Add Spectrum gradient fill toggle in settings

Mirror the existing Wideband gradient fill option for the main spectrum:
a "Spectrum gradient fill" checkbox on the Display settings tab gates the
under-curve gradient in TSpectrumView.DrawSpectrum. The curve, grid,
filter band and VFO markers always draw; only the gradient is optional.

Persisted as spectrum_fill in settings JSON (default True, preserving
current appearance). Wired through Settings -> SettingsForm visibility
event -> MainForm -> TSpectrumView.FillSpectrum, same path as
WidebandFill.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

MainForm.pas

@@ -241,6 +241,7 @@ type
     FShowWaterfall:  Boolean;
     FShowWideband:   Boolean;
     FWidebandFill:   Boolean;
+    FSpectrumFill:   Boolean;
     FDisplayFPS:     Integer;
     FWaterfallDirty: Boolean;
     FWidebandDirty:  Boolean;
@@ -729,7 +730,7 @@ type
     function  PullSoundCardMic(MaxN: Integer): Integer;
     function  BuildMicLineSelectByte: Byte;
     procedure ApplyVisibility(ShowSpectrum, ShowWaterfall, ShowWideband,
-      WidebandFill: Boolean);
+      WidebandFill, SpectrumFill: Boolean);
     procedure ApplyFPS(FPS: Integer);
     procedure ApplyFreqMhzDigits(Digits: Integer);
 
@@ -951,6 +952,7 @@ begin
   Result.ShowWaterfall   := FShowWaterfall;
   Result.ShowWideband    := FShowWideband;
   Result.WidebandFill    := FWidebandFill;
+  Result.SpectrumFill    := FSpectrumFill;
   Result.DisplayDuplex   := FDisplayDuplex;
   Result.DisplayFPS      := FDisplayFPS;
   Result.LightTheme      := FLightTheme;
@@ -1295,6 +1297,7 @@ begin
   FShowWaterfall := True;
   FShowWideband  := False;
   FWidebandFill  := False;
+  FSpectrumFill  := True;
   FDisplayFPS    := 60;
   FFreqMhzDigits := 3;
   FSplitterRatio := 0.40;
@@ -4098,6 +4101,8 @@ begin
   FWidebandFill  := G_Settings.WidebandFill;
   if Assigned(FWidebandView) then
     FWidebandView.SetFillSpectrum(FWidebandFill);
+  FSpectrumFill  := G_Settings.SpectrumFill;
+  FSpecView.FillSpectrum := FSpectrumFill;
   FDisplayDuplex := G_Settings.DisplayDuplex;
   if BtnDUP <> nil then StyleButton(BtnDUP, FDisplayDuplex);
   if G_Settings.DisplayFPS > 0 then
@@ -7503,14 +7508,16 @@ begin
 end;
 
 procedure TMainForm.ApplyVisibility(ShowSpectrum, ShowWaterfall,
-  ShowWideband, WidebandFill: Boolean);
+  ShowWideband, WidebandFill, SpectrumFill: Boolean);
 begin
   FShowSpectrum  := ShowSpectrum;
   FShowWaterfall := ShowWaterfall;
   FShowWideband  := ShowWideband;
   FWidebandFill  := WidebandFill;
+  FSpectrumFill  := SpectrumFill;
   if Assigned(FWidebandView) then
     FWidebandView.SetFillSpectrum(FWidebandFill);
+  FSpecView.FillSpectrum := FSpectrumFill;
   if Assigned(FNetwork) and FNetwork.Connected then
     FNetwork.ConfigureWideband(0, FShowWideband, 512, 16, 70, 32);
   ResizeSpectrumPanels;
@@ -7597,7 +7604,8 @@ begin
     FCATLastGlobal.CATTcpPort);
   // Перечисляем PA устройства
   SF.RefreshAudioDevices(FAudioOut, FAudioIn);
-  SF.LoadVisibility(FShowSpectrum, FShowWaterfall, FShowWideband, FWidebandFill);
+  SF.LoadVisibility(FShowSpectrum, FShowWaterfall, FShowWideband, FWidebandFill,
+    FSpectrumFill);
   SF.LoadWfAGCNF(FWfAGCEnabled, FWfNFEnabled);
   SF.LoadADCSettings(FDitherEnabled, FRandomEnabled);
   SF.LoadWebSettings(FWebEnabled, FWebPort, FWebBindAddr, FWebUser, FWebPass);

