Visual Programming: Cantata Basics

A Hands-on Approach to Visual Programming

1. Executing cantata: from the command line execute cantata, wait until an empty workspace is displayed on your screen.

     % cantata (foreground execution)  
     % cantata& (background execution)
   

   
   Cantata: empty workspace

   To exit click on the Quit button.

2. Selecting an operator/glyph: using the mouse press down on Input/Output and from the Data Files option select User defined. Position the selected "operator/glyph" in the workspace.

   
   User defined operator/glyph

3. Using the mouse press down on Visualization and from the Non-Interactive Display option select Display Image. Position the selected "operator/glyph" within the workspace.

   
   Display Image operator/glyph

4. Connect both operators by "clicking" the mouse on the input and output arrows of each operator. A network of operators is known as a visual program.

   
   A visual program

5. Manipulating Connections: once a data flow or control connection has been made between two glyphs, the user can delete, save data to a file (for data flow connections only), or set connection options. Clicking the left mouse button on a connection will bring the options described above. Clicking the middle mouse button will bring the connections options menu directly.

   
   Manipulating connections: left mouse button (without input file selected)

   
   Manipulating connections: middle mouse button

6. Selection of operators/glyphs: operators can be found via menus, by using the Routines and/or Finder submenus selection buttons.

   
   Menus selection buttons

7. Explore the options provided by the submenu Routines.

   
   Routines selection button options

8. Explore the options provided by the submenu Finder.

   
   Finder selection button options

9. Modifying parameters/options of an operator:click on the "pane button" (middle button) of an operator to access its internal parameters.

   
   Glyph pane button

   Click on the Pane button of the User defined glyph. Once the pane is displayed, at the bottom clear the line and type "$DIP/data/" followed with a carriage return. Click on the Input File button. Now you have access to the directory containing all the images for this course. Select an image by clicking on it. To exit the pane click on the Close button.

   
   User defined operator pane options

10. To "browse" the contents of the image files in this directory click on the Input File button. Select an image by clicking on it. Note the browser will go away once a selection has been made. Use the scroll bar to browse through the contents of this directory. To exit click on the Cancel button.

    
    Input File browser

11. Executing/Halting a glyph: click on the "off/on" switch found on each executable glyph.

    ---------
    Glyph off-on switch

12. To kill (destroy) a glyph click on the red "bomb".

    
    Glyph kill/destroy button

13. Glyph Error Indicator: the YUCKY FACE will appear under the glyph when the operator has encountered an error during execution.

    
    Glyph Error Indicator

    Clicking on the YUCKY FACE will display a subform with the error message. For instance,

    
    Error Pane

14. Workspace Command Bar and the Workspace Submenu: these two interfaces enable the user to execute the features provided in cantata. The first interface is the Workspace Submenu options.

    
    Workspace Submenu options

    The second interface to the cantata features is the Workspace Command Bar. This interface appears above the cantata workspace, and it is made of two parts:

    1. a set of command buttons
    2. a single command string selection

    
    Workspace Command Bar

    • Executing/Halting an entire workspace: click on the main workspace "off/on" switch or select Run from the Workspace submenu.

      ----------
      Workspace off-on or Run Workspace switch

      This will execute/halt ALL glyphs of a new visual program, or will re-execute/halt only those operators affected by a change.

    • Single stepping through a visual program: click on the "single step" switch. This enables the user to examine intermediate results, debug the visual program, or verify operator parameters.

      
      Single Step Execute switch

    • Reset a workspace: clicking the "Reset" switch will "touch" (re-initialize) all operators. This function can also be accessed via the Workspace submenu.

      
      Reset Workspace switch

    • Clear a workspace: clicking on the "Clear" switch will erase (clear) all operators/glyphs from a workspace. That is, it will erase al visual program(s) from the workspace.

      
      Clear Workspace switch

    • Check a workspace: clicking the "Check" switch will call the scheduler to verify if required connections are missing or other errors exist in a workspace. The user will be notified via error messages. This function can also be accessed via the Workspace submenu.

      
      Check Workspace switch

    • Redraw a workspace: selecting the Redraw option from the Wokspace submenu will refresh all glyphs in the workspce. This function can also be accessed via the Workspace submenu.
    • Workspace information: selecting this switch will calculate a few statistics on the workspace (eg. number of glyphs, procedures, etc).

      
      Display Workspace Information switch

    • Show Workspace GUI: this function can also be accessed via the Workspace submenu. This option will display the GUI for the workspace when a visual program has been encapsulated.

      
      Show Workspace GUI switch

      • For advanced cantata capabilities click HERE.
    • Export Selection: this option will export the arguments of selected operators to the Worspace GUI. Click on the Export Selection option found in the Workspace submenu.
      • For advanced cantata capabilities click HERE.
    • Encapsulate Workspace: this option will you to encapsulate a visual program into a stand-alone application. Click on the Encapsulate Workspace option found in the Workspace submenu.
      • For advanced cantata capabilities click HERE.
    • Create Procedure: this function can also be accessed via the Workspace submenu. This option enables the user to create a subprocedure from a set of selected operators.

