This information is valid for Ren’Py 7.3.x. I believe it should work all the way back to Ren’Py 7.x. The names and values I use for the variables do not need to be yours.
This tutorial’s going to reference the last one a bit. We’re going to use the Preferences screen with persistent variables again. Only this time, we’re playing with a slider and transforms. The goal is for the player to adjust how opaque they want the dialogue background (but not the dialogue), because it can increase readability in different circumstances.
Open up your script editor and define the persistent variable, probably in options.rpy or wherever you have other persistent variables stored.
Below’s where I put the code, in between the stock gui.about variable and the game’s short name:
define gui.about = _p("""
""")
# additional persistent variables begin here
define persistent.dialogueBoxOpacity = 1.0
# end extra variables
## A short name for the game used for executables and directories in the built
## distribution. This must be ASCII-only, and must not contain spaces, colons,
## or semicolons.
We’ve named the persistent variable dialogueBoxOpacity, but you can name it whatever you want. We set the default value to 1 because that means completely opaque.
Next, we figure out where on the Preferences screen you want to add the slider that will control the opacity. Your Preferences screen is probably defined pretty far down in the screens.rpy file, in the screen preferences() function.
In this case I’ll put it in a new column (vbox). Here’s the code for the menu setting:
label _("Dialogue box opacity")
bar value FieldValue(persistent, "dialogueBoxOpacity", range=1.0, style="slider")
The label value is what you want the user to see headingwise. The bar is a Ren’Py object that is used when you want more fine-grained control of your variables.
In the parentheses, persistent means we’re setting the value of a persistent variable. The next string should be the same as the persistent variable name you used above.
The range=1.0 statement defines the max value of the bar, which is something we can set to correspond to the values we want possible for the opacity setting. All bars have a minimum value of 0.
That wraps up our work in the preferences screen part of the file.
Now, this is a bit more complicated than the style refresh we used to change the background of the dialogue window. Since there isn’t a predefined style for the opacity, I don’t know how to just inject that.
Instead, I put a transform for opacity in the Say screen. Every time this window gets rendered, it will check the opacity of the dialogue box and render that before it renders any text (so the text is always opaque).
The Say screen is traditionally defined about a hundred lines in to the stock screens.rpy file.
Under id “window”, we’ll add the following line:
window background Transform(Frame("gui/textbox.png",xalign=0.5, yalign=1.0), alpha=persistent.dialogueBoxOpacity)
window background Transform, uh transforms the window background. Frame is used to define a window that has a background. We need to specify the background being rendered, which is traditionally saved as textbox.png in the gui folder.
xalign=0.5, yalign=1.0 puts the window at the bottom of the screen, centered. You may have different settings in your custom GUI, in which case you should change these values to whatever you have defined in your style window: block.
alpha=persistent.dialogueBoxOpacity applies an alpha transform to the window. Here, the code consults the persistent variable to determine how opaque your image will be.
You should be good to go. Any questions or things I should clear up?
Further notes
As it is, this code allows you to use only one background. You can have the name of the background be a persistent variable too, but I’m assuming this is not a common use case. If you want to do it, leave a comment.