ewsdr/SpectrumViewOpengl.pas

unit SpectrumViewOpengl;

{
  OpenGL renderer for the spectrum pane.

  The class keeps the public TSpectrumView contract so MainForm can switch it
  with --opengl without changing DSP/web data flow. Waterfall, ruler and S-meter
  remain delegated to the base sub-views; only the spectrum paint path uses GL.
}

{$IFDEF FPC}
  {$MODE Delphi}
{$ENDIF}

interface

uses
  Classes, SysUtils, Graphics, Controls, Math, Types,
  OpenGLContext, GL,
  AppTheme, SpectrumView, WaterfallViewOpengl;

type
  TGLTextureCache = record
    Tex: GLuint;
    W: Integer;
    H: Integer;
    Dirty: Boolean;
  end;

  TSpectrumViewOpenGL = class(TSpectrumView)
  private
    FGLControl: TOpenGLControl;
    FGridDirty: Boolean;
    FOverlayDirty: Boolean;
    FSampleOverlayDirty: Boolean;
    FVfoOverlayDirty: Boolean;
    FGridLabelTex: TGLTextureCache;
    FAGCLabelTex: TGLTextureCache;
    FAGCHangLabelTex: TGLTextureCache;
    FMarkerLabelTex: TGLTextureCache;
    FADCOverlayTex: TGLTextureCache;
    FSampleOverlayTex: TGLTextureCache;
    FVfoOverlayTex: TGLTextureCache;
    FLastAGCText: string;
    FLastAGCY: Integer;
    FLastAGCHangY: Integer;
    FLastMarkerText: string;
    FLastMarkerX: Integer;
    FLastADCVisible: Boolean;
    FLastSampleX: Integer;
    FLastSampleY: Integer;
    FLastSampleW: Integer;
    FLastSampleH: Integer;
    FLastVfoX: Integer;
    FLastVfoY: Integer;
    FLastVfoW: Integer;
    FLastVfoH: Integer;
    FGLSpectrumW: Integer;
    FGLSpectrumH: Integer;
    FSpY: array of Integer;

    procedure DeleteTexture(var T: TGLTextureCache);
    procedure UploadBitmap(var T: TGLTextureCache; B: TBitmap; Keyed: Boolean;
      FixedAlpha: Byte);
    procedure UploadAlphaMask(var T: TGLTextureCache; B: TBitmap; AColor: TColor);
    procedure UploadText(var T: TGLTextureCache; const S: string; AColor: TColor;
      FontSize: Integer; Bold: Boolean);
    procedure DrawTexture(const T: TGLTextureCache; X, Y: Integer);
    procedure DrawRect(X1, Y1, X2, Y2: Integer; C: TColor; Alpha: Single);
    procedure DrawLine(X1, Y1, X2, Y2: Integer; C: TColor; Width: Single;
      Stipple: Boolean);
    procedure DrawVerticalGradient(W, H: Integer);
    procedure DrawGrid(W, H: Integer; DBmax, DBmin, InvRange: Double);
    procedure DrawFilterAndCursors(W, H: Integer);
    procedure DrawAGCLines(W, H: Integer; DBmax, InvRange: Double);
    procedure DrawSpectrumCurve(W, H: Integer; DBmax, InvRange: Double);
    procedure DrawMarker(W, H: Integer);
    procedure DrawADCOverlay(W, H: Integer);
    procedure DrawCachedOverlays(W, H: Integer);
    function FormatFreqGL(Hz: Double): string;
    function ActiveVfoFrequency: Double;
  public
    constructor Create;
    destructor Destroy; override;
    procedure AttachControl(C: TOpenGLControl);
    procedure AttachWaterfallControl(C: TOpenGLControl);
    procedure SetSpectrumBitmapSize(W, H: Integer); override;
    function SpectrumBitmapWidth: Integer; override;
    procedure DrawSpectrum; override;
    procedure PaintSpectrum(Sender: TObject); override;
    procedure InvalidateGridCache; override;
    procedure InvalidateOverlayCache; override;
    procedure SetTheme(const T: TAppTheme); override;
  end;

