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Positionin a popup menu

Posted on 1998-02-20
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Last Modified: 2010-04-16
I am creating a Swing-based application. One of the frames in that application displays a tree. When user clicks with a right mouse button on a tree node a popup menu apperas. My question is related to the positioning of that menu.

Does anyone has a code or an algorithm which allows to position a popup menu in such a way that the menu is always completely visible (that is it is not completetly or partially hidden by the edge of the screen or edge of the parent frame. That means it has to be positioned based on the cursor location as well as various edges.  I am looking for a behavior similar to that of popup menus in Microsoft Windows Explorer in 95 and NT.

I am not looking for a general description of the approach I shoud take but rather for an exact algorithm or even better a code which implements such behavior.
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Question by:msmolyak
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gwalters earned 200 total points
ID: 1233171
Dimension sz=menu.size();
Dimension scrsz=Toolkit.getDefaultToolkit.getScreenSize();
Point loc=CURSOR_LOCATION;
menu.move(Math.max(loc.x,scrsz.width-sz.width),Math.max(loc.y,scrsz.height-sz.height));




I put a holder for CURSOR_LOCATION because, without your code, I didn't know how you would get that.

Basically, the x,y coordinate of the click is the preferred location.  Move it up or to the left if putting it there would cause it to be offscreen.
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Expert Comment

by:gwalters
ID: 1233172
Oops, those should be Math.min, not Math.max!

sorry.
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by:msmolyak
ID: 1233173
I slightly modified you logic to come up with

// Position the menu on the screen
Dimension sz=menu.size();
Dimension scrsz=Toolkit.getDefaultToolkit().getScreenSize();
if (scrsz.width - (parentFrame.getLocationOnScreen().x + x) < sz.width)
{
    // If the cursor is close to the right edge of the screen,
    // position the menu to the left of the cursor
    x = (parentFrame.getLocationOnScreen().x + x) - sz.width;
}
else
{
    // Position the menu to the right of the cursor
    x = parentFrame.getLocationOnScreen().x + x + 10;
}
y = Math.min(parentFrame.getLocationOnScreen().y + y + 25,
             scrsz.height-sz.height);

this.menu.setLocation(x,y);

Thanks for your help.
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