VirtualScroller Items Not Visible Using V-show

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Introduction

VirtualScroller is a powerful component in PrimeVue that enables efficient rendering of large datasets by only rendering the visible items. However, when the visibility of the VirtualScroller changes, the list of items may not be rendered as expected. This issue is particularly problematic when using v-show to toggle the visibility of the VirtualScroller.

Describe the bug

When the VirtualScroller's visibility changes (not directly, but via one of its ancestors), the list of items is not rendered. This issue is not resolved by updating the PrimeVue version, as demonstrated by the reproducer. The problem persists even after updating the PrimeVue version, and only one of the two problems has been fixed.

Issue #7354

Although issue #7354 is closed, the problem persists. This suggests that the fix may not have addressed the root cause of the issue or that there are additional factors at play.

Reproducer

The reproducer is available at https://stackblitz.com/edit/primevue-4-vite-issue-template-pr9xwosf?file=src%2FApp.vue. This reproducer demonstrates the issue with two VirtualScrollers: one inside a container div with a v-show condition and another inside a container div with a conditional height.

Environment

The environment used to reproduce the issue is as follows:

  • Vite v5.3.2
  • Vue version 3.4.31
  • PrimeVue version 4.3.3

Steps to reproduce the behavior

To reproduce the behavior, follow these steps:

  1. Open the reproducer at https://stackblitz.com/edit/primevue-4-vite-issue-template-pr9xwosf?file=src%2FApp.vue.
  2. Wait for 2 seconds, during which time the first container will appear, and the second container will be resized.
  3. Observe that the VirtualScroller inside the first container remains empty, while the VirtualScroller inside the second container is rendered.

Expected behavior

The expected behavior is that on VirtualScroller visibility change, the list of items should be rendered. This means that when the visibility of the VirtualScroller changes, the list of items should be updated accordingly.

Conclusion

The issue of VirtualScroller items not being visible using v-show is a complex problem that persists even after updating the PrimeVue version. The reproducer demonstrates the issue with two VirtualScrollers, and the expected behavior is that the list of items should be rendered when the visibility of the VirtualScroller changes.

Possible solutions

To resolve this issue, possible solutions could include:

  • Updating the PrimeVue version to the latest release
  • Modifying the v-show condition to use a different approach, such as using a separate component for the VirtualScroller
  • Using a different component, such as a TabPanel, which does not use lazy loading
  • Implementing a custom solution using JavaScript to update the VirtualScroller when its visibility changes

Recommendations

Based on the analysis of the issue, the following recommendations are made:

  • Update the PrimeVue version to the latest release to ensure that the issue is resolved
  • Use a different approach for toggling the visibility of the VirtualScroller, such as using a separate component
  • Consider using a different component, such as a TabPanel, which does not use lazy loading
  • Implement a custom solution using JavaScript to update the VirtualScroller when its visibility changes

Future work

To further investigate this issue, the following tasks are recommended:

  • Create a new reproducer that demonstrates the issue with a simpler setup
  • Collaborate with the PrimeVue team to resolve the issue
  • Implement a custom solution using JavaScript to update the VirtualScroller when its visibility changes

Timeline

The timeline for resolving this issue is as follows:

  • Short-term (next 2 weeks): Update the PrimeVue version to the latest release and modify the v-show condition to use a different approach
  • Medium-term (next 4 weeks): Implement a custom solution using JavaScript to update the VirtualScroller when its visibility changes
  • Long-term (next 8 weeks): Collaborate with the PrimeVue team to resolve the issue and implement a permanent fix.
    VirtualScroller items not visible using v-show: Q&A =====================================================

Q: What is the VirtualScroller component in PrimeVue?

A: The VirtualScroller component in PrimeVue is a powerful component that enables efficient rendering of large datasets by only rendering the visible items. It is designed to improve the performance of applications that need to render large amounts of data.

Q: What is the issue with VirtualScroller items not being visible using v-show?

A: The issue is that when the VirtualScroller's visibility changes (not directly, but via one of its ancestors), the list of items is not rendered. This means that when the visibility of the VirtualScroller changes, the list of items does not update accordingly.

Q: Why is this issue a problem?

A: This issue is a problem because it can cause the application to appear broken or unresponsive. When the visibility of the VirtualScroller changes, the user expects the list of items to update accordingly. If the list of items does not update, it can be confusing and frustrating for the user.

Q: What are some possible solutions to this issue?

A: Some possible solutions to this issue include:

  • Updating the PrimeVue version to the latest release
  • Modifying the v-show condition to use a different approach, such as using a separate component for the VirtualScroller
  • Using a different component, such as a TabPanel, which does not use lazy loading
  • Implementing a custom solution using JavaScript to update the VirtualScroller when its visibility changes

Q: How can I update the PrimeVue version to the latest release?

A: To update the PrimeVue version to the latest release, you can follow these steps:

  1. Check the PrimeVue documentation for the latest version number
  2. Update the version number in your project's package.json file
  3. Run the command npm install or yarn install to update the dependencies
  4. Update the PrimeVue version in your project's configuration files, such as the Vue CLI configuration file

Q: How can I modify the v-show condition to use a different approach?

A: To modify the v-show condition to use a different approach, you can try the following:

  1. Use a separate component for the VirtualScroller
  2. Use a different component, such as a TabPanel, which does not use lazy loading
  3. Implement a custom solution using JavaScript to update the VirtualScroller when its visibility changes

Q: How can I implement a custom solution using JavaScript to update the VirtualScroller when its visibility changes?

A: To implement a custom solution using JavaScript to update the VirtualScroller when its visibility changes, you can try the following:

  1. Use the mounted lifecycle hook to add an event listener to the VirtualScroller's visibility change event
  2. Use the updated lifecycle hook to update the VirtualScroller's items when its visibility changes
  3. Use a JavaScript library, such as Vue.js's built-in watch function, to watch for changes to the VirtualScroller's visibility and update its items accordingly

Q: What are some best practices for using the VirtualScroller component in PrimeVue?

A: Some best practices for using the VirtualScroller component in PrimeVue include:

  • Using the VirtualScroller component only when necessary, such as when rendering large datasets
  • Ensuring that the VirtualScroller component is properly configured and initialized
  • Using the VirtualScroller component in conjunction with other PrimeVue components, such as the TabPanel component
  • Testing the VirtualScroller component thoroughly to ensure that it is working as expected

Q: What are some common mistakes to avoid when using the VirtualScroller component in PrimeVue?

A: Some common mistakes to avoid when using the VirtualScroller component in PrimeVue include:

  • Not properly configuring and initializing the VirtualScroller component
  • Not using the VirtualScroller component only when necessary
  • Not testing the VirtualScroller component thoroughly
  • Not using the VirtualScroller component in conjunction with other PrimeVue components, such as the TabPanel component.