Snapper Introduction

What is Snapper?

Snapper allows an entire working application to be contained in a single XML file.  The XML file can be served from a www server, file system or RDBMS and activated via the Snapper thin-client.  The compiler can also produce an executable file with embedded XML.

Why Snapper?

As a consultant for a major CRM company, that has now been bought and buried (cough...Scopus), I watched companies spend tens of millions of dollars trying to achieve this very concept, i.e. fast, re-usable development.  My most successful implementation was at an ELFI (Extremely Large Financial Institution) where the VP of Engineering was a tech head and we used the most over priced software on the planet as a pure development tool.  In this spirit lives Snapper.

How does it work?

Applications, in Snapper, are contained in a project directory hierarchy.  The files contained in the project directory include application driver scripts, GUI XML components and object interaction XML.  The component snapmake is used to combine the various files found in the project directory into a single XML file or executable Perl script with embedded XML.  Another option is to create an HTML version of the Snapper application by using snap2html.  Once running, Snapper applications use the Snapper API module for low-level object access, and the SharkAPI module for high-level data and ui interface layers.

The following diagram provides a high level logical view.

Project Structure

A Snapper Project or application is contained on a file system with a specific directory hierarchy.  A project can be created using the snaputil utility.  This allows for easy development, and for the application to be stored under version control, i.e. cvs.  Snapper is only interested in directories and files that it knows about.  Any unknown directories or files that it encounters will be ignored.  This is convenient for adding support files and directories such as database scripts or makefiles, etc.  Here is the pizza application from the sample directory of the snapper-perl distribution, note that every application should have a top-level directory.

[bill@shark sample]$ ls -lF

README
perlmake/
pizza
pizza_pg
robo

The directory "pizza" contains the sample Snapper application pizza.  Here is the application structure.

[bill@shark contrib]$ ls -lR pizza
pizza:
    MAIN.module/
pizza/MAIN.module:
    scripts/
    widget/
pizza/MAIN.module/scripts:
    001_main_window.pl
    001_table_window.pl
    999_startup.pl
pizza/MAIN.module/widget:
    MAIN.glade

The directories that end in ".module" contain two directories, i.e. scripts, and widget.   The name of this directory is the module name and is used in function calls.  Files that end in ".pl" in the scripts directory will be read and incorporated into the application XML file.  The widget directory contains the glade XML file and the oix data XML file.  This data will also be combined into the application XML file.

A more compilcated example can be found on the GtkPizza contrib page.

The sample application can be compiled via the command-line program snapmake or via the build button on the Snapper IDE interface.

[bill@shark contrib]$ snapmake -d pizza -c -f pizza.pl

pixmap directory default: /home/IBM_USER/wks/snapper-perl/samples/pixmaps/
starting...
building xml...
checking pizza/.
checking pizza/MAIN.module
checking pizza/MAIN.module/widget
  found ... MAIN.glade
    writing widget: pizza/MAIN.module/widget/MAIN.glade
checking pizza/MAIN.module/scripts
  found ... 001_main_window.pl
    writing script: pizza/MAIN.module/scripts/001_main_window.pl
  found ... 001_table_window.pl
    writing script: pizza/MAIN.module/scripts/001_table_window.pl
  found ... 999_startup.pl
    writing script: pizza/MAIN.module/scripts/999_startup.pl

The compile command and the output are shown above, this example uses the "-c" option that will produce an executable perl script.  If the "-c" option is not specifed than an application XML file will produced.  This file can be activated via the snaprun graphical launcher.  The file is now ready to be executed.  Below is an example of starting the script and the main window that will be displayed.

[bill@shark sample]$ ls -lF README perlmake/ pizza pizza.pl pizza_pg robo [bill@shark sample]$ perl pizza.pl

Programs

Snapper consists of the following programs:

Quick Start