feat: structure gauge along the line of the selected path in the OpenGL view

rendering/editoroverlay.h

@@ -0,0 +1,42 @@
+/*
+This Source Code Form is subject to the
+terms of the Mozilla Public License, v.
+2.0. If a copy of the MPL was not
+distributed with this file, You can
+obtain one at
+http://mozilla.org/MPL/2.0/.
+*/
+
+#pragma once
+
+#include <vector>
+
+#include <glm/glm.hpp>
+
+namespace gfx
+{
+
+// flat coloured geometry the editor shows in the 3d view, drawn with the depth test over the translucent scenery
+struct editor_overlay
+{
+	struct batch
+	{
+		glm::vec4 color{1.0f};
+		unsigned int type{0}; // GL primitive
+		bool offset{false}; // pulled towards the camera, to show over the coplanar surfaces
+		std::vector<glm::vec3> points; // relative to the origin
+	};
+	glm::dvec3 origin{0.0};
+	std::vector<batch> batches;
+	unsigned int revision{0}; // changed with every new content
+
+	void clear()
+	{
+		batches.clear();
+		++revision;
+	}
+};
+
+} // namespace gfx
+
+inline gfx::editor_overlay EditorOverlay;