Dynamic Control Positions
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	CDragBar CDragBar implements a vertical bar which may be dragged to reposition other Child Windows. All the Child Windows are positioned by the owner.

In the parent window create an owner-draw button and subclass it.
For example, in a Dialog, use the Resource Editor to make a Button Control, set [Owner Draw] to checked and in the OnInitDialog have the line:

  DragBar.SubclassDlgItem(IDC_DragBar,this);

You can now give the Bar a default position to go to when the user double-clicks it (0.0=Left, 0.5=Middle, 1.0=Right):

  DragBar.SetDefault(0.3);

If your applications other child window redraw slowly you may wish to stop them redrawing during dragging with:

  DragBar.SetLive(false);

Since you will be redrawing controls during OnSize, you need to know when OnInitDialog has created al its child win
dows with a bool:

  Updated=true;

Now you can set the initial positions by calling Move with no arguments:

  DragBar.Move();

The OnSize Handler would look like this:

void CDragBarTesterDlg::OnSize(UINT nType, int cx, int cy) {
  CDialog::OnSize(nType, cx, cy);
  if(!Updated) return; // Don't access windows before they've been created
  DrawControls();
}

CDragBar passes a special nType to OnSize (SIZE_BAR_DRAGGED) which you can use to filter this message if you need to:

  if(nType==SIZE_BAR_DRAGGED) DrawControls();

This would mean that you wouldn't need the "Updated" flag, and that the controls would only move when you tell them to.
Since there isn't a simple event which signals the end of a resize drag, this only seems useful for non-resizing windows.

DrawControls() should use the GetClientRect and DragBar.GetPostion functions to move and redraw the controls:

  CRect Rect;
  GetClientRect(&Rect);
  int L=DragBar.GetPosition(Rect.Width()); // Left of the DragBar
  const int W=DragBar.Width+1;
  ...more sums...
  GetDlgItem(IDC_EDIT1)->MoveWindow(x,y,cx,cy);
  ...more moves...

Occasionally you'll need to Redraw a control because MoveWindow doesn't make Listboxes redraw their backgrounds etc.

  GetDlgItem(IDC_LIST1)->RedrawWindow(NULL, NULL, RDW_INVALIDATE | RDW_UPDATENOW); // Don't need to erase background.

You can download an example project here:

• DragBarTester.zip

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