[Archive] Warning when event functions are defined and there is no draw()

[villares]

[UPDATE: This idea turned out to be unnecessary due to other fixes/behavioral changes in py5!]

py5 already has a number of very useful error messages, like when you are trying to import py5 but the sketch is being executed by the sketch runner for imported mode .

I wonder if it would be a good idea to have a console warning when you define any of the event functions (like mouse_pressed() or key_pressed()) but you forget to define a draw() function (which provides the main loop, even when empty).

I would not want this to raise an exception, to abort execution, as I have left unused event functions and used setup() only sketches as exploratory/debugging steps (commenting out draw()) during development. Just a message like "It seems like you might have defined one or more event functions.... Beware you need to define draw() for your sketch to be able to invoke them."

Do you think this is overkill? I think I learned about this a long time a go, maybe in some "interaction" tutorial.

[hx2A]

This is a good idea, and might potentially alleviate some confusion for someone someday. I'll use the Python warnings library to do it. This is an easy thing to add.

[hx2A]

@villares so I coded these warning messages and tested it and discovered that mouse_clicked() and key_pressed() events do in fact get called in a sketch that has no draw() method. Ha! Not what we expected. This is the case for the default renderer and P2D. I am working on Linux.

It is possible this is a side effect of my fix for #89 & #82, so you might see something different when you test on your machine. I don't think it is a problem that they do get called, I think it is actually an improvement. Do you agree? And if so, that there is no need to add a warning message?

[villares]

Wow, that's curious! So they are allowed to update the drawing even without an explicit draw()!
Only some of the events, like, mouse_clicked(), but not mouse_pressed()? key_pressed(), but not key_released()?

I agree, no need for the warning then....

I'm mostly on Linux too, so when I get the chance I'll try it on windows... And I have to check I have the most recent build.

[hx2A]

It is possible this is a side effect of my fix for #89 & #82, so you might see something different when you test on your machine.

My hunch was correct. If I used the latest release, the user event functions do not get called if there is no draw() method. If I use the development build, which contains the fix for #89 and #82, the user event functions do get called.

There's no longer a need for a warning message and I'll close the issue I opened for this change.