C# picture viewer can not focus on

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I write a picture viewer in C#4.0. When mouse wheel scrolls, I want the picture to be able to shrink and grow focus on the mouse point. Then I drag a PictureBox in window Form, and add mouseWheel event, but when I wheel my mouse, the Vscroll bar moved, the same time the PictureBox shrinks and grows. Does any one know the method how to reduce the action(Vscroll bar moved with mouse wheel),when wheel my mouse? Thank you.

Posted 22-Oct-12 16:53pm

bubifengyun

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Sergey Alexandrovich Kryukov · Accepted Answer · 2012-10-22T18:29:00

The "focus" always means "keyboard focus" and nothing else. You need to make your control focusable. Please see:
http://msdn.microsoft.com/en-us/library/system.windows.forms.control.canfocus.aspx[^].

You should not use PictureBox for your purpose. More exactly, in principle, this is possible, but totally pointless. I explained it in my past answers. Please see:
How do I clear a panel from old drawing[^],
draw a rectangle in C#[^],
Append a picture within picturebox[^].

See also:
Drawing Lines between mdi child forms[^],
capture the drawing on a panel[^],
What kind of playful method is Paint? (DataGridViewImageCell.Paint(...))[^].

In addition to the techniques explained in my answers referenced above, you can organize scrolling in a very simple way. You can use the class already designed for this purpose: System.Windows.Forms.ScrollableControl:
http://msdn.microsoft.com/en-us/library/system.windows.forms.scrollablecontrol.aspx[^].

You need to calculate the "whole area" of the scene in pixels and assign it to the property AutoScrollMinSize, which is used by the control to determine how much to scroll in each direction. The property AutoScroll should be true. Please see other "AutoScroll…" members of this class for further detail.

—SA