implementation

const
  KEY_COLOR = TColor($00FF00FF);

function ClampI(V, Lo, Hi: Integer): Integer;
begin
  if V < Lo then Result := Lo
  else if V > Hi then Result := Hi
  else Result := V;
end;

procedure ColorToRGB(C: TColor; out R, G, B: GLFloat);
begin
  R := (C and $FF) / 255.0;
  G := ((C shr 8) and $FF) / 255.0;
  B := ((C shr 16) and $FF) / 255.0;
end;

constructor TSpectrumViewOpenGL.Create;
begin
  inherited Create;
  FWaterfall.Free;
  FWaterfall := TWaterfallViewOpenGL.Create;
  FWaterfall.WfFrameInterval := 1;
  FGridDirty := True;
  FOverlayDirty := True;
  FSampleOverlayDirty := True;
  FVfoOverlayDirty := True;
  FLastAGCY := -MaxInt;
  FLastAGCHangY := -MaxInt;
  FLastMarkerX := -MaxInt;
  FLastADCVisible := False;
end;

destructor TSpectrumViewOpenGL.Destroy;
begin
  if Assigned(FGLControl) and FGLControl.MakeCurrent then
  begin
    DeleteTexture(FGridLabelTex);
    DeleteTexture(FAGCLabelTex);
    DeleteTexture(FAGCHangLabelTex);
    DeleteTexture(FMarkerLabelTex);
    DeleteTexture(FADCOverlayTex);
    DeleteTexture(FSampleOverlayTex);
    DeleteTexture(FVfoOverlayTex);
  end;
  inherited Destroy;
end;

procedure TSpectrumViewOpenGL.AttachControl(C: TOpenGLControl);
begin
  FGLControl := C;
end;

procedure TSpectrumViewOpenGL.AttachWaterfallControl(C: TOpenGLControl);
begin
  if FWaterfall is TWaterfallViewOpenGL then
    TWaterfallViewOpenGL(FWaterfall).AttachControl(C);
end;

procedure TSpectrumViewOpenGL.DeleteTexture(var T: TGLTextureCache);
begin
  if T.Tex <> 0 then
    glDeleteTextures(1, @T.Tex);
  T.Tex := 0;
  T.W := 0;
  T.H := 0;
  T.Dirty := True;
end;

procedure TSpectrumViewOpenGL.UploadBitmap(var T: TGLTextureCache; B: TBitmap;
  Keyed: Boolean; FixedAlpha: Byte);
var
  X, Y, I: Integer;
  Src: PByte;
  Buf: array of Byte;
  IsKey: Boolean;
begin
  if (B = nil) or (B.Width <= 0) or (B.Height <= 0) then Exit;
  if T.Tex = 0 then glGenTextures(1, @T.Tex);
  T.W := B.Width;
  T.H := B.Height;
  SetLength(Buf, T.W * T.H * 4);
  B.BeginUpdate(False);
  try
    I := 0;
    for Y := 0 to T.H - 1 do
    begin
      Src := PByte(B.ScanLine[Y]);
      for X := 0 to T.W - 1 do
      begin
        IsKey := Keyed and (Src[0] = $FF) and (Src[1] = $00) and (Src[2] = $FF);
        Buf[I] := Src[2];
        Buf[I + 1] := Src[1];
        Buf[I + 2] := Src[0];
        if IsKey then Buf[I + 3] := 0 else Buf[I + 3] := FixedAlpha;
        Inc(Src, 4);
        Inc(I, 4);
      end;
    end;
  finally
    B.EndUpdate(False);
  end;
  glBindTexture(GL_TEXTURE_2D, T.Tex);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, T.W, T.H, 0, GL_RGBA,
    GL_UNSIGNED_BYTE, @Buf[0]);
  glBindTexture(GL_TEXTURE_2D, 0);
  T.Dirty := False;
end;

