraphics*>(this)->m_eLastMirrorMode = eNewMirrorMode;
 
-        if(w)
+        switch (eNewMirrorMode)
         {
-            if (bMirrorDeviceLTRButBiDiRtlSet)
+            // mirror this window back
+            case MirrorMode::AntiparallelBiDi:
             {
                 /* This path gets exercised in calc's RTL UI (e.g. SAL_RTL_ENABLED=1)
                    with its LTR horizontal scrollbar */
 
                 // Original code was:
-                //      // mirror this window back
                 //      double devX = w-i_rOutDev.GetOutputWidthPixel()-i_rOutDev.GetOutOffXPixel();   // re-mirrored mnOutOffX
                 //      aRet.setX( devX + (i_rPoint.getX() - i_rOutDev.GetOutOffXPixel()) );
-                // I do not really understand the comment 'mirror this window back', so cannot guarantee
-                // that this works as before, but I have reduced this (by re-placing and re-formatting) to
-                // a simple translation:
                 const_cast<SalGraphics*>(this)->m_aLastMirror = basegfx::utils::createTranslateB2DHomMatrix(
-                    nMirrorDeviceLTRButBiDiRtlTranslate, 0.0);
+                   nTranslate, 0.0);
+                break;
             }
-            else
+            case MirrorMode::Antiparallel:
+            {
+                /* This path gets exercised in writers's LTR UI with a RTL horizontal
+                   scrollbar, cross-reference dialog populated from contents from a
+                   RTL document tdf#131725 */
+
+                // Original code was;
+                //      tools::Long devX = rOutDev.GetOutOffXPixel();   // re-mirrored mnOutOffX
+                //      x = rOutDev.GetOutputWidthPixel() - (x - devX) + rOutDev.GetOutOffXPixel() - 1;
+                const_cast<SalGraphics*>(this)->m_aLastMirror = basegfx::utils::createScaleTranslateB2DHomMatrix(
+                    -1.0,
+                    1.0,
+                    nTranslate,
+                    0.0);
+                break;
+            }
+            case MirrorMode::BiDi:
             {
                 // Original code was:
                 //      aRet.setX( w-1-i_rPoint.getX() );
@@ -324,13 +363,13 @@ const basegfx::B2DHomMatrix& SalGraphics::getMirror( const OutputDevice& i_rOutD
                 const_cast<SalGraphics*>(this)->m_aLastMirror = basegfx::utils::createScaleTranslateB2DHomMatrix(
                     -1.0,
                     1.0,
-                    w-1,
+                    nTranslate,
                     0.0);
+                break;
             }
-        }
-        else
-        {
-            const_cast<SalGraphics*>(this)->m_aLastMirror.identity();
+            case MirrorMode::NONE:
+                const_cast<SalGraphics*>(this)->m_aLastMirror.identity();
+                break;
         }
     }