• Matlab GUI vs others
• Similar to RAD such as C++ builder and VB
• Most GUI work across platforms
• Can perform most functions as traditional GUI through tricks
• Can link platform dependent code using MEX programs
• Problems with GUI
• Not as flexible
• Cross platform appearance may not be the same
• Often must use tricks and unfriendly techniques
• MEX code GUI eliminates cross platform operation

• GUI elements are treated as objects. They encapsulate data and method.
• Menu: uimenu
• Controls: pushbutton, checkbox, radio buttons, text (static), slider (scroll bar), edit (interactive), listbox, popupmenu, frame : uicontrol
• Graphics: plots, text, axis, image, surface, shading : axes, image, line, patch, surface, text, light
• Others: almost all visible elements on screen except command window : e.g., msgbox

• Use "helpdesk"
• launch default web browser, usually Netscape
• enter "helpdesk" from matlab prompt. Click on handle graphics objects
• Experiment with properties
• example: create a plot and enter "set(gcf),pause,set(gca)"
• "get" only shows the properties, "set" can set and show
• Try "guide", "cbedit", "toolpal", "aligntool"; good for simple GUI generation
• "guide" is the mother of all tools

• Simple syntax: msgbox(message,title,'modal' or 'nonmodal')
• Used to pop up a dialog box with Ok button on it
• Message and title are strings; title is optional, default is 'nonmodal'
• For example,

msgbox('I am afraid I CAN do that, Mik.')

• Other types of message boxes are
• errordlg(message,title,'modal' or 'nonmodal'): msgbox with error icon
• warndlg(message,title,'modal' or 'nonmodal'): msgbox with warning icon

• Used to ask the user to input information
• Simple syntax: answer=inputdlg(Prompt,Title,LineNo,DefaultAnswer)
• Uses cells as parameters for prompt and default answer; must convert to useful data before and after
• For example,

prompt={'name', 'function to call', 'number'}
defans={'mik', 'hamming', '123'}
fields = {'name','func', 'num'}
info = inputdlg(prompt, 'give it to me!', 1, defans)
if ~isempty(info)              %see if user hit cancel
   info = cell2struct(info,fields)
   myname = info.name
   myfunc = info.func
   mynum = str2num(info.num)   %convert string to number
   mycall = [myfunc '(' num2str(mynum) ')']
   eval(mycall)                %evaluate expression
   msgbox([myname ', I hope ' mycall ' was what you wanted.'], 'Cool!')
end
%you can and should put ; on all line endings in practical program
%also, str2num and num2str are not necessary, just there for demo purpose

• Close all open figures using "close all" command
• Start guide and place a pushbutton on "Figure No.1"

• Double click on pushbutton; place check mark on "show property list"
• Click on "Callback" and put " 'msgbox(''hello mik'')' "

• Click on "String" and put " 'greetings' "
• Select "Options->Activate Figure" from "Figure No. 1" window; save and name it "test.m"
• Click on "greetings" button and see the message box
• Get back to editing more by double clicking on " Active #1 " in "Guide-Controlled Figure List"
• Summary of simple GUI generation
• Created button: create object
• Specify method: specify what the button will do in callback
• Specify data: specify the label for the button

• Starts with file name as function name

function test()
% This is the machine-generated representation of a MATLAB object
% and its children.  Note that handle values may change when these
% objects are re-created. This may cause problems with some callbacks.
% The command syntax may be supported in the future, but is currently 
% incomplete and subject to change.
%
% To re-open this system, just type the name of the m-file at the MATLAB
% prompt. The M-file and its associtated MAT-file must be on your path.

