Custom column icons question

[ownedbycats]

I'm setting up a bunch of "composed icons w/ no text" column icons in a Formats column.

So far I've set up rules to show the images for my most used types and they all work as expected. However I'm stuck on the last one. I want it to show a question mark image if there's a format that's not one of these common types.

I set up a "does not match pattern - (epub|pdf|azw3|mobi|cbz|paperbook)" which sort of works, unless there's a common type available.

Any suggestions?

[capink]

Maybe try using an advanced rule with this template

program:
    fmts = field('formats');
    common = 'epub, pdf, azw3, mobi, cbz, paperbook';
    diff = list_difference(fmts, common, ', ');
    cnt = count(diff, ',');
    test(cmp(cnt,0,'','','gt'),'question-mark.png','')

replace 'question-mark.png' with the name of your icon. Also note that the multiple assignments here make the template slower, but more readable.

[chaley]

Originally Posted by capink

Maybe try using an advanced rule with this template

program:
    fmts = field('formats');
    common = 'epub, pdf, azw3, mobi, cbz, paperbook';
    diff = list_difference(fmts, common, ', ');
    cnt = count(diff, ',');
    test(cmp(cnt,0,'','','gt'),'question-mark.png','')

replace 'question-mark.png' with the name of your icon. Also note that the multiple assignments here make the template slower, but more readable.

FWIW: that last line can now be written

if cnt ># 0 then 'question-mark.png' fi

[capink]

Originally Posted by chaley

FWIW: that last line can now be written

if cnt ># 0 then 'question-mark.png' fi

That does make things look better, I saw you using it but have not checked the docs on it.

Now that I think of it, the count step is redundant, and using chaley's new if statement the template can be further simplified as follows:

program:
    if list_difference(field('formats'), 'epub, pdf, azw3, mobi, cbz, paperbook', ', ') then 'question-mark.png' fi

This does not use assignments and should have better performance. I wonder whether putting this in a custom column instead might be better performance wise?

[chaley]

Originally Posted by capink

This does not use assignments and should have better performance. I wonder whether putting this in a custom column instead might be better performance wise?

No. Color and icon rules cache the compiled template, as does a composite column, so there is no difference in execution time. Calibre also caches the results of rule evaluation, so a rule is reevaluated only if calibre thinks the data might have changed. This is roughly the same as the process used to cache composite column evaluation results.

Of note:

• calibre generates GPM templates for all color/icon rules. There is no additional overhead in using advanced rules.
• If your rules use stored templates then the compiled stored template is also included in the cache.
• The new GPM template parser 'compiles' the template into an interpretable tree. The old parser 'compiled' the template into a stream of lexical tokens. The new scheme will be faster than the old one, especially for complex templates.
• The "test" function used to evaluate both the "true" and the "false" branches then pick the right one. The function is now inlined as "if-then-else" where the unused branch is not evaluated.

[capink]

That's interesting. Can I somehow use this cache in my own custom functions? I have a function that opens a json file and reads a dict and then it does a lookup based on a column value. I would like to be able to cache that dictionary instead of repeating this step for each row.

[ownedbycats]

I used the template in post #4. It worked as expected. Thank you

[chaley]

Originally Posted by capink

That's interesting. Can I somehow use this cache in my own custom functions? I have a function that opens a json file and reads a dict and then it does a lookup based on a column value. I would like to be able to cache that dictionary instead of repeating this step for each row.

You have a custom (Python) template function? If so, then yes you can cache results. The reason: each function is compiled into its own persistent class. You can store stuff as class attributes, which will persist until the next time calibre restarts, you change the library, or are running the function in a separate job.

The approach is to check if the desired cache class attribute exists. If so, use it. If not then fetch and store it, then use it. Sample code:

	x = getattr(self, 'foobar', None)
	if x is None:
		self.foobar = {'element': 'value'} # do what it takes to set foobar's value
	# use self.foobar in whatever way you want

It is up to you to invalidate the attribute (the 'cache') when needed. Simply restarting calibre will do it.

[ownedbycats]

Originally Posted by chaley

No. Color and icon rules cache the compiled template, as does a composite column, so there is no difference in execution time. Calibre also caches the results of rule evaluation, so a rule is reevaluated only if calibre thinks the data might have changed. This is roughly the same as the process used to cache composite column evaluation results.

Is that part of the reason why an icon based on a composite template doesn't always immediately update when a column is modified by a plugin instead of the user?

For example: A #lastread date column, which is used for a composite psuedobool #currentlyreading. (It also checks the #read bool for a 'false' value.)

Column icons are set to display an icon if #currentlyreading returns a "true."

If the user manually edits the #lastread date, the icon appears immediately.

If the Job Spy plugin autopopulates the #lastread, the icon doesn't appear until the list is resorted (or occasionally until a new search is done, not sure why).

[capink]

Originally Posted by chaley

You have a custom (Python) template function? If so, then yes you can cache results. The reason: each function is compiled into its own persistent class. You can store stuff as class attributes, which will persist until the next time calibre restarts, you change the library, or are running the function in a separate job.

The approach is to check if the desired cache class attribute exists. If so, use it. If not then fetch and store it, then use it. Sample code:

	x = getattr(self, 'foobar', None)
	if x is None:
		self.foobar = {'element': 'value'} # do what it takes to set foobar's value
	# use self.foobar in whatever way you want

It is up to you to invalidate the attribute (the 'cache') when needed. Simply restarting calibre will do it.

That should do it.

[chaley]

Originally Posted by ownedbycats

Is that part of the reason why an icon based on a composite template doesn't always immediately update when a column is modified by a plugin instead of the user?

For example: A #lastread date column, which is used for a composite text psuedobool #currentlyreading. (It also checks the #read bool for a 'false' value.)

Column icons are set to display an icon if #currentlyreading returns a "true."

If the user manually edits the #lastread date, the icon appears immediately.

If the Job Spy plugin autopopulates the #lastread, the icon doesn't appear until the list is resorted (though occasionally it won't show up until a new search is done, not sure why).

Its complicated.

First, simply updating a field using db.set_field doesn't clear the composite column cache. As far as I can tell, one must call db.clear_caches() to do that.

In addition, if data is changed then the GUI must be told so it can clear the various caches (rule, icon, emblem, covers, etc) , using get_gui().library_view.model().refresh_ids().

Sorting in the GUI *should* refresh the GUI cache. It doesn't refresh the DB search/composite cache so you can still get "old" results.

Searching in the GUI will (as far as I can see) refresh the GUI cache. The AFAICS comes from the fact that the GUI search has the option of not refreshing and I don't know where that option is used. It doesn't refresh the DB caches.

Does doing a bulk metadata edit, changing nothing, then pressing OK cause the icons to show correctly?

I would guess that switching between list and cover view would also clear caches.

[ownedbycats]

When it fails to update icons after a resort, either doing a new search or editing a metadata cell on any book (even if no actual changes are made) tends to fix it. I figure it's just some sort of weird Qt glitch.