Add love.graphics.drawShaderVertices (name subject to change).

It draws a number of vertices, or a number of indices from an index buffer, without using any vertex data from a vertex buffer. A custom shader is required while using it.

It is useful when a custom GLSL3 vertex shader which uses love_VertexID is used to pull or compute per-vertex information from other sources.

src/modules/graphics/wrap_Graphics.cpp

@@ -2938,6 +2938,42 @@ int w_drawInstanced(lua_State *L)
 	return 0;
 }
 
+int w_drawShaderVertices(lua_State *L)
+{
+	if (luax_istype(L, 1, Buffer::type))
+	{
+		// Indexed drawing.
+		Buffer *t = luax_checkbuffer(L, 1);
+
+		int indexcount = (int) luaL_checkinteger(L, 2);
+		int instancecount = (int) luaL_optinteger(L, 3, 1);
+		int indexstart = (int) luaL_optinteger(L, 4, 1) - 1;
+
+		Texture *tex = nullptr;
+		if (!lua_isnoneornil(L, 5))
+			tex = luax_checktexture(L, 5);
+
+		luax_catchexcept(L, [&]() { instance()->drawShaderVertices(t, indexcount, instancecount, indexstart, tex); });
+	}
+	else
+	{
+		const char *primstr = luaL_checkstring(L, 1);
+		PrimitiveType primtype = PRIMITIVE_TRIANGLES;
+		if (!getConstant(primstr, primtype))
+			return luax_enumerror(L, "primitive type", getConstants(primtype), primstr);
+
+		int vertexcount = (int) luaL_checkinteger(L, 2);
+		int instancecount = (int) luaL_optinteger(L, 3, 1);
+
+		Texture *tex = nullptr;
+		if (!lua_isnoneornil(L, 4))
+			tex = luax_checktexture(L, 4);
+
+		luax_catchexcept(L, [&]() { instance()->drawShaderVertices(primtype, vertexcount, instancecount, tex); });
+	}
+	return 0;
+}
+
 int w_print(lua_State *L)
 {
 	std::vector<Font::ColoredString> str;
@@ -3614,6 +3650,7 @@ static const luaL_Reg functions[] =
 	{ "draw", w_draw },
 	{ "drawLayer", w_drawLayer },
 	{ "drawInstanced", w_drawInstanced },
+	{ "drawShaderVertices", w_drawShaderVertices },
 
 	{ "print", w_print },
 	{ "printf", w_printf },