These special images are the crewmates, Level Complete, and Game
Complete images. They flashed depending on if you were lucky and
happened to got your delta-timesteps just right when text boxes were
fading in and out.
Honestly, I'm surprised text box fading in/out hasn't ran into this
issue before. It's insane luck that this issue hasn't occurred before or
anything.
Well, anyways, to fix this, there's now an attribute `allowspecial` on
text boxes, and an optional parameter of the same name for
Graphics::createtextbox(). This attribute is the only thing that will
let these special text box images render. And any createtextbox()es that
utilize these special images have been updated accordingly.
This makes text boxes fade in and out pretty smoothly.
This requires that the textboxclass::setcol() be in Graphics::drawgui(),
so now it's moved there.
Text box fading is only really noticeable if you're playing in slowmode.
As a result of the previous commit, textboxclass::clear() is now unused.
textboxclass::firstcreate() was already useless. So remove both those
functions and initialize the values in the textboxclass constructor.
This removes the variables graphics.ntextbox, as well as removing
'active' from each text box object. Thus, all text boxes are really
real, and you don't have to check its 'active' variable.