Settings.pas

@@ -224,6 +224,7 @@ type
     ShowWaterfall:     Boolean;  // True = draw waterfall on main form
     ShowWideband:      Boolean;  // True = draw raw ADC wideband pane on main form
     WidebandFill:      Boolean;  // True = fill wideband spectrum with gradient
+    SpectrumFill:      Boolean;  // True = fill main spectrum under the curve with gradient
     DisplayDuplex:     Boolean;  // DUP: при TX показывать RX-водопад, TX-фильтр overlay'ем
     // --- Display FPS ---
     DisplayFPS:        Integer;  // spectrum/waterfall timer fps (1..100)
@@ -402,6 +403,7 @@ begin
   G.ShowWaterfall    := True;
   G.ShowWideband     := False;
   G.WidebandFill     := False;
+  G.SpectrumFill     := True;
   G.DisplayDuplex    := False;
   G.DisplayFPS       := 60;
   G.FreqMhzDigits    := 3;
@@ -621,6 +623,7 @@ begin
   G.ShowWaterfall := JB(GObj,'show_waterfall',True);
   G.ShowWideband  := JB(GObj,'show_wideband',False);
   G.WidebandFill  := JB(GObj,'wideband_fill',False);
+  G.SpectrumFill  := JB(GObj,'spectrum_fill',True);
   G.DisplayDuplex := JB(GObj,'display_duplex',False);
   G.DisplayFPS    := JI(GObj,'display_fps',60);
   G.LightTheme    := JB(GObj,'light_theme',False);
@@ -708,6 +711,7 @@ begin
   JW(O,'show_waterfall',G.ShowWaterfall);
   JW(O,'show_wideband',G.ShowWideband);
   JW(O,'wideband_fill',G.WidebandFill);
+  JW(O,'spectrum_fill',G.SpectrumFill);
   JW(O,'display_duplex',G.DisplayDuplex);
   JW(O,'display_fps',G.DisplayFPS);
   JW(O,'light_theme',G.LightTheme);

SettingsForm.pas

@@ -50,7 +50,7 @@ type
   TOnAudioInDevChange = procedure(DevIndex: Integer; const DevName: string) of object;
   TOnAudioBufferChange = procedure(BufferSize: Integer) of object;
   TOnVisibilityChange = procedure(ShowSpectrum, ShowWaterfall, ShowWideband,
-    WidebandFill: Boolean) of object;
+    WidebandFill, SpectrumFill: Boolean) of object;
   TOnFPSChange = procedure(FPS: Integer) of object;
   TOnThemeChange = procedure(LightTheme: Boolean) of object;
   TOnWfAGCNFChange = procedure(WfAGC, WfNF: Boolean) of object;
@@ -123,6 +123,7 @@ type
     FChkShowWaterfall:   TFlatCheckBox;
     FChkShowWideband:    TFlatCheckBox;
     FChkWidebandFill:    TFlatCheckBox;
+    FChkSpectrumFill:    TFlatCheckBox;
     FCmbFPS:             TFlatComboBox;
     FChkLightTheme:      TFlatCheckBox;
     FCmbFreqMhzDigits:   TFlatComboBox;
@@ -375,7 +376,7 @@ type
     procedure RefreshAudioDevices(AudioOut: TAudioOutput; AudioIn: TAudioInput);
     procedure LoadAudioBufferSize(BufferSize: Integer);
     procedure LoadVisibility(ShowSpectrum, ShowWaterfall, ShowWideband,
-      WidebandFill: Boolean);
+      WidebandFill, SpectrumFill: Boolean);
     procedure LoadFPS(FPS: Integer);
     procedure LoadLightTheme(ALight: Boolean);
     procedure LoadFreqMhzDigits(Digits: Integer);
@@ -846,6 +847,16 @@ begin
   FChkWidebandFill.Font.Size := 9;
   FChkWidebandFill.OnChange := OnVisibilityChkChange;
 
+  FChkSpectrumFill := TFlatCheckBox.Create(Self);
+  FChkSpectrumFill.Parent := Grp;
+  FChkSpectrumFill.Caption := 'Spectrum gradient fill';
+  FChkSpectrumFill.SetBounds(PAD, R1 + 28, CHKW, 22);
+  FChkSpectrumFill.Checked := True;
+  FChkSpectrumFill.Font.Color := CLR_TEXT;
+  FChkSpectrumFill.Font.Name := UI_FONT;
+  FChkSpectrumFill.Font.Size := 9;
+  FChkSpectrumFill.OnChange := OnVisibilityChkChange;
+
   Grp := MakeGroupPanel(FPageDisplay, 'Performance', MARGIN, 212, 650, 92);
 
