Make FlatComboPopup accessible and do not ignore prototype display value

[etsinko]

There are cases when FlatComboBoxUI and FlatComboPopup need to be customized (i.e. to fix this problem: https://bugs.java.com/bugdatabase/view_bug.do?bug_id=4618607)

Currently FlatComboPopup is private and cannot be overriden by any class that inherits from FlatComobBoxUI. This leads to unnecessary copy/paste.

[DevCharly]

Good idea. Changed in master branch.

But FlatLaf uses wider popup for comboboxes by default:

Does this not work for you?

[etsinko]

Hmm.. This is exactly what we need! But, for some reason, I thought FlatLaf didn't implement it.

[etsinko]

Also, this is not related to the issue here, but in FlatComboPopup there are these lines:

FlatLaf/flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatComboBoxUI.java

Lines 484 to 489 in 97d5792

	Object prototype = comboBox.getPrototypeDisplayValue();
	if( prototype != null )
	comboBox.setPrototypeDisplayValue( null );
	Dimension displaySize = getDisplaySize();
	if( prototype != null )
	comboBox.setPrototypeDisplayValue( prototype );

The problem for us is that we use prototype to speed up these calculations. Unfortunately, here it is set to null and then getDisplaySize() is called which iterates over all items in combo box if there is no prototype.

Is there any specific reason why prototype display value is set to null here?

[DevCharly]

I think the idea was to use the prototype to calculate the width of the combobox itself and then ignore it when computing popup width to get wider popup.

But this contrary to what the prototype is mainly there: increase performance.

I think I should change this...

[etsinko]

I agree,
the most important function of prototype is to improve the performance of scroll pane width/height calculation. If the resulting width ends up incorrect, then it is up to the client code to either fix the prototype or remove it.

[DevCharly]

Now changed in master branch.
Thanks for pointing out the issue 👍

[DevCharly]

fixed in 0.29