MATLAB: Incorrect results for button output of ginput returned when double clicking

MATLAB

When clicking the center or right mouse buttons multiple times very quickly, the second and third results for the 'button' output is incorrectly given as 1 (left mouse click).

Running the following code and click the right button rapidly on the axes.

[x,y,button] = ginput(3)

The 'button' output has many 1's registered. Why does this happen?

Best Answer

This is the expected behavior. Based on the documentation, the 3rd return argument from this function can be a "_vector of integers indicating which mouse buttons you pressed (1 for left, 2 for middle, 3 for right)_".

When double-clicking quickly using the middle button the Figure's SelectionType property becomes "Open" based on the documentation. This can be verified by the following:

f = gcf;
f.SelectionType %should return 'normal'
[x,y,button] = ginput(3) %click right button rapidly on axes
f.SelectionType %should now be 'open'

This is considered to be a "Left click" in ginput. When clicks are made rapidly several times, ginput will register all those clicks and since all clicks after the first are "Open", they all translate to button "1" or left click.

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This can be accomplished with the zoom accessor object. The following example illustartes how this can be done:

% Define the context menu
cmenu = uicontextmenu;
% Define the line and associate it with the context menu
hline = plot(1:10,'UIContextMenu', cmenu);
% Define callbacks for context menu items
cb1 = ['set(hline, ''LineStyle'', ''--'')'];
cb2 = ['set(hline, ''LineStyle'', '':'')'];
cb3 = ['set(hline, ''LineStyle'', ''-'')'];
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item2 = uimenu(cmenu, 'Label', 'dotted', 'Callback', cb2);
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MATLAB: Question about mouse click on figure

This code snippet should get you started:

 button = 1;
 getpt  = 1;
 [x,y,button] = ginput(1);
 XY           = [x y];
 while (getpt == 1)
    if (button == 1) % draw line for left mouse click
        [xn,yn,button] = ginput(1);
        XY = [XY; xn yn];
        hold on
        plot([x; xn],[y; yn])
        x = xn; y = yn;
    end
    if (button == 3) % clear lines for right mouse click
        children = get(gca, 'children');
        delete(children);
        getpt = 0;
    end
 end

Best Answer

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MATLAB: How to override the zoom uicontextmenu with a custom uicontextmenu, when in zoom mode, in MATLAB 7.3 (R2006b)

MATLAB: Question about mouse click on figure

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