From a7da90fdfcbc17673cccb9f761930ccb812fcfe9 Mon Sep 17 00:00:00 2001
From: quanticsoul4772 <71096528+quanticsoul4772@users.noreply.github.com>
Date: Sun, 25 Oct 2026 16:51:56 -0700
Subject: [PATCH] fix(effects): run no sharpen pass when its slider is at 0
 (#1398)

Disable the sharpen pass when its intensity is zero.

Contribution by @quanticsoul4772.
---
 changelog.d/1398-sharpen-zero-off.md |  2 ++
 docs/CURRENT-STATE.md                |  2 ++
 src/ui/visualEffects.js              | 14 +++++++++++++-
 src/ui/visualEffects.test.mjs        | 18 ++++++++++++++++++
 4 files changed, 35 insertions(+), 1 deletion(-)
 create mode 100644 changelog.d/1398-sharpen-zero-off.md

diff --git a/changelog.d/1398-sharpen-zero-off.md b/changelog.d/1398-sharpen-zero-off.md
new file mode 100644
index 000000000..ab05aa6f2
--- /dev/null
+++ b/changelog.d/1398-sharpen-zero-off.md
@@ -0,0 +1,2 @@
+- The Sharpen slider at 0 now turns the sharpen pass off instead of still
+  sharpening at a low amount (quanticsoul4772, #1398).
diff --git a/docs/CURRENT-STATE.md b/docs/CURRENT-STATE.md
index 07daef46c..e2e24fc7d 100644
--- a/docs/CURRENT-STATE.md
+++ b/docs/CURRENT-STATE.md
@@ -1301,6 +1301,8 @@ Stopping the controller revokes animation before asynchronous UI teardown; final
 destruction removes its stages and restores the borrowed bloom configuration.
 Snow's sideways sway stays within a fixed range at any session age; Wind scales
 its amplitude.
+Sharpen runs only when enabled with intensity above 0.001. At slider zero its
+stage is disabled; raising the slider resumes it when sharpen is enabled.
 
 ## Display control ownership
 
diff --git a/src/ui/visualEffects.js b/src/ui/visualEffects.js
index 8b5234ef2..9d10f0cef 100644
--- a/src/ui/visualEffects.js
+++ b/src/ui/visualEffects.js
@@ -159,18 +159,30 @@ export class VisualEffects {
     this.requestRender('bloom');
   }
 
+  /**
+   * Sharpen runs only when it is on and its slider is above 0, as the style
+   * stages do: the pass costs the same at any amount (~1.5 ms GPU per frame
+   * on the Arc, 2026-10-24), and `0.1 + value * 2` still sharpened at 0.
+   */
+  syncSharpenEnabled() {
+    if (this.stopped || !this.sharpenStage) return;
+    this.sharpenStage.enabled =
+      this.sharpenEnabled && this.sharpenIntensity > 0.001;
+  }
+
   applySharpenIntensity(value) {
     if (this.stopped) return;
     this.sharpenIntensity = value;
     if (this.sharpenStage)
       this.sharpenStage.uniforms.amount = 0.1 + value * 2.0;
+    this.syncSharpenEnabled();
     this.requestRender('sharpen');
   }
 
   setSharpenEnabled(enabled) {
     if (this.stopped) return;
     this.sharpenEnabled = !!enabled;
-    if (this.sharpenStage) this.sharpenStage.enabled = this.sharpenEnabled;
+    this.syncSharpenEnabled();
     this.requestRender('sharpen');
   }
 
diff --git a/src/ui/visualEffects.test.mjs b/src/ui/visualEffects.test.mjs
index 68fa45962..9e9542c52 100644
--- a/src/ui/visualEffects.test.mjs
+++ b/src/ui/visualEffects.test.mjs
@@ -224,6 +224,24 @@ test('sharpen uses the existing uniform scale and keeps values while disabled',
   f.effects.destroy();
 });
 
+test('sharpen at 0 runs no pass, and comes back with the slider', () => {
+  const f = fixture();
+  f.effects.initPostProcess(0.49);
+  f.effects.setSharpenEnabled(true);
+  assert.equal(f.effects.sharpenStage.enabled, true);
+  f.effects.applySharpenIntensity(0);
+  assert.equal(
+    f.effects.sharpenStage.enabled,
+    false,
+    'no residual sharpen at 0',
+  );
+  f.effects.setSharpenEnabled(true);
+  assert.equal(f.effects.sharpenStage.enabled, false, 'on at 0 is still off');
+  f.effects.applySharpenIntensity(0.2);
+  assert.equal(f.effects.sharpenStage.enabled, true);
+  f.effects.destroy();
+});
+
 test('stop revokes pending work immediately but retains stages until final destruction', () => {
   const f = fixture();
   f.effects.initStyles();