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20. XODUS Mouse Clicks -- a summary of syntax conventions

Author: Upinder S. Bhalla, Mount Sinai School of Medicine.

20.1 Conventions

In the text, when I use the term ``widget'' or ``X widget'', it means the X widget implementation of the graphical user interface (GUI). The term ``xodus'' refers to the GENESIS objects that control the corresponding X widgets. When I say ``XODUS'', it means the combined GUI, including both the GENESIS objects, the X widgets, and the infrastructure that links them together.

20.2 Overview

In this version of XODUS, there has been a complete overhaul of how GUI events, such as mouse clicks, affect XODUS and GENESIS. The fundamental change is that GUI events are now mapped directly onto GENESIS actions, and are handled by the action mechanism in the xodus objects. I have also reimplemented the mechanism for calling script functions in response to GUI events. The previous XODUS 1 when functionality has been abandoned; instead all script calls are accessed through the script field of the widgets and pixes. The sequence of operations is :

  1. User action, e.g. a mouse click
  2. X generates an event
  3. Widget decides if it can use the event
  4. Widget passes event to a translator, using callbacks
  5. Translator invokes appropriate xodus action
  6. xodus object executes action
  7. If action call corresponds to a script function, the script function is executed.

Script functions are suffixed with a GUI event identifier, which decides which events are allowed to call that script function. I have imposed a strict convention on argument passing into scripts, so that a great deal of relevant information is automatically available to the script function. This should greatly simplify writing user interfaces.

20.3 Graphical User Interface Actions.

A subset of X events (the exact subset is dependent on widget implementation) is mapped into xodus actions. If the xodus object is written so as to be able to execute that action as a script call, it invokes the script functions from the script field in the xodus element. If a function suffix matches the action, then the function is called.

Action name suffix(es) Description
*B1DOWN d1 d Mouse button 1 was pressed
*B2DOWN d2 d Mouse button 2 was pressed
*B3DOWN d3 d Mouse button 3 was pressed
*B1UP u1 u Mouse button 1 was released in a toggle
*B2UP u2 u Mouse button 2 was released in a toggle
*B3UP u3 u Mouse button 3 was released in a toggle
B1DOUBLE D1 D Mouse button 1 double click
B2DOUBLE D2 D Mouse button 2 double click
B3DOUBLE D3 D Mouse button 3 double click
B1MOVE m1 m Motion with mouse button 1 pressed
B2MOVE m2 m Motion with mouse button 2 pressed
B3MOVE m3 m Motion with mouse button 3 pressed
B1ENTER e1 e Entry with mouse button 1 pressed
B2ENTER e2 e Entry with mouse button 2 pressed
B3ENTER e3 e Entry with mouse button 3 pressed
B1LEAVE l1 l Leave widget with mouse b1 pressed
B2LEAVE l2 l Leave widget with mouse b2 pressed
B3LEAVE l3 l Leave widget with mouse b3 pressed
KEYPRESS k<key> k Keyboard key <key> was pressed
XUPDATE x Widget was refreshed
XODRAG drag y Drag event, called on source widget
XODROP drop p Drop event, called on destination widget
XOWASDROPPEDwasdropped w Called on source widget only if drop happened
XOCOMMAND command c Called from the script language

* The actions listed with an asterisk will also call the unadorned (i.e., no suffix) script command.

NOTE: The B1DOWN/B2DOWN/B3DOWN event will always precede an event of which it is a subset. Thus, all double clicks will be preceded by a .d event, as will all drags.

