Welcome!

Microsoft Cloud Authors: Andreas Grabner, Stackify Blog, Liz McMillan, David H Deans, Automic Blog

Blog Feed Post

PB Event Order

PowerBuilder - Events and Precedence


     The order in which events happen within a PowerBuilder Classic application is in most cases, a very predictable model. The PB developer should be aware of this aspect when developing GUI based applications. For instance, when focus is shifted from one object to another object, the first object will experience the Modified and LoseFocus events before the second object experiences a get focus event.

To understand this further, consider the following scenarios and the resulting events.
 

An Application starts and window "A" is opened

APPLICATION OPEN
WINDOW "A" OPEN
WINDOW "A" ACTIVATE
CHILD OBJECT GET FOCUS (First object in tab order)
 

Window "B" is opened (Window "A" stays open)

WINDOW "A" CURRENT OBJECT LOSE FOCUS
WINDOW "A" DEACTIVATE
WINDOW "B" OPEN
WINDOW "B" ACTIVATE
WINDOW "B" CHILD OBJECT GET FOCUS (First object in tab order)

Window "B" closed, return to Window "A".

WINDOW "B" CLOSEQUERY
WINDOW "B" CURRENT OBJECT LOSE FOCUS
WINDOW "B" CLOSE
WINDOW "B" DEACTIVATE
WINDOW "A" ACTIVATE
OBJECT GET FOCUS (Last object that had focus)
 

"Click" on new object within Same Window

OBJECT 1 MODIFIED (if changed)
OBJECT 1 LOSE FOCUS
OBJECT 2 GET FOCUS
OBJECT 2 CLICKED
 

"Tab" to new object within Same Window

OBJECT 1 MODIFIED (if changed)
OBJECT 1 LOSE FOCUS
OBJECT 2 GET FOCUS (next object in tab order)

Interestingly enough, events can and will occur even when no actions are performed by the user. If you are
using a screen saver, such as the one in Windows, the following will happen.

Flip to screen saver (After period of inactivity)
   WINDOW DEACTIVATE
   OBJECT LOSE FOCUS
Return from screen saver
   WINDOW ACTIVATE
   OBJECT GET FOCUS


DataWindows and Events

A DataWindow is a single object within a window. As such, events happen to the DataWindow as a single object (DW COntrol) and not to the individual items that are within the DataWindow object itself. In order to make up for this, there are a number of special events that exist only for DataWindows. These events are not quite the same as those of other Window objects and therefore must be considered on their own.

Consider the following scenario:

The User Clicks on a field in a data window, keys something, clicks on another field within the data window, keys something and then clicks on a Command Button (outside of the DataWindow). The sequence of DataWindow events is as follows:

DW GET FOCUS
DW CLICKED
DW EDIT CHANGED (once for each keystroke)
DW CLICKED
DW ITEMCHANGED
DW ITEM FOCUS CHANGED
DW EDIT CHANGED (once for each keystroke)
DW LOSE FOCUS

COMMAND BUTTON GET FOCUS
COMMAND BUTTON CLICKED

A number of significant aspects are happening at this time! For example: there was only one get focus and one lose focus event. Only one item changed event occurred (even though two items were changed). A clicked event occurred two times. One edit changed event occurred for every keystroke made within the DataWindow.

If DataWindow edits were behind the two modified fields, only the first field would have been edited. For all intents and purposes, the second field has nothing in it!

Now let us insert the ACCEPTTEXT() function into the command button Clicked script. Now the sequence of events flows as follows:

DW GET FOCUS
DW CLICKED
DW EDIT CHANGED (once for each keystroke)
DW CLICKED
DW ITEMCHANGED
DW ITEM FOCUS CHANGED
DW EDIT CHANGED (once for each keystroke)
DW LOSE FOCUS

COMMAND BUTTON GET FOCUS
COMMAND BUTTON CLICKED

DW ITEMCHANGED

The last item changed event was triggered by the AcceptText ( ) functionality. You might be tempted to put this function in the DataWindow Control's losefocus event script, but this makes it very difficult for a user to cancel a transaction when they can not get past the edit rule!
 

Events Precedence Table

The following is a table that shows the order of events for each object type:

Objects Events Order Notes

Window
Open 1
Activate 2 Also after closing of
another Window
Key 3 Each Keystroke (not all objects)
CloseQuery 4
Close 5
Deactivate 6

Single Line Edit, Multi Line Edit
Get Focus 1
Modified 2
LoseFocus 3

List Box, Drop Down List Box
GetFocus 1
SelectionChanged 2 When choice made from list
Modified 3
DoubleClicked 4 Only possible when "always show
list box" is active
LoseFocus 5

Static Text, Picture, Picture Button
GetFocus 1
Clicked 2
DoubleClicked 3 Always issues a Clicked event first
LoseFocus 4

Check Box, Command Button, Radio Button
GetFocus 1
Clicked 2
LoseFocus 3

DataWindow
GetFocus 1
Clicked 2
DoubleClicked 3 Always issues a Clicked event first
EditChanged 4 Once for each keystroke
ItemError 5 When item doesn't pass validation
ItemChanged 6 When object loses focus within dw
RowFocusChanged 7
ItemFocusChanged 8
LoseFocus 9
 

Events Notes

Triggerevent Function

At any time in an application, an event can occur through use of the TRIGGEREVENT() function. This can be a very handy thing to know and use. It can also cause problems if the application is counting on certain events to occur in a certain sequence.

