Fix via placement when pressing V before starting to route

When the user presses V to place a via before clicking to start routing,
the via placement intent was being ignored because ToggleViaPlacement()
only works during active routing. The via would only appear if the user
moved the mouse after pressing V.

Add a flag to remember when V is pressed in pre-routing state and enable
via placement after routing starts.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/19814

(cherry picked from commit f6a0b6b836)

pcbnew/router/router_tool.cpp

@@ -209,7 +209,8 @@ ROUTER_TOOL::ROUTER_TOOL() :
         m_lastTargetLayer( UNDEFINED_LAYER ),
         m_originalActiveLayer( UNDEFINED_LAYER ),
         m_inRouterTool( false ),
-        m_inRouteSelected( false )
+        m_inRouteSelected( false ),
+        m_startWithVia( false )
 {
 }
 
@@ -1311,6 +1312,13 @@ void ROUTER_TOOL::performRouting( VECTOR2D aStartPosition )
     // Set initial cursor
     setCursor();
 
+    // If the user pressed 'V' before starting to route, enable via placement now
+    if( m_startWithVia )
+    {
+        m_startWithVia = false;
+        handleLayerSwitch( ACT_PlaceThroughVia.MakeEvent(), true );
+    }
+
     while( TOOL_EVENT* evt = Wait() )
     {
         setCursor();
@@ -1767,6 +1775,7 @@ int ROUTER_TOOL::MainLoop( const TOOL_EVENT& aEvent )
 
     m_router->SetMode( mode );
     m_cancelled = false;
+    m_startWithVia = false;
 
     if( aEvent.HasPosition() )
         m_toolMgr->PrimeTool( aEvent.Position() );
@@ -1834,6 +1843,7 @@ int ROUTER_TOOL::MainLoop( const TOOL_EVENT& aEvent )
         }
         else if( evt->IsAction( &ACT_PlaceThroughVia ) )
         {
+            m_startWithVia = true;
             m_toolMgr->RunAction( PCB_ACTIONS::layerToggle );
         }
         else if( evt->IsAction( &PCB_ACTIONS::layerChanged ) )

pcbnew/router/router_tool.h

@@ -103,6 +103,8 @@ private:
 
     bool                         m_inRouterTool;         // Re-entrancy guard
     bool                         m_inRouteSelected;
+
+    bool                         m_startWithVia;         // User pressed V before routing started
 };
 
 #endif