/// <summary>
/// Removes / un-registers a definition instance.
/// </summary>
/// <remarks>
/// If the collection of registered definitions becomes empty
/// instantiates self removal from owner's collection.
/// </remarks>
internal void RemoveMember(DefinitionBase member)
{
Invalidate();
_registry.Remove(member);
if (_registry.Count == 0)
{
_sharedSizeScope.Remove(_sharedSizeGroupId);
}
}
internal DistributionOrderIndexComparer(DefinitionBase[] definitions)
{
Invariant.Assert(definitions != null);
this.definitions = definitions;
}
/// <summary>
/// Adds / registers a definition instance.
/// </summary>
internal void AddMember(DefinitionBase member)
{
Debug.Assert(!_registry.Contains(member));
_registry.Add(member);
Invalidate();
}
/// <summary>
/// Calculates and sets final size for all definitions in the given array.
/// </summary>
/// <param name="definitions">Array of definitions to process.</param>
/// <param name="finalSize">Final size to lay out to.</param>
/// <param name="rows">True if sizing row definitions, false for columns</param>
private void SetFinalSize(
DefinitionBase[] definitions,
double finalSize,
bool columns)
{
int starDefinitionsCount = 0; // traverses form the first entry up
int nonStarIndex = definitions.Length; // traverses from the last entry down
double allPreferredArrangeSize = 0;
bool useLayoutRounding = this.UseLayoutRounding;
int[] definitionIndices = DefinitionIndices;
double[] roundingErrors = null;
// If using layout rounding, check whether rounding needs to compensate for high DPI
double dpi = 1.0;
if (useLayoutRounding)
{
dpi = columns ? FrameworkElement.DpiScaleX : FrameworkElement.DpiScaleY;
roundingErrors = RoundingErrors;
}
for (int i = 0; i < definitions.Length; ++i)
{
// if definition is shared then is cannot be star
Debug.Assert(!definitions[i].IsShared || !definitions[i].UserSize.IsStar);
if (definitions[i].UserSize.IsStar)
{
double starValue = definitions[i].UserSize.Value;
if (_IsZero(starValue))
{
// cach normilized star value temporary into MeasureSize
definitions[i].MeasureSize = 0;
definitions[i].SizeCache = 0;
}
else
{
// clipping by c_starClip guarantees that sum of even a very big number of max'ed out star values
// can be summed up without overflow
starValue = Math.Min(starValue, c_starClip);
// Note: normalized star value is temporary cached into MeasureSize
definitions[i].MeasureSize = starValue;
double maxSize = Math.Max(definitions[i].MinSizeForArrange, definitions[i].UserMaxSize);
maxSize = Math.Min(maxSize, c_starClip);
definitions[i].SizeCache = maxSize / starValue;
if (useLayoutRounding)
{
roundingErrors[i] = definitions[i].SizeCache;
definitions[i].SizeCache = UIElement.RoundLayoutValue(definitions[i].SizeCache, dpi);
}
}
definitionIndices[starDefinitionsCount++] = i;
}
else
{
double userSize = 0;
switch (definitions[i].UserSize.GridUnitType)
{
case (GridUnitType.Pixel):
userSize = definitions[i].UserSize.Value;
break;
case (GridUnitType.Auto):
userSize = definitions[i].MinSizeForArrange;
break;
}
double userMaxSize;
if (definitions[i].IsShared)
{
// overriding userMaxSize effectively prevents squishy-ness.
// this is a "solution" to avoid shared definitions from been sized to
// different final size at arrange time, if / when different grids receive
// different final sizes.
userMaxSize = userSize;
}
else
{
userMaxSize = definitions[i].UserMaxSize;
}
definitions[i].SizeCache = Math.Max(definitions[i].MinSizeForArrange, Math.Min(userSize, userMaxSize));
if (useLayoutRounding)
{
roundingErrors[i] = definitions[i].SizeCache;
definitions[i].SizeCache = UIElement.RoundLayoutValue(definitions[i].SizeCache, dpi);
}
allPreferredArrangeSize += definitions[i].SizeCache;
definitionIndices[--nonStarIndex] = i;
}
}
// indices should meet
Debug.Assert(nonStarIndex == starDefinitionsCount);
if (starDefinitionsCount > 0)
{
StarDistributionOrderIndexComparer starDistributionOrderIndexComparer = new StarDistributionOrderIndexComparer(definitions);
Array.Sort(definitionIndices, 0, starDefinitionsCount, starDistributionOrderIndexComparer);
// the 'do {} while' loop below calculates sum of star weights in order to avoid fp overflow...
