Chart Panning+Zooming

AuraTrader/AuraTrader.dproj

@@ -4,7 +4,7 @@
         <ProjectVersion>20.3</ProjectVersion>
         <FrameworkType>FMX</FrameworkType>
         <Base>True</Base>
-        <Config Condition="'$(Config)'==''">Debug</Config>
+        <Config Condition="'$(Config)'==''">Release</Config>
         <Platform Condition="'$(Platform)'==''">Win64</Platform>
         <ProjectName Condition="'$(ProjectName)'==''">AuraTrader</ProjectName>
         <TargetedPlatforms>3</TargetedPlatforms>

AuraTrader/MainForm.pas

@@ -165,7 +165,7 @@ begin
     var chart := TMycChart.Create(Self);
     AlignControl( chart );
     chart.Height := Layout.ChildrenRect.Width*9/16;
-    chart.Lookback.Value := 1000;
+    chart.Lookback.Value := 50000;
 
     /////
 

AuraTrader/Myc.Fmx.Chart.pas

@@ -14,6 +14,7 @@ uses
     FMX.Types,
     FMX.Controls,
     FMX.Graphics,
+    FMX.Forms,
     Myc.Trade.DataPoint,
     Myc.Signals,
     Myc.Lazy;
@@ -22,32 +23,41 @@ type
     TCandleStyle = (csCandleStick, csHiLoBar);
 
     TMycChart = class(TStyledControl)
-        type
-            TSeries = class abstract(TObject)
-            private
-                FOwner: TMycChart;
-                function GetMainSeries: TSeries;
-            protected
-                function GetCount: Int64; virtual; abstract;
-                function GetValueRange(StartIndex, Count: Int64; out Min, Max: Double): Boolean; virtual; abstract;
-                function Update: Boolean; virtual; abstract;
-                procedure Paint(const ACanvas: TCanvas; Lookback: Int64; const AXForm, AYForm: TFunc<Double, Single>); virtual; abstract;
+    public type
+        TSeries = class abstract(TObject)
+        private
+            FOwner: TMycChart;
+            function GetMainSeries: TSeries;
+        protected
+            function GetCount: Int64; virtual; abstract;
+            function GetValueRange(StartIndex, Count: Int64; out Min, Max: Double): Boolean; virtual; abstract;
+            function Update: Boolean; virtual; abstract;
+            // The signature is changed to support viewport painting
+            procedure Paint(const ACanvas: TCanvas; StartIndex, Count: Int64; const AXForm, AYForm: TFunc<Double, Single>); virtual; abstract;
+            property MainSeries: TSeries read GetMainSeries;
+        public
+            constructor Create(AOwner: TMycChart);
+            property Count: Int64 read GetCount;
+            property Owner: TMycChart read FOwner;
+        end;
 
