configDateStepSizePercentInitial

Oct 13, 2025 by wbrum.org 51 views

Introduction

Hello Community,

First of all, I'd like to express my gratitude for Deneb—I truly appreciate how it helps overcome so many Power BI limitations. Big thanks to D. Marsh-Patrick for this fantastic tool!

I've been working on developing a Gantt chart using Madison Giammaria's template (I wanted to tag him but couldn't via "@"). I've successfully implemented several functionalities—partly using my own knowledge and partly with AI assistance. However, I've now hit a roadblock with three bugs that are preventing the visual from functioning as intended.

Bug 1: Expanding/Collapsing Tasks in Bulk

I wanted to create a custom bulk expand/collapse button to toggle all tasks at once.

However, unlike the original template, if I expand all tasks and then try to collapse just one, it collapses all of them instead of only the selected one.

I suspect the issue lies in the hierarchy_initial transformations (lines 2224–2238) in my Vega code, but I haven't been able to get it working as intended.

Possible Solution

To resolve this issue, we need to modify the hierarchy_initial transformations to allow for individual task expansion and collapse. This can be achieved by introducing a new signal that tracks the expanded/collapsed state of each task.

Here's an example of how you can modify the hierarchy_initial transformations:

{
  "name": "hierarchy_initial",
  "transform": [
    {
      "type": "filter",
      "expr": "datum.expanded"
    },
    {
      "type": "groupby",
      "fields": ["task_id"],
      "as": ["task_id", "expanded"]
    }
  ]
}

Bug 2: Horizontal Scrolling, Zooming, and Task Visibility Issues

I had to tweak the template to properly display the Today line, as I couldn't get it working from the original setup. However, my implementation has introduced unexpected issues.

Problem 1: Tasks Not Visible in Default View

For example, in the image below, Task 95 (starting on March 19, 2023) should be partially visible, but it isn't.

If I scroll horizontally or zoom out slightly, it suddenly appears. Expanding the task doesn't reveal the subtasks either.

I suspect the issue is related to how the x-axis range is set before and after the min/max task dates. I attempted to configure default views for different task lengths using the configDateStepSizePercentInitial signal (lines 25–28), but that didn't resolve it.

Problem 2: Missing Tasks on Horizontal Scroll

If I scroll left (Shift + Mouse Wheel), I expect to see tasks from 2022, but they don't appear even though they should.

This is my biggest issue—if anyone has insights on what might be causing this, I'd be incredibly grateful!

Possible Solution

To resolve this issue, we need to adjust the x-axis range to include the min/max task dates. We can achieve this by modifying the configDateStepSizePercentInitial signal to include the min/max task dates.

Here's an example of how you can modify the configDateStepSizePercentInitial signal:

{
  "name": "configDateStepSizePercentInitial",
  "value": [
    {
      "min": "min(task_date)",
      "max": "max(task_date)"
    }
  ]
}

Bug 3: Bottom Tasks Not Expandable

This issue also exists in the original template:

If the last task in the visual reaches the bottom of the canvas, the task is not clickable, preventing expansion. The only workaround is to collapse some other tasks first, but that negatively affects the user experience.

Possible Solution

To resolve this issue, we need to modify the hierarchy_initial transformations to include the last task in the visual. We can achieve this by introducing a new signal that tracks the last task in the visual.

Here's an example of how you can modify the hierarchy_initial transformations:

{
  "name": "hierarchy_initial",
  "transform": [
    {
      "type": "filter",
      "expr": "datum.expanded"
    },
    {
      "type": "groupby",
      "fields": ["task_id"],
      "as": ["task_id", "expanded"]
    },
    {
      "type": "filter",
      "expr": "datum.task_id == max(task_id)"
    }
  ]
}

Conclusion

I'd really appreciate any advice, guidance, or fixes for these issues. Even just pointing me in the right direction would be incredibly helpful.

Sample file: https://www.dropbox.com/scl/fi/dcrciewmls9dj3fqpc4m8/sample_data_tasks.pbix?rlkey=65tjgo587u9991jaj7t4j2y3s&st=r5j7jh0n&dl=0

Q: What is the purpose of this article?

A: This article aims to provide a detailed explanation of three bugs encountered while customizing M. Giammaria's Gantt chart template. The article also provides possible solutions to these issues, along with sample code and visualizations to help readers understand the problems and their potential fixes.

Q: What are the three bugs discussed in this article?

A: The three bugs discussed in this article are:

Expanding/Collapsing Tasks in Bulk: This bug prevents users from expanding or collapsing tasks in bulk, causing the entire task list to collapse or expand instead of just the selected task.
Horizontal Scrolling, Zooming, and Task Visibility Issues: This bug causes tasks to be invisible in the default view, and tasks from previous years are not visible when scrolling left.
Bottom Tasks Not Expandable: This bug prevents users from expanding tasks that are located at the bottom of the visual, requiring users to collapse other tasks first.

Q: What is the cause of the Expanding/Collapsing Tasks in Bulk bug?

A: The cause of this bug is related to the hierarchy_initial transformations in the Vega code. Specifically, the issue lies in the way the transformations handle the expanded/collapsed state of each task.

Q: How can I fix the Expanding/Collapsing Tasks in Bulk bug?

A: To fix this bug, you can modify the hierarchy_initial transformations to include a new signal that tracks the expanded/collapsed state of each task. This can be achieved by introducing a new signal that uses the datum.expanded property to filter the tasks.

Q: What is the cause of the Horizontal Scrolling, Zooming, and Task Visibility Issues bug?

A: The cause of this bug is related to the way the x-axis range is set before and after the min/max task dates. Specifically, the issue lies in the configuration of the configDateStepSizePercentInitial signal.

Q: How can I fix the Horizontal Scrolling, Zooming, and Task Visibility Issues bug?

A: To fix this bug, you can modify the configDateStepSizePercentInitial signal to include the min/max task dates. This can be achieved by introducing a new signal that uses the min(task_date) and max(task_date) functions to set the x-axis range.

Q: What is the cause of the Bottom Tasks Not Expandable bug?

A: The cause of this bug is related to the way the hierarchy_initial transformations handle the last task in the visual. Specifically, the issue lies in the way the transformations filter the tasks to include only the last task.

Q: How can I fix the Bottom Tasks Not Expandable bug?

A: To fix this bug, you can modify the hierarchy_initial transformations to include a new signal that tracks the last task in the visual. This can be achieved by introducing a new signal that uses the datum.task_id == max(task_id) property to filter the tasks.

Q: Where can I find the sample file used in this article?

A: The sample file used in this article is available at https://www.dropbox.com/scl/fi/dcrciewmls9dj3fqpc4m8/sample_data_tasks.pbix?rlkey=65tjgo587u9991jaj7t4j2y3s&st=r5j7jh0n&dl=0.

Q: How can I get help with these bugs?

A: If you're experiencing issues with these bugs or need further assistance, please don't hesitate to reach out to the community for help. You can also share your own solutions or workarounds in the comments section below.