Fix setting "pressed" bitmap for wxToggleButton.

Move wxAnyButton::GetNormalState(), which allows wxToggleButton to override
what "normal" means for it, down to the platform-independent wxAnyButtonBase
class and use it now in wxGTK as well to correctly choose the pressed bitmap
for a toggle button in this state.

Closes #16771.

include/wx/anybutton.h

@@ -135,6 +135,13 @@ public:
         State_Max
     };
 
+    // return the current setting for the "normal" state of the button, it can
+    // be different from State_Normal for a wxToggleButton
+    virtual State GetNormalState() const
+    {
+        return State_Normal;
+    }
+
     // return true if this button shouldn't show the text label, either because
     // it doesn't have it or because it was explicitly disabled with wxBU_NOTEXT
     bool DontShowLabel() const

include/wx/msw/anybutton.h

@@ -36,7 +36,6 @@ public:
     virtual WXLRESULT MSWWindowProc(WXUINT nMsg, WXWPARAM wParam, WXLPARAM lParam);
 
     virtual bool MSWOnDraw(WXDRAWITEMSTRUCT *item);
-    virtual State GetNormalState() const { return State_Normal; }
 
     // returns true if the platform should explicitly apply a theme border
     virtual bool CanApplyThemeBorder() const { return false; }

include/wx/msw/tglbtn.h

@@ -46,8 +46,6 @@ public:
     virtual bool MSWCommand(WXUINT param, WXWORD id);
     virtual void Command(wxCommandEvent& event);
 
-    virtual State GetNormalState() const;
-
     // returns true if the platform should explicitly apply a theme border
     virtual bool CanApplyThemeBorder() const { return false; }
 

include/wx/tglbtn.h

@@ -36,6 +36,12 @@ public:
     virtual void SetValue(bool state) = 0;
     virtual bool GetValue() const = 0;
 
+    // The current "normal" state for the toggle button depends upon its value.
+    virtual State GetNormalState() const wxOVERRIDE
+    {
+        return GetValue() ? State_Pressed : State_Normal;
+    }
+
     void UpdateWindowUI(long flags) wxOVERRIDE
     {
         wxControl::UpdateWindowUI(flags);