procedure TSpectrumViewOpenGL.UploadAlphaMask(var T: TGLTextureCache; B: TBitmap;
  AColor: TColor);
var
  X, Y, I: Integer;
  Src: PByte;
  Buf: array of Byte;
  R, G, BB, A: Byte;
begin
  if (B = nil) or (B.Width <= 0) or (B.Height <= 0) then Exit;
  if T.Tex = 0 then glGenTextures(1, @T.Tex);
  T.W := B.Width;
  T.H := B.Height;
  R := AColor and $FF;
  G := (AColor shr 8) and $FF;
  BB := (AColor shr 16) and $FF;
  SetLength(Buf, T.W * T.H * 4);
  B.BeginUpdate(False);
  try
    I := 0;
    for Y := 0 to T.H - 1 do
    begin
      Src := PByte(B.ScanLine[Y]);
      for X := 0 to T.W - 1 do
      begin
        A := Max(Src[0], Max(Src[1], Src[2]));
        Buf[I] := R;
        Buf[I + 1] := G;
        Buf[I + 2] := BB;
        Buf[I + 3] := A;
        Inc(Src, 4);
        Inc(I, 4);
      end;
    end;
  finally
    B.EndUpdate(False);
  end;
  glBindTexture(GL_TEXTURE_2D, T.Tex);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
  glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, T.W, T.H, 0, GL_RGBA,
    GL_UNSIGNED_BYTE, @Buf[0]);
  glBindTexture(GL_TEXTURE_2D, 0);
  T.Dirty := False;
end;

procedure TSpectrumViewOpenGL.UploadText(var T: TGLTextureCache; const S: string;
  AColor: TColor; FontSize: Integer; Bold: Boolean);
var
  B: TBitmap;
  TW, TH: Integer;
begin
  if S = '' then
  begin
    DeleteTexture(T);
    Exit;
  end;
  B := TBitmap.Create;
  try
    B.PixelFormat := pf32bit;
    B.SetSize(8, 8);
    B.Canvas.Font.Name := 'Courier New';
    B.Canvas.Font.Size := FontSize;
    if Bold then B.Canvas.Font.Style := [fsBold] else B.Canvas.Font.Style := [];
    TW := Max(1, B.Canvas.TextWidth(S) + 4);
    TH := Max(1, B.Canvas.TextHeight(S) + 2);
    B.SetSize(TW, TH);
    B.Canvas.Brush.Color := clBlack;
    B.Canvas.Brush.Style := bsSolid;
    B.Canvas.Pen.Style := psClear;
    B.Canvas.FillRect(Rect(0, 0, TW, TH));
    B.Canvas.Brush.Style := bsClear;
    B.Canvas.Font.Name := 'Courier New';
    B.Canvas.Font.Size := FontSize;
    if Bold then B.Canvas.Font.Style := [fsBold] else B.Canvas.Font.Style := [];
    B.Canvas.Font.Color := clWhite;
    B.Canvas.TextOut(2, 1, S);
    UploadAlphaMask(T, B, AColor);
  finally
    B.Free;
  end;
end;

procedure TSpectrumViewOpenGL.DrawTexture(const T: TGLTextureCache; X, Y: Integer);
begin
  if (T.Tex = 0) or (T.W <= 0) or (T.H <= 0) then Exit;
  glEnable(GL_TEXTURE_2D);
  glBindTexture(GL_TEXTURE_2D, T.Tex);
  glColor4f(1, 1, 1, 1);
  glBegin(GL_QUADS);
    glTexCoord2f(0, 0); glVertex2f(X, Y);
    glTexCoord2f(1, 0); glVertex2f(X + T.W, Y);
    glTexCoord2f(1, 1); glVertex2f(X + T.W, Y + T.H);
    glTexCoord2f(0, 1); glVertex2f(X, Y + T.H);
  glEnd;
  glBindTexture(GL_TEXTURE_2D, 0);
  glDisable(GL_TEXTURE_2D);
end;

procedure TSpectrumViewOpenGL.DrawRect(X1, Y1, X2, Y2: Integer; C: TColor;
  Alpha: Single);
var R, G, B: GLFloat;
begin
  ColorToRGB(C, R, G, B);
  glColor4f(R, G, B, Alpha);
  glBegin(GL_QUADS);
    glVertex2f(X1, Y1); glVertex2f(X2, Y1);
    glVertex2f(X2, Y2); glVertex2f(X1, Y2);
  glEnd;
end;

