Move timestamp setting where it will alwasy get set.

Also update the rest of the symbol-chooser usage to current
specs, including examining the timestamp to see if the list
needs loading at all.

Partial fix to: lp:1760936
* https://bugs.launchpad.net/kicad/+bug/1760936

common/widgets/footprint_select_widget.cpp

@@ -101,15 +101,17 @@ void FOOTPRINT_SELECT_WIDGET::Load( KIWAY& aKiway, PROJECT& aProject )
     try
     {
         auto fp_lib_table = aProject.PcbFootprintLibs( aKiway );
+        m_fp_list = FOOTPRINT_LIST::GetInstance( aKiway );
 
-        if( m_fp_loader.GetProgress() == 0 || !m_fp_loader.IsSameTable( fp_lib_table ) )
+        if( m_fp_list->RequiresLoading( fp_lib_table ) )
         {
-            m_fp_list = FOOTPRINT_LIST::GetInstance( aKiway );
             m_fp_loader.SetList( &*m_fp_list );
             m_fp_loader.Start( fp_lib_table );
-        }
 
-        m_progress_timer->Start( 200 );
+            m_progress_timer->Start( 200 );
+        }
+        else
+            FootprintsLoaded();
     }
     catch( ... )
     {
@@ -128,18 +130,27 @@ void FOOTPRINT_SELECT_WIDGET::OnProgressTimer( wxTimerEvent& aEvent )
         wxBusyCursor busy;
 
         m_fp_loader.Join();
-        m_fp_filter.SetList( *m_fp_list );
         m_progress_timer->Stop();
 
-        m_book->SetSelection( PAGE_SELECT );
-        m_finished_loading = true;
-
-        if( m_update )
-            UpdateList();
+        FootprintsLoaded();
     }
 }
 
 
+void FOOTPRINT_SELECT_WIDGET::FootprintsLoaded()
+{
+    m_progress_ctrl->SetValue( 100 );
+
+    m_fp_filter.SetList( *m_fp_list );
+
+    m_book->SetSelection( PAGE_SELECT );
+    m_finished_loading = true;
+
+    if( m_update )
+        UpdateList();
+}
+
+
 void FOOTPRINT_SELECT_WIDGET::OnComboBox( wxCommandEvent& aEvent )
 {
     wxCommandEvent evt( EVT_FOOTPRINT_SELECTED );

include/footprint_info.h

@@ -242,6 +242,15 @@ public:
         return error;
     }
 
+    /**
+     * Indicates whether or not the table requires loading for the given \a aNickname.
+     */
+    virtual bool RequiresLoading( FP_LIB_TABLE* aTable, const wxString* aNickname = nullptr )
+    {
+        return true;    // Implementations which support caching should implement this.
+    }
+
+
     /**
      * Read all the footprints provided by the combination of aTable and aNickname.
      *

include/widgets/footprint_select_widget.h

@@ -149,6 +149,7 @@ private:
     FOOTPRINT_FILTER         m_fp_filter;
     bool                     m_zero_filter;
 
+    void FootprintsLoaded();
     void OnProgressTimer( wxTimerEvent& aEvent );
     void OnComboBox( wxCommandEvent& aEvent );
     void OnComboInteractive( wxCommandEvent& aEvent );

pcbnew/footprint_info_impl.cpp

@@ -115,6 +115,12 @@ void FOOTPRINT_LIST_IMPL::loader_job()
 }
 
 
+bool FOOTPRINT_LIST_IMPL::RequiresLoading( FP_LIB_TABLE* aTable, const wxString* aNickname )
+{
+    return m_list_timestamp != aTable->GenerateTimestamp( aNickname );
+}
+
+
 bool FOOTPRINT_LIST_IMPL::ReadFootprintFiles( FP_LIB_TABLE* aTable, const wxString* aNickname,
                                               WX_PROGRESS_REPORTER* aProgressReporter )
 {
@@ -166,7 +172,6 @@ bool FOOTPRINT_LIST_IMPL::ReadFootprintFiles( FP_LIB_TABLE* aTable, const wxStri
                     ( _( "Loading incomplete; cancelled by user." ), nullptr, nullptr, 0 ) );
     }
 
-    m_list_timestamp = aTable->GenerateTimestamp( aNickname );;
     m_progress_reporter = nullptr;
 
     return m_errors.empty();
@@ -178,6 +183,7 @@ void FOOTPRINT_LIST_IMPL::StartWorkers( FP_LIB_TABLE* aTable, wxString const* aN
 {
     m_loader = aLoader;
     m_lib_table = aTable;
+    m_library = aNickname;
 
     // Clear data before reading files
     m_count_finished.store( 0 );
@@ -292,6 +298,11 @@ bool FOOTPRINT_LIST_IMPL::JoinWorkers()
             []( std::unique_ptr<FOOTPRINT_INFO> const&     lhs,
                     std::unique_ptr<FOOTPRINT_INFO> const& rhs ) -> bool { return *lhs < *rhs; } );
 
+    if( m_cancelled )
+        m_list_timestamp = 0;       // God knows what we got before we were cancelled
+    else
+        m_list_timestamp = m_lib_table->GenerateTimestamp( m_library );;
+
     return m_errors.empty();
 }
 

pcbnew/footprint_info_impl.h

@@ -58,6 +58,7 @@ protected:
 class FOOTPRINT_LIST_IMPL : public FOOTPRINT_LIST
 {
     FOOTPRINT_ASYNC_LOADER*  m_loader;
+    const wxString*          m_library;
     std::vector<std::thread> m_threads;
     SYNC_QUEUE<wxString>     m_queue_in;
     SYNC_QUEUE<wxString>     m_queue_out;
@@ -89,8 +90,10 @@ public:
     FOOTPRINT_LIST_IMPL();
     virtual ~FOOTPRINT_LIST_IMPL();
 
-    virtual bool ReadFootprintFiles( FP_LIB_TABLE* aTable, const wxString* aNickname = nullptr,
-                                     WX_PROGRESS_REPORTER* aProgressReporter = nullptr ) override;
+    bool RequiresLoading( FP_LIB_TABLE* aTable, const wxString* aNickname = nullptr ) override;
+
+    bool ReadFootprintFiles( FP_LIB_TABLE* aTable, const wxString* aNickname = nullptr,
+                             WX_PROGRESS_REPORTER* aProgressReporter = nullptr ) override;
 };
 
 extern FOOTPRINT_LIST_IMPL GFootprintList;        // KIFACE scope.