Why does scrolling position change after refocusing the Form?

Question

Why does scrolling position change after refocusing the Form?

Situation:

Design mode and application just started Remark the scroll panel position.

Scrolling manually the panel to left with mouse

Changing the focus to other application and refocusing back our application(click/click)

You can see that when the application loses the focus and then retrieves it back, the scroll position is "reseted".

Why and how stop it?

Answer 1

It happens because when the form regains focus, it will focus on a control within the form (setting ActiveControl). Since it looks like your controls are to the right, it fill focus on them and move to the right. A quick fix would be to add a panel to the form and set the Dock to Fill and AutoScroll to True, then add all your controls on top of the panel. Then the form will focus on the panel and not move the scrollbar.

If the above doesnt work automatically, then based on this site, you could do this for a work around:

  private Point mPreviousScrollPosition = new Point();

  public void Form1_Deactivate(object sender, EventArgs e)
  {
     mPreviousScrollPosition = outer_most_panel.AutoScrollPosition;
  }

  public void Form1_Activated(object sender, EventArgs e)
  {
     mPreviousScrollPosition.X *= -1;
     mPreviousScrollPosition.Y *= -1;
     outer_most_panel.AutoScrollPosition = mPreviousScrollPosition;
  }