// partial sum value is stored in each definition's SizeCache member.
// this way the algorithm guarantees (starValue <= definition.SizeCache) and thus
// (starValue / definition.SizeCache) will never overflow due to sum of star weights becoming zero.
// this is an important change from previous implementation where the following was possible:
// ((BigValueStar + SmallValueStar) - BigValueStar) resulting in 0...
double allStarWeights = 0;
int i = starDefinitionsCount - 1;
do
{
allStarWeights += definitions[definitionIndices[i]].MeasureSize;
definitions[definitionIndices[i]].SizeCache = allStarWeights;
} while (--i >= 0);
i = 0;
do
{
double resolvedSize;
double starValue = definitions[definitionIndices[i]].MeasureSize;
if (_IsZero(starValue))
{
resolvedSize = definitions[definitionIndices[i]].MinSizeForArrange;
}
else
{
double userSize = Math.Max(finalSize - allPreferredArrangeSize, 0.0) * (starValue / definitions[definitionIndices[i]].SizeCache);
resolvedSize = Math.Min(userSize, definitions[definitionIndices[i]].UserMaxSize);
resolvedSize = Math.Max(definitions[definitionIndices[i]].MinSizeForArrange, resolvedSize);
}
definitions[definitionIndices[i]].SizeCache = resolvedSize;
if (useLayoutRounding)
{
roundingErrors[definitionIndices[i]] = definitions[definitionIndices[i]].SizeCache;
definitions[definitionIndices[i]].SizeCache = UIElement.RoundLayoutValue(definitions[definitionIndices[i]].SizeCache, dpi);
}
allPreferredArrangeSize += definitions[definitionIndices[i]].SizeCache;
} while (++i < starDefinitionsCount);
}
if ( allPreferredArrangeSize > finalSize
&& !_AreClose(allPreferredArrangeSize, finalSize) )
{
DistributionOrderIndexComparer distributionOrderIndexComparer = new DistributionOrderIndexComparer(definitions);
Array.Sort(definitionIndices, 0, definitions.Length, distributionOrderIndexComparer);
double sizeToDistribute = finalSize - allPreferredArrangeSize;
for (int i = 0; i < definitions.Length; ++i)
{
int definitionIndex = definitionIndices[i];
double final = definitions[definitionIndex].SizeCache + (sizeToDistribute / (definitions.Length - i));
double finalOld = final;
final = Math.Max(final, definitions[definitionIndex].MinSizeForArrange);
final = Math.Min(final, definitions[definitionIndex].SizeCache);
if (useLayoutRounding)
{
roundingErrors[definitionIndex] = final;
final = UIElement.RoundLayoutValue(finalOld, dpi);
final = Math.Max(final, definitions[definitionIndex].MinSizeForArrange);
final = Math.Min(final, definitions[definitionIndex].SizeCache);
}
sizeToDistribute -= (final - definitions[definitionIndex].SizeCache);
definitions[definitionIndex].SizeCache = final;
}
allPreferredArrangeSize = finalSize - sizeToDistribute;
}
if (useLayoutRounding)
{
if (!_AreClose(allPreferredArrangeSize, finalSize))
{
// Compute deltas
for (int i = 0; i < definitions.Length; ++i)
{
roundingErrors[i] = roundingErrors[i] - definitions[i].SizeCache;
definitionIndices[i] = i;
}
// Sort rounding errors
RoundingErrorIndexComparer roundingErrorIndexComparer = new RoundingErrorIndexComparer(roundingErrors);
Array.Sort(definitionIndices, 0, definitions.Length, roundingErrorIndexComparer);
double adjustedSize = allPreferredArrangeSize;
double dpiIncrement = UIElement.RoundLayoutValue(1.0, dpi);
if (allPreferredArrangeSize > finalSize)
{
int i = definitions.Length - 1;
while ((adjustedSize > finalSize && !_AreClose(adjustedSize, finalSize)) && i >= 0)
{
DefinitionBase definition = definitions[definitionIndices[i]];
double final = definition.SizeCache - dpiIncrement;
final = Math.Max(final, definition.MinSizeForArrange);
if (final < definition.SizeCache)
{
adjustedSize -= dpiIncrement;
}
definition.SizeCache = final;
i--;
}
}
else if (allPreferredArrangeSize < finalSize)
{
int i = 0;
while ((adjustedSize < finalSize && !_AreClose(adjustedSize, finalSize)) && i < definitions.Length)
{
DefinitionBase definition = definitions[definitionIndices[i]];
double final = definition.SizeCache + dpiIncrement;
final = Math.Max(final, definition.MinSizeForArrange);
if (final > definition.SizeCache)
{
adjustedSize += dpiIncrement;
}
definition.SizeCache = final;
i++;
}
}
}
}
definitions[0].FinalOffset = 0.0;
for (int i = 0; i < definitions.Length; ++i)
{
definitions[(i + 1) % definitions.Length].FinalOffset = definitions[i].FinalOffset + definitions[i].SizeCache;
}
}
/// <summary>
/// Calculates final (aka arrange) size for given range.
