[7.4.6] Transform: on show non-functional

[hasnogame]

Recently updated from an older version of Ren'Py to a newer build and found that on show: transform blocks were no longer functional.

To recreate the issue, create a new project and add this code:

define e = Character("Eileen")

transform basicfade:
    on show:
        alpha 0.0
        linear 1.0 alpha 1.0
    on hide:
        linear 1.0 alpha 0.0

label start:

    scene bg room

    show eileen happy at basicfade

This code results in a failure to display eileen, as seen here:

If I run the exact same project in 7.4.5, the code works fine.

Footnotes:

• The issue is still present when using a fresh install of the 7.4.6 SDK
• "on hide:" functions properly, completing the transform as expected (e.g. fading the character out using the above code)
• This issue affects character and image displayables

[AndriWilford]

This appears to be a result of
db30a5a

There's alot of context I don't understand, but perhaps the following word work, or may give an idea..

1. Revert the above commit
   Later.. EXCEPT the removal of the 'self.execute(self, self.st, self.at)' line.. oops. That should remain gone, I believe.

2. At:

renpy/renpy/display/transform.py

Lines 886 to 892 in db30a5a

	fr = self.execute(self, self.st, self.at)
	# Order a redraw, if necessary.
	if fr is not None:
	renpy.display.render.redraw(self, fr)
	self.active = True

Change to:

    if not (self.at == 0 and self.transform_event == "replace" and self.atl.animation):
        fr = self.execute(self, self.st, self.at)

        # Order a redraw, if necessary.
        if fr is not None:
            renpy.display.render.redraw(self, fr)

    self.active = True

The idea is that, if the atl block is an 'animation' block (so timebase will be at), and if the action is a 'replace' and the "at" timebase is currently 0, then this is a 'replace' of an already-showing displayable with an "animation" atl block showing. The initial execute is just skipped, and the update is called later, after the old transform data has been copied into the new one..

This does have a possibly unintuitive side-effect:
If one creates two different "animation" atl blocks, then "shows" them consecutively on a displayable with the same tags, then the second showing will continue at the same "at" time, even though the transform is a different transform.
It seems that this was kinda intended already, since the original example this was fixing showed a displayable without a transform applied, then later showed the displayable with an "animation" transform, that then continued at the "at" time the first "show" had accrued...

[renpytom]

I believe this is fixed in the nightlies.