-                property MainSeries: TSeries read GetMainSeries;
-
-            public
-                constructor Create(AOwner: TMycChart);
-                property Count: Int64 read GetCount;
-                property Owner: TMycChart read FOwner;
-            end;
-
-    private
-        FSeriesList: TList<TSeries>;
-        FLookback: TWriteable<Int64>;
-        FIdleSubscrId: TMessageSubscriptionId;
-    protected
+private
+    FSeriesList: TList<TSeries>;
+    FLookback: TWriteable<Int64>;
+    FIdleSubscrId: TMessageSubscriptionId;
+    FViewStartIndex: Int64;
+    FViewCount: Int64;
+    FIsDragging: Boolean;
+    FDragStartPoint: TPointF;
+    FJumpButtonRect: TRectF;
+    FJumpButtonHot: Boolean;
+    FJumpButtonPressed: Boolean;    protected
         procedure Paint; override;
         procedure DoIdle;
+        procedure MouseWheel(Shift: TShiftState; WheelDelta: Integer; var Handled: Boolean); override;
+        procedure MouseDown(Button: TMouseButton; Shift: TShiftState; X, Y: Single); override;
+        procedure MouseMove(Shift: TShiftState; X, Y: Single); override;
+        procedure MouseUp(Button: TMouseButton; Shift: TShiftState; X, Y: Single); override;
     public
         constructor Create(AOwner: TComponent); override;
         destructor Destroy; override;
@@ -120,8 +130,8 @@ type
         FDownColor: TAlphaColor;
         FStyle: TCandleStyle;
     protected
-        function GetValueRange(StartIndex, Count: Int64; out Min, Max: Double): Boolean; override;
-        procedure Paint(const ACanvas: TCanvas; Lookback: Int64; const AXForm, AYForm: TFunc<Double, Single>); override;
+        function GetValueRange(StartIndex, Count: Int64; out MinValue, MaxValue: Double): Boolean; override;
+        procedure Paint(const ACanvas: TCanvas; StartIndex, Count: Int64; const AXForm, AYForm: TFunc<Double, Single>); override;
     public
         constructor Create(
             AOwner: TMycChart;
@@ -137,8 +147,8 @@ type
         FLineColor: TAlphaColor;
         FLineWidth: Single;
     protected
-        function GetValueRange(StartIndex, Count: Int64; out Min, Max: Double): Boolean; override;
-        procedure Paint(const ACanvas: TCanvas; Lookback: Int64; const AXForm, AYForm: TFunc<Double, Single>); override;
+        function GetValueRange(StartIndex, Count: Int64; out MinValue, MaxValue: Double): Boolean; override;
+        procedure Paint(const ACanvas: TCanvas; StartIndex, Count: Int64; const AXForm, AYForm: TFunc<Double, Single>); override;
     public
         constructor Create(
             AOwner: TMycChart;
@@ -159,7 +169,7 @@ end;
 function TMycChart.TSeries.GetMainSeries: TSeries;
 begin
     Result := nil;
-    if Owner.FSeriesList.Count > 0 then
+    if (Owner.FSeriesList.Count > 0) then
         Result := Owner.FSeriesList[0];
 end;
 
@@ -170,7 +180,10 @@ begin
     inherited Create(AOwner);
     FSeriesList := TObjectList<TSeries>.Create(true);
 
-    FLookback := TWriteable<Int64>.CreateWriteable( 100 );
+    FLookback := TWriteable<Int64>.CreateWriteable( 1000 ); // Load more data for panning
+    FViewStartIndex := 0;
+    FViewCount := 100; // Show 100 items by default
+    FIsDragging := false;
 
     FIdleSubscrId :=
         TMessageManager
@@ -212,13 +225,219 @@ begin
 end;
 
