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Context information – PB Docs 70 – PowerBuilder Library

Context information – PB Docs 70

  2. Powerbuilder Documentation
  3. Powerbuilder Documentation Older
  4. Powerbuilder Documentation 7.0
  5. Context information – PB Docs 70

Context information

The PowerBuilder context feature allows applications to access
certain host (non-PowerBuilder) services. This is a PowerBuilder implementation
of functionality similar to the COM QueryInterface. PowerBuilder provides access
to the following host services:

PowerBuilder creates service objects appropriate for the current
execution context (native PowerBuilder, PowerBuilder window plug-in, PowerBuilder window
ActiveX, transaction server). This allows your application to take
full advantage of the execution environment. For example, in a PowerBuilder window
plug-in, your application can access parameters specified in the Embed
element. Additionally, when running the PowerBuilder window ActiveX
under Internet Explorer, your application can access the ActiveX automation
server, which allows your program to access and control the Internet
browser.

The context feature uses six PowerBuilder service objects: ContextInformation,
ContextKeyword, ErrorLogging, Inet, TransactionServer, and SSLServiceProvider,
and the InternetResult object. (The context feature is sometimes
called the Context object, but it is not
a PowerBuilder system object.)

For more information about these objects,
see Objects and Controls
or the PowerBuilder Browser.

Terminology

This discussion assumes specific definitions for certain terms:

  • Platform Hardware platform: Intel or UNIX
  • Environment Windows 95, Windows 98, Windows NT, Sun Solaris, HP-UX, or
    AIX
  • Context Native PowerBuilder, Jaguar CTS, MTS, PowerBuilder window ActiveX,
    or PowerBuilder window plug-in
  • Context feature A PowerBuilder feature that manages services. The context feature
    is built into the PowerBuilder virtual machine (PBVM70.DLL) the PowerBuilder window
    ActiveX (PBRX70.OCX or PBRXS70.OCX), and the PowerBuilder window plug-in
    (NPPBA70.DLL or NPPBS70.DLL)
  • Service One of a fixed set of capabilities enabled through the GetContextService
    function

Enabling a service

Before you use a service, you instantiate it by calling the
GetContextService function. When you call this function, PowerBuilder returns
a reference to the instantiated service. Use this reference in dot
notation when calling the service’s functions.

proc.gif To enable a service:

  1. Establish an instance variable of the appropriate
    type:

  2. Instantiate the instance variable by calling the
    GetContextService function:

Using a CREATE statement

You can instantiate a service object with a PowerScript CREATE
statement. However, this always creates an object for the default
context (native PowerBuilder execution environment), regardless of
where the application is running.

Context information service

You use the context information service to obtain information
about an application’s execution context. The service provides
current version information, as well as whether it’s running
in the PowerBuilder execution environment and whether as a PowerBuilder window
plug-in or a PowerBuilder window ActiveX. Using this information,
you can modify display characteristics and application behavior.
For example, you might hide a Close command button when running
as a plug-in or ActiveX. Additionally, when running in the PowerBuilder window
ActiveX under Internet Explorer, the context information service
can return a reference to an ActiveX automation server object. Your
application can use this reference to call functions that control
the Web browser.

note.gif Cross-platform support The context information service is available on all platforms.

Accessing context information

Using the context information service, you can access the
following information:

Item Use this function Comment
Full context name GetName Value returned depends on the context:

  • Default: PowerBuilder Runtime
  • Window plug-in: PowerBuilder window Plug-in
  • Window ActiveX: PowerBuilder window ActiveX
Abbreviated context name GetShortName Value returned depends on the context:

  • Default: PBRUN
  • Window plug-in: PBWinPlugin
  • Window ActiveX: PBRTX
Company name GetCompanyName Returns Sybase, Inc.
Version GetVersionName Returns the full version number (for example,
7.0.02)
Major version GetMajorVersion Returns the major version number (for example,
7)
Minor version GetMinorVersion Returns the minor version number (for example,
0)
Fix version GetFixesVersion Returns the fix version number (for example,
2)

Using the ClassName function

You can also use the ClassName function to determine the context
of the object. The return value of the ClassName function differs
by context. For example, for the Window plug-in the return value
is plugincontextinformation, and for the Window ActiveX it is rtxcontextinformation.

