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Avoid redundant property round-trips between platform and xplat across multiple controls #29970

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eecedf3
Skip mapping if value is set from handler
bhavanesh2001 Jun 12, 2025
5c76217
set selecteditem with FromHandler specificity on ios
bhavanesh2001 Jun 12, 2025
a3466e8
remove count
bhavanesh2001 Jun 12, 2025
0f9a218
add a dummy specificity
bhavanesh2001 Jun 19, 2025
570f503
Revert "add a dummy specificity"
bhavanesh2001 Jun 24, 2025
044c288
Merge branch 'main' into avoid_round_trips
bhavanesh2001 Jun 24, 2025
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8 changes: 7 additions & 1 deletion src/Controls/src/Core/Element/Element.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -641,8 +641,14 @@ private protected override void OnBindablePropertySet(BindableProperty property,

base.OnBindablePropertySet(property, original, value, changed, willFirePropertyChanged);
_pendingHandlerUpdatesFromBPSet.Remove(property.PropertyName);
UpdateHandlerValue(property.PropertyName, changed);

var specificity = GetContext(property).Values.GetSpecificity();
if (specificity == SetterSpecificity.FromHandler)
{
return;
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@StephaneDelcroix
Currently, SetterSpecificity.FromHandler is used in several places where the value is not actually coming from the handler, and this is blocking what we're trying to achieve here.

Here are the locations where it's used:

maui/src/Controls/src/Core/BindableObject.cs

Lines 288 to 289 in af4b90c

public void SetBinding(BindableProperty targetProperty, BindingBase binding)
=> SetBinding(targetProperty, binding, binding != null && targetProperty != null && binding.GetRealizedMode(targetProperty) == BindingMode.TwoWay ? SetterSpecificity.FromHandler : SetterSpecificity.FromBinding);

maui/src/Controls/src/Core/BindableObjectExtensions.cs

Lines 27 to 28 in af4b90c

// support normal/code properties
self.SetValue(property, value, SetterSpecificity.FromHandler);

Wouldn't it make more sense to introduce a separate, low-priority fallback specificity for these cases instead of overloading FromHandler, which is intended for platform-set values?

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@StephaneDelcroix thoughts?

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the new name is very confusing. could you pick a good, self-explanatory one, so we know what this is supposed to do when we come back here next time ?

}

UpdateHandlerValue(property.PropertyName, changed);
}

/// <summary>Method that is called when a bound property is changed.</summary>
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3 changes: 2 additions & 1 deletion src/Controls/src/Core/Handlers/Items/SelectableItemsViewHandler.Windows.cs
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Expand Up @@ -181,7 +181,8 @@ void UpdateVirtualSingleSelection()
if (ItemsView != null)
{
_ignoreVirtualSelectionChange = true;
ItemsView.SelectedItem = selectedItem;
ItemsView.SetValueFromRenderer(SelectableItemsView.SelectedItemProperty, selectedItem);


_ignoreVirtualSelectionChange = false;
}
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3 changes: 2 additions & 1 deletion src/Controls/src/Core/Handlers/Items/iOS/SelectableItemsViewController.cs
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Expand Up @@ -87,7 +87,8 @@ void FormsSelectItem(NSIndexPath indexPath)
case SelectionMode.None:
break;
case SelectionMode.Single:
ItemsView.SelectedItem = GetItemAtIndex(indexPath);
var item = GetItemAtIndex(indexPath);
ItemsView.SetValueFromRenderer(SelectableItemsView.SelectedItemsProperty,item);
break;
case SelectionMode.Multiple:
ItemsView.SelectedItems.Add(GetItemAtIndex(indexPath));
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3 changes: 2 additions & 1 deletion src/Controls/src/Core/Handlers/Items2/iOS/SelectableItemsViewController2.cs
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Expand Up @@ -87,7 +87,8 @@ void FormsSelectItem(NSIndexPath indexPath)
case SelectionMode.None:
break;
case SelectionMode.Single:
ItemsView.SelectedItem = GetItemAtIndex(indexPath);
var item = GetItemAtIndex(indexPath);
ItemsView.SetValueFromRenderer(SelectableItemsView.SelectedItemsProperty,item);
break;
case SelectionMode.Multiple:
ItemsView.SelectedItems.Add(GetItemAtIndex(indexPath));
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6 changes: 6 additions & 0 deletions src/Controls/src/Core/Slider/Slider.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -145,6 +145,12 @@ public double Value
set { SetValue(ValueProperty, value); }
}

double IRange.Value
{
get => Value;
set => SetValue(ValueProperty, value, SetterSpecificity.FromHandler);
}

public event EventHandler<ValueChangedEventArgs> ValueChanged;
public event EventHandler DragStarted;
public event EventHandler DragCompleted;
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6 changes: 6 additions & 0 deletions src/Controls/src/Core/Stepper/Stepper.cs
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Expand Up @@ -110,6 +110,12 @@ public double Value

double IStepper.Interval => Increment;

double IRange.Value
{
get => Value;
set => SetValue(ValueProperty, value, SetterSpecificity.FromHandler);
}

private protected override string GetDebuggerDisplay()
{
return $"{base.GetDebuggerDisplay()}, Value = {Value}";
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