• Comment lines tell you it may cause problems; also note the spelling error
• Load variable values stored in file; not very good since its difficult to change

load test

• Create figure (figure is a window) using specific parameters

a = figure('Color',[0.8 0.8 0.8], ...
        'Colormap',mat0, ...
        'PointerShapeCData',mat1, ...
        'Position',[564 166 672 504], ...
        'Tag','Fig1');

• a is the handle of the window; all objects have handles associated with them
• Handle is nothing more than a number referencing the object
• gcf is the handle of current figure and gca is the handle of current axis
• other "current" handles are gcbo (get current callback object), gco (get current object), gcbf (get current callback figure), but not often used in practice
• Color is RGB values between 0 and 1
• Colormap is matrix of defined colors for the window
• Position is the position of the window in pixels, [left, bottom, width, height]
• default units is pixels, but can be changed to other units using "units" property
• Tag is user defined name for the object which can be used to located the object easily using "findobj" function without knowing the handle

• Create the pushbutton object using specific parameters

b = uicontrol('Parent',a, ...
         'Units','points', ...
         'Callback','msgbox(''hello mik'')', ...
         'Position',[124.759 62.6897 83.1724 30.4138], ...
         'String','greetings', ...
         'Tag','Pushbutton1');

• b is the handle of pushbutton
• Parent points to a, the figure; this means the object belongs to this figure and should be placed in it
• Callback is the method that should be executed
• Units is points which means the locations are specified as 1/72 inch
• Position is the location of the control in 1/72 inch. Format is [left, bottom, width, height]
• Tag works the same for all objects and this works the same as for figure (for use with findobj function)

• From Matlab command prompt, execute test.m
• Enter " get(gcf) "; note the many default settings already in place
• Enter " get(get(gcf, 'children')) "; note the many settings for the child
• It is not necessary to set all parameters when creating a control
• For our example, only the callback and name for the button was necessary and we didn't care about anything else (maybe position)
• The new code could be

function test1()
uicontrol('style', 'pushbutton', ...
        'parent', figure, ...
        'string', 'greetings', ...
        'callback','msgbox(''hello mik'')', ...
        'position', [10 10 100 30]);
return

• "guide" is good for basic GUI generation
• positioning of the controls
• generating template for larger GUI programs
• simple code for copy paste into other m files
• "guide" drawbacks
• Very slow in changing and viewing properties
• Cannot make modifications outside of "guide" environment; will cause problems
• Cannot easily change default properties since some values are stored in mat file
• Generated code doesn't use informative handle names (a for figure, b for pushbutton, etc.)

• BackgroundColor
• BusyAction
• ButtonDownFcn
• Callback
• Children
• Clipping
• CreateFcn
• DeleteFcn
• Enable
• Extent
• FontAngle
• FontName
• FontSize
• FontUnits
• FontWeight
• ForegroundColor
• HandleVisibility
• HorizontalAlignment
• Interruptible
• ListboxTop
• Max
• Min
• Parent
• Position
• Selected
• SelectionHighlight
• SliderStep
• String
• Style
• Tag
• Type
• Units
• UserData
• Value
• Visible

• zoom on / zoom off
• Zooms in on a 2D graph using mouse drag; double click moves to full graph
• For example,

plot(sin(0:.1:20));
zoom on

• ginput(numberOfPoints): mouse input
• Allows the user to click on the graph (or figure or image) and returns the x and y coordinates
• Useful for finding the number shown on the graph
• For example, combined with text command for placing some text on the figure and 45 degree rotation,

[x y] = ginput(1);
txthandle = text(x, y, [num2str(x) ', ' num2str(y)]);
set(txthandle, 'rotation', 45);

• rotate3d on / rotate3d off
• Allows interactive rotation of 3D graphics; does work with 2D graphs, but not very useful

x = 0:.01:.6;
[x y] = meshgrid(x,x);
z = sin(x^2 - y^2);
surf(x, y, z);
rotate3d on;

• uigetfile : opens the file/open dialog box

• uiputfile : opens the file/save dialog box

• waitforbuttonpress : suspects all activity until user presses a key or click the mouse

• Problems with callback property
• Works on global scope; does not recognize functions in local file
• Without workaround, each callback must exist as separate files
• Work around: recursion and global
• Place all or most functions within one file and call them using recursive calls
• Use global variable to pass information
• Need to preserve some information such as object handles
• Matlab doesn't support static variable
• An example of what can be done with Matlab

• Call itself with parameter description what would execute code other than the originating code
• Switch / case statement is your friend
• For example

function recurs(param)
switch param
case 'first'
   msgbox('this is 1');
   recurs('second');
case 'second'
   msgbox('this is 2');
otherwise
   msgbox('this is zero');
   recurs('first');
end
return

