GUIDATA updating "handles" in GUIDE with nested functions - matlab

Question

I have a simple GUIDE with 2 push buttons:
Button #1 plots a sine graph.
Button #2 adds a "movable" vertical line to the graph.
Everything works fine and I can drag vertical line as desired.
What I'm trying to do now is to record x-position of vertical line (x_history) as I move it and save this x_history to the handles (via guidata) such that if I stop moving the line (mouse-up) and then resume moving the line (mouse-down and mouse-move) I can restore previous x_history from handles (via guidata).
The problem I'm facing is that every time go mouse-up the handles resets(!) the x_history field (removes the field), so I loose the previous record of x_history when I resume mouse-down and move the line.
What am I missing here?
PS: I found these posts relevant but not exactly applicable to my case given the presence of nested functions.
Post 1
Post 2
Post 3
Thanks,
Alborz
Here is the code:
function varargout = plot_test(varargin)
gui_Singleton = 1;
gui_State = struct('gui_Name', mfilename, ...
'gui_Singleton', gui_Singleton, ...
'gui_OpeningFcn', #plot_vertline_handles_OpeningFcn, ...
'gui_OutputFcn', #plot_vertline_handles_OutputFcn, ...
'gui_LayoutFcn', [] , ...
'gui_Callback', []);
if nargin && ischar(varargin{1})
gui_State.gui_Callback = str2func(varargin{1});
end
if nargout
[varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});
else
gui_mainfcn(gui_State, varargin{:});
end
end
function plot_vertline_handles_OpeningFcn(hObject,~,handles,varargin)
handles.output = hObject;
guidata(hObject, handles);
end
function varargout = plot_vertline_handles_OutputFcn(~,~,handles)
varargout{1} = handles.output;
end
%% Vertline Callback
function pushbutton_vertline_Callback(hObject,~,handles) %#ok<*DEFNU>
axis_h = handles.axis_h;
vertline_h = line('parent',axis_h,'xdata',[1 1],'ydata',[-1 1],...
'ButtonDownFcn', #mouseDown );
handles.vertline_h = vertline_h;
guidata(hObject,handles)
function mouseDown(~,~)
mousedown = true;
handles.mousedown = mousedown;
guidata(hObject,handles)
end
end
%% Plot Callback
function pushbutton_plot_Callback(hObject,~,handles)
clc;
open_figs_h = get(0,'children');
close(open_figs_h(2:end));
x = -pi:0.01:pi;
y = sin(x);
fig_h = figure('units','normalized','outerposition',[0.2 0.2 .5 .5],...
'WindowButtonMotionFcn', #MouseMove, 'WindowButtonUpFcn', #MouseUp );
axis_h = axes('parent',fig_h,'position',[0.1 0.1 .8 .8]);
line('parent',axis_h,'xdata',x,'ydata',y);
handles.axis_h = axis_h;
guidata(hObject,handles);
function MouseUp(~,~)
handles = guidata(hObject);
handles.mousedown = 0;
guidata(hObject,handles);
end
function MouseMove(~,~)
try handles = guidata(hObject);catch, end
if isfield(handles,'mousedown')
mousedown = handles.mousedown;
else
mousedown = 0;
end
if mousedown
x_current = get(axis_h,'CurrentPoint' );
vertline_h = handles.vertline_h;
set (vertline_h, 'XData',[x_current(1,1) x_current(1,1)] );
if isfield(handles,'x_history')
disp('Field "x_history" Exists in handles')
handles.x_history = [handles.x_history x_current(1,1)]
else
disp('Field "x_history" Does Not Exist in handles')
handles.x_history = x_current(1,1)
end
guidata(hObject,handles);
end
end
end

Answer 1

With Jan Simon's guideline, I figured what was missing in the code:
In the mouseDown callback (the nested function in pushbutton_vertline_Callback), I was missing to get the updated copy of handles. So, I needed to add this line to that nested function:
handles = guidata(hObject);