unit Myc.Fmx.AstEditor.Layout;

interface

uses
    System.SysUtils,
    System.Classes,
    System.Types,
    System.Math,
    System.Math.Vectors,
    System.Generics.Collections,
    FMX.Types,
    FMX.Controls;

type
    TLayoutOrientation = (loVertical, loHorizontal);
    TLayoutAlignment = (laCenter, laFlush);

    TAutoFitControl = class(TControl)
    private
        FUpdatingOwnSize: Boolean;
        FNeedRecalcSize: Boolean;
        FOrientation: TLayoutOrientation;
        FAlignment: TLayoutAlignment;
        procedure RecalcOwnSize;
        procedure SetOrientation(const Value: TLayoutOrientation);
        procedure SetAlignment(const Value: TLayoutAlignment);
    protected
        procedure ParentContentChanged; override;
        procedure PaddingChanged; override;
        procedure ChangeChildren; override;
        procedure Loaded; override;
        procedure DoEndUpdate; override;
    public
        constructor Create(AOwner: TComponent); override;
        function GetInsertionIndex(const P: TPointF; ItemClass: TClass = nil): Integer;

    published
        property Padding;
        property Orientation: TLayoutOrientation read FOrientation write SetOrientation default TLayoutOrientation.loHorizontal;
        property Alignment: TLayoutAlignment read FAlignment write SetAlignment default TLayoutAlignment.laCenter;
    end;

implementation

{ TAutoFitControl }

constructor TAutoFitControl.Create(AOwner: TComponent);
begin
    inherited Create(AOwner);
    HitTest := True;
    FOrientation := TLayoutOrientation.loHorizontal;
    FAlignment := TLayoutAlignment.laCenter;
end;

procedure TAutoFitControl.SetAlignment(const Value: TLayoutAlignment);
begin
    if FAlignment <> Value then
    begin
        FAlignment := Value;
        RecalcOwnSize;
    end;
end;

procedure TAutoFitControl.SetOrientation(const Value: TLayoutOrientation);
begin
    if FOrientation <> Value then
    begin
        FOrientation := Value;
        RecalcOwnSize;
    end;
end;

function TAutoFitControl.GetInsertionIndex(const P: TPointF; ItemClass: TClass = nil): Integer;
var
    i: Integer;
    child: TControl;
    center: Single;
    relevantChildren: TList<TControl>;
begin
    relevantChildren := TList<TControl>.Create;
    try
        for i := 0 to ChildrenCount - 1 do
        begin
            if Children[i] is TControl then
            begin
                child := TControl(Children[i]);
                if child.Visible and (child.Align = TAlignLayout.None) then
                begin
                    if (ItemClass = nil) or (child.InheritsFrom(ItemClass)) then
                        relevantChildren.Add(child);
                end;
            end;
        end;

        Result := relevantChildren.Count;

        for i := 0 to relevantChildren.Count - 1 do
        begin
            child := relevantChildren[i];

            if FOrientation = TLayoutOrientation.loVertical then
            begin
                // Fix: Robustere Erkennung. Wenn P.Y kleiner als Mitte ist -> Insert
                center := child.Position.Y + (child.Height / 2);
                if P.Y < center then
                    Exit(i);
            end
            else
            begin
                center := child.Position.X + (child.Width / 2);
                if P.X < center then
                    Exit(i);
            end;
        end;
    finally
        relevantChildren.Free;
    end;
end;

procedure TAutoFitControl.RecalcOwnSize;
var
    i: Integer;
    child: TControl;
    childrenToLayout: TList<TControl>;
    currentX, currentY: Single;
    requiredWidth, requiredHeight: Single;
    childWidthWithMargins, childHeightWithMargins: Single;
    hasVisibleChild: Boolean;
begin
    if FUpdatingOwnSize then
        exit;
    if IsUpdating then
    begin
        FNeedRecalcSize := True;
        exit;
    end;

