VideoCore: Fix values of unset components in input attribute arrays

If an input attribute array had a field with less than 4 components, the
remaining components were left unset if not specified by a default
vertex attribute. If neither mechanism would set a component, it would
assume a garbage value.

It has been verified that the hardware behavior is to instead to set the
missing components from the fixed default of (0 0 0 1). The default
vertex attribute values aren't used at all if a vertex array is
specified for that attribute.

Fixes UI graphics on Fire Emblem: Awakening, a small texturing glitch
when selecting a character in Cubic Ninja, as well as eliminating the
unset-W hack which was required for Ocarina of Time to not have
garbled triangles.

This change has been tested against hardware.

src/video_core/command_processor.cpp

@@ -217,20 +217,14 @@ static inline void WritePicaReg(u32 id, u32 value, u32 mask) {
                 // Initialize data for the current vertex
                 VertexShader::InputVertex input;
 
-                // Load a debugging token to check whether this gets loaded by the running
-                // application or not.
-                static const float24 debug_token = float24::FromRawFloat24(0x00abcdef);
-                input.attr[0].w = debug_token;
-
                 for (int i = 0; i < attribute_config.GetNumTotalAttributes(); ++i) {
-                    // Load the default attribute if we're configured to do so, this data will be overwritten by the loader data if it's set
-                    if (attribute_config.IsDefaultAttribute(i)) {
-                        input.attr[i] = g_state.vs.default_attributes[i];
-                        LOG_TRACE(HW_GPU, "Loaded default attribute %x for vertex %x (index %x): (%f, %f, %f, %f)",
-                                  i, vertex, index,
-                                  input.attr[i][0].ToFloat32(), input.attr[i][1].ToFloat32(),
-                                  input.attr[i][2].ToFloat32(), input.attr[i][3].ToFloat32());
-                    }
+                    if (vertex_attribute_elements[i] != 0) {
+                        // Default attribute values set if array elements have < 4 components. This
+                        // is *not* carried over from the default attribute settings even if they're
+                        // enabled for this attribute.
+                        static const float24 zero = float24::FromFloat32(0.0f);
+                        static const float24 one = float24::FromFloat32(1.0f);
+                        input.attr[i] = Math::Vec4<float24>(zero, zero, zero, one);
 
                         // Load per-vertex data from the loader arrays
                         for (unsigned int comp = 0; comp < vertex_attribute_elements[i]; ++comp) {
@@ -256,17 +250,19 @@ static inline void WritePicaReg(u32 id, u32 value, u32 mask) {
                                 vertex_attribute_strides[i] * vertex + comp * vertex_attribute_element_size[i],
                                 input.attr[i][comp].ToFloat32());
                         }
+                    } else if (attribute_config.IsDefaultAttribute(i)) {
+                        // Load the default attribute if we're configured to do so
+                        input.attr[i] = g_state.vs.default_attributes[i];
+                        LOG_TRACE(HW_GPU, "Loaded default attribute %x for vertex %x (index %x): (%f, %f, %f, %f)",
+                                  i, vertex, index,
+                                  input.attr[i][0].ToFloat32(), input.attr[i][1].ToFloat32(),
+                                  input.attr[i][2].ToFloat32(), input.attr[i][3].ToFloat32());
+                    } else {
+                        // TODO(yuriks): In this case, no data gets loaded and the vertex remains
+                        //              with the last value it had. This isn't currently maintained
+                        //              as global state, however, and so won't work in Cita yet.
+                    }
                 }
-
-                // HACK: Some games do not initialize the vertex position's w component. This leads
-                //       to critical issues since it messes up perspective division. As a
-                //       workaround, we force the fourth component to 1.0 if we find this to be the
-                //       case.
-                //       To do this, we additionally have to assume that the first input attribute
-                //       is the vertex position, since there's no information about this other than
-                //       the empiric observation that this is usually the case.
-                if (input.attr[0].w == debug_token)
-                    input.attr[0].w = float24::FromFloat32(1.0);
 
                 if (g_debug_context)
                     g_debug_context->OnEvent(DebugContext::Event::VertexLoaded, (void*)&input);