title: Draw custom grid in Blender view
body: <p>I'm trying to add a custom grid that will be drawn in blender's viewport, just like default grid.
  The problem is, i dont understand how should i continuously run the draw code, and how should i attach it to a button the right way.</p>
  <p>Here i have the drawing code:</p>
  <pre><code>def create_batch(self, context):
      self.shader = gpu.shader.from_builtin('3D_UNIFORM_COLOR')
      self.batch = batch_for_shader(self.shader, 'LINES', {'pos': [(0,0,0), (1,0,0)]})
          
  def draw_callback(self, context):
      self.shader.bind()
      self.shader.uniform_float('color', context.scene.cdtrk_grid.color)
      self.batch.draw(self.shader)
  </code></pre>
  <p>and here is the property class</p>
  <pre><code>class CDTRKGridProps(bpy.types.PropertyGroup):
      enabled         : bpy.props.BoolProperty (
          name        = 'enabled',
          default     = False
      )
  
      color           : bpy.props.FloatVectorProperty (
          name        = 'color',
          subtype     = 'COLOR',
          default     = (0.13, 0.25, 0.03)
      )
  
      def register():
          bpy.types.Scene.cdtrk_grid = bpy.props.PointerProperty(type=CDTRKGridProps)
  </code></pre>
  <p>I tried creating an operator which would run the draw code, but im not sure where should i call the operator so it works from the start, and i didn't understand how to make it run everytime and not once.</p>