desktop: fix laggy bars blur by blurring a narrower offscreen copy (#7556)

Skia's raster blur runs at full resolution, so each bar blurred width x (bar + 6 sigma) pixels every frame: about 80 ms per frame for the two bars of a chat at the default radius, which cut scrolling to 5-9 fps on the software renderer. Scaling the layer cannot help, because a layer's filter is evaluated in device space and the scale is applied to the sigma too. The bar is now drawn into an offscreen surface up to 8x narrower and blurred there, which measured 5-6x cheaper and within 0.25/255 of the original. Blurring a copy means the bar no longer follows the content on its own, so the scroll containers bump a version on the app bar handler and the bar depends on it. Co-authored-by: Evgeny Poberezkin <evgeny@poberezkin.com>
2026-10-05 23:07:57 +00:00 · 2026-09-26 12:42:36 +01:00
parent 9cd1c46606
commit ef66e5e520
7 changed files with 249 additions and 27 deletions
@@ -0,0 +1,6 @@
+package chat.simplex.common.platform
+
+import androidx.compose.ui.graphics.drawscope.DrawScope
+
+// Android blurs the bars with a RenderEffect on the layer itself, so this is never called there.
+actual fun DrawScope.drawBarsBlurred(radiusPx: Float, barWidth: Float, barHeight: Float, drawBar: DrawScope.() -> Unit) = drawBar()