DataWindow Clicked Event

Often, the clicked event in a data window is used to trigger a choice made by the user. In the script for this event it is always a good policy to check that the clicked row value is greater than zero. If the click is made on the borders or white space of a data window, the GETCLICKEDROW function will return a zero.

Although the ItemError! event listed after EditChanged! event under dw events order is a bit confusing, I am
sure it is correct as per the 4 phases of validation:

. edit-changed check
. data-type check (ItemError! fires here...)
. item-changed check
. validation-rule check

***********************************************************
Note: You can not safely predict the event model in PB.Net applications as the object drawing and interaction is outside the application's control in the WPF layer of the O/S. WPF controls all aspects of event handling and even imposes restrictions for the PB.Net application! 
***********************************************************

Regards ... Chris

Read the original blog entry...

More Stories By Chris Pollach

Chris Pollach is a Senior Consultant with over 30 years experience in Systems and Software Analysis, Development, Maintenance and Technical Support, mainly in the areas of GUI Design, MS-Windows Programming, Java / .NET Programming, Wireless, Application / Web Server Design & Programming, Object Oriented Development Tools and Methodologies, Data Base, Data Communications and Network application development. He has participated in numerous technical, planning and management roles, as well as consulted and educated in these fields for a diverse clientele. He is also the owner of “Software Tool & Die Inc.” a company dedicated to provide custom software and education solutions on Object Oriented business systems.

As an educator, Chris is certified to teach PowerBuilder (first in Canada), MS-SQLServer, Sybase’s Enterprise Application Studio and EAServer integrated application/web development environment. He is former Certified SilverStream developer (CSSD) and current Certified PowerBuilder Developer – Associate / Professional (CPD-P) as well as a Certified Sybase Tools Instructor (CSI).

Chris has written numerous articles in various popular personal computer magazines, newsletters and is the author of the PowerGuide and PowerExpert products as well as the STD Foundation Classes. Currently, Chris has developed a Foundation Class library for Sybase's PocketBuilder, SAP's PowerBulder and EAServer products and now Appeon Web & mobile products that integrates JSP or ASP web development, Section 508 / CLF web standards and mobile applications. A new Web Service framework has also been released for IIs to support PowerBuilder based web service NVUO's!

Chris recently became a 2nd Degree Black in the TaeKwonDo martial art and has developed a Martial Art multimedia study guide using the Component-One “Doc2Help” and Sybase PowerBuilder products. Since the fall of 2004 he became a TaeKwonDo instructor for the City of Ottawa’s Goulbourn program. He has also been certified with the World TaeKwonDo Federation (February 2005 - 1st Dan and October 2008 - 2nd Dan).

Chris was awarded the Sybase “Innovation and Achievement” award for 2005 as voted for by the International Sybase User Group (ISUG). This award was presented for innovations to the PocketBuilder mobile development product, contributions to the PowerBuilder News groups and support of the Ottawa Sybase User Group.

To round his management and leadership skills, Chris is the former president of the Kiwanis Club of Goulbourn and still volunteers his time with the service clubs in his area. He is also the coordinator of the Ottawa Sybase User group and a certified NAUI scuba instructor. For the last three years, Chris has been voted onto the ISUG Board of Directors and holds the position of "Director - North American User Groups".

