How to compose a formula in a GUI

Hello,

In my GUI a have a list box (lstVariables) with variable names and an edit box (txtEditor) where I want to write a formula. When I click in the list box, I want to add the selected variable in the edit box. The difficulty is that I want to add it on the place where the cursor was.

Example : I have in the edit box the text : "var1 + var2 + var3", I select in the edit box "var2" (so it's highlighted) and than I click in the listbox on var4. The result should be : "var1 + var4 + var3". How can I find which part of the edit box is selected ?

My Example code up to now :

function lstVariables_Callback(hObject, eventdata, handles)
varnames = cellstr(get(hObject,'String')) 
varname =  varnames{get(hObject,'Value')} 
set(handles.txtEditor,'String',varname);

All help is appreciated.

Best regards,

Luc.

Answer 1

[Walter Roberson]

You will have to work at the Java level for this, in order to find out what was highlighted. I recommend that you look at Yair Altman's site, http://undocumentedmatlab.com

Answer 2

[Luc]

Thank you for the answer, Walter. Based upon Yair Altmans information I composed this code:

function StoreSelectionPositions(hObject, handles) 
jEdit = findjobj(hObject); 
SelectionStart = get(jEdit, 'SelectionStart'); 
SelectionEnd = get(jEdit, 'SelectionEnd'); 
set(handles.lblMessage,'String',[num2str(SelectionStart) ' ' num2str(SelectionEnd)]); 
set(hObject,'UserData',[SelectionStart SelectionEnd]);

I call this code in the KeyPressFcn Callback and it works fine when I use the arrow keys to select something. I use the same code in the ButtonDownFcn, but the code is NOT executed when I use the mouse to select part of the text. Any idea how I can fix this ?

[Walter Roberson]

No text would have been selected at ButtonDownFcn time; the selection is made at ButtonUpFcn time.