Porting GL4 geometry shaders. Likely not working.

src/xenia/gpu/vulkan/shaders/point_list.geom

@@ -0,0 +1,48 @@
+// NOTE: This file is compiled and embedded into the exe.
+//       Use `xenia-build genspirv` and check in any changes under bin/.
+
+#version 450
+#extension all : warn
+
+in gl_PerVertex {
+  vec4 gl_Position;
+  float gl_PointSize;
+  float gl_ClipDistance[];
+} gl_in[];
+
+out gl_PerVertex {
+  vec4 gl_Position;
+  float gl_PointSize;
+  float gl_ClipDistance[];
+};
+
+struct VertexData {
+  vec4 o[16];
+};
+layout(location = 1) in VertexData in_vtx[];
+layout(location = 1) out VertexData out_vtx;
+
+// TODO(benvanik): fetch default point size from register and use that if
+//     the VS doesn't write oPointSize.
+// TODO(benvanik): clamp to min/max.
+// TODO(benvanik): figure out how to see which interpolator gets adjusted.
+
+layout(points) in;
+layout(triangle_strip, max_vertices = 4) out;
+
+void main() {
+  const vec2 offsets[4] = {
+    vec2(-1.0,  1.0),
+    vec2( 1.0,  1.0),
+    vec2(-1.0, -1.0),
+    vec2( 1.0, -1.0),
+  };
+  vec4 pos = gl_in[0].gl_Position;
+  float psize = gl_in[0].gl_PointSize;
+  for (int i = 0; i < 4; ++i) {
+    gl_Position = vec4(pos.xy + offsets[i] * psize, pos.zw);
+    out_vtx = in_vtx[0];
+    EmitVertex();
+  }
+  EndPrimitive();
+}