 procedure TMycChart.DoIdle;
+var
+    doRepaint: Boolean;
+    mainSeries: TSeries;
+    isLiveView: Boolean;
+    prevCount, newCount, newCandles: Int64;
 begin
-    var doRepaint := false;
+    if (FSeriesList.Count = 0) then
+    begin
+        exit;
+    end;
+
+    mainSeries := FSeriesList[0];
+    if (mainSeries = nil) then
+    begin
+        exit;
+    end;
+
+    // Remember state before update
+    isLiveView := (FViewStartIndex = 0);
+    prevCount := mainSeries.Count;
+
+    // Check all series for updates
+    doRepaint := false;
     for var series in FSeriesList do
+    begin
         if series.Update then
+        begin
             doRepaint := true;
+        end;
+    end;
+
     if doRepaint then
+    begin
+        newCount := mainSeries.Count;
+        newCandles := newCount - prevCount;
+
+        // Adjust viewport only if user was not watching the live data
+        if (not isLiveView) and (newCandles > 0) then
+        begin
+            FViewStartIndex := FViewStartIndex + newCandles;
+        end;
+        // If the view was live, it implicitly stays at StartIndex = 0, showing the new data.
+
         Repaint;
+    end;
+end;
+
+procedure TMycChart.MouseDown(Button: TMouseButton; Shift: TShiftState; X, Y: Single);
+begin
+    // Check for button press first
+    if (Button = TMouseButton.mbLeft) and (FViewStartIndex > 0) and FJumpButtonRect.Contains(PointF(X, Y)) then
+    begin
+        FJumpButtonPressed := true;
+        Repaint;
+        exit; // Prevent chart dragging
+    end;
+
+    inherited MouseDown(Button, Shift, X, Y);
+    if (Button = TMouseButton.mbLeft) then
+    begin
+        FIsDragging := true;
+        FDragStartPoint := TPointF.Create(X, Y);
+    end;
+end;
+
+procedure TMycChart.MouseUp(Button: TMouseButton; Shift: TShiftState; X, Y: Single);
+begin
+    // Check if a button press was active
+    if FJumpButtonPressed then
+    begin
+        FJumpButtonPressed := false;
+        // If mouse is released over the button, trigger the action
+        if (FViewStartIndex > 0) and FJumpButtonRect.Contains(PointF(X, Y)) then
+        begin
+            FViewStartIndex := 0; // Jump to the latest candle
+        end;
+        Repaint;
+        exit;
+    end;
+
+    inherited MouseUp(Button, Shift, X, Y);
+    if (Button = TMouseButton.mbLeft) then
+    begin
+        FIsDragging := false;
+    end;
+end;
+
+procedure TMycChart.MouseMove(Shift: TShiftState; X, Y: Single);
+var
+    isHot: Boolean;
+    dx: Single;
+    indexDelta: Int64;
+    mainSeries: TSeries;
+    maxIndex: Int64;
+begin
+    // Update button hot state
+    if (FViewStartIndex > 0) then
+    begin
+        isHot := FJumpButtonRect.Contains(PointF(X, Y));
+        if (isHot <> FJumpButtonHot) then
+        begin
+            FJumpButtonHot := isHot;
+            Repaint;
+        end;
+    end
+    else
+    begin
+        // Ensure hot state is off when button is not visible
+        if FJumpButtonHot then
+        begin
+            FJumpButtonHot := false;
+            Repaint;
+        end;
+    end;
+
+    // Panning logic
+    inherited MouseMove(Shift, X, Y);
+    if FIsDragging then
+    begin
+        dx := X - FDragStartPoint.X;
+        if Abs(dx) < 2 then // Threshold to avoid jitter
+        begin
+            exit;
+        end;
+
+        if (FSeriesList.Count = 0) or (FViewCount <= 0) then
+        begin
+            exit;
+        end;
+
+        indexDelta := Round(dx / (Self.Width / FViewCount));
+
+        // To move content left (natural), view must shift to newer data (lower index).
+        // Drag left (dx < 0) -> FViewStartIndex must decrease.
+        // The formula for that is FViewStartIndex := FViewStartIndex + indexDelta; -> StartIndex + (negative) = decrease.
+        FViewStartIndex := FViewStartIndex + indexDelta;
+
+
+        // Clamp values
+        mainSeries := FSeriesList[0];
+        maxIndex := 0;
+        if (mainSeries <> nil) then
+        begin
+            maxIndex := mainSeries.Count - FViewCount;
+        end;
+        if (maxIndex < 0) then
+        begin
+            maxIndex := 0;
+        end;
+
+        if (FViewStartIndex < 0) then FViewStartIndex := 0;
+        if (FViewStartIndex > maxIndex) then FViewStartIndex := maxIndex;
+
+        FDragStartPoint := TPointF.Create(X, Y);
+        Repaint;
+    end;
+end;
+
+procedure TMycChart.MouseWheel(Shift: TShiftState; WheelDelta: Integer; var Handled: Boolean);
+var
+    mousePos: TPointF;
+    anchorIndex: Double;
+    zoomFactor: Double;
+    newViewCount: Int64;
+    ratio: Double;
+    mainSeries: TSeries;
+begin
+    Handled := true;
+
+    if (FSeriesList.Count = 0) then
+    begin
+        exit;
+    end;
+    mainSeries := FSeriesList[0];
+    if (mainSeries = nil) or (mainSeries.Count = 0) or (Self.Width <= 0) then
+    begin
+        exit;
+    end;
+
+    mousePos := Self.ScreenToLocal(Screen.MousePos);
+
+    // Correctly calculate the anchor index for a right-to-left axis
+    anchorIndex := FViewStartIndex + ((Self.Width - mousePos.X) / Self.Width) * FViewCount;
+
+    if (WheelDelta > 0) then
+        zoomFactor := 0.8 // Zoom In
+    else
+        zoomFactor := 1.25; // Zoom Out
+
+    newViewCount := Round(FViewCount * zoomFactor);
+
+    // Clamp zoom level
+    if (newViewCount < 10) then newViewCount := 10;
+    if (newViewCount > mainSeries.Count) then newViewCount := mainSeries.Count;
+    if (newViewCount = FViewCount) then exit;
+
+    // Adjust start index to keep anchor point stable
+    if (FViewCount > 0) then
+        ratio := (anchorIndex - FViewStartIndex) / FViewCount
+    else
+        ratio := 0;
+
+    FViewStartIndex := Round(anchorIndex - (ratio * newViewCount));
+    FViewCount := newViewCount;
+
+    // Clamp start index
+    if (FViewStartIndex < 0) then FViewStartIndex := 0;
+    if (FViewStartIndex + FViewCount > mainSeries.Count) then
+    begin
+        FViewStartIndex := mainSeries.Count - FViewCount;
+    end;
+
+    Repaint;
 end;
 
