Use alphatest as a fallback shader for unlit

Adjust graph shader when advanced pipeline off, and no srgb prefilled
texture when advanced pipeline off

data/shaders/sps_0_solid.xml

@@ -31,7 +31,7 @@
                       (default N).
 
         srgb: Sample mesh texture layers in srgb or not (in 6 Ys / Ns), when
-              advanced lighting is off, srgb will always be false
+              advanced lighting is off, srgb will always be false,
               default (Y Y N N N N), even if any texture layer is unused in
               shader, you cannot skip it from the above Y / N array.
 
@@ -85,6 +85,8 @@
                           (cannot be empty).
 
                     srgb: Sample in srgb or not (specify in Y/N, default is N).
+                          When advanced lighting is off, srgb will always be
+                          false.
 
                     sampler: nearest, nearest_clamped, bilinear,
                              bilinear_clamped, trilinear, trilinear_clamped

data/shaders/sps_5_unlit.xml

@@ -1,5 +1,5 @@
 <spshader>
-    <shader-info name="unlit" fallback-shader="solid" use-alpha-channel="Y"/>
+    <shader-info name="unlit" fallback-shader="alphatest" use-alpha-channel="Y"/>
     <first-pass vertex-shader="sp_pass.vert"
         fragment-shader="sp_unlit.frag" skinned-mesh-shader="sp_skinning.vert">
     </first-pass>

src/graphics/sp/sp_shader_manager.cpp

@@ -353,10 +353,12 @@ void SPShaderManager::loadPassInfo(const XMLNode* pass, PassInfo& pi)
                 prefilled_texture->get("name", &name);
                 prefilled_texture->get("file", &file);
                 prefilled_texture->get("srgb", &srgb_props);
+#ifndef SERVER_ONLY
                 if (!srgb_props.empty())
                 {
-                    srgb = srgb_props == "Y";
+                    srgb = srgb_props == "Y" && CVS->isDefferedEnabled();
                 }
+#endif
                 prefilled_texture->get("sampler", &sampler_props);
                 if (!sampler_props.empty() &&
                     m_official_sampler_types.find(sampler_props) !=

src/tracks/graph.cpp

@@ -348,8 +348,14 @@ void Graph::createMeshSP(bool show_invisible, bool enable_transparency,
     spmb->setSPMVertices(vertices);
     spmb->setIndices(indices);
     spmb->recalculateBoundingBox();
-    spmb->setSTKMaterial(material_manager->getDefaultSPMaterial(
-        enable_transparency ? "alphablend" : "unlit"));
+    std::string shader_name = enable_transparency ? "alphablend" : "unlit";
+#ifndef SERVER_ONLY
+    if (!CVS->isDefferedEnabled())
+    {
+        shader_name = "solid";
+    }
+#endif
+    spmb->setSTKMaterial(material_manager->getDefaultSPMaterial(shader_name));
     spm->addSPMeshBuffer(spmb);
     spm->setBoundingBox(spmb->getBoundingBox());
 #endif