Add some Right-To-Left language workarounds.

MixerBoard, LyricsWindow, Screenshot and most effects are now LTR in RTL locales.
Also added a pref so this can be overridden.  As RTL affects window creation, the language choice and this preference may only fully take effect after a restart of Audacity.

src/Audacity.h

@@ -229,4 +229,15 @@ void QuitAudacity();
 // pointer like std::unique_ptr or std::shared_ptr.
 #define safenew new
 
+// Right to left languages fail in many wx3 dialogs with missing buttons.
+// The workaround is to use LTR in those dialogs.
+#ifndef __WXMAC__
+#define RTL_WORKAROUND( pWnd ) \
+   if ( gPrefs->Read( "/GUI/RtlWorkaround", true) ) \
+       pWnd->SetLayoutDirection(wxLayout_LeftToRight); 
+#else
+   #define RTL_WORKAROUND( pWnd ) 
+#endif
+
+
 #endif // __AUDACITY_H__

src/LyricsWindow.cpp

@@ -114,6 +114,8 @@ LyricsWindow::LyricsWindow(AudacityProject *parent):
    //pToolBar->Realize();
 
    mLyricsPanel = safenew LyricsPanel(this, -1, panelPos, panelSize);
+   RTL_WORKAROUND(mLyricsPanel);
+
 
    //vvv Highlight style is broken in ported version.
    //switch (mLyricsPanel->GetLyricsStyle())

src/MixerBoard.cpp

@@ -912,6 +912,7 @@ MixerBoard::MixerBoard(AudacityProject* pProject,
 //      mScrolledWindow->SetBackgroundColour(wxSystemSettings::GetColour(wxSYS_COLOUR_3DSHADOW));
 //   #endif
    mScrolledWindow->SetBackgroundColour( theTheme.Colour( clrMedium ) );
+   RTL_WORKAROUND(mScrolledWindow);
 
    mScrolledWindow->SetScrollRate(10, 0); // no vertical scroll
    mScrolledWindow->SetVirtualSize(size);

src/Screenshot.cpp

@@ -308,6 +308,7 @@ void ScreenFrame::Populate()
 void ScreenFrame::PopulateOrExchange(ShuttleGui & S)
 {
    wxPanel *p = S.StartPanel();
+   RTL_WORKAROUND(p);
    {
       S.SetBorder(3);
 

src/effects/Effect.cpp

@@ -2973,6 +2973,7 @@ int EffectUIHost::ShowModal()
 bool EffectUIHost::Initialize()
 {
    EffectPanel *w = safenew EffectPanel(this);
+   RTL_WORKAROUND(w);
    {
       auto vs = std::make_unique<wxBoxSizer>(wxVERTICAL);
       {

src/prefs/GUIPrefs.cpp

@@ -197,6 +197,11 @@ void GUIPrefs::PopulateOrExchange(ShuttleGui & S)
       S.TieCheckBox(_("B&lend system and Audacity theme"),
                     wxT("/GUI/BlendThemes"),
                     true);
+#ifndef __WXMAC__
+      S.TieCheckBox(_("Use mostly Left-to-Right layouts in RTL languages"),
+         "/GUI/RtlWorkaround",
+         true);
+#endif
    }
    S.EndStatic();