From f5622c60dd9e10365901f33f226da748b0fae944 Mon Sep 17 00:00:00 2001
From: barbeque-squared <barbeque.squared@gmail.com>
Date: Thu, 3 Nov 2022 15:41:46 +0100
Subject: [PATCH] make the rendering of the oscilloscope significantly less
 expensive. the more players, the bigger the impact

---
 src/base/UDraw.pas | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/base/UDraw.pas b/src/base/UDraw.pas
index 6a1fa0bb6..729985f93 100644
--- a/src/base/UDraw.pas
+++ b/src/base/UDraw.pas
@@ -363,6 +363,9 @@ procedure SingDrawOscilloscope(X, Y, W, H: real; NrSound: integer);
   Sound:       TCaptureBuffer;
   MaxX, MaxY:  real;
   Col: TRGB;
+const
+  // arbitrarily chosen, but this makes it draw only 4096/SampleIndexStep line segments
+  SampleIndexStep = 32;
 begin;
   Sound := AudioInputProcessor.Sound[NrSound];
 
@@ -382,13 +385,16 @@ procedure SingDrawOscilloscope(X, Y, W, H: real; NrSound: integer);
   MaxX := W-1;
   MaxY := (H-1) / 2;
 
+  SampleIndex := 0;
+
   Sound.LockAnalysisBuffer();
 
   glBegin(GL_LINE_STRIP);
-    for SampleIndex := 0 to High(Sound.AnalysisBuffer) do
+    while SampleIndex < High(Sound.AnalysisBuffer) do
     begin
       glVertex2f(X + MaxX * SampleIndex/High(Sound.AnalysisBuffer),
                  Y + MaxY * (1 - Sound.AnalysisBuffer[SampleIndex]/-Low(Smallint)));
+      SampleIndex := SampleIndex + SampleIndexStep;
     end;
   glEnd;