3rd attempt to fix opengl initialization on linux

lib/Slic3r/GUI/3DScene.pm

@@ -2194,7 +2194,7 @@ sub load_object {
     $instance_idxs ||= [0..$#{$model_object->instances}];
 #==============================================================================================================================
     my $volume_indices = $self->volumes->load_object(
-        $model_object, $obj_idx, $instance_idxs, $self->color_by, $self->select_by, $self->drag_by, $useVBOs);
+        $model_object, $obj_idx, $instance_idxs, $self->color_by, $self->select_by, $self->drag_by, $useVBOs && Slic3r::GUI::_3DScene::is_shader_enabled($self));
 #    my $volume_indices = $self->volumes->load_object(
 #        $model_object, $obj_idx, $instance_idxs, $self->color_by, $self->select_by, $self->drag_by,
 #        $self->UseVBOs);

xs/src/slic3r/GUI/3DScene.cpp

@@ -1839,6 +1839,11 @@ bool _3DScene::is_layers_editing_allowed(wxGLCanvas* canvas)
     return s_canvas_mgr.is_layers_editing_allowed(canvas);
 }
 
+bool _3DScene::is_shader_enabled(wxGLCanvas* canvas)
+{
+    return s_canvas_mgr.is_shader_enabled(canvas);
+}
+
 void _3DScene::enable_layers_editing(wxGLCanvas* canvas, bool enable)
 {
     s_canvas_mgr.enable_layers_editing(canvas, enable);

xs/src/slic3r/GUI/3DScene.hpp

@@ -571,6 +571,7 @@ public:
 
     static bool is_layers_editing_enabled(wxGLCanvas* canvas);
     static bool is_layers_editing_allowed(wxGLCanvas* canvas);
+    static bool is_shader_enabled(wxGLCanvas* canvas);
 
     static void enable_layers_editing(wxGLCanvas* canvas, bool enable);
     static void enable_warning_texture(wxGLCanvas* canvas, bool enable);

xs/src/slic3r/GUI/GLCanvas3D.cpp

@@ -1175,6 +1175,11 @@ bool GLCanvas3D::is_layers_editing_allowed() const
     return m_layers_editing.is_allowed();
 }
 
+bool GLCanvas3D::is_shader_enabled() const
+{
+    return m_shader_enabled;
+}
+
 void GLCanvas3D::enable_layers_editing(bool enable)
 {
     m_layers_editing.set_enabled(enable);

xs/src/slic3r/GUI/GLCanvas3D.hpp

@@ -359,6 +359,7 @@ public:
 
     bool is_layers_editing_enabled() const;
     bool is_layers_editing_allowed() const;
+    bool is_shader_enabled() const;
 
     void enable_layers_editing(bool enable);
     void enable_warning_texture(bool enable);

xs/src/slic3r/GUI/GLCanvas3DManager.cpp

@@ -352,6 +352,12 @@ bool GLCanvas3DManager::is_layers_editing_allowed(wxGLCanvas* canvas) const
     return (it != m_canvases.end()) ? it->second->is_layers_editing_allowed() : false;
 }
 
+bool GLCanvas3DManager::is_shader_enabled(wxGLCanvas* canvas) const
+{
+    CanvasesMap::const_iterator it = _get_canvas(canvas);
+    return (it != m_canvases.end()) ? it->second->is_shader_enabled() : false;
+}
+
 void GLCanvas3DManager::enable_layers_editing(wxGLCanvas* canvas, bool enable)
 {
     CanvasesMap::iterator it = _get_canvas(canvas);

xs/src/slic3r/GUI/GLCanvas3DManager.hpp

@@ -75,6 +75,7 @@ public:
 
     bool is_layers_editing_enabled(wxGLCanvas* canvas) const;
     bool is_layers_editing_allowed(wxGLCanvas* canvas) const;
+    bool is_shader_enabled(wxGLCanvas* canvas) const;
 
     void enable_layers_editing(wxGLCanvas* canvas, bool enable);
     void enable_warning_texture(wxGLCanvas* canvas, bool enable);

xs/xsp/GUI_3DScene.xsp

@@ -294,6 +294,14 @@ is_layers_editing_allowed(canvas)
     OUTPUT:
         RETVAL
 
+bool
+is_shader_enabled(canvas)
+        SV *canvas;
+    CODE:
+        RETVAL = _3DScene::is_shader_enabled((wxGLCanvas*)wxPli_sv_2_object(aTHX_ canvas, "Wx::GLCanvas"));
+    OUTPUT:
+        RETVAL
+
 void
 enable_layers_editing(canvas, enable)
         SV   *canvas;