Bug2105: Enable TAB to sliders on Mac...

... I think this is a defect in wxWidgets, but one we can work around with a
simple wrapper class around wxSlider overriding one method.

To make the fix complete, change all occurrences of "safenew wxSlider"
but the one in ShuttleGui.cpp covers most cases

src/FreqWindow.cpp

@@ -338,7 +338,7 @@ FreqWindow::FreqWindow(wxWindow * parent, wxWindowID id,
 
             S.AddSpace(5);
 
-            mZoomSlider = safenew wxSlider(this, FreqZoomSliderID, 100, 1, 100,
+            mZoomSlider = safenew wxSliderWrapper(this, FreqZoomSliderID, 100, 1, 100,
                wxDefaultPosition, wxDefaultSize, wxSL_VERTICAL);
             S.Prop(1);
             S.AddWindow(mZoomSlider, wxALIGN_CENTER_HORIZONTAL);

src/ShuttleGui.cpp

@@ -515,6 +515,15 @@ wxRadioButton * ShuttleGuiBase::AddRadioButtonToGroup(const wxString &Prompt)
    return pRad;
 }
 
+#ifdef __WXMAC__
+void wxSliderWrapper::SetFocus()
+{
+   // bypassing the override in wxCompositeWindow<wxSliderBase> which ends up
+   // doing nothing
+   return wxSliderBase::SetFocus();
+}
+#endif
+
 wxSlider * ShuttleGuiBase::AddSlider(const wxString &Prompt, int pos, int Max, int Min)
 {
    HandleOptionality( Prompt );
@@ -523,7 +532,7 @@ wxSlider * ShuttleGuiBase::AddSlider(const wxString &Prompt, int pos, int Max, i
    if( mShuttleMode != eIsCreating )
       return wxDynamicCast(wxWindow::FindWindowById( miId, mpDlg), wxSlider);
    wxSlider * pSlider;
-   mpWind = pSlider = safenew wxSlider(GetParent(), miId,
+   mpWind = pSlider = safenew wxSliderWrapper(GetParent(), miId,
       pos, Min, Max,
       wxDefaultPosition, wxDefaultSize,
       Style( wxSL_HORIZONTAL | wxSL_LABELS | wxSL_AUTOTICKS )

src/ShuttleGui.h

@@ -17,6 +17,7 @@
 #include "Audacity.h"
 
 #include <vector>
+#include <wx/slider.h> // to inherit
 #include "MemoryX.h"
 
 #include "WrappedType.h"
@@ -76,6 +77,19 @@ class Shuttle;
 
 class WrappedType;
 
+#ifdef __WXMAC__
+/// Fix a defect in TAB key navigation to sliders, known to happen in wxWidgets
+/// 3.1.1 and maybe in earlier versions
+class wxSliderWrapper : public wxSlider
+{
+public:
+   using wxSlider::wxSlider;
+   void SetFocus() override;
+};
+#else
+using wxSliderWrapper = wxSlider;
+#endif
+
 class AUDACITY_DLL_API ShuttleGuiBase /* not final */
 {
 public:

src/effects/Equalization.cpp

@@ -737,7 +737,7 @@ void EffectEqualization::PopulateOrExchange(ShuttleGui & S)
 
          for (int i = 0; (i < NUMBER_OF_BANDS) && (kThirdOct[i] <= mHiFreq); ++i)
          {
-            mSliders[i] = safenew wxSlider(mGraphicPanel, ID_Slider + i, 0, -20, +20,
+            mSliders[i] = safenew wxSliderWrapper(mGraphicPanel, ID_Slider + i, 0, -20, +20,
                wxDefaultPosition, wxDefaultSize, wxSL_VERTICAL | wxSL_INVERSE);
 
             mSliders[i]->Bind(wxEVT_ERASE_BACKGROUND,

src/effects/ScoreAlignDialog.cpp

@@ -83,7 +83,7 @@ ScoreAlignDialog::ScoreAlignDialog(ScoreAlignParams &params)
 
    //wxButton *ok = safenew wxButton(this, wxID_OK, _("OK"));
    //wxButton *cancel = safenew wxButton(this, wxID_CANCEL, _("Cancel"));
-   //wxSlider *sl = safenew wxSlider(this, ID_SLIDER, 0, 0, 100,
+   //wxSlider *sl = safenew wxSliderWrapper(this, ID_SLIDER, 0, 0, 100,
    //                     wxDefaultPosition, wxSize(20, 124),
    //                     wxSL_HORIZONTAL);
 

src/effects/VST/VSTEffect.cpp

@@ -2909,7 +2909,7 @@ void VSTEffect::BuildPlain()
                wxALIGN_RIGHT | wxST_NO_AUTORESIZE);
             gridSizer->Add(mNames[i], 0, wxALIGN_CENTER_VERTICAL | wxALIGN_RIGHT | wxALL, 5);
 
-            mSliders[i] = safenew wxSlider(scroller,
+            mSliders[i] = safenew wxSliderWrapper(scroller,
                ID_Sliders + i,
                0,
                0,

src/effects/ladspa/LadspaEffect.cpp

@@ -1313,7 +1313,7 @@ bool LadspaEffect::PopulateUI(wxWindow *parent)
                gridSizer->Add(1, 1, 0);
             }
 
-            mSliders[p] = safenew wxSlider(w, ID_Sliders + p,
+            mSliders[p] = safenew wxSliderWrapper(w, ID_Sliders + p,
                0, 0, 1000,
                wxDefaultPosition,
                wxSize(200, -1));

src/effects/lv2/LV2Effect.cpp

@@ -1714,7 +1714,7 @@ bool LV2Effect::BuildPlain()
                      gridSizer->Add(1, 1, 0);
                   }
 
-                  mSliders[p] = safenew wxSlider(w, ID_Sliders + p,
+                  mSliders[p] = safenew wxSliderWrapper(w, ID_Sliders + p,
                      0, 0, 1000,
                      wxDefaultPosition,
                      wxSize(150, -1));

src/export/Export.cpp

@@ -1356,7 +1356,7 @@ ExportMixerDialog::ExportMixerDialog( const TrackList *tracks, bool selectedOnly
          mChannelsText = safenew wxStaticText(this, -1, label);
          horSizer->Add(mChannelsText, 0, wxALIGN_LEFT | wxALL, 5);
 
-         wxSlider *channels = safenew wxSlider(this, ID_SLIDER_CHANNEL,
+         wxSlider *channels = safenew wxSliderWrapper(this, ID_SLIDER_CHANNEL,
             mMixerSpec->GetNumChannels(), 1, mMixerSpec->GetMaxNumChannels(),
             wxDefaultPosition, wxSize(300, -1));
          channels->SetName(label);