Compute foreground and background colours for setEnabled and setEditable in StyledText

[elsazac]

This PR adds consistent handling of both foreground and background colors for both setEnabled and setEditable functions

The foreground and background colors were computed only for setEnabled. This has to be done for setEditable as
well to achieve consistency. Both the functions setEditable and setEnabled now recomputes foreground and background colour (earlier only applied in setEnabled)
This commit also adds a distinct foreground and background colour combination. Earlier the editable and non-editable state showed no difference. This now improves visual differentiation in StyledText.

Test Snippet : Test.txt

The StyledText behaviour in non editable state is shown below :

Before :

After :

Fixes: #3132, Fixes: #230

[github-actions]

Test Results

  170 files  ±0    170 suites  ±0   27m 38s ⏱️ + 1m 14s
4 678 tests ±0  4 657 ✅ ±0   21 💤 ±0  0 ❌ ±0 
6 586 runs  ±0  6 431 ✅ ±0  155 💤 ±0  0 ❌ ±0 

Results for commit 032bd55. ± Comparison against base commit b829b31.

♻️ This comment has been updated with latest results.

[BeckerWdf]

Does this still work fine when CSS styling is used in the IDE?

[sratz]

This is going to resolve, #230, correct?

[Copilot]

Pull request overview

This PR makes StyledText apply consistent foreground/background color recomputation for both setEnabled(...) and setEditable(...), and introduces a distinct visual style for the non-editable (but enabled) state.

Changes:

• Added a shared updateColors(enabled, editable) helper and invoked it from both setEnabled and setEditable.
• Introduced new system color choices for the enabled-but-non-editable state to improve visual differentiation.
• Guarded resetCache(...) / caret recomputation in setBackground/setForeground when content is not yet initialized.

[Copilot]

SWT.COLOR_TITLE_INACTIVE_BACKGROUND is semantically a title-bar color and can render inconsistently across platforms/themes when used as a text background. For an enabled-but-non-editable text area, consider using text/widget-related system colors (or a derived variant of the normal text background) to better track platform theming and maintain consistent look-and-feel.

Suggested change

	setBackground(display.getSystemColor(SWT.COLOR_TITLE_INACTIVE_BACKGROUND));
	setBackground(display.getSystemColor(SWT.COLOR_LIST_BACKGROUND));

[elsazac]

Both editable and enabled are true :

When editable is true and enabled is false :

When editable is false and enabled is true :

when editable and enabled are both false :

[elsazac]

This is going to resolve, #230, correct?

The enabled case wasn’t handled earlier, but it is now covered with most recent changes