Delphi拖动是否可以“升级"?对接? [英] Can Delphi dragging be "promoted" to docking?

问题描述

我有一个TPageControl，其页面都是使用ManualDock()附加的各种形式.用户应该能够通过拖动来重新排列选项卡，这已经可以了.但是，也应该可以取消停靠的表单.

I have a TPageControl whose pages are all various forms that are attached using ManualDock(). The user should be able to rearrange the tabs by dragging them, which works already. It should however also be possible to undock the docked forms.

现在我有以下代码:

procedure TMainForm.PageControlMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  if (Button = mbLeft) and (Shift * [ssShift, ssCtrl] = [])
    and PageControl.DockSite
  then begin
    PageControl.BeginDrag(False, 32);
  end;
end;

如果按住 Shift 或 Ctrl 键，则将启动对接操作，否则可以通过拖动它们来重新排列选项卡.

If either the Shift or the Ctrl key are held down, then a docking operation will be started, otherwise the tabs can be rearranged by dragging them.

使用键作为修饰符是很尴尬的.当鼠标光标在页面控件的选项卡区域之外时，是否有任何方法可以取消活动的拖动操作，并开始停靠子窗体?这是Delphi 2009的版本.

Using the keys as modifiers is awkward though. Is there any way to cancel the active drag operation when the mouse cursor is outside of the tab area of the page control, and start docking the child form? This is with Delphi 2009.

推荐答案

我现在有一个对我有用的解决方案，所以我会自己回答-也许有人对此也有帮助.

I have a solution now which works for me, so I'll answer myself - maybe somebody has a use for this too.

让我们从一个小的示例应用程序开始，该应用程序创建具有8个停靠表单的TPageControl，并带有允许对选项卡进行运行时重新排序的代码.选项卡将实时移动，并且取消拖动后，活动的选项卡索引将恢复为其原始值:

Let's start with a small sample application that creates a TPageControl with 8 docked forms, with code to allow for runtime reordering of the tabs. Tabs will be moved live, and when the dragging is canceled the active tab index will revert to its original value:

unit uDragDockTest;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  ComCtrls;

type
  TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
  private
    fPageControl: TPageControl;
    fPageControlOriginalPageIndex: integer;
    function GetPageControlTabIndex(APosition: TPoint): integer;
  public
    procedure PageControlDragDrop(Sender, Source: TObject; X, Y: Integer);
    procedure PageControlDragOver(Sender, Source: TObject; X, Y: Integer;
      AState: TDragState; var AAccept: Boolean);
    procedure PageControlEndDrag(Sender, Target: TObject; X, Y: Integer);
    procedure PageControlMouseDown(Sender: TObject; AButton: TMouseButton;
      AShift: TShiftState; X, Y: Integer);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
const
  FormColors: array[1..8] of TColor = (
    clRed, clGreen, clBlue, clYellow, clLime, clMaroon, clTeal, clAqua);
var
  i: integer;
  F: TForm;
begin
  fPageControlOriginalPageIndex := -1;

  fPageControl := TPageControl.Create(Self);
  fPageControl.Align := alClient;
  // set to False to enable tab reordering but disable form docking
  fPageControl.DockSite := True;
  fPageControl.Parent := Self;

  fPageControl.OnDragDrop := PageControlDragDrop;
  fPageControl.OnDragOver := PageControlDragOver;
  fPageControl.OnEndDrag := PageControlEndDrag;
  fPageControl.OnMouseDown := PageControlMouseDown;

  for i := Low(FormColors) to High(FormColors) do begin
    F := TForm.Create(Self);
    F.Caption := Format('Form %d', [i]);
    F.Color := FormColors[i];
    F.DragKind := dkDock;
    F.BorderStyle := bsSizeToolWin;
    F.FormStyle := fsStayOnTop;
    F.ManualDock(fPageControl);
    F.Show;
  end;
end;

const
  TCM_GETITEMRECT = $130A;

function TForm1.GetPageControlTabIndex(APosition: TPoint): integer;
var
  i: Integer;
  TabRect: TRect;
begin
  for i := 0 to fPageControl.PageCount - 1 do begin
    fPageControl.Perform(TCM_GETITEMRECT, i, LPARAM(@TabRect));
    if PtInRect(TabRect, APosition) then
      Exit(i);
  end;
  Result := -1;
end;

procedure TForm1.PageControlDragDrop(Sender, Source: TObject; X, Y: Integer);
var
  Index: integer;
begin
  if Sender = fPageControl then begin
    Index := GetPageControlTabIndex(Point(X, Y));
    if (Index <> -1) and (Index <> fPageControl.ActivePage.PageIndex) then
      fPageControl.ActivePage.PageIndex := Index;
  end;
end;

procedure TForm1.PageControlDragOver(Sender, Source: TObject; X, Y: Integer;
  AState: TDragState; var AAccept: Boolean);
var
  Index: integer;
begin
  AAccept := Sender = fPageControl;
  if AAccept then begin
    Index := GetPageControlTabIndex(Point(X, Y));
    if (Index <> -1) and (Index <> fPageControl.ActivePage.PageIndex) then
      fPageControl.ActivePage.PageIndex := Index;
  end;
end;

procedure TForm1.PageControlEndDrag(Sender, Target: TObject; X, Y: Integer);
begin
  // restore original index of active page if dragging was canceled
  if (Target <> fPageControl) and (fPageControlOriginalPageIndex > -1)
    and (fPageControlOriginalPageIndex < fPageControl.PageCount)
  then
    fPageControl.ActivePage.PageIndex := fPageControlOriginalPageIndex;
  fPageControlOriginalPageIndex := -1;
end;

procedure TForm1.PageControlMouseDown(Sender: TObject; AButton: TMouseButton;
  AShift: TShiftState; X, Y: Integer);
begin
  if (AButton = mbLeft)
    // undock single docked form or reorder multiple tabs
    and (fPageControl.DockSite or (fPageControl.PageCount > 1))
  then begin
    // save current active page index for restoring when dragging is canceled
    fPageControlOriginalPageIndex := fPageControl.ActivePageIndex;
    fPageControl.BeginDrag(False);
  end;
end;

end.

