hammerspoon: How to handle `Warning: LuaSkin: hs.canvas:delete - explicit delete is no longer required for canvas objects; garbage collection occurs automatically`

@cmsj I know this is closed (should it be?) but, I found the line that causes this to print: https://github.com/Hammerspoon/hammerspoon/blob/02f60327d753ccffe13fb4f7bf95492bdd66c60f/extensions/canvas/libcanvas.m#L3184 It looks like I was wrong about when this is printed to the console. Seems like it happens iff the :delete() method actually gets called, and only if the warnedAboutDelete counter is < 10.

I checked and re-checked my code, and I already removed all explicit references to hs.canvas:delete(). But I’m still getting 6 of these in my console every time HS launches. Is it possibly being referenced somewhere else internally? Any way to find out what module or line is calling?

edit: I found at least 2 internal references in drawing_canvasWrapper.lua at line 168 & 216 e.g:

drawingMT.delete = function(self)
    drawingMT.delete = function(self)
    self.canvas = self.canvas:delete()
    setmetatable(self, nil)
end

changing to:

drawingMT.delete = function(self)
    drawingMT.delete = function(self)
    -- self.canvas = self.canvas:delete()
    self.canvas = nil
    collectgarbage()
    setmetatable(self, nil)
end

eliminated the warnings on startup for me. I am sure there are others, I believe hs.alert has some as well…

Hmmm… the number of elements shouldn’t matter (the example code had 1 after all that we didn’t explicitly clear), but I’ll dig in to it deeper next week (I have a whole week with nothing else going on for once!)… and the callbacks… again, they should be cleared in the __gc function for the object… unless one of them refers to the canvas as an up-value… I’ll give it some thought and see if there might be a work around I can implement… or at least update the documentation or wiki examples to explain best practices and what to do to avoid the problem.

Try the following in the console:

First, type in the following:

d = hs.canvas.new{x = 100, y = 100, h = 100, w = 100}:show():appendElements{ type = "rectangle" }

After the red rectangle appears, next type in the following and it should disappear:

d = nil ; collectgarbage()

If that doesn’t work, then one or more of the recent updates has broken something; if it does, then your items are being held somewhere else, either as up-values or in other variables… I’d need to see your code to tell for certain.