World|Sector: Non-drawable materials classify for "missing texture" m…

…ap hacks

The first texture defined in the TEXTURE1/2 lump of the IWAD is never
drawn by the original software renderer due to a resource management
quirk. Some mods take advantage of this behavior by applying it to
missing texture map hacks instead of omitting a texture.

doomsday/client/include/world/surface.h

@@ -172,12 +172,24 @@ class Surface : public de::MapElement
      * Convenient helper method for determining whether a sky-masked material
      * is bound to the surface.
      *
-     * @return  @c true iff a sky-masked material is bound; otherwise @c 0.
+     * @return  @c true iff a sky-masked material is bound.
      */
     inline bool hasSkyMaskedMaterial() const {
         return hasMaterial() && material().isSkyMasked();
     }
 
+    /**
+     * Convenient helper method for determining whether a drawable, non @em fix
+     * material is bound to the surface.
+     *
+     * @return  @c true iff drawable, non @em fix masked material is bound.
+     *
+     * @see hasMaterial(), hasFixMaterial(), Material::isDrawable()
+     */
+    inline bool hasDrawableNonFixMaterial() const {
+        return hasMaterial() && !hasFixMaterial() && material().isDrawable();
+    }
+
     /**
      * Returns the attributed material of the surface.
      *

doomsday/client/src/world/sectorcluster.cpp

@@ -290,24 +290,24 @@ DENG2_OBSERVES(Plane, HeightChange)
 
                     flags &= ~AllSelfRef;
 
-                    if(frontSide.bottom().hasMaterial() && !frontSide.bottom().hasFixMaterial())
+                    if(frontSide.bottom().hasDrawableNonFixMaterial())
                     {
                         flags &= ~AllMissingBottom;
                     }
 
-                    if(frontSide.top().hasMaterial() && !frontSide.top().hasFixMaterial())
+                    if(frontSide.top().hasDrawableNonFixMaterial())
                     {
                         flags &= ~AllMissingTop;
                     }
 
                     if(backCluster->floor().height() < self.sector().floor().height() &&
-                       backSide.bottom().hasMaterial() && !backSide.bottom().hasFixMaterial())
+                       backSide.bottom().hasDrawableNonFixMaterial())
                     {
                         flags &= ~AllMissingBottom;
                     }
 
                     if(backCluster->ceiling().height() > self.sector().ceiling().height() &&
-                       backSide.top().hasMaterial() && !backSide.top().hasFixMaterial())
+                       backSide.top().hasDrawableNonFixMaterial())
                     {
                         flags &= ~AllMissingTop;
                     }