• Parameters should contain what action to take
• Function call without parameter should also be handled
• Use nargin, number of input parameters

function recurs(param)
if nargin == 0
   param = '???';
end

switch param
case 'first'
   msgbox('this is 1');
   recurs('second');
case 'second'
   msgbox('this is 2');
otherwise
   msgbox('this is zero');
   recurs('first');
end
return

• nargout returns the number of output parameters

• Necessary due to Matlab not having static variables
• Must declare in each function used
• Should declare early for memory efficiency
• Good place is to declare just before first executable code
• For example,

function recurs(param)
global x y z;
if nargin == 0
   param = '???';
end

switch param
.
.
.
return

• Name: general purpose graph pal (gpgp)
• Add buttons to any figure
• Display value clicked on the plot
• Remove a text generated by gpgp with mouse click
• Remove all text generated by gpgp
• Edit text with mouse click
• Zoom on/off
• Quit gpgp, leave text behind
• Drag and move generated text

• Need 6 buttons
• use guide to place them and save as gpgp.m
• do not use alignment tool or anything else other than guide
• Open gpgp.m in text editor and make changes
• Remove all comments and line "load gpgp"
• Remove a = figure(...) since we will only be working with existing figure
• For each button, change the parent to gcf

• Add "string" property to each button with appropriate titles
• PlotVal
• Remove
• RemoveAll
• Edit
• Zoom Off
• Quit
• Give meaningful names to handles (use modified Hungarian notation)
• hbtn_plotval
• hbtn_remove
• hbtn_removeall
• hbtn_edit
• hbtn_zoom
• hbtn_quit
• Declare the handle names as global variable

function gpgp()
global hbtn_plotval hbtn_remove hbtn_removeall hbtn_edit hbtn_zoom hbtn_quit;

• Delete references to "tag" property for all buttons; it's not used in this program
• Save as gpgp and call gpgp from Matlab; positioning of buttons is next

• All buttons are next to each other and same size
• Use variable to specify bottom, width, and height of the buttons; also the left of first button

btnlef = 2.48276;
btnbot = 3.10345;
btnwid = 47.1724;
btnhei = 14.8966;

• Change the button positions using the variables in gpgp.m

'Position',[btnlef+0*btnwid btnbot btnwid btnhei], ...
'Position',[btnlef+1*btnwid btnbot btnwid btnhei], ...
'Position',[btnlef+2*btnwid btnbot btnwid btnhei], ...
'Position',[btnlef+3*btnwid btnbot btnwid btnhei], ...
'Position',[btnlef+4*btnwid btnbot btnwid btnhei], ...
'Position',[btnlef+5*btnwid btnbot btnwid btnhei], ...

• Save and call gpgp and verify the buttons look the way you want

• Change the function declaration with one parameter
• Add the statements to handle no parameter case; no parameter means initialize

function gpgp(param)
global hbtn_plotval hbtn_remove hbtn_removeall hbtn_edit hbtn_zoom hbtn_quit;

if nargin == 0
   param = 'init';
end
{rest of the code from previous step}

• Add switch case statement around button generation routine for case 'init'
• Add return statement at the end of the function

switch(param)
case 'init'
   btnlef = 2.48276;
.
.
.
{make button routines from previous step}
end
return

• Function with one parameter, few global variables, and switch statement

function gpgp(param)
global hbtn_plotval hbtn_remove hbtn_removeall hbtn_edit hbtn_zoom hbtn_quit;

