lazarus/examples/dockmanager/package/felasticsite.pas

unit fElasticSite;
(* Demonstrate elastic dock sites.
  This form has dock sites (panels) on its left, right and bottom.

  Empty panels should be invisible, what's a bit tricky. They cannot have
  Visible=False, because this would disallow to dock anything into them.
  So the width/height of the panels is set to zero instead.

  When a first control is docked, the dock site is enlarged.
  Fine adjustment can be made with the splitters beneath the controls.

  When the last control is undocked, the dock site is shrinked again.
*)

(* Observed problems:

Object Inspector says: the bottom panel's OnGetSiteInfo method is incompatible
  with other OnGetSiteInfo methods.

When the form is resized, the dock sites report their old (designed) extent.
  This makes initial docking problematic, only the upper-/leftmost parts of the sites
  work as dock targets.
*)

{$mode objfpc}{$H+}

{$DEFINE ExpandFlag} //using AutoExpand property?

interface

uses
  Classes, SysUtils, FileUtil, LResources, Forms, Controls, Graphics, Dialogs,
  ExtCtrls, ComCtrls,
  EasyDockSite;

type
  TDockingSite = class(TForm)
    pnlBottom: TPanel;
    pnlLeft: TPanel;
    pnlRight: TPanel;
    splitBottom: TSplitter;
    splitLeft: TSplitter;
    splitRight: TSplitter;
    StatusBar1: TStatusBar;
    procedure pnlLeftDockDrop(Sender: TObject; Source: TDragDockObject;
      X, Y: Integer);
    procedure pnlLeftDockOver(Sender: TObject; Source: TDragDockObject;
      X, Y: Integer; State: TDragState; var Accept: Boolean);
    procedure pnlLeftGetSiteInfo(Sender: TObject; DockClient: TControl;
      var InfluenceRect: TRect; MousePos: TPoint; var CanDock: Boolean);
    procedure pnlLeftUnDock(Sender: TObject; Client: TControl;
      NewTarget: TWinControl; var Allow: Boolean);
  protected
    FAutoExpand: boolean;
{$IFDEF ExpandFlag}
  published
    property AutoExpand: boolean read FAutoExpand write FAutoExpand default True;
{$ELSE}
  //become property of the docksite (panel)
{$ENDIF}
  end;

//var DockingSite: TDockingSite;

procedure Register;

implementation

uses
  LCLIntf, LCLProc;

//uses  fDockClient;  //test only

procedure Register;
begin
  RegisterComponents('DoDi', [TDockingSite]);
end;

{ TDockingSite }

procedure TDockingSite.pnlLeftDockDrop(Sender: TObject;
  Source: TDragDockObject; X, Y: Integer);
var
  w: integer;
  r: TRect;
  Site: TWinControl absolute Sender;
begin
(* Adjust docksite extent, if required.
  H/V depending on align LR/TB.
  Take 1/3 of the form's extent for the dock site.
  When changed, ensure that the form layout is updated.
*)
  if (TWinControl(Source.DragTarget).DockClientCount > 1)
  or ((Site.Width > 1) and (Site.Height > 1)) //NoteBook!
  then
    exit; //no adjustments of the dock site required
//this is the first drop - handle AutoExpand
  with Source do begin
    if DragTarget.Align in [alLeft, alRight] then begin
      w := self.Width div 3;
      if DragTarget.Width < w then begin
      //enlarge docksite
        DisableAlign; //form(?)
        DragTarget.Width := w;
        if DragTarget.Align = alRight then begin
          if AutoExpand then begin
            r := self.BoundsRect;
            inc(r.Right, w);
            BoundsRect := r;
          end else begin
            DragTarget.Left:=DragTarget.Left-w;
            splitRight.Left:=splitRight.Left-w;
          end;
        end else if AutoExpand then begin
        //enlarge left
          r := BoundsRect;
          dec(r.Left, w);
          BoundsRect := r;
        end;
        EnableAlign;
      end;
    end else begin //alBottom
      w := self.Height div 3;
      if DragTarget.Height < w then begin
      //enlarge docksite
        DisableAlign; //form(?)
        DragTarget.Height := w;
        if DragTarget.Align = alBottom then begin
          if AutoExpand then begin
            //dec(self.Left, w);
            r := self.BoundsRect;
            inc(r.Bottom, w);
            BoundsRect := r;
            StatusBar1.Top:=StatusBar1.Top+w;
          end else begin
            splitBottom.Top:=splitBottom.Top-w;
            DragTarget.Top:=DragTarget.Top-w;
          end;
        end;
        EnableAlign;
      end;
    end;
  end;
end;

procedure TDockingSite.pnlLeftDockOver(Sender: TObject;
  Source: TDragDockObject; X, Y: Integer; State: TDragState;
  var Accept: Boolean);
var
  r: TRect;

  procedure Adjust(dw, dh: integer);
  begin
  (* r.TopLeft in screen coords, r.BottomRight is W/H(?)
    negative values mean expansion towards screen origin
  *)
    if dw <> 0 then begin
      r.Right := r.Left;
      inc(r.Bottom, r.Top);
      if dw > 0 then
        inc(r.Right, dw)
      else
        inc(r.Left, dw);
    end else begin
      r.Bottom := r.Top;
      inc(r.Right, r.Left);
      if dh > 0 then
        inc(r.Bottom, dh)
      else
        inc(r.Top, dh);
    end;
  end;

var
  Site: TWinControl;  // absolute Sender;
  dw, dh: integer;
const
  d = 10; //shift mousepos with InfluenceRect
begin
(* This handler has to determine the intended DockRect,
  and the alignment within this rectangle.

