RFR: 7093691: Nimbus LAF: disabled JComboBox using renderer has bad font color

[Abhishek Kumar]

On Thu, 2 Feb 2023 16:33:06 GMT, Damon Nguyen <dnguyen at openjdk.org> wrote:

> Before the fix, a JComboBox in Nimbus L&F would have normal black text even when the JComboBox was disabled if SynthComboBoxRenderer was replaced with a DefaultListCellRenderer. This text should be greyed out like in other L&F's. When looking into the defaults for Nimbus L&F files for attributes and states of a JComboBox, it confirm that the intention for disabled JComboBoxes is nimbusDisabledText (which is grey text).
> 
> SynthComboBoxes have an additional check in its default SynthComboBoxRenderer that enables/disables the renderer itself. The SynthComboBoxRenderer inherits its enabled state from the parent ComboBox. Since the renderer with DefaultListCellRenderer is in a separate class without a reference to the comboBox, a listener was added to SynthComboBoxUI.
> 
> An additional issue occurred in DefaultListCellRenderer because the renderer overrode the listener's re-assigned enabled state. In testing, setting the enabled state in DefaultListCellRenderer is redundant for all L&F's and is not needed here. However, instead of removing it altogether, a conditional was added specifically to allow ComboBoxes to skip setting enabled state here.
> 
> After the fix, the Nimbus JComboBox with DLCR set matches the appearance of a normal Nimbus JComboBox. I can enable/disable the JComboBoxes in the test, and the UI elements behave and appear as expected.

test/jdk/javax/swing/JComboBox/DisabledComboBoxFontTest.java line 2:

> 1: /*
> 2:  * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.

Copyright year can be changed to 2023.

test/jdk/javax/swing/JComboBox/DisabledComboBoxFontTest.java line 118:

> 116:         hasNimbus = false;
> 117: 
> 118:         for (LookAndFeelInfo info : UIManager.getInstalledLookAndFeels()) {

It seems the intention to run the test is in Nimbus LAF only. I think you can directly set the Nimbus LAF using `UIManager.setLookAndFeel("javax.swing.plaf.nimbus.NimbusLookAndFeel");` and can avoid the `for-loop, condition check` and `hasNimbus `variable.

To print the error message, LAF can be set within try-catch block.

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PR: https://git.openjdk.org/jdk/pull/12390