PowerBuilder SetRedraw: Boost Performance & User Experience

Hey guys! Let’s dive into a crucial aspect of PowerBuilder development: the SetRedraw function. Understanding and using SetRedraw effectively can significantly improve your application’s performance and enhance the user experience, especially when dealing with frequent updates or complex visual changes. So, buckle up, and let’s get started!

Understanding the PowerBuilder SetRedraw Function

At its core, the SetRedraw function controls whether a window or control is visually updated on the screen after each change. When SetRedraw is set to FALSE , the window or control suspends its redrawing process. This means that any modifications to its properties, such as text, color, or position, are not immediately displayed. Instead, these changes are buffered, and the window or control is only redrawn once SetRedraw is set back to TRUE . This mechanism is incredibly useful in scenarios where multiple changes occur in quick succession, preventing flickering and significantly reducing the overhead associated with frequent screen updates.

Why is this important? Imagine a scenario where you are updating a listbox with hundreds of items. Without SetRedraw , the listbox would redraw after each item is added, resulting in a slow and visually jarring experience. By disabling redrawing during the update process, you can drastically improve the performance and provide a smoother user experience. The SetRedraw function essentially gives you fine-grained control over when and how your application updates its visual elements.

Furthermore, SetRedraw isn’t limited to just listboxes. It can be applied to various controls and windows within PowerBuilder, including datawindows, edit masks, and even entire windows. This flexibility makes it a powerful tool for optimizing the performance of a wide range of applications. It’s particularly beneficial when performing batch updates, complex calculations that affect visual elements, or any operation that involves numerous changes to a control or window.

However, remember to always set SetRedraw back to TRUE after you’re done making changes. Failing to do so will leave the control or window in a state where it doesn’t update, leading to a blank or outdated display. It’s like turning off the lights and forgetting to turn them back on – nobody can see what’s going on!

In summary, the SetRedraw function is a vital tool in any PowerBuilder developer’s arsenal. It provides a simple yet effective way to optimize performance, reduce flickering, and enhance the overall user experience. By understanding how it works and when to use it, you can create more responsive and visually appealing applications. So, go ahead and experiment with SetRedraw in your projects – you’ll be amazed at the difference it can make!

Syntax and Usage of SetRedraw

Okay, let’s get down to the nitty-gritty of how to actually use the SetRedraw function in your PowerBuilder code. The syntax is pretty straightforward, but understanding the nuances can help you avoid common pitfalls. The basic syntax is as follows:

control.SetRedraw(boolean)

Where:

• control is the name of the control or window you want to affect.
• boolean is a boolean value that specifies whether redrawing should be enabled or disabled. TRUE enables redrawing, and FALSE disables it.

Example:

Let’s say you have a listbox called lb_items that you want to update. Here’s how you would use SetRedraw to optimize the update process:

lb_items.SetRedraw(FALSE) // Disable redrawing

// Add items to the listbox
FOR i = 1 TO 100
 lb_items.AddItem("Item " + String(i))
NEXT

lb_items.SetRedraw(TRUE) // Enable redrawing

In this example, we first disable redrawing for the lb_items listbox. Then, we add 100 items to the listbox. Finally, we re-enable redrawing. This ensures that the listbox is only redrawn once, after all the items have been added, resulting in a much smoother and faster update.

Important Considerations:

• Always Pair SetRedraw(FALSE) with SetRedraw(TRUE) : For every SetRedraw(FALSE) call, there should be a corresponding SetRedraw(TRUE) call. Failing to do so will leave the control or window in a non-updating state.
• Use Try-Finally Blocks for Error Handling: To ensure that SetRedraw is always set back to TRUE , even if an error occurs, it’s good practice to use a try-finally block:

TRY
 lb_items.SetRedraw(FALSE)
 // Add items to the listbox
 FOR i = 1 TO 100
 lb_items.AddItem("Item " + String(i))
 NEXT

CATCH (Exception e)
 // Handle the exception
FINALLY
 lb_items.SetRedraw(TRUE)
END TRY

This ensures that SetRedraw(TRUE) is always called, even if an exception is thrown during the update process.

• Consider Using LockWindowUpdate for Windows: For more complex scenarios involving multiple controls or windows, you might consider using the LockWindowUpdate function (an external function call to the Windows API). This function locks the updates of an entire window, providing even greater performance benefits. However, it requires more careful handling and is generally used in more advanced scenarios.

By understanding the syntax and usage of SetRedraw , and by following these best practices, you can effectively optimize the performance of your PowerBuilder applications and provide a better user experience. So, go forth and conquer those performance bottlenecks!

Practical Examples and Use Cases

Now that we’ve covered the basics of the SetRedraw function, let’s explore some practical examples and use cases where it can be particularly beneficial. Understanding these scenarios will help you identify opportunities to optimize your own PowerBuilder applications.

1. Populating a DataWindow with a Large Dataset:

DataWindows are a cornerstone of PowerBuilder development, and they often handle large datasets. When populating a DataWindow with a significant amount of data, redrawing can become a major performance bottleneck. Using SetRedraw can significantly improve the loading time.

dw_1.SetRedraw(FALSE)
dw_1.Retrieve()
dw_1.SetRedraw(TRUE)

In this example, we disable redrawing before retrieving the data into the DataWindow and then re-enable it after the retrieval is complete. This prevents the DataWindow from redrawing after each row is added, resulting in a much faster loading time.

2. Updating a TreeView Control:

TreeView controls are often used to display hierarchical data. When updating a TreeView with numerous nodes, especially when expanding or collapsing nodes, the redrawing process can be slow. SetRedraw can help optimize these updates.

tv_1.SetRedraw(FALSE)
// Add or update nodes in the TreeView
tv_1.SetRedraw(TRUE)

By disabling redrawing during the update process, you can prevent the TreeView from flickering and improve the overall responsiveness of the application.