      
      Create Procedure switch

    • Create Count Loop: this function can also be accessed via the Workspace submenu. This option enables the user to create a control structure from a set of selected glyphs.

      
      Create Count Loop switch

    • Create While Loop: this function can also be accessed via the Workspace submenu. This option enables the user to create a while control structure from a set of selected glyphs.

      
      Create While Loop switch

15. Workspace Command Bar and the Edit Submenu: these two interfaces enable the user to visually edit a visual program in cantata. The first interface is the Edit submenu options.

    
    Edit Submenu

    The second interface to the cantata features is the Workspace Command Bar. This interface appears above the cantata workspace as described above.

    • Show Workspace Clipboard: the "clipboard" is used to store selected glyphs for cut, copy and paste operations. Selecting this option will cause the clipboard to be displayed.

      
      Show Workspace Clipboard

    • Copy: this option when selected from the "Edit" submenu copies the selected glyphs from the workspace into the clipboard. The original glyphs in the workspace remain untouched. The selected glyphs will remain in the clipboard until they are transferred back into the workspace using the Paste option.
    • Cut: will remove the selected glyphs from the worspace and transfer them into the clipboard. The selected glyphs will remain in the clipboard until they are transferred back into the workspace using the Paste option. The glyphs moved into the clipboard by the Cut operation will be over-written by any successive Copy or Cut operations.

      
      Cut Selected Glyphs to Clipboard switch

    • Paste: will copy all selected glyphs in the clipboard to the workspace.

      
      Paste Clipboard to Workspace switch

    • Duplicate: operates like a combination of Copy and Paste operations. It copies the selected glyph from the workspace and immediately pastes them back into the workspace.

      
      Duplicate Selected Glyphs switch

    • Raise: will raise selected glyphs above other glyphs that may obscure them.
    • Lower: will lower selected glyphs above other glyphs that they may be obscuring.
    • Delete: will delete all selected glyphs.

      
      Delete Selected Glyphs switch

    • Undo Delete: Deleted glyphs are stored in a stack. Undo Delete pops the stack.

      
      Undo Deletion switch

    • Select All: this option will automatically select every glyph in the workspace.

      
      Select All Glyphs switch

    • Unselect All: this option will automatically unselect every glyph in the workspace.

      
      Unselect All Glyphs switch

16. Saving/Restoring Workspaces: these two interfaces enable the user to save and restore workspaces. The first interface is the Files submenu option. A subform will be displayed with the available options. In the Save Workspace row type in a filename for the workspace you wish to save. If you wish to restore a workspace type in the filename of it in the Restore Workspace row.

    
    Save/Restore Workspaces

    The second interface utilizes swithes in the Workspace Command Bar.

    • Show Workspace Attributes: this option will display the attributes of a workspace.

      
      Unselect All Glyphs switch

    • Restore Workspace:i this option automatically brings up the file browser in Aliaases mode so that you can select a workspace to restore.

      
      Restore Workspace switch

    • Save Workspace: enable you to save a workspace. Be careful so that you do not over-write a workspace.

      
      Save Workspace switch

17. Workspace Attributes: clicking on the Attributes submenu will a subform to be displayed. This subform allows you to set parameters which control various aspects of cantata.

    
    Workspace Attributes subform

    • Set Canvas Grid To: this option makes the grid "Visible" or "Invisible". The grid assists in the alignment of glyphs.
    • Canvas Grid Size: allows the user to modify the grid size (in number of pixels).
    • Connection Type: enables the user to select the type of connection between gluphs.
    • Rubberband Connections: this option refers to how the glyphs connections are adjusted whenever a glyph is moved. Continuously (true) or after the glyph has been placed (flase).
    • Interactive Placement: when you create a glyph, it will be automatically placed for you (false) or you can place it manually (true).
    • Always Display Glyph: this attribute determines whether or not the glyp should be unmapped when its pane is opened.
    • Show Data Available: this option provides visual feedback as to whether or not data is available to a glyph. A dot next to an input/output connection indicates the availability of data.
    • Show Modified Glyphs: this option enables the user to visualize whether or not a glyph has been modified from its last execution.
    • Parallel Execution: this option is valid when parallel and independent visual programs exist on a workspace. Making this option true makes the programs to execute faster (each network executes simultaneously).
    • Echo Execution: this option when is set to true will echo all processes being executed to the console.
    • Use Global Variables: variables and expressions can be local to a procedure or global to the entire workspace. Setting this option to false makes the variables to be local to a procedure.
      For advanced cantata capabilities click HERE.
    • Enable Remote Execution: (not available yet)
    • Responsive Execution: (not available yet)
    • Draw Color:
    • Grid Color: allows the user to change the color used for the grid.
    • Fill Color: allows the user to change the color used for
    • Background Pixmap: allows the user to change the background pixmap of the canvas.

In summary, cantata is used by the visual programmer to interactively develop visual programs by combining glyphs into a visual program or network.

Advanced programming capabilities in cantata.