fix: stop sending movement input when the window is unfocused

[soloturn]

Summary

• LocalPlayerSystem.processInput() sent a CharacterMoveInputEvent every frame unconditionally, even with zero keys held and no window focus - a per-frame heartbeat, not edge-triggered on actual input.
• Under a normal frame rate the resulting client/server clock skew is small enough to pass ServerCharacterPredictionSystem's overflow check. When macOS throttles a backgrounded window's render loop to a much lower rate (e.g. after Cmd+Tab), the network-queue delivery granularity no longer scales with it, so a small residual skew leaks past the check every single frame - spamming the "dropping input" warning continuously for as long as the window stays unfocused.
• Fixed by gating processInput() on DisplayDevice.hasFocus(), the same check InputSystem.isCapturingMouse() already uses for raw device polling - no movement input gets generated at all while unfocused.

Test plan

• gradle :engine:compileJava succeeds
• Cmd+Tab away from the game window and confirm no more "dropping input" spam in the log

🤖 Generated with Claude Code

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📝 Walkthrough

Summary by CodeRabbit

• Bug Fixes
  • Improved input handling so keyboard and mouse actions are ignored when the game window isn’t focused.
  • Prevented stale movement, look, and jump input from being processed or triggering unintended gameplay interactions while the display is inactive.

Walkthrough

LocalPlayerSystem now receives DisplayDevice through dependency injection. When the display is unfocused, processInput clears input state and skips event emission.

Changes

Local player input

Layer / File(s)	Summary
Display focus input guard engine/src/main/java/org/terasology/engine/logic/players/LocalPlayerSystem.java	Injects DisplayDevice. When the display lacks focus, processInput clears movement, look deltas, and jump state before returning.

Estimated code review effort: 1 (Trivial) | ~3 minutes

Poem

A rabbit checks the display light,
Then clears stale hops from sight.
No jump or turn can travel through,
Until the window gains its view.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: preventing movement input while the window is unfocused.
Description check	✅ Passed	The description directly explains the unfocused-window input bug, the fix, and the test status.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch soloturn-unfocused-input

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Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In
`@engine/src/main/java/org/terasology/engine/logic/players/LocalPlayerSystem.java`:
- Around line 145-148: Update processInput() so that when display.hasFocus() is
false, relativeMovement, lookPitchDelta, lookYawDelta, and jump are reset or
invalidated before returning; ensure these input values cannot persist and be
reused when focus is restored without new input.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: a07093b4-31ee-40b1-bea0-c9ec5ccb74e2

📥 Commits

Reviewing files that changed from the base of the PR and between 0018a0a and 4cb010e.

📒 Files selected for processing (1)

• engine/src/main/java/org/terasology/engine/logic/players/LocalPlayerSystem.java

[Cervator]

I tested this, admittedly on Windows, and while movement stops when I press ESC it does not stop if I Alt+Tab away from the window, nor if I use the Windows key to otherwise lose focus. That's single player and not on a Mac, however, and I did not go hunting for the logging.

Not sure how much of that was already an issue before this PR, but I wonder if we should cover it as well / test fully on different OSes?

[soloturn]

looked again at it. with josariassurvival, when switching away with tab, it gives endless:

20:45:28.288 [main] WARN  o.t.e.l.c.ServerCharacterPredictionSystem - Received too much input from EntityRef{id = 1330, netId = 2061, prefab = 'engine:player'}, dropping input. Delta difference: 22.0
20:45:28.416 [main] WARN  o.t.e.l.c.ServerCharacterPredictionSystem - Received too much input from EntityRef{id = 1330, netId = 2061, prefab = 'engine:player'}, dropping input. Delta difference: 28.0
20:45:28.537 [main] WARN  o.t.e.l.c.ServerCharacterPredictionSystem - Received too much input from EntityRef{id = 1330, netId = 2061, prefab = 'engine:player'}, dropping input. Delta difference: 20.0
20:45:28.658 [main] WARN  o.t.e.l.c.ServerCharacterPredictionSystem - Received too much input from EntityRef{id = 1330, netId = 2061, prefab = 'engine:player'}, dropping input. Delta difference: 22.0
20:45:28.777 [main] WARN  o.t.e.l.c.ServerCharacterPredictionSystem - Received too much input from EntityRef{id = 1330, netId = 2061, prefab = 'engine:player'}, dropping input. Delta difference: 18.0
20:45:28.897 [main] WARN  o.t.e.l.c.ServerCharacterPredictionSystem - Received too much input from EntityRef{id = 1330, netId = 2061, prefab = 'engine:player'}, dropping input. Delta difference: 19.0

with core gameplay not. applying this pr stops the output for JSS.

[soloturn]

tested on linux, unfocussed error with terasologylauncher downloaded game.