if nargin == 0
   param = 'init';
end

switch(param)
case 'init'
   btnlef = 2.48276;
   btnbot = 3.10345;
   btnwid = 47.1724;
   btnhei = 14.8966;
   hbtn_plotval = uicontrol('Parent',gcf, ...
      'Units','points', ...
      'Position',[btnlef+0*btnwid btnbot btnwid btnhei], ...
      'String','PlotVal');   
   hbtn_remove = uicontrol('Parent',gcf, ...
      'Units','points', ...
      'Position',[btnlef+1*btnwid btnbot btnwid btnhei], ...
      'String','Remove');
   hbtn_removeall = uicontrol('Parent',gcf, ...
      'Units','points', ...
      'Position',[btnlef+2*btnwid btnbot btnwid btnhei], ...
      'String','RemoveAll');
   hbtn_edit = uicontrol('Parent',gcf, ...
      'Units','points', ...
      'Position',[btnlef+3*btnwid btnbot btnwid btnhei], ...
      'String','Edit');
   hbtn_zoom = uicontrol('Parent',gcf, ...
      'Units','points', ...
      'Position',[btnlef+4*btnwid btnbot btnwid btnhei], ...
      'String','Zoom Off');
   hbtn_quit = uicontrol('Parent',gcf, ...
      'Units','points', ...
      'Position',[btnlef+5*btnwid btnbot btnwid btnhei], ...
      'String','Quit');
end
return

• Assume the user knows he / she should click on the graph
• Add callback property to PlotVal button; use modified Hungarian notation

   hbtn_plotval = uicontrol('Parent',gcf, ...
      'Units','points', ...
      'Position',[btnlef+0*btnwid btnbot btnwid btnhei], ...
      'String','PlotVal', ...
      'callback', 'gpgp(''hbtn_plotval_click'');');

• Another case statement to handle the button click; use Hungarian notation

case 'hbtn_plotval_click'
   [x y] = ginput(1);
   if isempty(x)
      return;
   end
   txt = [num2str(x) num2str(y)];
   text(x, y, txt);

• Save it and try it out on any graph

• Text object is "lost" since its handle isn't kept
• Add global variable to keep track of text handles

global hbtn_plotval hbtn_remove hbtn_removeall hbtn_edit hbtn_zoom hbtn_quit htxt;

• Add text handles in callback function for PlotVal button (case 'hbtn_plotval_click')
• replace the line where text is created to save the handle in global variable

   text(x, y, txt);

gets replaced with

   htxt = [htxt text(x, y, txt)];

• Step 1: specify the callback function property

   hbtn_removeall = uicontrol('Parent',gcf, ...
      'Units','points', ...
      'Position',[btnlef+2*btnwid btnbot btnwid btnhei], ...
      'String','RemoveAll', ...
      'callback', 'gpgp(''hbtn_removeall_click'');');

• Step 2: tell all buttons to die

case 'hbtn_removeall_click'
   delete(htxt(ishandle(htxt)));
   htxt = [];

• Note: htxt is a vector (array), so set operates on all values in vector without having to explicitly specify each value

• Quit only eliminates the buttons, but keeps text
• If gpgp is called again, it should remember existing text
• Need to do memory clean up
• Step 1: add callback

   hbtn_quit = uicontrol('Parent',gcf, ...
      'Units','points', ...
      'Position',[btnlef+5*btnwid btnbot btnwid btnhei], ...
      'String','Quit', ...
      'callback', 'gpgp(''hbtn_quit_click'');');

• Step 2: specify what callback should do
• delete all objects, then free the memory taken by objects
• check to see if htxt is empty; if so, remove it from memory

case 'hbtn_quit_click'
   delete(hbtn_plotval);
   delete(hbtn_remove);
   delete(hbtn_removeall);
   delete(hbtn_edit);
   delete(hbtn_zoom);
   delete(hbtn_quit);
   clear global hbtn_plotval;
   clear global hbtn_remove;
   clear global hbtn_removeall;
   clear global hbtn_edit;
   clear global hbtn_zoom;
   clear global hbtn_quit;
   htxt(~ishandle(htxt)) = [];
   if isempty(htxt)
      clear global htxt;
   end

• Step 3: test it
• Enter gpgp; click on PlotVal and create some text
• Click on quit; restart gpgp and see if RemoveAll deletes existing text

