From 1eecd974fc9cc33d36a91bfbd3afa32c06f27a8b Mon Sep 17 00:00:00 2001
From: Uladzimir Karpenka <i@vladimir.cc>
Date: Sun, 24 May 2026 18:51:41 +0300
Subject: [PATCH] Reduce timer-tick CPU load by removing per-tick ResizeSMeter
 and throttling AGC line updates

- Remove ResizeSMeter (Pango font measurement + multiple SetBounds) from 60 Hz timer tick;
  it is still called on actual resize events
- Throttle UpdateAGCLines WDSP API calls from 60 Hz to ~10 Hz (every 6 ticks)
- Optimize spectrum alpha-fix loop: write-only byte access instead of read-modify-write DWORD

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 MainForm.pas     | 13 +++++++++----
 SpectrumView.pas |  9 ++++++---
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/MainForm.pas b/MainForm.pas
index 4bfd5dd..9d86d7a 100644
--- a/MainForm.pas
+++ b/MainForm.pas
@@ -301,6 +301,7 @@ type
     // Waterfall frame timing
     FWaterfallFrameInterval: Integer;
     FWaterfallFrameCounter:  Integer;
+    FAgcLineCounter:         Integer;
     // ---- Splitter ----
     FSplitterDrag:   Boolean;
     FSplitterDragY0: Integer;
@@ -2874,7 +2875,6 @@ begin
                         ((PbWaterfall.Width <> FSpectrumWidth) or
                          (PbWaterfall.Height <> FWaterfallHeight))) then
     ResizeSpectrumPanels;
-  ResizeSMeter;
   if FSpectrumWidth <= 0 then Exit;
   SyncSpecViewFreq;
 
@@ -2920,9 +2920,14 @@ begin
     begin
       FLastSMeter := FDSPEngine.GetSMeterDBm;
       FDSPEngine.SetSpectrumWidth(FSpectrumWidth);
-      FDSPEngine.UpdateAGCLines(FSpectrumWidth);
-      FSpecView.AGCThresh    := FDSPEngine.AGCThresh;
-      FSpecView.AGCHangLevel := FDSPEngine.AGCHangLevel;
+      Inc(FAgcLineCounter);
+      if FAgcLineCounter >= 6 then
+      begin
+        FDSPEngine.UpdateAGCLines(FSpectrumWidth);
+        FSpecView.AGCThresh    := FDSPEngine.AGCThresh;
+        FSpecView.AGCHangLevel := FDSPEngine.AGCHangLevel;
+        FAgcLineCounter := 0;
+      end;
     end;
     FSpecView.WDSPReady := FWDSPReady;
     // Обновляем оверлей если видим
diff --git a/SpectrumView.pas b/SpectrumView.pas
index 5667a20..febc724 100644
--- a/SpectrumView.pas
+++ b/SpectrumView.pas
@@ -696,7 +696,7 @@ procedure TSpectrumView.DrawSpectrum;
 var
   C, GC: TCanvas;
   i, Yp, W, H, GX: Integer;
-  AlphaRow: PCardinal;
+  AlphaPtr: PByte;
   DBmin, DBmax, dB: Double;
   VfoX, X1, X2: Integer;
   TXVfoX, TXX1, TXX2: Integer;
@@ -907,9 +907,12 @@ begin
   FSpectrumBitmap.BeginUpdate(False);
   for i := 0 to H - 1 do
   begin
-    AlphaRow := PCardinal(FSpectrumBitmap.ScanLine[i]);
+    AlphaPtr := PByte(FSpectrumBitmap.ScanLine[i]) + 3;
     for Yp := 0 to W - 1 do
-      AlphaRow[Yp] := AlphaRow[Yp] or $FF000000;
+    begin
+      AlphaPtr^ := $FF;
+      Inc(AlphaPtr, 4);
+    end;
   end;
   FSpectrumBitmap.EndUpdate(False);
 end;