   MakeLbl(Grp, 'Refresh rate', PAD, R1 + 5, LW);
@@ -2328,7 +2339,7 @@ begin
 end;
 
 procedure TSettingsForm.LoadVisibility(ShowSpectrum, ShowWaterfall,
-  ShowWideband, WidebandFill: Boolean);
+  ShowWideband, WidebandFill, SpectrumFill: Boolean);
 begin
   FLoading := True;
   try
@@ -2336,6 +2347,7 @@ begin
     FChkShowWaterfall.Checked := ShowWaterfall;
     FChkShowWideband.Checked  := ShowWideband;
     FChkWidebandFill.Checked  := WidebandFill;
+    FChkSpectrumFill.Checked  := SpectrumFill;
   finally
     FLoading := False;
   end;
@@ -2357,7 +2369,7 @@ begin
   if FLoading then Exit;
   if not Assigned(FOnVisibilityChange) then Exit;
   FOnVisibilityChange(FChkShowSpectrum.Checked, FChkShowWaterfall.Checked,
-    FChkShowWideband.Checked, FChkWidebandFill.Checked);
+    FChkShowWideband.Checked, FChkWidebandFill.Checked, FChkSpectrumFill.Checked);
 end;
 
 procedure TSettingsForm.OnLightThemeChkChange(Sender: TObject);

SpectrumView.pas

@@ -39,6 +39,7 @@ type
     FFMGridLastSpan:   Double;
     FSpPts:           array of TPoint;
     FSpPtsLen:        Integer;
+    FFillSpectrum:    Boolean;
     // ── Тема ─────────────────────────────────────────────────────────────────
     FTheme:           TAppTheme;
     FLightTheme:      Boolean;
@@ -95,6 +96,7 @@ type
     procedure SetTXSpanHz(V: Double);
     procedure SetMarkerActive(V: Boolean);
     procedure SetMarkerX(V: Integer);
+    procedure SetFillSpectrum(V: Boolean);
     procedure DrawSpectrumGradient(const SpPts: array of TPoint; W, H: Integer);
     procedure DrawMarkerLine(C: TCanvas; W, H: Integer);
     procedure BlendBand(X1, X2, H: Integer; R, G, B, Alpha: Byte);
@@ -191,6 +193,7 @@ type
 
     // ── Флаги обновления ──────────────────────────────────────────────────────
     property SpectrumDirty:  Boolean read FSpectrumDirty  write FSpectrumDirty;
+    property FillSpectrum:   Boolean read FFillSpectrum   write SetFillSpectrum;
     property WaterfallDirty:  Boolean read GetWaterfallDirty  write SetWaterfallDirty;
     property WfFrameInterval: Integer read GetWfFrameInterval write SetWfFrameInterval;
 
@@ -304,6 +307,7 @@ begin
   FSpectrumBufCount  := 1024;
   FSpectrumDirty     := True;
   FLightTheme  := False;
+  FFillSpectrum := True;
   FTheme       := DarkTheme;
   // Sub-views
   FWaterfall := TWaterfallView.Create;
@@ -388,6 +392,13 @@ begin
   FWaterfall.MarkerX := V;
 end;
 
+procedure TSpectrumView.SetFillSpectrum(V: Boolean);
+begin
+  if FFillSpectrum = V then Exit;
+  FFillSpectrum := V;
+  FSpectrumDirty := True;
+end;
+
 function TSpectrumView.GetWaterfallDirty: Boolean;
 begin
   Result := FWaterfall.WaterfallDirty;
@@ -898,9 +909,12 @@ begin
     end;
   FSpPts[W] := Point(W-1, H); FSpPts[W+1] := Point(0, H);
 
-  // ── 5. Градиент ───────────────────────────────────────────────────────────
+  // ── 5. Градиент (заливка под кривой) ──────────────────────────────────────
-  C.Brush.Style := bsSolid; C.Pen.Style := psClear;
+  if FFillSpectrum then
-  DrawSpectrumGradient(FSpPts, W, H);
+  begin
+    C.Brush.Style := bsSolid; C.Pen.Style := psClear;
+    DrawSpectrumGradient(FSpPts, W, H);
+  end;
 
   // ── 6. Линия спектра ──────────────────────────────────────────────────────
   C.Pen.Style := psSolid; C.Pen.Color := FTheme.SpecLine; C.Pen.Width := 1;