Fallback to Cairo when OpenGL is not supported

Fixes: lp:1741787
* https://bugs.launchpad.net/kicad/+bug/1741787

common/draw_panel_gal.cpp

@@ -121,7 +121,7 @@ EDA_DRAW_PANEL_GAL::~EDA_DRAW_PANEL_GAL()
 {
     StopDrawing();
 
-    assert( !m_drawing );
+    wxASSERT( !m_drawing );
 
     delete m_viewControls;
     delete m_view;
@@ -163,10 +163,10 @@ void EDA_DRAW_PANEL_GAL::onPaint( wxPaintEvent& WXUNUSED( aEvent ) )
 
     m_viewControls->UpdateScrollbars();
 
-    m_view->UpdateItems();
-
     try
     {
+        m_view->UpdateItems();
+
         m_gal->BeginDrawing();
         m_gal->SetClearColor( settings->GetBackgroundColor() );
         m_gal->SetCursorColor( settings->GetLayerColor( LAYER_CURSOR ) );
@@ -188,13 +188,17 @@ void EDA_DRAW_PANEL_GAL::onPaint( wxPaintEvent& WXUNUSED( aEvent ) )
     }
     catch( std::runtime_error& err )
     {
-        assert( GetBackend() != GAL_TYPE_CAIRO );
+        constexpr auto GAL_FALLBACK = GAL_TYPE_CAIRO;
-
-        // Cairo is supposed to be the safe backend, there is not a single "throw" in its code
-        SwitchBackend( GAL_TYPE_CAIRO );
 
         if( m_edaFrame )
-            m_edaFrame->UseGalCanvas( true );
+        {
+            bool use_gal = m_edaFrame->SwitchCanvas( GAL_FALLBACK );
+            m_edaFrame->UseGalCanvas( use_gal );
+        }
+        else
+        {
+            SwitchBackend( GAL_TYPE_CAIRO );
+        }
 
         DisplayError( m_parent, wxString( err.what() ) );
     }
@@ -363,6 +367,7 @@ bool EDA_DRAW_PANEL_GAL::SwitchBackend( GAL_TYPE aGalType )
     }
     catch( std::runtime_error& err )
     {
+        // Create a dummy GAL
         new_gal = new KIGFX::GAL( m_options );
         aGalType = GAL_TYPE_NONE;
         DisplayError( m_parent, wxString( err.what() ) );

include/draw_frame.h

@@ -337,6 +337,12 @@ public:
     bool ShowPageLimits() const { return m_showPageLimits; }
     void SetShowPageLimits( bool aShow ) { m_showPageLimits = aShow; }
 
+    virtual bool SwitchCanvas( EDA_DRAW_PANEL_GAL::GAL_TYPE aCanvasType )
+    {
+        wxFAIL_MSG( "SwitchCanvas not implemented" );
+        return false;
+    }
+
     EDA_DRAW_PANEL* GetCanvas() { return m_canvas; }
 
     virtual wxString GetScreenDesc() const;

include/wxBasePcbFrame.h

@@ -40,7 +40,6 @@
 #include <eda_text.h>                // EDA_DRAW_MODE_T
 #include <richio.h>
 #include <class_pcb_screen.h>
-
 #include <pcb_display_options.h>
 #include <pcb_general_settings.h>
 
@@ -648,6 +647,8 @@ public:
     void OnTogglePolarCoords( wxCommandEvent& aEvent );
     void OnTogglePadDrawMode( wxCommandEvent& aEvent );
 
+    virtual void OnSwitchCanvas( wxCommandEvent& aEvent );
+
     // User interface update event handlers.
     void OnUpdateCoordType( wxUpdateUIEvent& aEvent );
     void OnUpdatePadDrawMode( wxUpdateUIEvent& aEvent );
@@ -688,7 +689,7 @@ public:
     /**
      * switches currently used canvas (default / Cairo / OpenGL).
      */
-    virtual void SwitchCanvas( wxCommandEvent& aEvent );
+    bool SwitchCanvas( EDA_DRAW_PANEL_GAL::GAL_TYPE aCanvasType ) override;
 
     /**
      * Update UI called when switches currently used canvas (default / Cairo / OpenGL).

pcbnew/basepcbframe.cpp

@@ -480,6 +480,25 @@ void PCB_BASE_FRAME::OnTogglePadDrawMode( wxCommandEvent& aEvent )
 }
 
