/// <inheritdoc />
public void Arrange(Size finalSize, Rect visibleBounds, Size desiredSize)
{
if (!(_popup.Child is FrameworkElement child))
{
return;
}
if (_combo.IsPopupFullscreen)
{
child.Arrange(new Rect(new Point(), finalSize));
return;
}
var comboRect = _combo.GetAbsoluteBoundsRect();
var frame = new Rect(comboRect.Location, desiredSize.AtMost(visibleBounds.Size));
// On windows, the popup is Y-aligned accordingly to the selected item in order to keep
// the selected at the same place no matter if the drop down is open or not.
// For instance if selected is:
// * the first option: The drop-down appears below the combobox
// * the last option: The dop-down appears above the combobox
// However this would requires us to determine the actual location of the SelectedItem container's
// which might not be ready at this point (we could try a 2-pass arrange), and to scroll into view to make it visible.
// So for now we only rely on the SelectedIndex and make a highly improvable vertical alignment based on it.
var itemsCount = _combo.NumberOfItems;
var selectedIndex = _combo.SelectedIndex;
if (selectedIndex < 0 && itemsCount > 0)
{
selectedIndex = itemsCount / 2;
}
var stickyThreshold = Math.Max(1, Math.Min(4, (itemsCount / 2) - 1));
if (selectedIndex >= 0 && selectedIndex < stickyThreshold)
{
// Try to appear below
frame.Y = comboRect.Top;
}
else if (selectedIndex >= 0 && selectedIndex >= itemsCount - stickyThreshold
// As we don't scroll into view to the selected item, this case seems awkward if the selected item
// is not directly visible (i.e. without scrolling) when the drop-down appears.
// So if we detect that we should had to scroll to make it visible, we don't try to appear above!
&& (itemsCount <= _itemsToShow && frame.Height < (_combo.ActualHeight * _itemsToShow) - 3))
{
// Try to appear above
frame.Y = comboRect.Bottom - frame.Height;
}
else
{
// Try to appear centered
frame.Y = comboRect.Top - (frame.Height / 2.0) + (comboRect.Height / 2.0);
}
// Make sure that the popup does not appears out of the viewport
if (frame.Left < visibleBounds.Left)
{
frame.X = visibleBounds.X;
}
else if (frame.Right > visibleBounds.Width)
{
// On UWP, the popup is just aligned to the right on the window if it overflows on right
// Note: frame.Width is already at most visibleBounds.Width
frame.X = visibleBounds.Width - frame.Width;
}
if (frame.Top < visibleBounds.Top)
{
frame.Y = visibleBounds.Y;
}
else if (frame.Bottom > visibleBounds.Height)
{
// On UWP, the popup always let 1 px free at the bottom
// Note: frame.Height is already at most visibleBounds.Height
frame.Y = visibleBounds.Height - frame.Height - 1;
}
if (this.Log().IsEnabled(LogLevel.Debug))
{
this.Log().Debug($"Layout the combo's dropdown at {frame} (desired: {desiredSize} / available: {finalSize} / visible: {visibleBounds} / selected: {selectedIndex} of {itemsCount})");
}
child.Arrange(frame);
}
/// <inheritdoc />
public void Arrange(Size finalSize, Rect visibleBounds, Size desiredSize, Point?upperLeftLocation)
{
if (!(_popup.Child is FrameworkElement child))
{
return;
}
if (_combo.IsPopupFullscreen)
{
Point getChildLocation()
{
switch (child.VerticalAlignment)
{
default:
case VerticalAlignment.Top:
return(new Point());
case VerticalAlignment.Bottom:
return(new Point(0, finalSize.Height - child.DesiredSize.Height));
}
}
var childSize = new Size(finalSize.Width, Math.Min(finalSize.Height, child.DesiredSize.Height));
var finalRect = new Rect(getChildLocation(), childSize);
if (this.Log().IsEnabled(LogLevel.Debug))
{
this.Log().Debug($"FullScreen Layout for dropdown (desired: {desiredSize} / available: {finalSize} / visible: {visibleBounds} / finalRect: {finalRect} )");
}
child.Arrange(finalRect);
return;
}
var comboRect = _combo.GetAbsoluteBoundsRect();
var frame = new Rect(comboRect.Location, desiredSize.AtMost(visibleBounds.Size));
// On windows, the popup is Y-aligned accordingly to the selected item in order to keep
// the selected at the same place no matter if the drop down is open or not.
// For instance if selected is:
// * the first option: The drop-down appears below the combobox
// * the last option: The dop-down appears above the combobox
// However this would requires us to determine the actual location of the SelectedItem container's
// which might not be ready at this point (we could try a 2-pass arrange), and to scroll into view to make it visible.
// So for now we only rely on the SelectedIndex and make a highly improvable vertical alignment based on it.
var itemsCount = _combo.NumberOfItems;
var selectedIndex = _combo.SelectedIndex;
if (selectedIndex < 0 && itemsCount > 0)
{
selectedIndex = itemsCount / 2;
}
var placement = Uno.UI.Xaml.Controls.ComboBox.GetDropDownPreferredPlacement(_combo);
var stickyThreshold = Math.Max(1, Math.Min(4, (itemsCount / 2) - 1));
switch (placement)
{
case DropDownPlacement.Below:
case DropDownPlacement.Auto when selectedIndex >= 0 && selectedIndex < stickyThreshold:
frame.Y = comboRect.Top;
break;
case DropDownPlacement.Above:
case DropDownPlacement.Auto when
selectedIndex >= 0 && selectedIndex >= itemsCount - stickyThreshold
// As we don't scroll into view to the selected item, this case seems awkward if the selected item
// is not directly visible (i.e. without scrolling) when the drop-down appears.
// So if we detect that we should had to scroll to make it visible, we don't try to appear above!
&& (itemsCount <= _itemsToShow && frame.Height < (_combo.ActualHeight * _itemsToShow) - 3):
frame.Y = comboRect.Bottom - frame.Height;
break;
case DropDownPlacement.Centered:
case DropDownPlacement.Auto: // For now we don't support other alignments than top/bottom/center, but on UWP auto can also be 2/3 - 1/3
default:
// Try to appear centered
frame.Y = comboRect.Top - (frame.Height / 2.0) + (comboRect.Height / 2.0);
break;
}
// Make sure that the popup does not appears out of the viewport
if (frame.Left < visibleBounds.Left)
{
frame.X = visibleBounds.X;
}
else if (frame.Right > visibleBounds.Width)
{
// On UWP, the popup is just aligned to the right on the window if it overflows on right
// Note: frame.Width is already at most visibleBounds.Width
frame.X = visibleBounds.Width - frame.Width;
}
if (frame.Top < visibleBounds.Top)
{
frame.Y = visibleBounds.Y;
}
else if (frame.Bottom > visibleBounds.Height)
{
// On UWP, the popup always let 1 px free at the bottom
// Note: frame.Height is already at most visibleBounds.Height
frame.Y = visibleBounds.Height - frame.Height - 1;
}
if (this.Log().IsEnabled(LogLevel.Debug))
{
this.Log().Debug($"Layout the combo's dropdown at {frame} (desired: {desiredSize} / available: {finalSize} / visible: {visibleBounds} / selected: {selectedIndex} of {itemsCount})");
}
if (upperLeftLocation is Point offset)
{
// Compensate for origin location is some popup providers (Android
// is one, particularly when the status bar is translucent)
frame.X -= offset.X;
frame.Y -= offset.Y;
}
child.Arrange(frame);
}