How to Change Line Color on Mouse Click Without Disabling Pan and Zoom in MATLAB?

I'm working on a MATLAB plot where I want to achieve the following functionality:

• Change the color of a line when it's clicked.
• Enable panning by dragging while clicking off the line.
• Enable zooming using the scroll wheel.

Here's the simple code I'm using:

% Plotting a simple line

h = plot([0,1],[0,1],'LineWidth',3);

% Setting the ButtonDownFcn to change line color (placeholder code)

h.ButtonDownFcn = @(~,~) disp(h);

In this example, clicking on the line displays its handle h in the Command Window, which is a placeholder for my actual code to change the line color.

The Problem:

Assigning a ButtonDownFcn to the line object seems to override MATLAB's built-in pan and zoom functionalities. After setting the ButtonDownFcn, I'm unable to pan by clicking and dragging off the line, and the scroll wheel zoom no longer works. It appears that the custom callback interferes with the default interactive behaviors, even when I'm not interacting directly with the line.

My Questions:

• Why does setting the ButtonDownFcn on the line object disable panning and zooming, even when interacting off the line?
• Is there a way to have both the custom click behavior (changing the line color when clicked) and retain the default pan and zoom functionalities when interacting elsewhere on the plot?

Answer 1

[ag]

Hi Vincent,

Using a ButtonDownFcn on a line object in MATLAB can interfere with the default interactive behaviors like panning and zooming as it captures mouse events that would otherwise be handled by these interactive tools.

To ensure the default pan and zoom functionalities are retained for the axes along with the added custom behaviour, I recommend using the below command before the callback:

>> enableDefaultInteractivity(gca)

For more details, please refer to the following MathWorks documentation: Enable built-in axes interactions - https://www.mathworks.com/help/matlab/ref/enabledefaultinteractivity.html

Hope this helps!

[Vincent]

Hi ag,

I tried using enableDefaultInteractivity(gca) as you suggested, but unfortunately, it's not resolving the issue. The ButtonDownFcn still interferes with the pan and zoom functionalities on the axes, preventing them from working correctly.

Any further suggestions would be appreciated!

Thanks.