    FUpdatingOwnSize := True;
    childrenToLayout := nil;
    try
        requiredWidth := Padding.Left + Padding.Right;
        requiredHeight := Padding.Top + Padding.Bottom;
        currentX := Padding.Left;
        currentY := Padding.Top;
        hasVisibleChild := False;

        childrenToLayout := TList<TControl>.Create;
        for i := 0 to ChildrenCount - 1 do
        begin
            if Children[i] is TControl then
            begin
                child := TControl(Children[i]);
                if child.Visible and (child.Align = TAlignLayout.None) then
                begin
                    childrenToLayout.Add(child);
                    hasVisibleChild := True;
                end;
            end;
        end;

        if hasVisibleChild then
        begin
            if FOrientation = TLayoutOrientation.loVertical then
            begin
                for child in childrenToLayout do
                begin
                    child.Position.Y := currentY + child.Margins.Top;
                    currentY := child.Position.Y + child.Height + child.Margins.Bottom;

                    childWidthWithMargins := Padding.Left + child.Margins.Left + child.Width + child.Margins.Right + Padding.Right;
                    requiredWidth := System.Math.Max(requiredWidth, childWidthWithMargins);
                end;
                requiredHeight := currentY + Padding.Bottom;

                if FAlignment = TLayoutAlignment.laFlush then
                begin
                    for child in childrenToLayout do
                    begin
                        child.Position.X := Padding.Left + child.Margins.Left;
                    end;
                end
                else
                begin
                    var contentWidth := requiredWidth - Padding.Left - Padding.Right;
                    for child in childrenToLayout do
                    begin
                        var childTotalWidth := child.Width + child.Margins.Left + child.Margins.Right;
                        var childX := Padding.Left + ((contentWidth - childTotalWidth) / 2) + child.Margins.Left;
                        child.Position.X := childX;
                    end;
                end;
            end
            else
            begin
                for child in childrenToLayout do
                begin
                    child.Position.X := currentX + child.Margins.Left;
                    currentX := child.Position.X + child.Width + child.Margins.Right;

                    childHeightWithMargins := Padding.Top + child.Margins.Top + child.Height + child.Margins.Bottom + Padding.Bottom;
                    requiredHeight := System.Math.Max(requiredHeight, childHeightWithMargins);
                end;
                requiredWidth := currentX + Padding.Right;

                if FAlignment = TLayoutAlignment.laFlush then
                begin
                    for child in childrenToLayout do
                    begin
                        child.Position.Y := Padding.Top + child.Margins.Top;
                    end;
                end
                else
                begin
                    var contentHeight := requiredHeight - Padding.Top - Padding.Bottom;
                    for child in childrenToLayout do
                    begin
                        var childTotalHeight := child.Height + child.Margins.Top + child.Margins.Bottom;
                        var childY := Padding.Top + ((contentHeight - childTotalHeight) / 2) + child.Margins.Top;
                        child.Position.Y := childY;
                    end;
                end;
            end;
        end
        else
        begin
            requiredWidth := Padding.Left + Padding.Right;
            requiredHeight := Padding.Top + Padding.Bottom;
        end;

        requiredWidth := System.Math.Max(0, requiredWidth);
        requiredHeight := System.Math.Max(0, requiredHeight);

        if not SameValue(requiredWidth, Width, TEpsilon.Position) or not SameValue(requiredHeight, Height, TEpsilon.Position) then
        begin
            FSize.SetSizeWithoutNotification(TSizeF.Create(requiredWidth, requiredHeight));
            HandleSizeChanged;
        end;

    finally
        childrenToLayout.Free;
        FUpdatingOwnSize := False;
    end;
end;

procedure TAutoFitControl.Loaded;
begin
    inherited Loaded;
    RecalcOwnSize;
end;

procedure TAutoFitControl.ChangeChildren;
begin
    inherited ChangeChildren;
    RecalcOwnSize;
end;

procedure TAutoFitControl.PaddingChanged;
begin
    inherited PaddingChanged;
    RecalcOwnSize;
end;

procedure TAutoFitControl.ParentContentChanged;
begin
    inherited ParentContentChanged;
    RecalcOwnSize;
end;

procedure TAutoFitControl.DoEndUpdate;
begin
    inherited;
    if FNeedRecalcSize then
    begin
        FNeedRecalcSize := False;
        RecalcOwnSize;
    end;
end;

end.