TAtlasGauge

Create constructor

constructor Create(AOwner: TComponent); override;

Creates a 240 x 100 gauge with a white background, range 0 to 100, warning 70, critical 90, value 0 and an empty caption.

Minimum property

property Minimum: Double read FMinimum;

Lower end of the range; change it with SetRange.

Maximum property

property Maximum: Double read FMaximum;

Upper end of the range; change it with SetRange.

Value property

property Value: Double read FValue write SetValue;

Current value, clamped to the range when set. NaN or infinity raises EArgumentException.

Gauge.Value := 320;

Caption property

property Caption: string read FCaption write SetCaption;

Text drawn above the value.

Align property

property Align;

Standard VCL alignment in the parent.

Anchors property

property Anchors;

Standard VCL anchors.

Color property

property Color;

Background; the constructor sets clWhite. The bar colours do not depend on it.

Font property

property Font;

Font of the caption and the value; the value is drawn bold.

ParentFont property

property ParentFont;

Standard VCL property: use the parent's font.

SetRange method

procedure SetRange(Minimum, Maximum: Double);

Sets the range. Both values must be finite with magnitude at most 1E100 and Minimum < Maximum, otherwise EArgumentException and nothing changes. Resets the warning and critical thresholds to 70% and 90% of the range and clamps the current value into it.

Gauge.SetRange(-50, 50); // thresholds are now 20 and 40

SetThresholds method

procedure SetThresholds(Warning, Critical: Double);

Sets the values from which the bar is amber and red. Requires Minimum <= Warning <= Critical <= Maximum, otherwise EArgumentException. Call it after SetRange.

Gauge.SetRange(0, 500);
Gauge.SetThresholds(300, 450);

Fraction method

function Fraction: Double;

Position of Value in the range, from 0 at Minimum to 1 at Maximum.

ValueColor method

function ValueColor: TColor;

Bar colour for the current value: $00423FC4 (red) at or above the critical threshold, $002D99CF (amber) at or above the warning threshold, otherwise $00699532 (green).

Gauge.Value := 95;
if Gauge.ValueColor = $00423FC4 then Beep;

Queue depth with custom thresholds

A 0 to 500 gauge that is amber from 300 and red from 450.

uses System.Classes, Vcl.Controls, Atlas.Gauges;

function AddQueueGauge(Owner: TComponent; Parent: TWinControl): TAtlasGauge;
begin
  Result := TAtlasGauge.Create(Owner);
  Result.Parent := Parent;
  Result.Align := alTop;
  Result.Caption := 'Queue depth';
  Result.SetRange(0, 500);
  Result.SetThresholds(300, 450); // after SetRange, which resets the thresholds
  Result.Value := 320;            // amber: at or above 300, below 450
end;

State of a gauge as text

Maps the bar colour to a word, for a status line or a log.

uses Atlas.Gauges;

function GaugeState(Gauge: TAtlasGauge): string;
begin
  if Gauge.ValueColor = $00423FC4 then Result := 'critical'
  else if Gauge.ValueColor = $002D99CF then Result := 'warning'
  else Result := 'normal';
end;