'WindowButtonDownFcn' cant detect handles data from other callbacks

Hi,

I've set the 'WindowButtonDownFcn' in my GUI opening function as below:

set(gcf, ...
   'WindowButtonDownFcn', @clickFcn, ...
   'WindowButtonUpFcn', @unclickFcn);

The @clickFcn looks like that below, with a Drag function within it:

function clickFcn(hObject, eventdata, handles)
allAxes = findobj(gcf, 'Type', 'axes');
hCur = nan(1, length(allAxes));
    for id = 1:length(allAxes)
        hCur(id) = line([NaN NaN], ylim(allAxes(id)), ...
        'Color', 'black', 'Parent', allAxes(id));
    end
        % Initiate cursor if clicked anywhere but the figure
        if strcmpi(get(gco, 'type'), 'figure')
           set(hCur, 'XData', [NaN NaN]);                % <-- EDIT
           set(hText, 'Position', [NaN NaN]);            % <-- EDIT
        else
           set(gcf, 'WindowButtonMotionFcn', @dragFcn)
           dragFcn();
        end

The drag function is:

function dragFcn(varargin)
        % Get mouse location
        pt = get(gca, 'CurrentPoint');
        % Update cursor line position
        set(hCur, 'XData', [pt(1), pt(1)]);
        % Update cursor text
        for idx = 1:length(allLines)
           xdata = get(allLines(idx), 'XData');
           ydata = get(allLines(idx), 'YData');
           if pt(1) >= xdata(1) && pt(1) <= xdata(end)
              y = interp1(xdata, ydata, pt(1));
              set(hText(idx), 'Position', [pt(1), y], ...
                 'String', sprintf('(%0.2f, %0.2f)', pt(1), y));
           else
              set(hText(idx), 'Position', [NaN NaN]);
           end
        end

When I click on the plot, I realized the clickfunction could not detect them. I've handles from other callbacks as below:

K>> handles

handles = 

                  figure1: [1x1 Figure]
                clear_all: [1x1 UIControl]
                 uipanel1: [1x1 Panel]
                 uipanel2: [1x1 Panel]
                 uipanel4: [1x1 Panel]
                 uipanel5: [1x1 Panel]
                 LoadFile: [1x1 UIControl]
             pop_filelist: [1x1 UIControl]
                 var_list: [1x1 UIControl]
                togglepan: [1x1 UIControl]
               togglezoom: [1x1 UIControl]
        selected_varlist2: [1x1 UIControl]
                 add_var2: [1x1 UIControl]
               plot2_push: [1x1 UIControl]
        selected_varlist1: [1x1 UIControl]
                 add_var1: [1x1 UIControl]
               plot1_push: [1x1 UIControl]
                    axes2: [1x1 Axes]
                    axes1: [1x1 Axes]
                    text6: [1x1 UIControl]
            select_folder: [1x1 UIControl]
                    text5: [1x1 UIControl]
                   output: [1x1 Figure]
                        b: 0
                   folder: 'C:\Users\r14ang\Documents\MATLAB'
                    count: 1
                   count2: 1
                    files: [9x1 struct]
            selected_file: 'C:\Users\r14ang\Documents\MATLAB\TZ24SKE_SCOP_F_Cut3.csv'
      selected_file_table: [3930x33 table]
            variable_list: {1x33 cell}
            sel_list_temp: {'ODPIPESENSOR'}
           sel_list_temp2: {'COMPTEMP'}
                time_sec2: [1x3930 double]

What have I done incorrectly?

Thanks in advance.

Answer 1

[Geoff Hayes]

James - it isn't clear where in your clickFcn you are trying to access the handles structure, unless you are assuming that it will be there due to the function signature of

 function clickFcn(hObject, eventdata, handles)

In the above, handles will always be an empty matrix because you are not explicitly passing it when you assign the callback as

 set(gcf, ...
   'WindowButtonDownFcn', @clickFcn, ...

By default, there will only be two input parameters for clickFcn: hObject and eventdata. If you want to pass a third (or fourth or fifth) parameter, you would need to modify the above to

 set(gcf, ...
   'WindowButtonDownFcn', {@clickFcn, param3},..

where param3 is a variable that you have defined previously. However, if you were to try and pass handles in as the third parameter, it would only be a copy of handles at the time that you assigned the callback. So if handles changes over time (due to being updated in another callback) your clickFcn will not see these changes because it is using an out-dated copy of handles.

