Merge pull request 'perf(backgrounds): animated chat backgrounds cost ~5% CPU instead of 50 to 70% (#337)' (#361) from fix/animated-bg-compositor into lotus

src/app/features/lotus/backgrounds/animAurora.ts

@@ -51,7 +51,7 @@ const dark: CSSProperties = {
   backgroundSize: '260% 240%, 300% 260%, 240% 280%, 220% 200%, 100% 100%, 100% 100%',
   backgroundPosition: '0% 30%, 100% 70%, 50% 0%, 20% 80%, 50% 50%, 50% 50%',
   backgroundRepeat: 'no-repeat',
-  animation: `${auroraFlow} 60s ease-in-out infinite`,
+  animation: `${auroraFlow} 60s steps(180) infinite`,
 };
 
 const light: CSSProperties = {
@@ -75,7 +75,7 @@ const light: CSSProperties = {
   backgroundSize: '260% 240%, 300% 260%, 240% 280%, 220% 200%, 100% 100%, 100% 100%',
   backgroundPosition: '0% 30%, 100% 70%, 50% 0%, 20% 80%, 50% 50%, 50% 50%',
   backgroundRepeat: 'no-repeat',
-  animation: `${auroraFlow} 60s ease-in-out infinite`,
+  animation: `${auroraFlow} 60s steps(180) infinite`,
 };
 
 export const animAurora: ChatBgVariants = { dark, light };

src/app/features/lotus/backgrounds/animFireflies.ts

@@ -55,7 +55,7 @@ export const animFireflies: ChatBgVariants = {
       '0 0', // wash A   (static)
       '0 0', // wash B   (static)
     ].join(','),
-    animation: `${firefliesDrift} 44s linear infinite`,
+    animation: `${firefliesDrift} 44s steps(528) infinite`,
   },
 
   // Light: a cozy warm dim-dusk. No harsh dots on white — soft amber motes with
@@ -93,6 +93,6 @@ export const animFireflies: ChatBgVariants = {
       '0 0', // wash A   (static)
       '0 0', // wash B   (static)
     ].join(','),
-    animation: `${firefliesDrift} 44s linear infinite`,
+    animation: `${firefliesDrift} 44s steps(528) infinite`,
   },
 };

src/app/features/lotus/backgrounds/animPulse.ts

@@ -76,7 +76,7 @@ export const animPulse: ChatBgVariants = {
       '0 0', // base wash
       '0 0', // vignette
     ].join(','),
-    animation: `${gridPulse} 22s ease-in-out infinite`,
+    animation: `${gridPulse} 22s steps(528) infinite`,
   },
 
   // Light: soft slate-blue grid on pale cool-white, a gentle luminance breathe.
@@ -116,6 +116,6 @@ export const animPulse: ChatBgVariants = {
       '0 0', // base wash
       '0 0', // vignette
     ].join(','),
-    animation: `${gridPulse} 22s ease-in-out infinite`,
+    animation: `${gridPulse} 22s steps(528) infinite`,
   },
 };

src/app/features/lotus/backgrounds/animRain.ts

@@ -97,7 +97,7 @@ export const animRain: ChatBgVariants = {
     ].join(','),
     backgroundSize: ['260px 200px', '100% 100%', '100% 100%', '100% 100%'].join(','),
     backgroundPosition: ['0 0', '0 0', '0 0', '0 0'].join(','),
-    animation: `${rainFall} 12s linear infinite`,
+    animation: `${rainFall} 12s steps(288) infinite`,
   },
 
   // Light: soft teal-grey streaks on a pale cool base — elegant, never neon.
@@ -118,6 +118,6 @@ export const animRain: ChatBgVariants = {
     ].join(','),
     backgroundSize: ['260px 200px', '100% 100%', '100% 100%', '100% 100%'].join(','),
     backgroundPosition: ['0 0', '0 0', '0 0', '0 0'].join(','),
-    animation: `${rainFall} 12s linear infinite`,
+    animation: `${rainFall} 12s steps(288) infinite`,
   },
 };

src/app/features/lotus/backgrounds/animStars.ts

@@ -68,7 +68,7 @@ export const animStars: ChatBgVariants = {
       '0 0', // nebula A
       '0 0', // nebula B
     ].join(','),
-    animation: `${starDrift} 90s linear infinite`,
+    animation: `${starDrift} 90s steps(1080) infinite`,
   },
 
   // Light: an airy pre-dawn sky. No literal white-on-white stars — instead very
@@ -112,6 +112,6 @@ export const animStars: ChatBgVariants = {
       '0 0', // wash A
       '0 0', // wash B
     ].join(','),
-    animation: `${starDrift} 100s linear infinite`,
+    animation: `${starDrift} 100s steps(1200) infinite`,
   },
 };

src/app/features/lotus/chatBackground.ts

@@ -149,6 +149,11 @@ export const getChatBg = (
   }
   // For animated backgrounds, promote the element to its own compositor layer so
   // background-position keyframes don't trigger repaints on descendant elements.
+  // [Gitea #337] background-position can't run on the compositor, so every
+  // animation frame repaints the whole chat area (45 to 70% main-thread busy
+  // at 60 fps). The drifts are slow (3–22 px/s), so each animation uses steps():
+  // ~12 updates/s for the slow ones, ~24/s for rain and pulse: visually the
+  // same, a fraction of the repaints.
   if (style.animation) {
     return { ...style, willChange: 'background-position', contain: 'paint' };
   }