Fix the mouse handling in the toolbar palettes

There were issues on OSX where the mouse being captured
by the parent toolbar would lead to seg faults, so release
the mouse on opening the palette.

Releasing the mouse then means that the mouse states become
confused, so we need to manually clear all the mouse states
when we open the popup.

Fixes https://gitlab.com/kicad/code/kicad/issues/5803

common/tool/action_toolbar.cpp

@@ -490,7 +490,9 @@ void ACTION_TOOLBAR::onItemDrag( wxAuiToolBarEvent& aEvent )
     {
         wxAuiToolBarItem* item = FindTool( toolId );
 
-        popupPalette( item );
+        // Use call after because opening the palette from a mouse handler
+        // creates a weird mouse state that causes problems on OSX.
+        CallAfter( &ACTION_TOOLBAR::popupPalette, item );
 
         // Don't skip this event since we are handling it
         return;
@@ -645,8 +647,23 @@ void ACTION_TOOLBAR::popupPalette( wxAuiToolBarItem* aItem )
             m_palette->EnableAction( *action, evt.GetEnabled() );
     }
 
+    // Release the mouse to ensure the first click will be recognized in the palette
+    ReleaseMouse();
+
     m_palette->SetPosition( pos );
     m_palette->Popup();
+
+    // Clear the mouse state on the toolbar because otherwise wxWidgets gets confused
+    // and won't properly display any highlighted items after the palette is closed.
+    // (This is the equivalent of calling the DoResetMouseState() private function)
+    RefreshOverflowState();
+    SetHoverItem( nullptr );
+    SetPressedItem( nullptr );
+
+    m_dragging   = false;
+    m_tipItem    = nullptr;
+    m_actionPos  = wxPoint( -1, -1 );
+    m_actionItem = nullptr;
 }