Add slab direction decorator.

It's useful when working with angled slabs. There is no UI for it yet.

src/bonsai/bonsai/bim/module/model/decorator.py

@@ -1211,3 +1211,63 @@ class WallAxisDecorator:
                 self.draw_batch("LINES", verts, selected_elements_color, [(0, 1)])
                 verts = [tuple(list(v) + [0.0]) for v in axis["side"]]
                 self.draw_batch("LINES", verts, unselected_elements_color, [(0, 1)])
+
+
+class SlabDirectionDecorator:
+    is_installed = False
+    handlers = []
+
+    @classmethod
+    def install(cls, context):
+        if cls.is_installed:
+            cls.uninstall()
+        handler = cls()
+        cls.handlers.append(SpaceView3D.draw_handler_add(handler.draw_wall_axis, (context,), "WINDOW", "POST_VIEW"))
+        cls.is_installed = True
+
+    @classmethod
+    def uninstall(cls):
+        for handler in cls.handlers:
+            try:
+                SpaceView3D.draw_handler_remove(handler, "WINDOW")
+            except ValueError:
+                pass
+        cls.is_installed = False
+
+    def draw_batch(self, shader_type, content_pos, color, indices=None):
+        shader = self.line_shader if shader_type == "LINES" else self.shader
+        batch = batch_for_shader(shader, shader_type, {"pos": content_pos}, indices=indices)
+        shader.uniform_float("color", color)
+        batch.draw(shader)
+
+    def draw_wall_axis(self, context):
+        self.addon_prefs = tool.Blender.get_addon_preferences()
+        selected_elements_color = self.addon_prefs.decorator_color_selected
+        unselected_elements_color = self.addon_prefs.decorator_color_unselected
+        special_elements_color = self.addon_prefs.decorator_color_special
+        decorator_color_background = self.addon_prefs.decorator_color_background
+
+        gpu.state.point_size_set(6)
+        gpu.state.blend_set("ALPHA")
+
+        self.line_shader = gpu.shader.from_builtin("POLYLINE_UNIFORM_COLOR")
+        self.line_shader.bind()  # required to be able to change uniforms of the shader
+        self.line_shader.uniform_float("viewportSize", (context.region.width, context.region.height))
+        self.shader = gpu.shader.from_builtin("UNIFORM_COLOR")
+        self.line_shader.uniform_float("lineWidth", 2.0)
+        dir = [(0, 0, 0), (0, 0.5, 0), (-0.25, 0.15, 0), (0.25, 0.15, 0)]
+        base = [(-2, 0, 0), (2, 0, 0)]
+        obj = context.active_object
+        if not obj:
+            return
+        element = tool.Ifc.get_entity(obj)
+        if (element 
+            and (
+                element.is_a("IfcSlab") 
+                or element.is_a("IfcRoof")
+                )
+            ):
+            dir = [obj.matrix_world @ Vector(d) for d in dir]
+            base = [obj.matrix_world @ Vector(d) for d in base]
+            self.draw_batch("LINES", dir, selected_elements_color, [(0, 1), (1, 2), (1, 3)])
+            self.draw_batch("LINES", base, selected_elements_color, [(0, 1)])