I found rather easy way for the Method 3 (click on pad).

I implemented in the same example,
namely, the third tab in $ROMESYS/examples/argus/menu.

You can add a macro which is executed when an event occurs on each pad  with,
   fCanvas->GetCanvas()->GetPad(1)->AddExec("ex1", ".x OpenCanvas.C");

Then you can write any function in the macro.
In this example, it opens a copy of canvas and save the clicked pad into a PDF file.

Ryu

> Dear Farrukh
> 
> What you want to do is probably possible ( I will write a possible method later.).
> However TPad has already several mouse operations (zoom, right-click menu, select active pad 
and so on); so I am not sure it is the best idea to add own mouse operation (which 
> could override other pre-implemented operations.)
> I will write three solutions below.
> I wrote an example of the first method.
> 
> == Method 1 : Menu ==
> For this solutions, I modified an example in the ROME package.
> The update is done only in the 'develop' branch.
> You can read the example by 'git checkout develop' command after you clone the ROME package.
> The example is in $ROMESYS/examples/argus/menu and the third tab (T3) is one for that.
> In ROME, you can easily add menu items in the menu bar. In the example, menu items to open and 
save a specific tab are prepared.
> 
> == Method 2 : dedicated buttons ==
> If you prefer buttons instead of menu, you can put dedicated buttons to trigger "OpenPad" function 
in the example instead of adding menus. The buttons can be implemented 
> either of the following two methods,
>  1) TGTextButton, which can work as the same way as your Save button
>  2) Writing own class derived from TBox or TMarker. A box or maker can be put on each canvas.
> 
> I hope the first method is obvious for you. You can make another button similar to your Save button 
and call "OpenPad" function.
> 
> The second method is a little more complicated; you make your own class and override 
"ExecuteEvent" method.
> In the overriding function, you can call any functions when the box or marker is single-clicked, 
double-clicked, mouse-over and so on.
> A disadvantage is that the box or marker is always visible, and will be drawn in the output PDF files 
too.
> 
> == Method 3: click on Pad ==
> You can probably do what you write with making own class derived from TPad; then you override 
"ExecuteEvent" function for calling a function to make a separated canvas and 
> draw a clone of itself.
> You may also need own TCanvas and TRootEmbeddedCanvas for using the customized classes 
instead of regular TPad and TCanvas.
> 
> If you are satisfied with the first method, please try the example.
> The second method with TGTextButton must not be very difficult.
> 
> If you prefer the second (using TBox or TMarker) and third method, I will investigate if it is actually 
possible.
> For the two methods, I think you need to write your own classes.
> 
> Best regards,
> 
> Ryu
> 
> > Dear Colleagues,
> > 
> > We are succesfully running a ROME executable both online and offline with an 
> > ARGUS display with a canvas that has multiple pads on it. We have also 
> > implemented a "Save" button which one can click on and save the _entire_ canvas 
> > (containing all the pads) and saves it to pdf.
> > 
> > I was wondering how one would go about making the following modification :
> > 
> > When a user moves a mouse over to a particular pad and clicks on it - then only 
> > the histogram on that pad is displayed on a separate canvas (so the user can 
> > examine it closely) and also save just this one histogram - with a save button 
> > similar to the one we've already written.
> > 
> > many thanks for any insight
> > 
> > Farrukh