[mikeysklar]

What

Stop a terminal color code from crashing the board when the terminal has no suitable palette.

Why

The terminal treats any color source as a palette, so a color code can corrupt memory or hard fault.

Found while testing #10478 and #11704.

import displayio, terminalio
fw, fh = terminalio.FONT.get_bounding_box()
g = displayio.TileGrid(terminalio.FONT.bitmap, pixel_shader=displayio.ColorConverter(),
                       width=10, height=2, tile_width=fw, tile_height=fh)
t = terminalio.Terminal(g, terminalio.FONT)
print("BEFORE")
t.write("\x1b[31mX")
print("AFTER")

Board	Before	After
CLUE nRF52840	Hard fault	Prints AFTER, 3 of 3
Metro M4 AirLift	Hard fault, 3 of 3	Prints AFTER, 3 of 3
Metro RP2040	Hard fault, 3 of 3	Prints AFTER, 3 of 3
Metro RP2350	Hard fault, 3 of 3	Prints AFTER, 3 of 3
Metro ESP32-S3	Hard fault, 3 of 3	Prints AFTER, 3 of 3
Feather nRF52840	Hard fault, 3 of 3	Prints AFTER, 3 of 3
Metro ESP32-S2	Hard fault, 3 of 3	Prints AFTER, 3 of 3
Feather STM32F405	Hard fault, 3 of 3	Prints AFTER, 3 of 3
Metro M0 Express	No fault, 3 of 3	No fault, 3 of 3. Color codes are compiled out on SAMD21, so this code is not in the build

Desktop lab, x86-64, 10 runs per case	Before	After
ColorConverter, TilePaletteMapper, including a shader swapped in later	Hard fault, 10 of 10	No fault
Palette(1) next to another object	Hard fault or neighbor corrupted, 10 of 10	No fault, neighbor intact
Palette(2), Palette(8), REPL	Colors change	Same readback
All 1,351 runs		0 faults, 0 tracebacks

Behavior change: ESC[4xm on a Palette(1) used to set entry 0 and is now ignored.

Flash cost: 64 to 92 bytes on CLUE, Feather nRF52840, M4, RP2350, STM32F405 and ESP32-S2.

@lynt-smitka your cp-desktop-lab found this crash before any hardware run.

AI assistance

Claude Code wrote the fix and ran the tests above on boards and the lab. Before and after share a commit on every board.

🤖 Generated with Claude Code

[dhalbert]

👍