/// </summary>
/// <param name="definitions">Array of definitions to process.</param>
/// <param name="start">Start of the range.</param>
/// <param name="count">Number of items in the range.</param>
/// <returns>Final size.</returns>
private double GetFinalSizeForRange(
DefinitionBase[] definitions,
int start,
int count)
{
double size = 0;
int i = start + count - 1;
do
{
size += definitions[i].SizeCache;
} while (--i >= start);
return (size);
}
/// <summary>
/// Resolves Star's for given array of definitions.
/// </summary>
/// <param name="definitions">Array of definitions to resolve stars.</param>
/// <param name="availableSize">All available size.</param>
/// <remarks>
/// Must initialize LayoutSize for all Star entries in given array of definitions.
/// </remarks>
private void ResolveStar(
DefinitionBase[] definitions,
double availableSize)
{
DefinitionBase[] tempDefinitions = TempDefinitions;
int starDefinitionsCount = 0;
double takenSize = 0;
for (int i = 0; i < definitions.Length; ++i)
{
switch (definitions[i].SizeType)
{
case (LayoutTimeSizeType.Auto):
takenSize += definitions[i].MinSize;
break;
case (LayoutTimeSizeType.Pixel):
takenSize += definitions[i].MeasureSize;
break;
case (LayoutTimeSizeType.Star):
{
tempDefinitions[starDefinitionsCount++] = definitions[i];
double starValue = definitions[i].UserSize.Value;
if (_IsZero(starValue))
{
definitions[i].MeasureSize = 0;
definitions[i].SizeCache = 0;
}
else
{
// clipping by c_starClip guarantees that sum of even a very big number of max'ed out star values
// can be summed up without overflow
starValue = Math.Min(starValue, c_starClip);
// Note: normalized star value is temporary cached into MeasureSize
definitions[i].MeasureSize = starValue;
double maxSize = Math.Max(definitions[i].MinSize, definitions[i].UserMaxSize);
maxSize = Math.Min(maxSize, c_starClip);
definitions[i].SizeCache = maxSize / starValue;
}
}
break;
}
}
if (starDefinitionsCount > 0)
{
Array.Sort(tempDefinitions, 0, starDefinitionsCount, s_starDistributionOrderComparer);
// the 'do {} while' loop below calculates sum of star weights in order to avoid fp overflow...
// partial sum value is stored in each definition's SizeCache member.
// this way the algorithm guarantees (starValue <= definition.SizeCache) and thus
// (starValue / definition.SizeCache) will never overflow due to sum of star weights becoming zero.
// this is an important change from previous implementation where the following was possible:
// ((BigValueStar + SmallValueStar) - BigValueStar) resulting in 0...
double allStarWeights = 0;
int i = starDefinitionsCount - 1;
do
{
allStarWeights += tempDefinitions[i].MeasureSize;
tempDefinitions[i].SizeCache = allStarWeights;
} while (--i >= 0);
i = 0;
do
{
double resolvedSize;
double starValue = tempDefinitions[i].MeasureSize;
if (_IsZero(starValue))
{
resolvedSize = tempDefinitions[i].MinSize;
}
else
{
double userSize = Math.Max(availableSize - takenSize, 0.0) * (starValue / tempDefinitions[i].SizeCache);
resolvedSize = Math.Min(userSize, tempDefinitions[i].UserMaxSize);
resolvedSize = Math.Max(tempDefinitions[i].MinSize, resolvedSize);
}
tempDefinitions[i].MeasureSize = resolvedSize;
takenSize += resolvedSize;
} while (++i < starDefinitionsCount);
}
}
/// <summary>
/// Calculates desired size for given array of definitions.
/// </summary>
/// <param name="definitions">Array of definitions to use for calculations.</param>
/// <returns>Desired size.</returns>
private double CalculateDesiredSize(
DefinitionBase[] definitions)
{
double desiredSize = 0;
for (int i = 0; i < definitions.Length; ++i)
{
desiredSize += definitions[i].MinSize;
}
return (desiredSize);
}
/// <summary>
/// Accumulates length type information for given definition's range.