将其粘贴到编辑器中并运行，所有必需的组件及其属性将在运行时创建和设置.

Paste this into the editor and run it, all necessary components and their properties will be created and set up at runtime.

请注意，只有通过双击选项卡才能取消停靠表单.不管距选项卡的距离如何，都将显示拖动光标直到鼠标左键释放为止，这在某种程度上是很丑陋的.如果鼠标位于页面控制选项卡区域之外且边缘有几个像素，那么如果自动取消拖动并取消固定表单，那就更好了.

Note that undocking the forms is possible only by double-clicking the tabs. It's also somewhat ugly that the drag cursor will be shown until the left mouse button is released, regardless of the distance from the tabs. It would be much better if the dragging was automatically canceled and the form be undocked instead, when the mouse is outside of the page control tab area with a few pixels margin.

这可以通过在页面控件的OnStartDrag处理程序中创建自定义DragObject来实现.在此对象中，鼠标被捕获，因此可以在其中处理拖动时的所有鼠标消息.当鼠标光标在选项卡影响矩形的外部时，将取消拖动，而是开始在活动页面控制表中进行表单的停靠操作:

This can be achieved by creating a custom DragObject in the OnStartDrag handler of the page control. In this object the mouse is captured, so all mouse messages while dragging can be handled in it. When the mouse cursor is outside of the tab influence rectangle the dragging is canceled, and a docking operation for the form in the active page control sheet is started instead:

type
  TConvertDragToDockHelper = class(TDragControlObjectEx)
  strict private
    fPageControl: TPageControl;
    fPageControlTabArea: TRect;
  protected
    procedure WndProc(var AMsg: TMessage); override;
  public
    constructor Create(AControl: TControl); override;
  end;

constructor TConvertDragToDockHelper.Create(AControl: TControl);
const
  MarginX = 32;
  MarginY = 12;
var
  Item0Rect, ItemLastRect: TRect;
begin
  inherited;
  fPageControl := AControl as TPageControl;
  if fPageControl.PageCount > 0 then begin
    // get rects of first and last tab
    fPageControl.Perform(TCM_GETITEMRECT, 0, LPARAM(@Item0Rect));
    fPageControl.Perform(TCM_GETITEMRECT, fPageControl.PageCount - 1,
      LPARAM(@ItemLastRect));
    // calculate rect valid for dragging (includes some margin around tabs)
    // when this area is left dragging will be canceled and docking will start
    fPageControlTabArea := Rect(
      Min(Item0Rect.Left, ItemLastRect.Left) - MarginX,
      Min(Item0Rect.Top, ItemLastRect.Top) - MarginY,
      Max(Item0Rect.Right, ItemLastRect.Right) + MarginX,
      Max(Item0Rect.Bottom, ItemLastRect.Bottom) + MarginY);
  end;
end;

procedure TConvertDragToDockHelper.WndProc(var AMsg: TMessage);
var
  MousePos: TPoint;
  CanUndock: boolean;
begin
  inherited;
  if AMsg.Msg = WM_MOUSEMOVE then begin
    MousePos := fPageControl.ScreenToClient(Mouse.CursorPos);
    // cancel dragging if outside of tab area with margins
    // optionally start undocking the docked form (can be canceled with [ESC])
    if not PtInRect(fPageControlTabArea, MousePos) then begin
      fPageControl.EndDrag(False);
      CanUndock := fPageControl.DockSite and (fPageControl.ActivePage <> nil)
        and (fPageControl.ActivePage.ControlCount > 0)
        and (fPageControl.ActivePage.Controls[0] is TForm)
        and (TForm(fPageControl.ActivePage.Controls[0]).DragKind = dkDock);
      if CanUndock then
        fPageControl.ActivePage.Controls[0].BeginDrag(False);
    end;
  end;
end;

该类是从TDragControlObjectEx而不是TDragControlObject派生的，因此它将被自动释放.现在，如果在示例应用程序中创建了TPageControl的处理程序(并为页面控制对象进行了设置):

The class descends from TDragControlObjectEx instead of from TDragControlObject so that it will be automatically freed. Now if a handler for the TPageControl in the sample application is created (and set for the page control object):

procedure TForm1.PageControlStartDrag(Sender: TObject;
  var ADragObject: TDragObject);
begin
  // do not cancel dragging unless page control has docking enabled
  if (ADragObject = nil) and fPageControl.DockSite then
    ADragObject := TConvertDragToDockHelper.Create(fPageControl);
end;

然后，当鼠标远离选项卡足够远时，选项卡拖动将被取消，并且如果活动页面是可停靠表单，则将开始其停靠操作，仍然可以通过取消ESC 键.

then the tab dragging will be canceled when the mouse moves far enough away from the tabs, and if the active page is a dockable form then a docking operation for it will be started, which can still be canceled with the ESC key.

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