CAMEL-23830: camel-jbang - Make TUI shell ANSI colors readable on dark terminals

[ammachado]

Description

Makes ANSI-colored output in the embedded shell panel of the Camel TUI readable on dark terminal themes (see CAMEL-23830).

Problem

In the shell panel, text echoed while typing a command (the command highlighter colors unrecognized commands red) and error output such as Unknown command: x rendered as a dim literal RGB(136,0,0), barely legible on a dark background. The prompt itself was fine (camel orange, version green, > white).

Root cause

JLine's ScreenTerminal flattens named ANSI colors into a 12-bit (4-bit-per-channel) value stored in the cell attribute. ShellPanel.convertAttrToStyle expanded that value straight back into a literal RGB color, bypassing the host terminal's theme. Standard ANSI red (palette index 1, 0x800000) therefore became a fixed dim RGB(136,0,0) instead of the terminal's themed, readable red.

Fix

When the 12-bit value matches one of the 16 standard ANSI palette colors, emit a terminal-themed Color.ansi(AnsiColor.X) instead of a literal RGB color, mirroring how TuiHelper.applySgr already maps SGR codes elsewhere in the TUI. True-color cells (such as the prompt's orange 0xF69123) do not match the palette and keep their literal RGB value.

The 16 encodings are derived from JLine's xterm palette (Colors.DEFAULT_COLORS_256[0..15]) reduced via ScreenTerminal.col24 (the top nibble of each channel), e.g. red 0x800000 -> 0x800, bright red 0xff0000 -> 0xf00, white 0xc0c0c0 -> 0xccc.

Tests

• New ShellPanelColorTest: pins all 16 ANSI encodings to their AnsiColor, asserts true-color values (e.g. the prompt orange 0xf92) stay unmapped, and includes a regression guard that ANSI red resolves to a themed Color.ansi(RED) rather than the old dim RGB.

Docs

• No documentation change: camel-jbang-tui.adoc has no shell-panel section, and this is a readability fix with no change to any default, option, or API, so it does not warrant an upgrade-guide entry.

Target

• I checked that the commit is targeting the correct branch (Camel 4 uses the main branch)

Tracking

• If this is a large change, bug fix, or code improvement, I checked there is a JIRA issue filed for the change (usually before you start working on it).

Apache Camel coding standards and style

• I checked that each commit in the pull request has a meaningful subject line and body.
• I have run mvn clean install -DskipTests locally from root folder and I have committed all auto-generated changes.

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Submitted by Claude Code on behalf of Adriano Machado.

[github-actions]

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[github-actions]

🧪 CI tested the following changed modules:

• dsl/camel-jbang/camel-jbang-plugin-tui

All tested modules (2 modules)

• Camel :: JBang :: Plugin :: TUI
• Camel :: Launcher :: Container

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