To get around this, you can use the guidata function to get the most recent handles structure. So we will leave the callback assignment as

 set(hObject, ...
    'WindowButtonDownFcn', @clickFcn, ...
    'WindowButtonUpFcn', @unclickFcn);

(Note that I changed gcf to hObject. These should be identical since you are doing the above in the _OpeningFcn of your GUI.) In the callback, we will use hObject to get handles

 function clickFcn(hObject, eventdata)

 handles = guidata(hObject);

 % etc.

Try the above and see what happens!

[James Ang]

Hi Geoff,

I think I get what you mean...I'll try it out..

[James Ang]

Hi Geoff,

It works now!

I've placed the windowbuttondown function after assigning the handles:

function vertical_cursor_pana(hObject, eventdata, handles)

      handles.allLines = [handles.al1 handles.al2];
      handles.hText = nan(1, length(handles.allLines));
                for id = 1:length(handles.allLines)
              handles.hText(id) = text(NaN, NaN, '', ...
              'Parent', get(handles.allLines(id), 'Parent'), ...
              'BackgroundColor', 'yellow', ...
              'Color', get(handles.allLines(id), 'Color'));
          end
        handles.allAxes = findobj(gcf, 'Type', 'axes');
      handles.hCur = nan(1, length(handles.allAxes));
          for id = 1:length(handles.allAxes)
              handles.hCur(id) = line([NaN NaN], ylim(handles.allAxes(id)), ...
              'Color', 'black', 'Parent', handles.allAxes(id));
          end

set(gcf, ...
   'WindowButtonDownFcn', {@clickFcn, handles}, ...
   'WindowButtonUpFcn', @unclickFcn);

guidata(hObject, handles);
if true
  % code
end

And modified the inputs of the clickfcn as you mentioned:

function clickFcn(hObject, eventdata, handles)

          if strcmpi(get(gco, 'type'), 'figure')

             set(handles.hCur, 'XData', [NaN NaN]);                % <-- EDIT
             set(handles.hText, 'Position', [NaN NaN]);            % <-- EDIT

          else

             set(gcf, 'WindowButtonMotionFcn', {@dragFcn, handles})
             dragFcn(hObject, eventdata, handles);

          end

guidata(hObject, handles);

The drag function is:

function dragFcn(hObject, eventdata, handles)

          % Get mouse location
          handles.pt = get(gca, 'CurrentPoint');
          handles.pt(:,1) = round(handles.pt(:,1));

          % Update cursor line position
          set(handles.hCur, 'XData', [handles.pt(1), handles.pt(1)]);

          % Update cursor text
          for idx = 1:length(handles.allLines)

             xdata = get(handles.allLines(idx), 'XData');
             ydata = get(handles.allLines(idx), 'YData');

             if handles.pt(1) >= xdata(1) && handles.pt(1) <= xdata(end)

                y = interp1(xdata, ydata, handles.pt(1));
                set(handles.hText(idx), 'Position', [handles.pt(1), y], ...
                   'String', sprintf('(%0.0f, %0.2f)', handles.pt(1), y));
                yall(:,idx) = y;                      
             else                 
                set(handles.hText(idx), 'Position', [NaN NaN]);               
             end             
          end

          handles.diff_table.Data(:, handles.cursornumber) =  yall';          
          if handles.cursornumber >= 2                
              handles.diff_table.Data(:,3) = handles.diff_table.Data(:,2) - handles.diff_table.Data(:,1);
          else
              %handles.diff_table.Data(:,3) = [];
          end

guidata(hObject, handles);

Thanks a lot Geoff!

[Geoff Hayes]

James - the above will work, but bear in mind that the handles being passed into the clickFcn or dragFcn are just copies of the handles structure at the time the callback is initialized or assigned at

 set(gcf, ...
   'WindowButtonDownFcn', {@clickFcn, handles},...

etc. So if other callbacks manipulate the handles structure and update with the

 guidata(hObject,handles);

then your clickFcn and dragFcn won't have access to the updated handles object. That is why it may be better to use the

 handles = guidata(hObject);

from within these callbacks.

