How can I use WindowButtonMotionFcn in an app?

Greetings!

I am exploring the app designer and attempting to create GUI for a script which I use frequently. The script is not something I wrote, I borrowed it from the FileExchange (PlotDigitizer).

I have managed to create the app layout and add callbacks and code to load the image and calibrate the plot axes. However, the code relies on WindowButtonMotionFcn to track the mouse pointer and for whatever reason, after the image is loaded, anytime the cursor hovers over the plot I get an error that says:

"Undefined function 'Get_Mouse_Location' for input arguments of type 'matlab.ui.Figure'.

Error while evaluating Figure WindowButtonMotionFcn."

I believe the code responsible for this starts at line 110, but I am at a loss as to why, although, I won't be surprised if it's something simple which I overlooked.

% Get mouse location

set(gcf, 'WindowButtonMotionFcn', @Get_Mouse_Location);

m_location = Get_Mouse_Location(app);

There is far too much code to post, so I have attached it instead. If anyone is up for helping me troubleshoot this so I can understand my mistake (and learn from it!), I would appreciate it.

Thanks in advance,

-Matt

PS - It might help if you tried PlotDigitizer first to understand how the script works, although, if you work from the app... Click Load Image first, locate and load the included plot. The errors will start popping up at that point.

Answer 1

[Kevin Holly]

Matt,

I cleaned up your code and changed the Get_Mouse_Location callback in line 110 (see attached). I got rid of the global variables as they are not needed.

[Matt Brown]

Thanks Kevin! This is much more elegant than my clumsy fix above.

I knew the global variables weren't needed and was going to work my way around to cleaning that up, eventually.

Answer 2

[Matt Brown]

After reviewing examples in the help documentation, I realized the issue was that Get_Mouse_Location was defined as a method and not a subfunction of the function that called it. By moving it inside the calling function, the errors resolve and everything seems to be working as expected. However, I am not sure how this will work out when I add the rest of the functions that call Get_Mouse_Location to the code. I feel like I am stumbling in the dark on this a bit, so if anyone wants to offer advice or clarification, I would appreciate it.

function [ ] = Display_Image(app )

% This function shows an image and croped image

global X_d Y

global x_min x_max y_min y_max

global ratio

global m_location

global data

% Draw main image

imagesc([x_min, x_max], [y_min, y_max], flipdim(X_d,1))

set(gca,'ydir','normal');

% Get mouse location

set(gcf, 'WindowButtonMotionFcn', @Get_Mouse_Location);

m_location = Get_Mouse_Location(app);

% Obtain cropped image

[px1, px2, py1, py2] = Get_Crop_Position(app);

Y = X_d(px1:px2, py1:py2,:);

hold on;

x1 = x_max + ratio*(x_min - x_max);

y1 = y_max + ratio*(y_min - y_max);

imagesc([x1, x_max], ...

[y1, y_max], flipdim(Y,1));

% Plot boarderline for cropped image

%plot( (x1 + x_max)/2, (y1 + y_max)/2, 'ro', 'MarkerSize', 10, 'MarkerFaceColor', 'red')

plot([1, 1] *(x1 + x_max)/2, [y1, y_max] , 'black:')

plot( [x1, x_max] , [1, 1]*(y1 + y_max)/2, 'black:')

plot([x1, x_max], [y1, y1 ], 'black')

plot([x1, x1 ], [y1, y_max], 'black')

hold off

% Temp: Mark data

if(data)

hold on;

plot(data(:,1), data(:,2), 'cyano--', 'linewidth', 1.0)

hold off

end

function [ Location ] = Get_Mouse_Location( app, object, eventdata )

% This function gets the location of the mouse pointer

Location = get(gca, 'CurrentPoint');

end

end

% function [ Location ] = Get_Mouse_Location( app, object, eventdata )

% % This function gets the location of the mouse pointer

% Location = get(gca, 'CurrentPoint');

% end