procedure TSpectrumViewOpenGL.DrawLine(X1, Y1, X2, Y2: Integer; C: TColor;
  Width: Single; Stipple: Boolean);
var R, G, B: GLFloat;
begin
  ColorToRGB(C, R, G, B);
  glColor4f(R, G, B, 1);
  glLineWidth(Width);
  if Stipple then
  begin
    glEnable(GL_LINE_STIPPLE);
    glLineStipple(1, $0F0F);
  end;
  glBegin(GL_LINES);
    glVertex2f(X1 + 0.5, Y1 + 0.5);
    glVertex2f(X2 + 0.5, Y2 + 0.5);
  glEnd;
  if Stipple then glDisable(GL_LINE_STIPPLE);
  glLineWidth(1);
end;

procedure TSpectrumViewOpenGL.SetSpectrumBitmapSize(W, H: Integer);
begin
  if (W <= 0) or (H <= 0) then Exit;
  FGLSpectrumW := W;
  FGLSpectrumH := H;
  FGridDirty := True;
  FOverlayDirty := True;
  FSpectrumDirty := True;
  if Assigned(FGLControl) then FGLControl.Invalidate;
end;

function TSpectrumViewOpenGL.SpectrumBitmapWidth: Integer;
begin
  Result := FGLSpectrumW;
end;

procedure TSpectrumViewOpenGL.DrawSpectrum;
begin
  FSpectrumDirty := False;
  if Assigned(FGLControl) then FGLControl.Invalidate;
end;

procedure TSpectrumViewOpenGL.InvalidateGridCache;
begin
  inherited InvalidateGridCache;
  FGridDirty := True;
  FOverlayDirty := True;
end;

procedure TSpectrumViewOpenGL.InvalidateOverlayCache;
begin
  inherited InvalidateOverlayCache;
  FOverlayDirty := True;
  FSampleOverlayDirty := True;
  FVfoOverlayDirty := True;
end;

procedure TSpectrumViewOpenGL.SetTheme(const T: TAppTheme);
begin
  inherited SetTheme(T);
  FGridDirty := True;
  FOverlayDirty := True;
end;

function TSpectrumViewOpenGL.FormatFreqGL(Hz: Double): string;
var Mhz: Int64; KHz, Rest: Integer;
begin
  Mhz := Trunc(Hz / 1000000);
  KHz := Trunc((Hz - Mhz * 1000000) / 1000);
  Rest := Trunc(Hz) mod 1000;
  Result := Format('%d.%3.3d.%3.3d', [Mhz, KHz, Rest]);
end;

function TSpectrumViewOpenGL.ActiveVfoFrequency: Double;
begin
  if FActiveVfo = 0 then Result := FVfoA else Result := FVfoB;
end;

procedure TSpectrumViewOpenGL.DrawVerticalGradient(W, H: Integer);
var
  R1, G1, B1, R2, G2, B2: GLFloat;
begin
  ColorToRGB(FTheme.SpecGradTop, R1, G1, B1);
  ColorToRGB(FTheme.SpecGradBot, R2, G2, B2);
  glBegin(GL_QUADS);
    glColor4f(R1, G1, B1, 1); glVertex2f(0, 0); glVertex2f(W, 0);
    glColor4f(R2, G2, B2, 1); glVertex2f(W, H); glVertex2f(0, H);
  glEnd;
  DrawRect(0, 0, 28, H, FTheme.SpecLabelBand, 1);
end;

procedure TSpectrumViewOpenGL.DrawGrid(W, H: Integer; DBmax, DBmin,
  InvRange: Double);
var
  I, Yp, GX, N, GridMult: Integer;
  DB, GridFreqS, GridLine, PixPerStep: Double;
  B: TBitmap;
begin
  DB := DBmax - FSpecGridStep;
  while DB >= DBmin do
  begin
    Yp := Round((DBmax - DB) * InvRange * H);
    DrawLine(0, Yp, W - 1, Yp, FTheme.SpecGrid, 1, False);
    DB := DB - FSpecGridStep;
  end;

