ext-stage-dock: use shader-based linear-gradient for the dock background

horizontal-gradient is RmlUi's legacy decorator: it bakes the ramp into
interpolated vertex colours through the plain colour shader, so it bypassed the
gradient dither and showed hard 8-bit alpha banding over light backgrounds.
Switch to linear-gradient(to right, ...), which renders per-pixel in our GL3
gradient shader (where the dither lives), giving a clean fade to transparent.

1 files changed, 6 insertions, 1 deletions

diff --git a/assets/ext-stage-dock/dock.rcss b/assets/ext-stage-dock/dock.rcss
index bbb23f3..13bdfec 100644
--- a/assets/ext-stage-dock/dock.rcss
+++ b/assets/ext-stage-dock/dock.rcss
@@ -20,7 +20,12 @@ body.dock {
 div.panel {
     width: 100%;
     height: 100%;
-    decorator: horizontal-gradient( #000000ff #00000000 );
+    /* Use the SHADER-based linear-gradient (not the legacy horizontal-gradient,
+       which renders via interpolated vertex colours and shows hard 8-bit alpha
+       banding over light backgrounds). linear-gradient is computed per-pixel in
+       our GL3 fragment shader, which also applies ~1 LSB TPDF dither to break the
+       alpha-ramp banding as it fades to transparent. */
+    decorator: linear-gradient( to right, #000000ff, #00000000 );
     padding: 8dp;
     font-family: Noto Sans;
     display: flex;