 procedure TMycChart.Paint;
@@ -229,12 +448,14 @@ var
     rangeInitialized: Boolean;
     xTransform: TFunc<Double, Single>;
     yTransform: TFunc<Double, Single>;
+    isButtonVisible: Boolean;
+    buttonColor: TAlphaColor;
+    path: TPathData;
 begin
     inherited;
     rect := Self.LocalRect;
-    var lookback := FLookback.Value;
 
-    if (FSeriesList.Count = 0) or (lookback <= 1) then
+    if (FSeriesList.Count = 0) or (FViewCount <= 1) then
     begin
         Canvas.Fill.Color := TAlphaColors.Gray;
         Canvas.FillText(rect, 'No Data', false, 1, [], TTextAlign.Center, TTextAlign.Center);
@@ -243,9 +464,10 @@ begin
 
     rangeInitialized := false;
 
+    // Determine value range for the visible viewport only
     for series in FSeriesList do
     begin
-        if series.GetValueRange(0, lookback, seriesMin, seriesMax) then
+        if series.GetValueRange(FViewStartIndex, FViewCount, seriesMin, seriesMax) then
         begin
             if not rangeInitialized then
             begin
@@ -271,18 +493,75 @@ begin
     if (globalMax - globalMin) = 0 then
         exit;
 
-    xTransform := function(index: Double): Single begin Result := rect.Right - (index / (lookback - 1)) * rect.Width; end;
+    // Transform maps an index from the viewport to a screen coordinate
+    xTransform := function(index: Double): Single
+        begin
+            if (FViewCount <= 1) then
+            begin
+                Result := rect.Left + rect.Width / 2;
+                exit;
+            end;
+            Result := rect.Right - (((index - FViewStartIndex) / (FViewCount - 1)) * rect.Width);
+        end;
 
     yTransform :=
-        function(value: Double): Single begin Result := rect.Top + (1 - (value - globalMin) / (globalMax - globalMin)) * rect.Height; end;
-
-    //    var T :=
-    //        TMatrix.CreateTranslation(rect.Left, rect.Top + rect.Height*globalMax / (globalMax - globalMin)) *
-    //        TMatrix.CreateScaling(rect.Width / (FLookback - 1), -rect.Height / (globalMax - globalMin));
+        function(value: Double): Single
+        begin
+            Result := rect.Top + (1 - (value - globalMin) / (globalMax - globalMin)) * rect.Height;
+        end;
 