  if FFMGridStepHz > 0 then
  begin
    GridFreqS := FCenterFreq - FSpanHz / 2;
    PixPerStep := W * FFMGridStepHz / FSpanHz;
    if PixPerStep >= 1.0 then GridMult := Max(1, Ceil(4.0 / PixPerStep))
    else GridMult := 0;
    if GridMult > 0 then
    begin
      N := Ceil(GridFreqS / FFMGridStepHz);
      GridLine := N * FFMGridStepHz;
      while GridLine <= FCenterFreq + FSpanHz / 2 + 0.5 do
      begin
        if (N mod GridMult) = 0 then
        begin
          GX := Round((GridLine - GridFreqS) / FSpanHz * W);
          if (GX >= 0) and (GX < W) then DrawLine(GX, 0, GX, H, FTheme.SpecGrid, 1, False);
        end;
        Inc(N);
        GridLine := GridLine + FFMGridStepHz;
      end;
    end;
  end
  else
    for I := 0 to 8 do
    begin
      GX := Round(I / 8 * W);
      DrawLine(GX, 0, GX, H, FTheme.SpecGrid, 1, False);
    end;

  if FGridDirty or FGridLabelTex.Dirty or (FGridLabelTex.H <> H) then
  begin
    B := TBitmap.Create;
    try
      B.PixelFormat := pf32bit;
      B.SetSize(28, H);
      B.Canvas.Brush.Color := clBlack;
      B.Canvas.Brush.Style := bsSolid;
      B.Canvas.Pen.Style := psClear;
      B.Canvas.FillRect(Rect(0, 0, 28, H));
      B.Canvas.Font.Name := 'Courier New';
      B.Canvas.Font.Size := 7;
      B.Canvas.Font.Color := clWhite;
      B.Canvas.Brush.Style := bsClear;
      DB := DBmax - FSpecGridStep;
      while DB >= DBmin do
      begin
        Yp := Round((DBmax - DB) * InvRange * H);
        B.Canvas.TextOut(1, Yp - 9, Format('%4.0f', [DB]));
        DB := DB - FSpecGridStep;
      end;
      UploadAlphaMask(FGridLabelTex, B, FTheme.SpecLabelText);
    finally
      B.Free;
    end;
    FGridDirty := False;
  end;
  DrawTexture(FGridLabelTex, 0, 0);
end;

procedure TSpectrumViewOpenGL.DrawFilterAndCursors(W, H: Integer);
var
  X1, X2, VfoX, TXX1, TXX2, TXVfoX: Integer;
begin
  TXX1 := 0;
  TXX2 := 0;
  TXVfoX := 0;
  if FActiveVfo = 0 then CalcFilterBandX(FVfoA, W, X1, X2, VfoX)
  else CalcFilterBandX(FVfoB, W, X1, X2, VfoX);

  if FTXOverlay then
  begin
    if FTXVfoIndex <> FActiveVfo then
    begin
      if X2 > X1 then DrawRect(X1, 0, X2, H, TColor($0030C030), 100 / 255);
      if FTXVfoIndex = 0 then CalcFilterBandX(FVfoA, W, TXX1, TXX2, TXVfoX)
      else CalcFilterBandX(FVfoB, W, TXX1, TXX2, TXVfoX);
      if TXX2 > TXX1 then DrawRect(TXX1, 0, TXX2, H, TColor($00E03030), 100 / 255);
    end
    else if X2 > X1 then DrawRect(X1, 0, X2, H, TColor($00E03030), 100 / 255);
  end
  else if X2 > X1 then
    DrawRect(X1, 0, X2, H, FTheme.SpecFilter, 1);