You can use this information for many purposes, including:

  • Modifying application appearance based
    on execution context     For example, you might hide a Close button when running in
    the PowerBuilder window plug-in and PowerBuilder window ActiveX (in
    a plug-in or ActiveX, closing the window results in a blank space
    in the HTML page).
  • Verifying that the context supports
    the current version     For example, if your application requires features or fixes
    from Version 6.5, you can use the context information service to
    check the version in the current execution context.

proc.gif To access context information:

  1. Declare an instance or global variable
    of type ContextInformation:

  2. Create the context information service by calling
    the GetContextService function:

  3. Call context information service functions as
    necessary.

    This example calls the GetShortName function to determine
    the current context and the GetVersionName function to determine
    the current version:

Accessing the ActiveX automation server

If you are running the PowerBuilder window ActiveX in Internet
Explorer Version 3.0 or greater, your application can call the context
information service’s GetHostObject function to obtain
a reference to an ActiveX automation server object (the hosting
object). Specifically, if you pass an uninstantiated OLEObject variable
to GetHostObject, it returns a reference to the IWebBrowserApp automation
server.

Your application can call and access IWebBrowserApp methods
and properties, which allow you to access and control certain aspects
of browser behavior, including:

  • Go back
  • Go forward
  • Go home
  • Refresh
  • Navigate to a specified Web page
  • Exit the browser

For more
information on the IWebBrowserApp interface, its methods, and its properties,
see the Internet Explorer documentation or access the Microsoft website.

proc.gif To access the ActiveX automation server:

  1. Declare instance or global variables of
    type ContextInformation and OLEObject:

  2. Create the context information service by calling
    the GetContextService function:

  3. Establish a reference to the ActiveX automation
    server by calling the GetHostObject function:

  4. Call IWebBrowserApp functions as necessary. This
    example calls the Navigate function to open the default Web browser
    displaying the Sybase home page:

    “Accessing component properties”

Keyword service

Use the keyword service to access environment information
for the current context. In the default environment, this service
returns host workstation environment variables. In the PowerBuilder window
plug-in, this service allows you to access parameters specified
in the plug-in’s Embed element. When running within Jaguar
CTS, you can use the keyword service to get component property values.

For information about using the keyword service in Jaguar
CTS, see “Accessing component properties”.

Accessing environment variables

When running in the PowerBuilder execution environment (the
default context), you use this service to return environment variables.

proc.gif To access environment variables:

  1. Declare an instance or global variable
    of type ContextKeyword. Also declare an unbounded array of type
    String to contain returned values:

  2. Create the context information service by calling
    the GetContextService function:

  3. Call the GetContextKeywords function to access
    the environment variable you want. This example calls the GetContextKeywords
    function to determine the current application Path:

  4. Extract values from the returned array as necessary.
    When accessing environment variables, the array should always have
    a single element:

Accessing Embed element parameters

The Embed element can contain additional, user-specified,
parameters. Additionally, the Embed element allows more than one
value for each parameter.

When running in the PowerBuilder window plug-in context, you
use this service to access parameters specified in the Embed element.
If the specified parameter isn’t found, the service tries
to match the specified parameter with an environment variable.

proc.gif To access Embed element parameters:

  1. Declare an instance or global variable
    of type ContextKeyword. Also declare an unbounded array of type
    String to contain returned values:

  2. Create the context information service by calling
    the GetContextService function:

  3. Call the GetContextKeywords function. This example
    calls the GetContextKeywords function to access values for the user-specified parameter,
    VALID:

  4. Extract values from the returned array as necessary.
    This example displays parameters in a listbox:

Internet service

Use the Internet service to:

  • Display
    a Web page in the default browser (HyperLinkToURL function, which
    starts the default browser with the specified URL)
  • Access the HTML for a specified page (GetURL function,
    which performs an HTTP Get)
  • Send data to a CGI, ISAPI, or NSAPI program (PostURL
    function, which performs an HTTP Post)

note.gif Cross-platform support The Internet service is only available on Windows.