@ThingsExpo Stories
Everywhere we turn in our industry we can find strong opinions about the direction, type and nature of cloud’s impact on computing and business. Another word that is used in every context in our industry is “hybrid.” In his session at 20th Cloud Expo, Alvaro Gonzalez, Director of Technical, Partner and Field Marketing at Peak 10, will use a combination of a few conceptual props and some research recently commissioned by Peak 10 to offer a real-world consideration of how the various categories of...
Five years ago development was seen as a dead-end career, now it’s anything but – with an explosion in mobile and IoT initiatives increasing the demand for skilled engineers. But apart from having a ready supply of great coders, what constitutes true ‘DevOps Royalty’? It’ll be the ability to craft resilient architectures, supportability, security everywhere across the software lifecycle. In his keynote at @DevOpsSummit at 20th Cloud Expo, Jeffrey Scheaffer, GM and SVP, Continuous Delivery Busine...
SYS-CON Events announced today that Outscale, a global pure play Infrastructure as a Service provider and strategic partner of Dassault Systèmes, will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Founded in 2010, Outscale simplifies infrastructure complexities and boosts the business agility of its customers. Outscale delivers a secure, reliable and industrial strength solution for its customers, which in...
SYS-CON Events announced today that CollabNet, a global leader in enterprise software development, release automation and DevOps solutions, will be a Bronze Sponsor of SYS-CON's 20th International Cloud Expo®, taking place from June 6-8, 2017, at the Javits Center in New York City, NY. CollabNet offers a broad range of solutions with the mission of helping modern organizations deliver quality software at speed. The company’s latest innovation, the DevOps Lifecycle Manager (DLM), supports Value S...
SYS-CON Events announced today that Peak 10, Inc., a national IT infrastructure and cloud services provider, will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Peak 10 provides reliable, tailored data center and network services, cloud and managed services. Its solutions are designed to scale and adapt to customers’ changing business needs, enabling them to lower costs, improve performance and focus intern...
A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, whic...
In order to meet the rapidly changing demands of today’s customers, companies are continually forced to redefine their business strategies in order to meet these needs, stay relevant and continue to see profitable growth. IoT deployment and development is integral in this transformation, and today businesses are increasingly seeing the value of investing their resources into IoT deployments. These technologies are able increase ROI through projects such as connecting supply chains or enabling sm...
In his opening keynote at 20th Cloud Expo, Michael Maximilien, Research Scientist, Architect, and Engineer at IBM, will motivate why realizing the full potential of the cloud and social data requires artificial intelligence. By mixing Cloud Foundry and the rich set of Watson services, IBM's Bluemix is the best cloud operating system for enterprises today, providing rapid development and deployment of applications that can take advantage of the rich catalog of Watson services to help drive insigh...
SYS-CON Events announced today that Super Micro Computer, Inc., a global leader in compute, storage and networking technologies, will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Supermicro (NASDAQ: SMCI), the leading innovator in high-performance, high-efficiency server technology, is a premier provider of advanced server Building Block Solutions® for Data Center, Cloud Computing, Enterprise IT, Hadoop/...
SYS-CON Events announced today that SoftLayer, an IBM Company, has been named “Gold Sponsor” of SYS-CON's 18th Cloud Expo, which will take place on June 7-9, 2016, at the Javits Center in New York, New York. SoftLayer, an IBM Company, provides cloud infrastructure as a service from a growing number of data centers and network points of presence around the world. SoftLayer’s customers range from Web startups to global enterprises.
With major technology companies and startups seriously embracing Cloud strategies, now is the perfect time to attend @CloudExpo | @ThingsExpo, June 6-8, 2017, at the Javits Center in New York City, NY and October 31 - November 2, 2017, Santa Clara Convention Center, CA. Learn what is going on, contribute to the discussions, and ensure that your enterprise is on the right path to Digital Transformation.
SYS-CON Events announced today that EARP Integration will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. EARP Integration is a passionate software house. Since its inception in 2009 the company successfully delivers smart solutions for cities and factories that start their digital transformation. EARP provides bespoke solutions like, for example, advanced enterprise portals, business intelligence systems an...
Existing Big Data solutions are mainly focused on the discovery and analysis of data. The solutions are scalable and highly available but tedious when swapping in and swapping out occurs in disarray and thrashing takes place. The resolution for thrashing through machine learning algorithms and support nomenclature is through simple techniques. Organizations that have been collecting large customer data are increasingly seeing the need to use the data for swapping in and out and thrashing occurs ...
Amazon started as an online bookseller 20 years ago. Since then, it has evolved into a technology juggernaut that has disrupted multiple markets and industries and touches many aspects of our lives. It is a relentless technology and business model innovator driving disruption throughout numerous ecosystems. Amazon’s AWS revenues alone are approaching $16B a year making it one of the largest IT companies in the world. With dominant offerings in Cloud, IoT, eCommerce, Big Data, AI, Digital Assis...
SYS-CON Events announced today that Progress, a global leader in application development, has been named “Bronze Sponsor” of SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Enterprises today are rapidly adopting the cloud, while continuing to retain business-critical/sensitive data inside the firewall. This is creating two separate data silos – one inside the firewall and the other outside the firewall. Cloud ISVs oft...
The 21st International Cloud Expo has announced that its Call for Papers is open. Cloud Expo, to be held October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA, brings together Cloud Computing, Big Data, Internet of Things, DevOps, Digital Transformation, Machine Learning and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding busin...
Internet of @ThingsExpo, taking place October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with the 21st International Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. @ThingsExpo Silicon Valley Call for Papers is now open.
As cloud adoption continues to transform business, today's global enterprises are challenged with managing a growing amount of information living outside of the data center. The rapid adoption of IoT and increasingly mobile workforce are exacerbating the problem. Ensuring secure data sharing and efficient backup poses capacity and bandwidth considerations as well as policy and regulatory compliance issues.
SYS-CON Events announced today that Interoute has been named “Bronze Sponsor” of SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Interoute is the owner operator of Europe's largest network and a global cloud services platform, which encompasses over 70,000 km of lit fiber, 15 data centers, 17 virtual data centers and 33 colocation centers, with connections to 195 additional partner data centers. Our full-service Unifie...
SYS-CON Events announced today that Progress, a global leader in application development, has been named “Bronze Sponsor” of SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Enterprises today are rapidly adopting the cloud, while continuing to retain business-critical/sensitive data inside the firewall. This is creating two separate data silos – one inside the firewall and the other outside the firewall. Cloud ISVs ofte...