  DrawLine(X1, 0, X1, H, FTheme.SpecFilterEdge, 1, False);
  DrawLine(X2, 0, X2, H, FTheme.SpecFilterEdge, 1, False);
  DrawLine(VfoX, 0, VfoX, H - 12, FTheme.SpecVfoCursor, 2, False);
  DrawRect(VfoX - 5, 0, VfoX + 5, 8, FTheme.SpecVfoCursor, 1);

  if FTXOverlay and (FTXVfoIndex <> FActiveVfo) then
  begin
    DrawLine(TXX1, 0, TXX1, H, TColor($002030E0), 1, False);
    DrawLine(TXX2, 0, TXX2, H, TColor($002030E0), 1, False);
    DrawLine(TXVfoX, 0, TXVfoX, H - 12, TColor($002030E0), 2, False);
    DrawRect(TXVfoX - 5, 0, TXVfoX + 5, 8, TColor($002030E0), 1);
  end;
end;

procedure TSpectrumViewOpenGL.DrawAGCLines(W, H: Integer; DBmax,
  InvRange: Double);
var
  AGCY, AGCHangY: Integer;
  Text: string;
begin
  if FWDSPReady then
  begin
    AGCY := Round((DBmax - FAGCThresh) * InvRange * H);
    Text := 'AGC T';
    if (AGCY >= 0) and (AGCY < H) then
    begin
      DrawLine(0, AGCY, W, AGCY, FTheme.SpecAgcColor, 1, True);
      if (Text <> FLastAGCText) or (AGCY <> FLastAGCY) or FAGCLabelTex.Dirty then
      begin
        UploadText(FAGCLabelTex, Text, FTheme.SpecAgcColor, 6, False);
        FLastAGCText := Text;
        FLastAGCY := AGCY;
      end;
      DrawTexture(FAGCLabelTex, 4, AGCY - 9);
    end;
    AGCHangY := Round((DBmax - FAGCHangLevel) * InvRange * H);
    if (AGCHangY >= 0) and (AGCHangY < H) and (Abs(AGCHangY - AGCY) > 4) then
    begin
      DrawLine(0, AGCHangY, W, AGCHangY, FTheme.SpecAgcHangColor, 1, True);
      if (AGCHangY <> FLastAGCHangY) or FAGCHangLabelTex.Dirty then
      begin
        UploadText(FAGCHangLabelTex, 'AGC H', FTheme.SpecAgcHangColor, 6, False);
        FLastAGCHangY := AGCHangY;
      end;
      DrawTexture(FAGCHangLabelTex, 4, AGCHangY + 2);
    end;
  end
  else
  begin
    AGCY := Round((DBmax - (-FAGCTop)) * InvRange * H);
    Text := Format('AGC -%ddB', [FAGCTop]);
    if (AGCY >= 0) and (AGCY < H) then
    begin
      DrawLine(0, AGCY, W, AGCY, FTheme.SpecAgcColor, 1, True);
      if (Text <> FLastAGCText) or (AGCY <> FLastAGCY) or FAGCLabelTex.Dirty then
      begin
        UploadText(FAGCLabelTex, Text, FTheme.SpecAgcColor, 6, False);
        FLastAGCText := Text;
        FLastAGCY := AGCY;
      end;
      DrawTexture(FAGCLabelTex, 4, AGCY - 9);
    end;
  end;
end;

procedure TSpectrumViewOpenGL.DrawSpectrumCurve(W, H: Integer; DBmax,
  InvRange: Double);
var
  I, SrcCount, S0, S1: Integer;
  SrcF, Frac, DBV: Double;
  R, G, B: GLFloat;
begin
  if Length(FSpY) <> W then SetLength(FSpY, W);
  SrcCount := ClampI(FSpectrumBufCount, 2, 1024);
  for I := 0 to W - 1 do
  begin
    if FTXMode and (FTXSpanHz > 0) and (FSpanHz > 0) then
    begin
      SrcF := FCenterFreq - FSpanHz * 0.5 + I * FSpanHz / Max(1, W - 1);
      Frac := SrcF - FTXFreq;
      if (Frac < -FTXSpanHz * 0.5) or (Frac > FTXSpanHz * 0.5) then DBV := -200.0
      else
      begin
        SrcF := (Frac + FTXSpanHz * 0.5) / FTXSpanHz * (SrcCount - 1);
        S0 := Min(Trunc(SrcF), SrcCount - 1);
        S1 := Min(S0 + 1, SrcCount - 1);
        Frac := SrcF - S0;
        DBV := FSpectrumBuf[S0] * (1.0 - Frac) + FSpectrumBuf[S1] * Frac;
      end;
    end
    else
    begin
      SrcF := I * (SrcCount - 1.0) / Max(1, W - 1);
      S0 := Min(Trunc(SrcF), SrcCount - 1);
      S1 := Min(S0 + 1, SrcCount - 1);
      Frac := SrcF - S0;
      DBV := FSpectrumBuf[S0] * (1.0 - Frac) + FSpectrumBuf[S1] * Frac;
    end;
    FSpY[I] := ClampI(Round((DBmax - DBV) * InvRange * H), 0, H - 1);
  end;

