The GLG Graphics Server is an AJAX-based thin-client
solution for deploying real-time process control and monitoring
screens on the web and mobile devices. It
is an alternative to the thick
client approach and
requires only minimal capabilities on the client.
With the AJAX-based thin client approach, the client side serves as a
display front end that uses only the industry-standard HTML
processing is performed on the central server. To display graphics that
update dynamically based on the input data, the server needs to render
image of the graphics on each image request.
Server performs the task of
rendering the image in response to the image generation requests. The
image is referred to as "dynamic" since it reflects the current state
of the dynamically changing data. The Graphics Server also
handles user interaction requests, including object selection with the
mouse and object tooltips, as well as clicking on
client side, it makes the image appear dynamic as it updates with real-time
data and responds to user
Both the ASP.NET and JSP
versions of the Graphics Server are available. In the ASP.NET environment,
the Graphics Server is deployed with IIS via custom
handlers written in C#. In the
Server Pages (JSP)
environment, the Graphics Server is deployed as a Java Servlet and may
be used with any compliant Java2EE Application server, such as Tomcat.
Interactive Graphical Editor
screens displayed on web pages are created
interactively using a graphical editor - the GLG Graphics Builder. Using
the Builder, a developer can draw graphical objects and edit their
properties, as well as define dynamic
and attach data sources for animating the drawing with real-time data.
The drawing is saved
into a file and
used by the Graphics Server for image generation.
In addition to creating drawings from scratch, the Graphics Builder
provides palettes of pre-built widgets, such as dials and meters, graphs and process control symbols, which can
be added to the drawing using Drag and Drop. The Builder also allows
the user to define
custom symbols and add them to a palette as reusable components.
With the help of the Builder, the job of creating and maintaining
graphics, from simple dashboards
to complex visualizations and custom HMI
screens, is done in an
interactive, point-and-click environment. The graphics may be easily
edited in the Builder with no programming involved. Once
the updated drawing is saved, it is ready to be used by the Graphics
Server without recompiling the source code.
The GLG drawings are screen-resolution
independent and may be scaled at run-time, as shown in
drawing may be used to render images of various resolutions
depending on the size of the client's screen.
Click here for more
information on the GLG Graphics Builder.
the Graphics Builder represent the dynamic graphics displayed on the
application's web pages at run time. For example, to create a custom Mobile Dashboard
displaying a few graphs and meters you can simply open a new
drawing in the Graphics Builder, add a few graphs and meters to it from
a palette, name them for run-time
access and save the drawing.
In addition to
simple dashboards, elaborate custom graphical displays
may be created in the Builder and deployed on a web page, as shown in the online demos.
While in the
Graphics Builder, you can also change object properties,
edit the object layout on the page, add custom labels and
annotations or draw custom decorations using the Builder's gradient,
shadow and transparency effects.
An alternative way to build an AJAX Dashboard is to combine several widgets on a single HTML page,
as shown in the GLG
Dashboard demo. Each self-contained widget is using its own server-side servlet
and it may be
deployed as a reusable component on multiple web pages.
Run-Time Image Generation
run-time, the Graphics
Server loads the GLG drawing and
uses it to generate dynamic images, updating the drawing with the
current data before processing each image request. The drawing contains
definitions of all graphical objects and their dynamic actions. Once
drawing is loaded, it is used to generate web images over and over
without the overhead of recreating the graphics on every
request, resulting in superior server performance.
When a client issues an image request, the Graphics Server creates a
snapshot image of the drawing using the current data. An image
request may contain parameters that define an image size, a value to be
displayed in a dial, a title for a graph or other custom attributes.
For example, in
demo the image request contains the show_pipes parameter. If this
parameter is set to 1, the generated image will display pipes
the tanks. The image generation parameters are passed to the Graphics
Server using the standard URL parameter syntax.
Before generating an image, the Graphics Server updates the drawing
with the current data by setting the drawing's resources. The resources
are defined in the Graphics Builder when the drawing is created and
accessed by the servlet at run time using the SetResource()
When the drawing is updated, the servlet generates an image by
simply invoking the CreateImage()
API method. This single method of the Graphics Server takes care of the complicated
task of rendering all
objects in the drawing in their current dynamic state.
here to see an example of a URL showing a dynamically generated
image. Reload the page to see
new data or change the width/height
parameters of the URL to change image size. A "&show_pipes=1"
parameter may be appended to the URL to activate the pipe display. In
image periodically to
display new data as shown in the demos.