/// </summary>
/// <param name="definitions">Source array of definitions to read values from.</param>
/// <param name="start">Starting index of the range.</param>
/// <param name="count">Number of definitions included in the range.</param>
/// <returns>Length type for given range.</returns>
private LayoutTimeSizeType GetLengthTypeForRange(
DefinitionBase[] definitions,
int start,
int count)
{
Debug.Assert(0 < count && 0 <= start && (start + count) <= definitions.Length);
LayoutTimeSizeType lengthType = LayoutTimeSizeType.None;
int i = start + count - 1;
do
{
lengthType |= definitions[i].SizeType;
} while (--i >= start);
return (lengthType);
}
/// <summary>
/// Distributes min size back to definition array's range.
/// </summary>
/// <param name="start">Start of the range.</param>
/// <param name="count">Number of items in the range.</param>
/// <param name="requestedSize">Minimum size that should "fit" into the definitions range.</param>
/// <param name="definitions">Definition array receiving distribution.</param>
/// <param name="percentReferenceSize">Size used to resolve percentages.</param>
private void EnsureMinSizeInDefinitionRange(
DefinitionBase[] definitions,
int start,
int count,
double requestedSize,
double percentReferenceSize)
{
Debug.Assert(1 < count && 0 <= start && (start + count) <= definitions.Length);
// avoid processing when asked to distribute "0"
if (!_IsZero(requestedSize))
{
DefinitionBase[] tempDefinitions = TempDefinitions; // temp array used to remember definitions for sorting
int end = start + count;
int autoDefinitionsCount = 0;
double rangeMinSize = 0;
double rangePreferredSize = 0;
double rangeMaxSize = 0;
double maxMaxSize = 0; // maximum of maximum sizes
// first accumulate the necessary information:
// a) sum up the sizes in the range;
// b) count the number of auto definitions in the range;
// c) initialize temp array
// d) cache the maximum size into SizeCache
// e) accumulate max of max sizes
for (int i = start; i < end; ++i)
{
double minSize = definitions[i].MinSize;
double preferredSize = definitions[i].PreferredSize;
double maxSize = Math.Max(definitions[i].UserMaxSize, minSize);
rangeMinSize += minSize;
rangePreferredSize += preferredSize;
rangeMaxSize += maxSize;
definitions[i].SizeCache = maxSize;
// sanity check: no matter what, but min size must always be the smaller;
// max size must be the biggest; and preferred should be in between
Debug.Assert( minSize <= preferredSize
&& preferredSize <= maxSize
&& rangeMinSize <= rangePreferredSize
&& rangePreferredSize <= rangeMaxSize );
if (maxMaxSize < maxSize) maxMaxSize = maxSize;
if (definitions[i].UserSize.IsAuto) autoDefinitionsCount++;
tempDefinitions[i - start] = definitions[i];
}
// avoid processing if the range already big enough
if (requestedSize > rangeMinSize)
{
if (requestedSize <= rangePreferredSize)
{
//
// requestedSize fits into preferred size of the range.
// distribute according to the following logic:
// * do not distribute into auto definitions - they should continue to stay "tight";
// * for all non-auto definitions distribute to equi-size min sizes, without exceeding preferred size.
//
// in order to achieve that, definitions are sorted in a way that all auto definitions
// are first, then definitions follow ascending order with PreferredSize as the key of sorting.
//
double sizeToDistribute;
int i;
Array.Sort(tempDefinitions, 0, count, s_spanPreferredDistributionOrderComparer);
for (i = 0, sizeToDistribute = requestedSize; i < autoDefinitionsCount; ++i)
{
// sanity check: only auto definitions allowed in this loop
Debug.Assert(tempDefinitions[i].UserSize.IsAuto);
// adjust sizeToDistribute value by subtracting auto definition min size
sizeToDistribute -= (tempDefinitions[i].MinSize);
}
for (; i < count; ++i)
{
// sanity check: no auto definitions allowed in this loop
Debug.Assert(!tempDefinitions[i].UserSize.IsAuto);
double newMinSize = Math.Min(sizeToDistribute / (count - i), tempDefinitions[i].PreferredSize);
if (newMinSize > tempDefinitions[i].MinSize) { tempDefinitions[i].UpdateMinSize(newMinSize); }
sizeToDistribute -= newMinSize;
}
// sanity check: requested size must all be distributed
Debug.Assert(_IsZero(sizeToDistribute));
}
else if (requestedSize <= rangeMaxSize)
{
//
// requestedSize bigger than preferred size, but fit into max size of the range.