3. Performing Batch Updates on Multiple Controls:

In some cases, you might need to perform batch updates on multiple controls simultaneously. For example, you might need to update the text and color of several labels based on a calculation. Using SetRedraw on the parent window can help optimize these updates.

w_main.SetRedraw(FALSE)
lb_1.Text = "New Text 1"
lb_1.Color = RGB(255, 0, 0)
lb_2.Text = "New Text 2"
lb_2.Color = RGB(0, 255, 0)
w_main.SetRedraw(TRUE)

By disabling redrawing on the parent window, you can prevent each individual control from redrawing after each update, resulting in a more efficient update process.

4. Custom Drawing and Animation:

When performing custom drawing or animation, you often need to make frequent changes to the visual elements. SetRedraw can be used to control when these changes are displayed, allowing you to create smoother and more visually appealing animations.

graphical_object.SetRedraw(FALSE)
// Perform custom drawing operations
graphical_object.SetRedraw(TRUE)

By disabling redrawing during the drawing process, you can prevent flickering and create a smoother animation effect.

These are just a few examples of how SetRedraw can be used to optimize PowerBuilder applications. By understanding these scenarios and experimenting with SetRedraw in your own projects, you can significantly improve the performance and user experience of your applications. Remember to always profile your code to identify performance bottlenecks and use SetRedraw strategically to address them.

Common Mistakes and Troubleshooting

Even with a clear understanding of the SetRedraw function, developers can sometimes run into issues. Let’s look at some common mistakes and how to troubleshoot them so you can keep your PowerBuilder apps running smoothly.

1. Forgetting to Re-enable Redrawing:

The most common mistake is forgetting to call SetRedraw(TRUE) after calling SetRedraw(FALSE) . This leaves the control or window in a non-updating state, which can be confusing for the user. Always ensure that every SetRedraw(FALSE) call has a corresponding SetRedraw(TRUE) call, preferably within a TRY...FINALLY block as mentioned earlier.

Troubleshooting: If a control or window is not updating, double-check your code for any missing SetRedraw(TRUE) calls. Use the debugger to step through your code and ensure that SetRedraw(TRUE) is being executed.

2. Calling SetRedraw Too Frequently:

While SetRedraw is designed to improve performance, calling it too frequently can actually have the opposite effect. Each call to SetRedraw incurs some overhead, so it’s best to minimize the number of calls. Only disable redrawing when you are performing a significant number of updates.

Troubleshooting: Profile your code to identify areas where SetRedraw is being called excessively. Consider restructuring your code to reduce the number of updates or to group updates together so that SetRedraw can be used more effectively.

3. Using SetRedraw on the Wrong Control:

Ensure that you are calling SetRedraw on the correct control or window. Calling it on the wrong control will have no effect and can lead to confusion. Double-check the control name and ensure that it matches the control you are trying to update.

Troubleshooting: Use the debugger to verify that you are calling SetRedraw on the intended control. Check the control hierarchy to ensure that you are not accidentally calling it on a parent or child control.

4. Conflicting Redrawing Operations:

In complex applications, it’s possible to have conflicting redrawing operations. For example, one part of the code might be disabling redrawing while another part is trying to force a redraw. This can lead to unpredictable behavior.

Troubleshooting: Review your code for any conflicting redrawing operations. Use the debugger to trace the execution flow and identify the source of the conflict. Consider restructuring your code to avoid these conflicts.

5. Incorrect Use of LockWindowUpdate :

If you are using the LockWindowUpdate function, ensure that you are using it correctly. This function locks the updates of an entire window, and it requires careful handling. Always unlock the window by calling LockWindowUpdate(0) when you are finished. Failing to do so can cause the entire application to freeze.

Troubleshooting: If your application freezes after calling LockWindowUpdate , double-check your code for any missing LockWindowUpdate(0) calls. Use the debugger to verify that the window is being unlocked correctly.

By avoiding these common mistakes and following these troubleshooting tips, you can effectively use the SetRedraw function to optimize your PowerBuilder applications and provide a better user experience. Remember to always test your code thoroughly and profile it to identify any performance bottlenecks.

Conclusion: Mastering SetRedraw for Optimal PowerBuilder Performance

Alright, folks! We’ve journeyed through the ins and outs of the SetRedraw function in PowerBuilder. From understanding its core purpose to exploring practical examples, use cases, common pitfalls, and troubleshooting techniques, you’re now well-equipped to leverage this powerful tool to optimize your applications.

Remember, the key takeaway is that SetRedraw is your ally in minimizing unnecessary screen updates, reducing flickering, and enhancing the overall responsiveness of your PowerBuilder applications. By strategically disabling redrawing during periods of intense activity and then re-enabling it when updates are complete, you can achieve significant performance gains, particularly when dealing with large datasets, complex controls, or batch operations.

But like any powerful tool, SetRedraw requires careful handling. Always ensure that you pair every SetRedraw(FALSE) call with a corresponding SetRedraw(TRUE) call, preferably within a TRY...FINALLY block to prevent any accidental lockouts. Be mindful of calling SetRedraw too frequently, and always double-check that you’re applying it to the correct control or window. And if you venture into the realm of LockWindowUpdate , tread carefully and ensure you unlock the window when you’re done.

By incorporating SetRedraw into your PowerBuilder development workflow, you’ll not only improve the performance of your applications but also deliver a smoother, more polished user experience. So, go ahead, experiment with SetRedraw in your projects, and witness the difference it can make. Your users will thank you for it!

Keep coding, keep optimizing, and keep pushing the boundaries of what’s possible with PowerBuilder! You’ve got this!