     for series in FSeriesList do
     begin
-        series.Paint(Self.Canvas, lookback, xTransform, yTransform);
+        series.Paint(Self.Canvas, FViewStartIndex, FViewCount, xTransform, yTransform);
+    end;
+
+    // --- Draw the "jump to latest" button ---
+    isButtonVisible := (FViewStartIndex > 0);
+    FJumpButtonHot := FJumpButtonHot and isButtonVisible;
+
+    if isButtonVisible then
+    begin
+        // Define button position and size
+        FJumpButtonRect := TRectF.Create(Self.Width - 44, Self.Height - 44, Self.Width - 10, Self.Height - 10);
+
+        // Determine color based on state
+        if FJumpButtonPressed then
+            buttonColor := $FF707070 // Pressed color
+        else if FJumpButtonHot then
+            buttonColor := $FF505050 // Hover color
+        else
+            buttonColor := $FF303030; // Default color
+
+        // Draw button background
+        Canvas.Fill.Color := buttonColor;
+        Canvas.FillRect(FJumpButtonRect, 4, 4, AllCorners, 0.7);
+
+        // Draw an icon (e.g., a "fast forward" double arrow)
+        Canvas.Stroke.Color := TAlphaColors.White;
+        Canvas.Stroke.Thickness := 1.5;
+
+        path := TPathData.Create;
+        try
+            var cx := FJumpButtonRect.CenterPoint.X;
+            var cy := FJumpButtonRect.CenterPoint.Y;
+            // First arrow
+            path.MoveTo(PointF(cx - 5, cy - 6));
+            path.LineTo(PointF(cx, cy));
+            path.LineTo(PointF(cx - 5, cy + 6));
+            // Second arrow
+            path.MoveTo(PointF(cx + 2, cy - 6));
+            path.LineTo(PointF(cx + 7, cy));
+            path.LineTo(PointF(cx + 2, cy + 6));
+            Canvas.DrawPath(path, 1);
+        finally
+            path.Free;
+        end;
+    end
+    else
+    begin
+        // Reset button state when not visible
+        FJumpButtonRect := TRectF.Empty;
+        FJumpButtonPressed := false;
     end;
 end;
 
@@ -330,43 +609,47 @@ begin
     FStyle := AStyle;
 end;
 
-function TChartOhlcSeries.GetValueRange(StartIndex, Count: Int64; out Min, Max: Double): Boolean;
+function TChartOhlcSeries.GetValueRange(StartIndex, Count: Int64; out MinValue, MaxValue: Double): Boolean;
 var
     i: Int64;
+    lastIndex: Int64;
 begin
     Result := GetCount > 0;
     if not Result then
         Exit;
 
-    Min := MaxDouble;
-    Max := -MaxDouble;
-    for i := StartIndex to System.Math.Min(GetCount - 1, StartIndex + Count - 1) do
+    MinValue := MaxDouble;
+    MaxValue := -MaxDouble;
+    lastIndex := Min(GetCount - 1, StartIndex + Count - 1);
+
+    for i := StartIndex to lastIndex do
     begin
         var dp := Data.Items[i];
-        Min := System.Math.Min(Min, dp.Data.Low);
-        Max := System.Math.Max(Max, dp.Data.High);
+        MinValue := Min(MinValue, dp.Data.Low);
+        MaxValue := Max(MaxValue, dp.Data.High);
     end;
-    Result := (Min <> MaxDouble);
+    Result := (MinValue <> MaxDouble);
 end;
 
-procedure TChartOhlcSeries.Paint(const ACanvas: TCanvas; Lookback: Int64; const AXForm, AYForm: TFunc<Double, Single>);
+procedure TChartOhlcSeries.Paint(const ACanvas: TCanvas; StartIndex, Count: Int64; const AXForm, AYForm: TFunc<Double, Single>);
 var
-    i, displayCount: Int64;
+    i: Int64;
+    lastIndex: Int64;
     x, candleWidth: Single;
     yOpen, yHigh, yLow, yClose: Single;
     item: TDataPoint<TOhlcItem>;
     isUp: boolean;
 begin
-    displayCount := System.Math.Min(Data.Count, Lookback);
-    if displayCount <= 0 then
+    if (Count <= 0) then
         Exit;
 
-    if displayCount > 1 then
-        candleWidth := Max(2, 0.8 * Abs((AXForm(1) - AXForm(0))))
+    if (Count > 1) then
+        candleWidth := Max(2, 0.8 * Abs((AXForm(StartIndex + 1) - AXForm(StartIndex))))
     else
         candleWidth := 10;
 