  This is impossible when the mouse leaves the InfluenceRect,
  i.e. when the site is not yet expanded :-(

  For a shrinked site we only can display the intended DockRect,
  and signal alClient.

  On the first drop, AutoExpand can be determined from the mouse position,
  inside or outside the form.
*)
  if Source.DragTarget = nil then begin
  (* Bug: DragTarget has not yet been initialized.
    Fix in TWinControl.DoDockOver, or earlier in the dragmanager?
  *)
    DebugLn('---------- Please fix bad DockOver call with DragTarget=nil ---------');
    exit; //shit happens :-(
  end;
  if State = dsDragMove then begin
    TObject(Site) := Source.DragTarget;
    if Site.DockClientCount > 0 then
      exit; //everything should be okay
  //make DockRect reflect the docking area
    r := Site.BoundsRect; //XYWH
    r.TopLeft := Site.Parent.ClientToScreen(r.TopLeft);
    dw := Width div 3;  //r.Right := r.Left + dw;
    dh := Height div 3; //r.Bottom := r.Top + dh;
  //determine inside/outside
  {$IFDEF ExpandFlag}
  //using AutoExpand flag
    case Site.Align of
    alLeft:   if AutoExpand then Adjust(-dw, 0) else Adjust(dw, 0);
    alRight:  if AutoExpand then Adjust(dw, 0) else Adjust(-dw, 0);
    alBottom: if AutoExpand then Adjust(0, dh) else Adjust(0, -dh);
    else      exit;
    end;
  {$ELSE}
  //dock inside/outside depending on mouse position
  //set temporary FAutoExpand
    case Site.Align of
    alLeft:
      begin
        FAutoExpand := Source.DragPos.x + d < r.Left;
        if FAutoExpand then Adjust(-dw, 0) else Adjust(dw, 0);
      end;
    alRight:
      begin
        FAutoExpand := Source.DragPos.x + d >= r.Left;
        if FAutoExpand then Adjust(dw, 0) else Adjust(-dw, 0);
      end;
    alBottom:
      begin
        FAutoExpand := Source.DragPos.y + d > r.Top;
        if FAutoExpand then Adjust(0, dh) else Adjust(0, -dh);
      end
    else
      exit;
    end;
  {$ENDIF}
    Source.DockRect := r;
    Accept := True;
  end;
end;

procedure TDockingSite.pnlLeftGetSiteInfo(Sender: TObject;
  DockClient: TControl; var InfluenceRect: TRect; MousePos: TPoint;
  var CanDock: Boolean);
begin
(* Signal acceptance.
  Inflate InfluenceRect, for easier docking into a shrinked site.
*)
  CanDock := True;
  InflateRect(InfluenceRect, 10, 10);
  //OffsetRect(InfluenceRect, 10, 10); //collides with other sites?
end;

procedure TDockingSite.pnlLeftUnDock(Sender: TObject; Client: TControl;
  NewTarget: TWinControl; var Allow: Boolean);
var
  Site: TWinControl absolute Sender;
  wh: integer;
  r: TRect;
begin
(* When the last client is undocked, shrink the dock site to zero extent.
  Called *before* the dock client is removed.
*)
  if Site.DockClientCount <= 1 then begin
  //become empty, hide the dock site
    DisableAlign;
    case Site.Align of
    alLeft:
      begin
        wh := Site.Width;
        Site.Width := 0; //behaves as expected
        if AutoExpand then begin
          r := BoundsRect;
          inc(r.Left, wh);
          BoundsRect := r;
        end;
      end;
    alRight:
      begin
        wh := Site.Width;
        Site.Width := 0;
        if AutoExpand then begin
          r := BoundsRect;
          dec(r.Right, wh);
          BoundsRect := r;
        end else begin
          Site.Left:=Site.Left+wh;
          splitRight.Left:=splitRight.Left+wh;
        end;
      end;
    alBottom:
      begin
        wh := Site.Height;
        Site.Height := 0;
        if AutoExpand then begin
          r := BoundsRect;
          dec(r.Bottom, wh);
          BoundsRect := r;
          splitBottom.Top:=splitBottom.Top-wh;
          StatusBar1.Top:=StatusBar1.Top-wh;
        end else begin
          Site.Top:=Site.Top+wh;
          splitBottom.Top := Site.Top - splitBottom.Height - 10;
        end;
      end;
    end;
    EnableAlign;
  end;
end;


initialization
  {$I felasticsite.lrs}
  DefaultDockManagerClass := TEasyTree;
end.