 
+void PCB_BASE_FRAME::OnSwitchCanvas( wxCommandEvent& aEvent )
+{
+    switch( aEvent.GetId() )
+    {
+    case ID_MENU_CANVAS_LEGACY:
+        SwitchCanvas( EDA_DRAW_PANEL_GAL::GAL_TYPE_NONE );
+        break;
+
+    case ID_MENU_CANVAS_CAIRO:
+        SwitchCanvas( EDA_DRAW_PANEL_GAL::GAL_TYPE_CAIRO );
+        break;
+
+    case ID_MENU_CANVAS_OPENGL:
+        SwitchCanvas( EDA_DRAW_PANEL_GAL::GAL_TYPE_OPENGL );
+        break;
+    }
+}
+
+
 void PCB_BASE_FRAME::OnUpdateCoordType( wxUpdateUIEvent& aEvent )
 {
     auto displ_opts = (PCB_DISPLAY_OPTIONS*)GetDisplayOptions();
@@ -949,38 +968,6 @@ void PCB_BASE_FRAME::SetPrevGrid()
 }
 
 
-void PCB_BASE_FRAME::SwitchCanvas( wxCommandEvent& aEvent )
-{
-    bool use_gal = false;
-    EDA_DRAW_PANEL_GAL::GAL_TYPE canvasType = EDA_DRAW_PANEL_GAL::GAL_TYPE_NONE;
-
-    switch( aEvent.GetId() )
-    {
-    case ID_MENU_CANVAS_LEGACY:
-        break;
-
-    case ID_MENU_CANVAS_CAIRO:
-        use_gal = GetGalCanvas()->SwitchBackend( EDA_DRAW_PANEL_GAL::GAL_TYPE_CAIRO );
-
-        if( use_gal )
-            canvasType = EDA_DRAW_PANEL_GAL::GAL_TYPE_CAIRO;
-        break;
-
-    case ID_MENU_CANVAS_OPENGL:
-        use_gal = GetGalCanvas()->SwitchBackend( EDA_DRAW_PANEL_GAL::GAL_TYPE_OPENGL );
-
-        if( use_gal )
-            canvasType = EDA_DRAW_PANEL_GAL::GAL_TYPE_OPENGL;
-        break;
-    }
-
-    UseGalCanvas( use_gal );
-
-    m_canvasType = canvasType;
-    m_canvasTypeDirty = true;
-}
-
-
 void PCB_BASE_FRAME::UseGalCanvas( bool aEnable )
 {
     EDA_DRAW_FRAME::UseGalCanvas( aEnable );
@@ -1019,6 +1006,18 @@ void PCB_BASE_FRAME::UseGalCanvas( bool aEnable )
 }
 
 
+bool PCB_BASE_FRAME::SwitchCanvas( EDA_DRAW_PANEL_GAL::GAL_TYPE aCanvasType )
+{
+    bool use_gal = GetGalCanvas()->SwitchBackend( aCanvasType );
+    use_gal &= aCanvasType != EDA_DRAW_PANEL_GAL::GAL_TYPE_NONE;
+    UseGalCanvas( use_gal );
+    m_canvasType = use_gal ? aCanvasType : EDA_DRAW_PANEL_GAL::GAL_TYPE_NONE;
+    m_canvasTypeDirty = true;
+
+    return use_gal;
+}
+
+
 void PCB_BASE_FRAME::OnUpdateSwitchCanvas( wxUpdateUIEvent& aEvent )
 {
     wxMenuBar* menuBar = GetMenuBar();

pcbnew/moduleframe.cpp

@@ -181,9 +181,9 @@ BEGIN_EVENT_TABLE( FOOTPRINT_EDIT_FRAME, PCB_BASE_FRAME )
     EVT_MENU( ID_MENU_PCB_SHOW_3D_FRAME, FOOTPRINT_EDIT_FRAME::Show3D_Frame )
 
