TAtlasChart

Create constructor

constructor Create(AOwner: TComponent); override;

Creates a 640 x 400 chart with a white background, Kind = acLine, an empty title and no series. Double buffering is on.

Destroy destructor

destructor Destroy; override;

Frees the chart and every series it owns. References returned by AddSeries become invalid.

SeriesCount property

property SeriesCount: Integer read GetSeriesCount;

Number of series in the chart.

Kind property

property Kind: TAtlasChartKind read FKind write SetKind default acLine;

Chart type; see TAtlasChartKind. Setting acPie raises EAtlasChartError, and keeps the previous kind, when the chart has more than one series or any non-missing negative value. Switching between acLine and acBar always succeeds.

Chart.Kind := acBar;

Title property

property Title: string read FTitle write SetTitle;

Bold text drawn at the top left. Setting it repaints the chart.

Align property

property Align;

Standard VCL alignment in the parent.

Anchors property

property Anchors;

Standard VCL anchors.

Color property

property Color;

Background of the whole chart; the constructor sets clWhite. TAtlasThemer sets it to the theme surface. Grid and axis lines are fixed greys.

Font property

property Font;

Font of the title, the axis values and the legend. The title is drawn bold.

ParentFont property

property ParentFont;

Standard VCL property: use the parent's font.

OnClick event

property OnClick;

Standard click event. The chart does not report which point or series was clicked.

OnDblClick event

property OnDblClick;

Standard double-click event.

AddSeries method

function AddSeries(const Caption: string; Color: TColor): TAtlasChartSeries;

Adds an empty series and returns it. The chart owns the series; do not free it. Caption appears in the legend; Color is used for the line, the point markers and the bars (a pie ignores it). Raises EAtlasChartError when Kind is acPie and the chart already has a series.

Series := Chart.AddSeries('Revenue', clNavy);
Series.Add(1, 120);
Series.Add(2, 135);

Clear method

procedure Clear;

Removes and frees every series; Kind and Title stay. Discard the series references you hold.

Chart.Clear;
Series := Chart.AddSeries('Forecast', clGreen);

Render method

procedure Render(Target: TCanvas; const Bounds: TRect);

Draws the chart into Bounds on any canvas, with the chart's Color, Font, Title and Kind; Paint calls it with the client rectangle. The chart does not need a parent or a window handle. Below 160 x 120 pixels only the title is drawn. The plot area is inset 70 pixels on the left, 60 at the top, 150 on the right (the legend) and 48 at the bottom. Without any non-missing point the plot shows No data; a pie whose values add up to zero shows No positive values. Raises EAtlasChartError if the coordinate span overflows a Double.

Bitmap.SetSize(640, 400);
Chart.Render(Bitmap.Canvas, Rect(0, 0, 640, 400));

BoundsOfData method

function BoundsOfData(out XMin, XMax, YMin, YMax: Double): Boolean;

Minimum and maximum X and Y over the non-missing points of all series, without the zero baseline and padding that Render adds. Returns False, with the outputs set to 0, 1, 0 and 1, when there is no such point.

if Chart.BoundsOfData(XMin, XMax, YMin, YMax) then
  Chart.Title := Format('Peak %.0f', [YMax]);

Line chart with a gap

Two series of monthly values; April has no actual figure yet, so the Actual line breaks there.

uses System.Classes, Vcl.Controls, Vcl.Graphics, Atlas.Charts;

function AddRevenueChart(Owner: TComponent; Parent: TWinControl): TAtlasChart;
var
  Actual, Target: TAtlasChartSeries;
  Month: Integer;
begin
  Result := TAtlasChart.Create(Owner);
  Result.Parent := Parent;
  Result.Align := alClient;
  Result.Title := 'Revenue by month';
  Actual := Result.AddSeries('Actual', $00876524);
  Target := Result.AddSeries('Target', clGray);
  for Month := 1 to 6 do
  begin
    Target.Add(Month, 100 + Month * 10);
    if Month = 4 then
      Actual.AddMissing(Month) // no figure yet: the line breaks here
    else
      Actual.Add(Month, 95 + Month * 12);
  end;
end;

Bar chart with category labels, saved as PNG

Every point has a caption, so the bars are labelled North, South and East. The chart is never shown.

uses System.Types, Vcl.Graphics, Vcl.Imaging.pngimage, Atlas.Charts;

procedure SaveRegionChart(const FileName: string);
var
  Chart: TAtlasChart;
  Series: TAtlasChartSeries;
  Bitmap: TBitmap;
  Png: TPngImage;
begin
  Chart := TAtlasChart.Create(nil);
  Bitmap := TBitmap.Create;
  Png := TPngImage.Create;
  try
    Chart.Kind := acBar;
    Chart.Title := 'Units by region';
    Series := Chart.AddSeries('Units', clNavy);
    Series.Add(1, 40, 'North');
    Series.Add(2, 25, 'South');
    Series.Add(3, 35, 'East');
    Bitmap.SetSize(640, 400);
    Chart.Render(Bitmap.Canvas, Rect(0, 0, 640, 400));
    Png.Assign(Bitmap);
    Png.SaveToFile(FileName);
  finally
    Png.Free;
    Bitmap.Free;
    Chart.Free;
  end;
end;

Pie chart

A pie takes a single series with non-negative values; the legend shows the point captions.

uses Vcl.Graphics, Atlas.Charts;

procedure ShowTicketShare(Chart: TAtlasChart);
var
  Share: TAtlasChartSeries;
begin
  Chart.Clear;              // a pie accepts only one series
  Chart.Kind := acPie;
  Chart.Title := 'Tickets by state';
  Share := Chart.AddSeries('Tickets', clBlack); // slices use the built-in palette
  Share.Add(1, 52, 'Open');
  Share.Add(2, 31, 'In progress');
  Share.Add(3, 17, 'Closed');
end;