[James Ang]

Oh I see...Noted. Thanks for pointing it out Geoff. I'll try it out.

[James Ang]

Geoff, I'm trying to pass the handles structure between 2 functions:

the first is:

   function add_var1_Callback(hObject, eventdata, handles)
    % hObject    handle to add_var1 (see GCBO)
    % eventdata  reserved - to be defined in a future version of MATLAB
    % handles    structure with handles and user data (see GUIDATA)

    %set(handles.hCur, 'XData', [NaN NaN]);                % <-- EDIT
     %set(handles.hText, 'Position', [NaN NaN]);  
    %%Plotting

    handles.time_sec1 = 1:size(handles.selected_file_table(:,'t'));

    for i = 1:handles.count;
        handles.al1(i) = ...
            plot(handles.axes1, handles.time_sec1, ...
            table2array(handles.selected_file_table(:,handles.selected_varlist1.String(i)))...
            ,'LineWidth',2);
        axes(handles.axes1); hold on

    end
        grid(handles.axes1,'on');
        handles.axes1.XMinorGrid = 'on';
        handles.axes1.YMinorGrid = 'on';
        hold off
        set(handles.axes1,'Color',[0.87058824300766 0.921568632125854 0.980392158031464],...
        'XColor',[0 0 0],'YColor',[0 0 0],'ZColor',[0 0 0]);
        % axes(handles.axes1) 
        legend(handles.selected_varlist1.String,'Location','northoutside','Orientation','horizontal')
        linkaxes([handles.axes1,handles.axes2],'x');
        handles.diff_table.Data=[];
        if handles.count2 == 0
            cla(handles.axes2)
        else
        end

        vertical_cursor_pana(hObject, eventdata, handles);

    guidata(hObject, handles);

The second function is:

function vertical_cursor_pana(hObject, eventdata, handles)
% What does this function do?
% 1) Prepare handles for All lines plotted on all axes
% 2) Prepare text handles - same number as number of lines
% 3) Prepare axes handles
% 4) Prepare verticle line handles - same number as number of axes
% 5) Set 'WindowButtonDownFcn' and 'WindowButtonUpFcn' functions

% set(gcf, ...
%    'WindowButtonDownFcn', {@clickFcn,handles},
%    'WindowButtonUpFcn', @unclickFcn);

      handles.allLines = [handles.al1 handles.al2];
      % handles.allLines = findobj(gcf, 'type', 'line');
      handles.hText = nan(1, length(handles.allLines));

          for id = 1:length(handles.allLines)
              handles.hText(id) = text(NaN, NaN, '', ...
              'Parent', get(handles.allLines(id), 'Parent'), ...
              'BackgroundColor', 'yellow', ...
              'Color', get(handles.allLines(id), 'Color'));
          end

      handles.allAxes = findobj(gcf, 'Type', 'axes');
      handles.hCur = nan(1, length(handles.allAxes));

          for id = 1:length(handles.allAxes)
              handles.hCur(id) = line([NaN NaN], ylim(handles.allAxes(id)), ... % Set y-limits for both axes
              'Color', 'black', 'Parent', handles.allAxes(id));
          end

% set(gcf, ...
%    'WindowButtonDownFcn', {@clickFcn, handles}, ...
%    'WindowButtonUpFcn', {@unclickFcn, handles});

handles = guidata(hObject);

I'm trying to pass handles.hCur to the first function. However, after the line

handles = guidata(hObject);

I noticed the handles.hCur object vanishes.

How can I pass the handles.hCur to the first function?

[Geoff Hayes]

James - why would you be calling the line

 handles = guidata(hObject);

when handles is already being passed in to this function?

The reason this is happening is because while the new hCur fields has been set in the handles structure it hasn't yet been saved to it using

 guidata(hObject,handles);

So you are passing in an updated copy of handles (into the vertical_cursor_pana before you save the new field to this structure with the call to guidata). So when you call the

 handles = guidata(hObject);

you are requesting a copy of the object at its last "saved" state i.e. what it was at the last time we called guidata(hObject,handles) which is a copy without the hCur field.