• Step 1: add callback to each button
• Step 2: specify what the callback should do
• Step 3: optional; rarely (if ever) practiced by software developers
• Source code so far

function gpgp(param)
global hbtn_plotval hbtn_remove hbtn_removeall hbtn_edit hbtn_zoom hbtn_quit htxt;

if nargin == 0
   param = 'init';
end

switch(param)
case 'init'
   btnlef = 2.48276;
   btnbot = 3.10345;
   btnwid = 47.1724;
   btnhei = 14.8966;
   hbtn_plotval = uicontrol('Parent',gcf, ...
      'Units','points', ...
      'Position',[btnlef+0*btnwid btnbot btnwid btnhei], ...
      'String','PlotVal', ...
      'callback', 'gpgp(''hbtn_plotval_click'');');
   hbtn_remove = uicontrol('Parent',gcf, ...
      'Units','points', ...
      'Position',[btnlef+1*btnwid btnbot btnwid btnhei], ...
      'String','Remove');
   hbtn_removeall = uicontrol('Parent',gcf, ...
      'Units','points', ...
      'Position',[btnlef+2*btnwid btnbot btnwid btnhei], ...
      'String','RemoveAll', ...
      'callback', 'gpgp(''hbtn_removeall_click'');');
   hbtn_edit = uicontrol('Parent',gcf, ...
      'Units','points', ...
      'Position',[btnlef+3*btnwid btnbot btnwid btnhei], ...
      'String','Edit');
   hbtn_zoom = uicontrol('Parent',gcf, ...
      'Units','points', ...
      'Position',[btnlef+4*btnwid btnbot btnwid btnhei], ...
      'String','Zoom Off');
   hbtn_quit = uicontrol('Parent',gcf, ...
      'Units','points', ...
      'Position',[btnlef+5*btnwid btnbot btnwid btnhei], ...
      'String','Quit', ...

      'callback', 'gpgp(''hbtn_quit_click'');');
   
case 'hbtn_plotval_click'
   [x y] = ginput(1);
   if isempty(x)
      return;
   end
   txt = [num2str(x) num2str(y)];
   htxt = [htxt text(x, y, txt)];
   
case 'hbtn_removeall_click'
   delete(htxt(ishandle(htxt)));
   htxt = [];
   
case 'hbtn_quit_click'
   delete(hbtn_plotval);
   delete(hbtn_remove);
   delete(hbtn_removeall);
   delete(hbtn_edit);
   delete(hbtn_zoom);
   delete(hbtn_quit);
   clear global hbtn_plotval;
   clear global hbtn_remove;
   clear global hbtn_removeall;
   clear global hbtn_edit;
   clear global hbtn_zoom;
   clear global hbtn_quit;
   htxt(~ishandle(htxt)) = [];
   if isempty(htxt)
      clear global htxt;
   end
   
end
return

• More than one instance of gpgp could create multiple controls
• Need to check if controls exist; if so, delete existing buttons before creating new ones
• Since the default zoom mode is off, explicitly turn off zoom

case 'init'
   if ishandle(hbtn_plotval)
      delete(hbtn_plotval);
      delete(hbtn_remove);
      delete(hbtn_removeall);
      delete(hbtn_edit);
      delete(hbtn_zoom);
      delete(hbtn_quit);
   end
   zoom off;
.
.
.

• Step 1: Specify callback on creation

   hbtn_zoom = uicontrol('Parent',gcf, ...
      'Units','points', ...
      'Position',[btnlef+4*btnwid btnbot btnwid btnhei], ...
      'String','Zoom Off', ...
      'callback', 'gpgp(''hbtn_zoom_click'');');

• Step 2: Change zoom state depending on current state of button (can you guess the significance of the comment?)

case 'hbtn_zoom_click'%error: zoom will distort movement and remove/edit
   a_str = get(hbtn_zoom, 'string');
   switch a_str
   case 'Zoom Off'
      zoom on;
      set(hbtn_zoom, 'string', 'Zoom On');
   otherwise
      zoom off;
      set(hbtn_zoom, 'string', 'Zoom Off');
   end

• 3 step process

• Step 1: Specify the function to execute when user clicks on the button

   hbtn_remove = uicontrol('Parent',gcf, ...
      'Units','points', ...
      'Position',[btnlef+1*btnwid btnbot btnwid btnhei], ...
      'String','Remove', ...
      'callback', 'gpgp(''hbtn_remove_click'');');

