[GUI Plugin] Action Chains

[chaley]

Originally Posted by ownedbycats

Regarding:

program:
	totalpage = $#pagecount;
	pagenum = globals(pagenum);
	newpercent = round(multiply ((totalpage / pagenum), 100));

"globals" is like "arguments", not really a function. You should say

globals(pagenum);

not

pagenum = globals(pagenum);

In your case it works by accident because globals returns the value it assigns to the last argument. It would stop working if you said

pagenum = globals(pagenum, foobar);

[capink]

OK, I think I understand what is happening to you now. Since you are still trying to configure an action without having run the chain, the value of pagenum is an empty string (chain variables are only assigned at runtime, even without the runtime option ticked).

So, at this point in time, the value of pagenum (empty string) cannot be used in mathematical operations, and the template evaluator will return an error and you will not be able to save it. To remedy this:

program:
   pagenum = ifempty(globals(pagenum), 1)
   pagenum = globals(pagenum=1)

This will give the evaluator a valid default, and the template should be accepted. You can use any numerical value, except ZERO, as you are using it as the denominator.

[chaley]

Originally Posted by capink

OK, I think I understand what is happening to you now. Since you are still trying to configure an action without having run the chain, the value of pagenum is an empty string (chain variables are only assigned at runtime, even without the runtime option ticked).

@capink: do the chain variables actually have the value of '', or are they undefined? If they are undefined then this will work:

    globals(pagenum=1)

[capink]

Originally Posted by chaley

@capink: do the chain variables actually have the value of '', or are they undefined? If they are undefined then this will work:

    globals(pagenum=1)

They are undefined. Your solution is better . I totally forgot about this.

Edit: Chain Variables documentation updated.

[ownedbycats]

That worked. Thank you

[ownedbycats]

quick question: Does the variable name need to be One_String_Without_Any_Spaces? I tried changing it to "Current Page" and couldn't get that into the template without an error. Current_Page works though.

[capink]

Spaces are not allowed in variable names.

[ownedbycats]

Question: How does Action Chains treat Calibre Action dialogs?

Does the chain wait until I press ok/cancel to close the dialog, or proceed running in the background?

[capink]

It depends on the dialog itself.

• For dialogs that block the main thread (e.g. Edit Metadata Dialog), action chains will naturally wait until the dialog finishes and hands back control of the main thread.
• For dialogs that do not block the main thread (e.g. progress bar dialogs, but other dialogs might do the same), but instead act from another thread, action chains will immediately proceed to the next action, even before the dialog finishes. This is almost always undesirable, hence, the option in Calibre Actions to wait for the dialog until it finishes. (see attachment).
  Note that this involves guesswork, and is sometimes susceptible to breaking as per the warning in the screenshot.

[ownedbycats]

Is it possible to use a module to set a variable?

Context: Mostly as curiosity/to figure out how the code works, I wanted to see if I could make a modification of this chain that, instead of raise chain.UserInterrupt when clicking 'no,' instead sets a specified variable to a specified value on clicking 'yes'. That could then be used in a chain modifier to enable a specific action.

Similar to the attached chain, but with a yes/no dialog in place of typing in 'yes' manually.

[capink]

Originally Posted by ownedbycats

Is it possible to use a module to set a variable?

Context: Mostly as curiosity/to figure out how the code works, I wanted to see if I could make a modification of this chain that, instead of raise chain.UserInterrupt when clicking 'no,' instead sets a specified variable to a specified value on clicking 'yes'. That could then be used in a chain modifier to enable a specific action.

Similar to the attached chain, but with a yes/no dialog in place of typing in 'yes' manually.

chain.set_chain_vars({'my_var_name': 'false'})

[ownedbycats]

It works. Thank you.

Just for confirming something I noticed: Are variable values case-sensitive?

[ownedbycats]

Also, silly question: Where exactly in single-field edit is the "add format from predefined path"? I only see the option to remove formats.

[capink]

Originally Posted by ownedbycats

It works. Thank you.

Just for confirming something I noticed: Are variable values case-sensitive?

Yes. They are case-sensitive.

[capink]

Originally Posted by ownedbycats

Also, silly question: Where exactly in single-field edit is the "add format from predefined path"? I only see the option to remove formats.

I was going to include that option and decided not to, since it can be done from the template option.