Not all widgets are able to handle all of the events listed above. The current capabilities are summarized below:
B1DOWN - - + + + + + +
B2DOWN - - + + + + + +
B3DOWN - - + + + + + +
B1UP - - - + - - - -
B2UP - - - + - - - -
B3UP - - - + - - - -
B1DOUBLE - - - - - + + +
B2DOUBLE - - - - - + + +
B3DOUBLE - - - - - + + +
B1MOVE - - - - - - - -
B2MOVE - - - - - - - -
B3MOVE - - - - - - - -
B1ENTER - - - - - - + +
B2ENTER - - - - - - + +
B3ENTER - - - - - - + +
B1LEAVE - - - - - - - -
B2LEAVE - - - - - - - -
B3LEAVE - - - - - - - -
KEYPRESS - - - - + - - -
XUPDATE + + + + + + + +
XODRAG - - - - - + - -
XODROP - - - - - + + +
XOWASDROPPED - - - - - + - -
XOCOMMAND - - + + + + + +

20.4 Scripts and Actions: Assigning the script Field

To the extent possible, the previous syntax with the script field will still work. In previous widgets, the ``script'' was not an accessible field, but could only be set on creation using the ``-script'' option. Subsequently it could be modified using the when command, which was rather cumbersome.

In most new widgets, there is a script field, and this can be set and modified with the usual GENESIS commands. The ``-script'' option for setting it at creation time remains for backwards compatibility.

There are two important additions to the obvious syntax of ``funcname arg1 arg2 ....''.

First, one can specify the action which calls the script using the appropriate suffix as defined above. For example, if one wished to have a script on element foo which was only called when button 2 was pressed, one could say:

     function testfunc(a,b,c)
         echo {a} {b} {c}
     setfield foo script "testfunc.d2 a b c"
Note that the suffix is NOT present in the function definition; in fact it is a syntax error.

Second, one can concatenate multiple scripts using a semicolon ``;'' separator:

     function anothertestfunc(a,b,c)
         echo {a} {b} {c}
     set foo script "testfunc.d2 a b c ; anothertestfunc i j k"

In this case, the element foo will say

                 a b c
                 i j k
when there is a button 2 click, and only
                 i j k
when there is a button 1 click.

Note that the scripts are executed in left-to-right order, which is what you would expect.

20.5 Scripts and Actions: Arguments Passed to the script Function.

A major enhancement to the GUI-GENESIS interface in GENESIS 2 is that a number of useful variables can be passed into the script function as arguments. These variables are specified using an extension of the old ``funcname <widget>'' syntax of previous versions.

The options in this version are:
Option Abbrev. Variable
<widget> <w> Passes in full pathname of widget or
pix in which an event occurred.
<name> <n> Alias for <widget>
<value> <v> Value of widget if it has a state
or value field.
<source> <s> First widget to be clicked in a
drag-drop operation, i.e., source widget.
<destination> <d> End point of drag-drop operation.
<SourceVal> <S> Value of source widget. Only works
for drop and wasdropped options.
<DestVal> <D> Value of dest widget. Only works
for drop and wasdropped options.
<x> <x> x coordinate of event.
<y> <y> y coordinate of event.
<z> <z> z coordinate of event.

These arguments can be interspersed with explicit arguments in any order, and can be repeated as often as required. Of course, not all of these arguments are relevant for all operations, or for all widgets. The arguments with a useful value are listed below:
Widget Useful arguments Notes
xbutton <w>
xtoggle <w> <v> The value is the state of the xtoggle.
This field determines whether the
widget is now depressed (1) or raised (0).
Note that the .d and .u suffixed scripts
will only be called if state is 1 or 0
respectively, so that provides another
way of checking the toggle state.
xdialog <w> <v> The value is the string in the dialog box.
xdraw <w> <v> for .e, .D, .c suffixes.
<w> <v> <x> <y> <z> for .d suffix
<w> <v> <s> <d> for .drop suffix
<x ><y> <z>
xgraph Same as xdraw
xpixes <w> <v> for .D, .drag suffixes
<w> <v> <x> <y> <z> for .d suffix
<w> <v> <s> <d> for .drop or .wasdropped suffix
<x> <y> <z>
<w> <v> [args] for .c suffix (args passed in to XOCOMMAND)

Note that in XOCOMMANDs, the arguments passed to the action ``call pix XOCOMMAND arg1 arg2 ...'' are appended to the variables passed into the script function. One normally passes in at least one argument on the XOCOMMAND argument line to identify the context of the call.

The example in the file clicks.g in the Scripts/examples/XODUS directory illustrates most of the options listed above, using as a script function the ``echo'' command to display all the arguments.

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