     // Switching canvases
-    EVT_MENU( ID_MENU_CANVAS_LEGACY, PCB_BASE_FRAME::SwitchCanvas )
+    EVT_MENU( ID_MENU_CANVAS_LEGACY, PCB_BASE_FRAME::OnSwitchCanvas )
-    EVT_MENU( ID_MENU_CANVAS_CAIRO, PCB_BASE_FRAME::SwitchCanvas )
+    EVT_MENU( ID_MENU_CANVAS_CAIRO, PCB_BASE_FRAME::OnSwitchCanvas )
-    EVT_MENU( ID_MENU_CANVAS_OPENGL, PCB_BASE_FRAME::SwitchCanvas )
+    EVT_MENU( ID_MENU_CANVAS_OPENGL, PCB_BASE_FRAME::OnSwitchCanvas )
 
     // UI update events.
     EVT_UPDATE_UI( ID_MODEDIT_DELETE_PART, FOOTPRINT_EDIT_FRAME::OnUpdateLibSelected )

pcbnew/pcb_draw_panel_gal.cpp

@@ -37,6 +37,7 @@
 #include <class_track.h>
 #include <class_marker_pcb.h>
 #include <wxBasePcbFrame.h>
+#include <confirm.h>
 
 #include <gal/graphics_abstraction_layer.h>
 
@@ -356,6 +357,19 @@ void PCB_DRAW_PANEL_GAL::OnShow()
 {
     PCB_BASE_FRAME* frame = dynamic_cast<PCB_BASE_FRAME*>( GetParent() );
 
+    try
+    {
+        // Check if the current rendering backend can be properly initialized
+        m_view->UpdateItems();
+    }
+    catch( const std::runtime_error& e )
+    {
+        // Fallback to software renderer
+        DisplayError( frame, e.what() );
+        bool use_gal = SwitchBackend( GAL_TYPE_CAIRO );
+        frame->UseGalCanvas( use_gal );
+    }
+
     if( frame )
     {
         SetTopLayer( frame->GetActiveLayer() );

pcbnew/pcbframe.cpp

@@ -187,9 +187,9 @@ BEGIN_EVENT_TABLE( PCB_EDIT_FRAME, PCB_BASE_FRAME )
     EVT_MENU( ID_MENU_PCB_SHOW_3D_FRAME, PCB_EDIT_FRAME::Show3D_Frame )
 
     // Switching canvases
-    EVT_MENU( ID_MENU_CANVAS_LEGACY, PCB_EDIT_FRAME::SwitchCanvas )
+    EVT_MENU( ID_MENU_CANVAS_LEGACY, PCB_EDIT_FRAME::OnSwitchCanvas )
-    EVT_MENU( ID_MENU_CANVAS_CAIRO, PCB_EDIT_FRAME::SwitchCanvas )
+    EVT_MENU( ID_MENU_CANVAS_CAIRO, PCB_EDIT_FRAME::OnSwitchCanvas )
-    EVT_MENU( ID_MENU_CANVAS_OPENGL, PCB_EDIT_FRAME::SwitchCanvas )
+    EVT_MENU( ID_MENU_CANVAS_OPENGL, PCB_EDIT_FRAME::OnSwitchCanvas )
 
     // Menu Get Design Rules Editor
     EVT_MENU( ID_MENU_PCB_SHOW_DESIGN_RULES_DIALOG, PCB_EDIT_FRAME::ShowDesignRulesEditor )
@@ -1176,10 +1176,10 @@ void PCB_EDIT_FRAME::OnLayerColorChange( wxCommandEvent& aEvent )
 }
 
 
-void PCB_EDIT_FRAME::SwitchCanvas( wxCommandEvent& aEvent )
+void PCB_EDIT_FRAME::OnSwitchCanvas( wxCommandEvent& aEvent )
 {
     // switches currently used canvas (default / Cairo / OpenGL).
-    PCB_BASE_FRAME::SwitchCanvas( aEvent );
+    PCB_BASE_FRAME::OnSwitchCanvas( aEvent );
 
     // The base class method reinit the layers manager.
     // We must upate the layer widget to match board visibility states,

pcbnew/wxPcbStruct.h

@@ -116,7 +116,7 @@ protected:
     /**
      * switches currently used canvas (default / Cairo / OpenGL).
      */
-    virtual void SwitchCanvas( wxCommandEvent& aEvent ) override;
+    virtual void OnSwitchCanvas( wxCommandEvent& aEvent ) override;
 
 #if defined(KICAD_SCRIPTING) && defined(KICAD_SCRIPTING_ACTION_MENU)
     /**