  ColorToRGB(TColor((FTheme.SpecGradB shl 16) or
    (FTheme.SpecGradG shl 8) or FTheme.SpecGradR), R, G, B);
  glBegin(GL_TRIANGLE_STRIP);
    for I := 0 to W - 1 do
    begin
      glColor4f(R, G, B, 200 / 255);
      glVertex2f(I + 0.5, FSpY[I] + 0.5);
      glColor4f(R, G, B, 0);
      glVertex2f(I + 0.5, H);
    end;
  glEnd;

  ColorToRGB(FTheme.SpecLine, R, G, B);
  glColor4f(R, G, B, 1);
  glBegin(GL_LINE_STRIP);
    for I := 0 to W - 1 do glVertex2f(I + 0.5, FSpY[I] + 0.5);
  glEnd;
end;

procedure TSpectrumViewOpenGL.DrawMarker(W, H: Integer);
var
  MX: Integer;
  MarkerFreq: Double;
  MarkerText: string;
begin
  if not FMarkerActive then Exit;
  MX := Round(FMarkerX / 1000.0 * W);
  if (MX < 0) or (MX >= W) then Exit;
  DrawLine(MX, 0, MX, H, TColor($004444FF), 1, False);
  MarkerFreq := (FCenterFreq - FSpanHz / 2) + FMarkerX / 1000.0 * FSpanHz;
  MarkerText := FormatFreqGL(Round(MarkerFreq));
  if (MarkerText <> FLastMarkerText) or (MX <> FLastMarkerX) or FMarkerLabelTex.Dirty then
  begin
    UploadText(FMarkerLabelTex, MarkerText, TColor($004444FF), 7, False);
    FLastMarkerText := MarkerText;
    FLastMarkerX := MX;
  end;
  if MX + 4 + FMarkerLabelTex.W < W then DrawTexture(FMarkerLabelTex, MX + 4, 4)
  else DrawTexture(FMarkerLabelTex, MX - 4 - FMarkerLabelTex.W, 4);
end;

procedure TSpectrumViewOpenGL.DrawADCOverlay(W, H: Integer);
var
  B: TBitmap;
begin
  if not FADCOverloadVisible then Exit;
  if (not FLastADCVisible) or FADCOverlayTex.Dirty then
  begin
    B := TBitmap.Create;
    try
      B.PixelFormat := pf32bit;
      B.SetSize(210, 38);
      B.Canvas.Brush.Color := TColor($00202020);
      B.Canvas.FillRect(Rect(0, 0, B.Width, B.Height));
      B.Canvas.Pen.Color := TColor($000030C0);
      B.Canvas.Brush.Style := bsClear;
      B.Canvas.Rectangle(0, 0, B.Width, B.Height);
      B.Canvas.Font.Name := 'Courier New';
      B.Canvas.Font.Size := 10;
      B.Canvas.Font.Style := [fsBold];
      B.Canvas.Font.Color := TColor($000030C0);
      B.Canvas.TextOut(12, 5, 'ADC OVERLOAD');
      B.Canvas.Font.Size := 7;
      B.Canvas.Font.Style := [];
      B.Canvas.Font.Color := TColor($00D0D0D0);
      B.Canvas.TextOut(12, 21, 'Input clipping detected');
      UploadBitmap(FADCOverlayTex, B, False, 232);
    finally
      B.Free;
    end;
  end;
  FLastADCVisible := True;
  DrawTexture(FADCOverlayTex, (W - FADCOverlayTex.W) div 2, 8);
end;