• Step 2: Specify what the function should do when the button is clicked

case 'hbtn_remove_click'
   if ~ishandle(htxt)
      return
   end   
   set(gcf, 'pointer', 'crosshair');
   set(htxt, 'ButtonDownFcn', 'gpgp(''fcn_removetxt'')');

• Step 3: Specify the button object to kill itself when clicked

case 'fcn_removetxt'
   set(gcf, 'pointer', 'arrow');
   set(htxt, 'ButtonDownFcn', 'gpgp(''fcn_text_click'');');
   htxt(htxt == gcbo) = [];
   delete(gcbo);

• Pretty much identical to the way Remove was implemented as 3 step process
• Step 1: creation

   hbtn_edit = uicontrol('Parent',gcf, ...
      'Units','points', ...
      'Position',[btnlef+3*btnwid btnbot btnwid btnhei], ...
      'String','Edit', ...
      'callback', 'gpgp(''hbtn_edit_click'');');

• Step 2 and 3: to do in callback functions

case 'hbtn_edit_click'
   if ~ishandle(htxt)
      return
   end   
   set(gcf, 'pointer', 'Ibeam');
   set(htxt, 'ButtonDownFcn', 'gpgp(''fcn_edittxt'')');
   
case 'fcn_edittxt'
   obj = gcbo;
   txt = {get(obj, 'string')};
   txtcell = inputdlg({'What is thy bidding, my master?'}, ...
      'New text value', 1, txt);
   set(gcf, 'pointer', 'arrow');
   set(htxt, 'ButtonDownFcn', 'gpgp(''fcn_text_click'');');
   if isempty(txtcell)
      return
   end
   txt = cell2struct(txtcell, {'txt'}, 1);
   set(obj, 'string', txt.txt);

• Allow the user to drag the text around with mouse drag
• Problem in Matlab: drag event is not available for text object
• Workaround
• Step 1: specify on text creation what should happen on mouse button down; need modification to hbtn_plotval_click callback (note: the code also contains method for removing orphaned handles)

case 'hbtn_plotval_click'
   [x y] = ginput(1);
   if isempty(x)
      return;
   end
   txt = [num2str(x) ', ' num2str(y)];
   txt = text(x, y, txt);
   set(txt, 'ButtonDownFcn', 'gpgp(''fcn_text_click'');');
   htxt = [htxt txt];
   htxt(~ishandle(htxt)) = [];

• Step 2: specify in callback for mouse button down to set the following
• Store which text handle should be manipulated for callbacks; use another global or use figure's userdata property
• Specify current figure callback for mouse motion
• Specify current figure callback for mouse button up

case 'fcn_text_click'
   obj = gcf;
   set(obj, 'userdata', gcbo);
   set(obj, 'windowbuttonmotionfcn', 'gpgp(''fcn_text_drag'')');
   set(obj, 'windowbuttonupfcn', 'gpgp(''fcn_text_drag_end'')');

• Step 3: create callback for mouse motion so that text location is according to mouse location

case 'fcn_text_drag'
   objfig = gcf;
   pt = get(gca, 'CurrentPoint');
   pt = pt(1, 1:2);
   objtxt = get(objfig, 'userdata');
   set(objtxt, 'position', pt);

• Step 4: create callback for mouse button up so that both previous callbacks are cleared in figure

case 'fcn_text_drag_end'
   objfig = gcf;
   set(objfig, 'windowbuttonmotionfcn', '');
   set(objfig, 'windowbuttonupfcn', '');

When figure is closed, all objects are deleted but the global variables remain

Moving the text around in zoom mode can cause confusion

When remove or edit is clicked and then new plot values is clicked without deleting a value, the new text objects don't initially behave the same as old ones

Consolidate all global variables into one global structure

Even better, get rid of all global variables in favor of using user data and/or children properties

• Matlab can generate most GUI of standard program
• The GUI elements are objects
• Matlab guide isn't too helpful in making large programs
• Most simple GUI are easy to generate
• Complex GUI programs need more work using recursion and data preserving techniques
• Some tasks require use of "twisted" method to generate appropriate responses
• Please e-mail mikkim@bigfoot.com for requests for code. However, you should be able to construct it using copy paste of various pieces from this tutorial.