Developing Custom Server-Side
In the ASP.NET environment, the Graphics
Server is deployed via a custom HTTP handler that is used with Windows
environment, the Graphics Server is deployed as a Java
servlet that may
be used with any compliant Java2EE Application server.
code of a sample
handler and a sample
servlet is provided and may be customized by the application
developers according to the application
requirements. For example, servlets and handlers may share one drawing
all servlet and handler instances or create a separate instance of the
each servlet session or an HTTP handler request.
When a custom drawing is
used, the servlet code may be
modified to set the application-specific resources defined in the
drawing, as well as handle an application-specific user interaction.
The ASP.NET version of the Graphics Handler uses Glg.NetServer.dll,
while the JSP version uses GlgServer.jar
file. Both files provide a class library that contains GLG Toolkit's
object and rendering engine.
The class library provides both the GLG Standard and Extended APIs
described in the C#
documentation. The GLG Standard API provides methods for
accessing resources to update the drawing with real-time data. The Extended API
provides methods for advanced features, such as creating objects
programmatically or querying a list
of all resources defined in the drawing.
For example, the Extended API may be used at run time to create a
variable number of dynamic icons representing airplanes as shown in
the GIS and AirTraffic Control demos.
Dynamic Data Supply
A server-side application
can query data from any data source, such as a PLC or
process database, using any preferred data
Alternatively, the data
may be supplied by the HTML or
The servlet updates the drawing with the new data by setting the
resources using GLG's
SetResource methods. The
for animating the drawing with data are defined in the Graphics Builder
when the drawing is created.
For example, in the drawing used in the process
control demo, an object named "Heater"
has a resource named "HeaterLevel"
that controls the fill level of the
heater's tank. When the drawing is used in the servlet, the servlet
updates the fill level by using the "Heater/HeaterLevel"
resource name as follows:
"Heater/HeaterLevel", heater_level_var );
The use of
resources helps to
separate graphics from the programming logic. The application simply
sets a logical resource named "Heater/HeaterLevel",
GLG's graphics engine takes care of all low-level details of
rendering the objects' graphics.
dynamic images, the servlet may handle user interaction by processing
AJAX-based requests for object
selection, tooltips and
user input, such as pressing buttons
in the drawing with the mouse. These features are demonstrated in the process
control and other demos.
To handle user interaction,
and onmousemove event handlers
to the image. When
the user clicks on the image or
moves the mouse over it, an event handler is invoked in the script. The
event handler sends an object selection AJAX request to the Graphics
Server, passing the mouse coordinates as parameters of the request. The
Graphics Server processes the request by finding an object selected by
the mouse coordinates. The servlet may process the selection on the
side or return the selection information back to the client for
The client may use the output of the selection request to popup a
tooltip, display the name of the selected object or execute a
drill-down action. For example, the process control demo displays
a dialog with the object's data when the object is selected with the
mouse. A tooltip is displayed when the mouse is moved over a named
object in the drawing. If
the Show 3D Pipes button at
the bottom of the drawing is pressed, the pipes connecting the tanks
and valves will be displayed in the image.
The tooltips and object
selection events are processed by the GLG Graphics
Server's engine on the server side, with no image maps or
objects created in the browser on the client side. This technique
handles a large number of vector objects in the drawing without the
performance limitations related to a number of used image maps.
here to see the
full source code of the GLG Servlet for generating images and
handling user interaction requests.
Since the selection and
tooltip events are processed on the server side with no image
maps embedded in HTML, the HTML pages
do not need to be regenerated when the geometry of the objects
the drawing is changed.
processing of selection events is the only practical option when the drawing contains dynamic moving icons,
as shown in the Airtraffic Control Demo. In this
case, generating static image maps for the icon selection is simply
impossible, since the icons change their position. Using AJAX to
maps dynamically every time the icon moves, would be also
impractical due to the performance limitations. This leaves the
selection processing as the only practical alternative.
The Mobile HMI Starter Package
starts from $1650
and includes the
Basic Edition of the Graphics Builder, a Graphics Server
with one Web-Server License and one widget
additional widget set may be added for $150.
Select one of
the following links for purchasing and pricing