Hyperlinking to a URL

You call the Internet service’s HyperLinkToURL function
to start the default browser with a specified URL.

proc.gif To hyperlink to a URL:

  1. Declare an instance or global variable
    of type Inet:

  2. Create the Internet service by calling the GetContextService
    function:

  3. Call the HyperLinkToURL function, passing the
    URL of the page to display when the browser starts:

Getting a URL

You call the Internet service’s GetURL function to
perform an HTTP Get, returning raw HTML for a specified URL. This
function returns the raw HTML via the InternetResult object.

proc.gif To perform an HTTP Get:

  1. Declare an instance or global variable
    of type Inet. Also declare an instance or global variable using
    the descendent InternetResult object as the data type (n_ir_msgbox
    in this example):

  2. Create the Internet service by calling the GetContextService
    function:

  3. Create an instance of the descendent InternetResult
    object:

  4. Call the GetURL function, passing the URL of the
    page to be returned and a reference to the instance of the descendent
    InternetResult object:

    When the GetURL function completes, it calls the InternetData
    function defined in the descendent InternetResult object, passing
    the HTML for the specified URL.

Posting to a URL

You call the Internet service’s PostURL function
to perform an HTTP Post, sending data to a CGI, ISAPI, or NSAPI
program. This function returns the raw HTML via the InternetResult
object.

proc.gif To perform an HTTP Post:

  1. Declare an instance or global variable
    of type Inet. Also declare an instance or global variable using
    the descendent InternetResult object as the data type (n_ir_msgbox
    in this example):

  2. Create the Internet service by calling the GetContextService
    function:

  3. Create an instance of the descendent InternetResult
    object:

  4. Establish the arguments to the PostURL function:

  5. Call the PostURL function, passing the URL of
    the routine to be executed, the arguments, the header, and a reference
    to the instance of the descendent InternetResult object:

    When the PostURL function completes, it calls the InternetData
    function defined in the descendent InternetResult object, passing
    the HTML returned by the specified routine.

Using the InternetResult object

The GetURL and PostURL functions both receive data in an InternetResult object.
This object acts as a buffer, receiving and caching the asynchronous data
as it is returned via the Internet. When all data is received, the InternetResult
object calls its InternetData function, which you override to process
the data as appropriate.

note.gif Implement this in descendants of InternetResult You implement this feature by creating standard class user
objects of type InternetResult. In each of these descendent user
objects, define an InternetData function to process the passed HTML
as appropriate.

proc.gif To implement a descendent InternetResult object:

  1. Create a standard class user object of
    type InternetResult.

  2. Declare a new user object function as follows:

    • Name InternetData
    • Access Public
    • Returns Integer
    • Argument name Data, passed by value
    • Argument data type Blob
  3. Add code to the InternetData function that processes
    the returned HTML as appropriate. This example simply displays the
    HTML in a MessageBox:

Transaction server service

Use the transaction server service to access information about
the context of an object running in a transaction server such as
Jaguar CTS or MTS. You can use the TransactionServer object to influence
transaction behavior programmatically, and to access the methods
of another component on the transaction server.

For more information, see Chapter 22, “Building a Jaguar Component” and Chapter 24, “Building a COM or MTS Component”.

Error logging service

To record errors generated by PowerBuilder objects running
in a transaction server to a log file, create an instance of the
ErrorLogging service object and invoke its log method. For example:

The errors are recorded in the Jaguar server log if the component
is running in Jaguar, and in the Windows NT system application log
if the component is running in MTS.

Secure Sockets Layer service

PowerBuilder allows you to establish Secure Sockets Layer
(SSL) connections to a Jaguar server. The SSL protocol allows connections
to be secured using public-key encryption and authentication algorithms
that are based on digital certificates. SSL is a “wrapper” protocol:
packets for another protocol are secured by embedding them inside
of SSL packets. For example, HTTPS is HTTP secured by embedding
each HTTP packet within an SSL packet. Likewise, IIOPS is IIOP embedded
within SSL.

You use an instance of the SSLServiceProvider object to establish
the connection from the client to the server. For more information,
see the PowerScript Reference
.

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PB Docs 70 Powerbuilder Application Techniques Powerbuilder Documentation Powerbuilder Documentation 7.0 Powerbuilder Documentation Older
August 3, 2023
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