-    for i := 0 to displayCount - 1 do
+    lastIndex := Min(Data.Count - 1, StartIndex + Count - 1);
+    for i := StartIndex to lastIndex do
     begin
         item := Data.Items[i];
         x := AXForm(i);
@@ -384,7 +667,7 @@ begin
 
         ACanvas.DrawLine(TPointF.Create(x, yHigh), TPointF.Create(x, yLow), 1);
 
-        if FStyle = csCandleStick then
+        if (FStyle = csCandleStick) then
         begin
             ACanvas.Fill.Color := ACanvas.Stroke.Color;
             if isUp then
@@ -409,55 +692,67 @@ begin
     FLineWidth := ALineWidth;
 end;
 
-function TChartLineSeries.GetValueRange(StartIndex, Count: Int64; out Min, Max: Double): Boolean;
+function TChartLineSeries.GetValueRange(StartIndex, Count: Int64; out MinValue, MaxValue: Double): Boolean;
 var
     i: Int64;
+    lastIndex: Int64;
 begin
     Result := GetCount > 0;
     if not Result then
         Exit;
 
-    Min := MaxDouble;
-    Max := -MaxDouble;
-    for i := StartIndex to System.Math.Min(Data.Count - 1, StartIndex + Count - 1) do
+    MinValue := MaxDouble;
+    MaxValue := -MaxDouble;
+    lastIndex := Min(Data.Count - 1, StartIndex + Count - 1);
+    for i := StartIndex to lastIndex do
     begin
         var v := Data.Items[i];
         if not IsNaN(v) then
         begin
-            Min := System.Math.Min(Min, v);
-            Max := System.Math.Max(Max, v);
+            MinValue := Min(MinValue, v);
+            MaxValue := Max(MaxValue, v);
         end;
     end;
-    Result := (Min <> MaxDouble);
+    Result := (MinValue <> MaxDouble);
 end;
 
-procedure TChartLineSeries.Paint(const ACanvas: TCanvas; Lookback: Int64; const AXForm, AYForm: TFunc<Double, Single>);
+procedure TChartLineSeries.Paint(const ACanvas: TCanvas; StartIndex, Count: Int64; const AXForm, AYForm: TFunc<Double, Single>);
+var
+    points: TPathData;
+    i, n: Int64;
+    lastIndex: Int64;
 begin
-    if not Assigned(MainSeries) or (Data.Count = 0) or (MainSeries.Count = 0) then
+    if (Data.Count = 0) or (Count < 2) then
         Exit;
 
-    var points := TPathData.Create;
+    lastIndex := Min(Data.Count - 1, StartIndex + Count - 1);
+    points := TPathData.Create;
+    try
+        // Skip warmup data
+        n := StartIndex;
+        while (n <= lastIndex) and (IsNaN(Data[n])) do
+        begin
+            inc(n);
+        end;
 
-    var displayCount := System.Math.Min(Data.Count, Lookback);
-    if displayCount < 2 then
-        Exit;
-
-    // Skip warmup data
-    var n := 0;
-    while IsNaN(Data[n]) do
-    begin
-        inc(n);
-        if n >= displaycount - 2 then
+        if (n > lastIndex) then
             exit;
+
+        points.MoveTo(TPointF.Create(AXForm(n), AYForm(Data[n])));
+        for i := n + 1 to lastIndex do
+        begin
+            if not IsNaN(Data[i]) then
+            begin
+                points.LineTo(TPointF.Create(AXForm(i), AYForm(Data[i])));
+            end;
+        end;
+
+        ACanvas.Stroke.Color := FLineColor;
+        ACanvas.Stroke.Thickness := FLineWidth;
+        ACanvas.DrawPath(points, 1);
+    finally
+        points.Free;
     end;
-
-    points.MoveTo(TPointF.Create(AXForm(n), AYForm(Data[n])));
-    for var i := n to displayCount - 1 do
-        points.LineTo(TPointF.Create(AXForm(i), AYForm(Data[i])));
-
-    ACanvas.Stroke.Color := FLineColor;
-    ACanvas.Stroke.Thickness := FLineWidth;
-    ACanvas.DrawPath(points, 1);
 end;
 
 { TChartSeriesReceiver<T> }