Implement dynamic configuration via fragment-based templating

[rahul-thakoor]

Migrate from a static weston.ini configuration to a flexible, fragment-based templating architecture using envsubst at container startup. This allows external configuration of Weston core and shell parameters via environment variables without requiring custom image rebuilds, facilitating the transition to a thin-client Wayland sidecar architecture.

• Add configuration default fallbacks via weston-env-defaults.sh.
• Split baseline settings into ordered templates under /etc/weston/templates/ (01-core.ini.template, 02-shell.ini.template, 03-libinput.ini.template).
• Correct libinput key from 'enable-middle-button-emulation' to 'middle-button-emulation' to align with official Weston specifications.
• Update entry.sh to conditionally execute envsubst across template fragments when WESTON_INI_PATH is unset.
• Expose an escape hatch (WESTON_INI_PATH) to bypass dynamic generation and load a user-supplied static configuration file for advanced, multi-instance use cases (e.g., complex multi-output matrices).
• Document environment variables, defaults, and advanced Dockerfile override patterns in README.md.

Change-type: minor

[rahul-thakoor]

Tests

---

Test 1: Baseline, no env vars configured

when no configuration environment variables are explicitly defined, the entry script generates weston.ini based on defaults

Logs:

Setting up XDG_RUNTIME_DIR at /run/user/0...
INFO: Generating dynamic weston.ini from template fragments...
--- LAUNCHING WESTON ---
Command: exec weston --socket=wayland-0 --config=/run/user/0/weston/weston.ini
Date: 2026-05-16 UTC
[02:49:48.351] weston 14.0.2
              https://wayland.freedesktop.org
              Bug reports to: https://gitlab.freedesktop.org/wayland/weston/issues/
              Build: 14.0.2
[02:49:48.351] Command line: weston --socket=wayland-0 --config=/run/user/0/weston/weston.ini
[02:49:48.351] OS: Linux, 6.12.47-yocto-standard, #1 SMP Mon Sep 15 02:39:40 UTC 2025, aarch64

cat /run/user/0/weston/weston.ini

[core]
shell=kiosk
idle-time=0
require-input=false

[shell]
locking=false
panel-position=none

[libinput]
enable-tap=true
middle-button-emulation=true

---

Test 2: Configure WESTON_INI_CORE_SHELL=desktop

cat /run/user/0/weston/weston.ini 
[core]
shell=desktop
idle-time=0
require-input=false
[shell]
locking=false
panel-position=none

[libinput]
enable-tap=true
middle-button-emulation=true

---

Test 3: Multi env Vars

WESTON_INI_CORE_SHELL=desktop
WESTON_INI_SHELL_PANEL_POSITION=bottom

---

Test 4: Set WESTON_INI_PATH

4.1 Missing File

if WESTON_INI_PATH is designated but no file exists at that target location, the entrypoint falls back to generating dynamic template

Setting up XDG_RUNTIME_DIR at /run/user/0...
INFO: Generating dynamic weston.ini from template fragments...
--- LAUNCHING WESTON ---
Command: exec weston --socket=wayland-0 --config=/run/user/0/weston/weston.ini

4.2 WESTON_INI_PATH Env var set and target file exists

FROM bh.cr/balena_solutions/display-%%BALENA_ARCH%%/0.1.0-1778896713634

COPY weston.ini /etc/weston/weston.ini

• cat /etc/weston/weston.ini

[core]
shell=desktop
idle-time=0
require-input=false

[shell]
locking=false
panel-position=right

[libinput]
enable-tap=true
middle-button-emulation=true

runtime env vars check:

root@43e8941:/# printenv | grep WESTON
WESTON_INI_SHELL_PANEL_POSITION=bottom
WESTON_INI_CORE_SHELL=kiosk
WESTON_INI_PATH=/etc/weston/weston.ini

Logs:

Setting up XDG_RUNTIME_DIR at /run/user/0...
INFO: WESTON_INI_PATH is set. Bypassing dynamic template generation.
INFO: Using static configuration file at: /etc/weston/weston.ini
--- LAUNCHING WESTON ---
Command: exec weston --socket=wayland-0 --config=/etc/weston/weston.ini

Note: WESTON_INI_SHELL_PANEL_POSITION=bottom and WESTON_INI_CORE_SHELL=kiosk variables were successfully ignored; panel-position=right from /etc/weston/weston.ini was applied

[chrisys]

Tested with/without env vars and a custom ini file in a random location - all works as expected.