procedure TSpectrumViewOpenGL.DrawCachedOverlays(W, H: Integer);
var
  B: TBitmap;
  OW, OH: Integer;
begin
  if Assigned(FSampleRateOverlay) then
  begin
    OW := Min(FSampleRateOverlay.Width, W - FSampleRateOverlay.Left);
    OH := Min(FSampleRateOverlay.Height, H - FSampleRateOverlay.Top);
    if (OW > 0) and (OH > 0) then
    begin
      if FOverlayDirty or FSampleOverlayDirty or FSampleOverlayTex.Dirty or
         (FLastSampleX <> FSampleRateOverlay.Left) or
         (FLastSampleY <> FSampleRateOverlay.Top) or
         (FLastSampleH <> OH) then
      begin
        B := TBitmap.Create;
        try
          FSampleRateOverlay.DrawOverlayBitmap(B, OW, OH);
          UploadBitmap(FSampleOverlayTex, B, False, 255);
        finally
          B.Free;
        end;
        FLastSampleX := FSampleRateOverlay.Left;
        FLastSampleY := FSampleRateOverlay.Top;
        FLastSampleW := FSampleOverlayTex.W;
        FLastSampleH := OH;
        FSampleOverlayDirty := False;
      end;
      DrawTexture(FSampleOverlayTex, FSampleRateOverlay.Left, FSampleRateOverlay.Top);
    end;
  end;

  if Assigned(FVfoOverlay) and FVfoOverlay.Visible then
  begin
    if FOverlayDirty or FVfoOverlayDirty or FVfoOverlayTex.Dirty or
       (FLastVfoX <> FVfoOverlay.Left) or (FLastVfoY <> FVfoOverlay.Top) or
       (FLastVfoW <> FVfoOverlay.Width) or (FLastVfoH <> FVfoOverlay.Height) then
    begin
      B := TBitmap.Create;
      try
        FVfoOverlay.DrawOverlayBitmap(B);
        UploadBitmap(FVfoOverlayTex, B, True, 218);
      finally
        B.Free;
      end;
      FLastVfoX := FVfoOverlay.Left;
      FLastVfoY := FVfoOverlay.Top;
      FLastVfoW := FVfoOverlay.Width;
      FLastVfoH := FVfoOverlay.Height;
      FVfoOverlayDirty := False;
    end;
    DrawTexture(FVfoOverlayTex, FVfoOverlay.Left, FVfoOverlay.Top);
  end;
  FOverlayDirty := False;
end;

procedure TSpectrumViewOpenGL.PaintSpectrum(Sender: TObject);
var
  W, H: Integer;
  DBmax, DBmin, InvRange: Double;
begin
  if Sender is TOpenGLControl then
    FGLControl := TOpenGLControl(Sender);
  if (FGLControl = nil) or (not FGLControl.MakeCurrent) then Exit;
  W := FGLControl.Width;
  H := FGLControl.Height;
  if (W <= 0) or (H <= 0) then Exit;

  glViewport(0, 0, W, H);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity;
  glOrtho(0, W, H, 0, -1, 1);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity;
  glDisable(GL_DEPTH_TEST);
  glEnable(GL_BLEND);
  glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
  glClearColor(0, 0, 0, 1);
  glClear(GL_COLOR_BUFFER_BIT);

  DBmax := FSpecRefLevel;
  DBmin := FSpecRefLevel - FSpecRange;
  InvRange := 1.0 / (DBmax - DBmin);

  DrawVerticalGradient(W, H);
  DrawGrid(W, H, DBmax, DBmin, InvRange);
  DrawFilterAndCursors(W, H);
  DrawAGCLines(W, H, DBmax, InvRange);
  DrawSpectrumCurve(W, H, DBmax, InvRange);
  DrawMarker(W, H);
  DrawADCOverlay(W, H);
  DrawCachedOverlays(W, H);

  FLastADCVisible := FADCOverloadVisible;
  FGLControl.SwapBuffers;
end;

end.