feat(treemap): Add rebuildToken parameter to support data value updates

[AcarFurkan]

Problem

SfTreemap doesn't update when data values change if dataCount stays the same.

FR: https://www.syncfusion.com/feedback/47083/provide-dynamic-update-support-for-treemap-datasource-without-changing-the-data

Previous Workaround

The only way to force a rebuild was using a Key:

SfTreemap(
  key: ValueKey(Object.hashAll(data.map((e) => e.hashCode))),
  dataCount: data.length,
  // ...
)

Downsides:
- Forces complete widget rebuild (loses state, animations)
- Not intuitive - key is meant for widget identity, not data changes

Solution

Added optional rebuildToken parameter. When this value changes, the widget rebuilds
even if dataCount is unchanged.

SfTreemap(
  dataCount: data.length,
  rebuildToken: Object.hashAll(data.map((e) => e.hashCode)),
  // ...
)

Or simply use an int counter:

int _rebuildCounter = 0;

// When data changes:
setState(() {
  _rebuildCounter++;
});

SfTreemap(
  dataCount: data.length,
  rebuildToken: _rebuildCounter,
  // ...
)

Advantages:
- Clean, declarative API
- Explicit intent - clearly indicates "rebuild when data changes"
- No breaking changes - parameter is optional with default null

Demo

Before (no update):

before.mov

After (with rebuildToken):

UPDATED.mov

Fixes #1396

[VijayakumarMariappan]

Hi @AcarFurkan

Currently, the SfTreemap widget does not provide a direct method to refresh its data source without rebuilding. As a workaround, you can assign a new UniqueKey to the widget, which forces a full rebuild:

late UniqueKey _treemapKey;

void updateDataSource() {
  // If old and new data count is same
  _treemapKey = UniqueKey();

  // Else
  // No need to change the key
}

SfTreemap(
  key: _treemapKey,
  dataCount: data.length,
)

This approach will trigger a complete rebuild of the widget, which may reset its state or interrupt animations.

We have already logged your feedback for this feature request here: https://www.syncfusion.com/feedback/47083

At this time, we do not have immediate plans to implement this support. Please note that our Syncfusion Flutter packages are not open-source, so we are not currently accepting external contributions. However, your suggestion has been added to our prioritization list for future consideration.

Thank you for your understanding and continued support.

[AcarFurkan]

Hi @VijayakumarMariappan ,
Thanks for the reply.

I already tried the key suggestion, but as you can see, when we use keys it doesn’t look good, and we can’t ship this to production like this:

before.mov

As you can also see, I’ve already added a small solution for this. It isn’t complicated and won’t break anything. I believe that if the developers take a look at my small changes, they’ll see that it’s very simple and brings good value