// distribute according to the following logic:
// * do not distribute into auto definitions, if possible - they should continue to stay "tight";
// * for all non-auto definitions distribute to euqi-size min sizes, without exceeding max size.
//
// in order to achieve that, definitions are sorted in a way that all non-auto definitions
// are last, then definitions follow ascending order with MaxSize as the key of sorting.
//
double sizeToDistribute;
int i;
Array.Sort(tempDefinitions, 0, count, s_spanMaxDistributionOrderComparer);
for (i = 0, sizeToDistribute = requestedSize - rangePreferredSize; i < count - autoDefinitionsCount; ++i)
{
// sanity check: no auto definitions allowed in this loop
Debug.Assert(!tempDefinitions[i].UserSize.IsAuto);
double preferredSize = tempDefinitions[i].PreferredSize;
double newMinSize = preferredSize + sizeToDistribute / (count - autoDefinitionsCount - i);
tempDefinitions[i].UpdateMinSize(Math.Min(newMinSize, tempDefinitions[i].SizeCache));
sizeToDistribute -= (tempDefinitions[i].MinSize - preferredSize);
}
for (; i < count; ++i)
{
// sanity check: only auto definitions allowed in this loop
Debug.Assert(tempDefinitions[i].UserSize.IsAuto);
double preferredSize = tempDefinitions[i].MinSize;
double newMinSize = preferredSize + sizeToDistribute / (count - i);
tempDefinitions[i].UpdateMinSize(Math.Min(newMinSize, tempDefinitions[i].SizeCache));
sizeToDistribute -= (tempDefinitions[i].MinSize - preferredSize);
}
// sanity check: requested size must all be distributed
Debug.Assert(_IsZero(sizeToDistribute));
}
else
{
//
// requestedSize bigger than max size of the range.
// distribute according to the following logic:
// * for all definitions distribute to equi-size min sizes.
//
double equalSize = requestedSize / count;
if ( equalSize < maxMaxSize
&& !_AreClose(equalSize, maxMaxSize) )
{
// equi-size is less than maximum of maxSizes.
// in this case distribute so that smaller definitions grow faster than
// bigger ones.
double totalRemainingSize = maxMaxSize * count - rangeMaxSize;
double sizeToDistribute = requestedSize - rangeMaxSize;
// sanity check: totalRemainingSize and sizeToDistribute must be real positive numbers
Debug.Assert( !double.IsInfinity(totalRemainingSize)
&& !DoubleUtil.IsNaN(totalRemainingSize)
&& totalRemainingSize > 0
&& !double.IsInfinity(sizeToDistribute)
&& !DoubleUtil.IsNaN(sizeToDistribute)
&& sizeToDistribute > 0 );
for (int i = 0; i < count; ++i)
{
double deltaSize = (maxMaxSize - tempDefinitions[i].SizeCache) * sizeToDistribute / totalRemainingSize;
tempDefinitions[i].UpdateMinSize(tempDefinitions[i].SizeCache + deltaSize);
}
}
else
{
//
// equi-size is greater or equal to maximum of max sizes.
// all definitions receive equalSize as their mim sizes.
//
for (int i = 0; i < count; ++i)
{
tempDefinitions[i].UpdateMinSize(equalSize);
}
}
}
}
}
}
/// <summary>
/// Validates layout time size type information on given array of definitions.
/// Sets MinSize and MeasureSizes.
/// </summary>
/// <param name="definitions">Array of definitions to update.</param>
/// <param name="treatStarAsAuto">if "true" then star definitions are treated as Auto.</param>
private void ValidateDefinitionsLayout(
DefinitionBase[] definitions,
bool treatStarAsAuto)
{
for (int i = 0; i < definitions.Length; ++i)
{
definitions[i].OnBeforeLayout(this);
double userMinSize = definitions[i].UserMinSize;
double userMaxSize = definitions[i].UserMaxSize;
double userSize = 0;
switch (definitions[i].UserSize.GridUnitType)
{
case (GridUnitType.Pixel):
definitions[i].SizeType = LayoutTimeSizeType.Pixel;
userSize = definitions[i].UserSize.Value;
// this was brought with NewLayout and defeats squishy behavior
userMinSize = Math.Max(userMinSize, Math.Min(userSize, userMaxSize));
break;
case (GridUnitType.Auto):
definitions[i].SizeType = LayoutTimeSizeType.Auto;
userSize = double.PositiveInfinity;
break;
case (GridUnitType.Star):
if (treatStarAsAuto)
{
definitions[i].SizeType = LayoutTimeSizeType.Auto;
userSize = double.PositiveInfinity;
}
else
{
definitions[i].SizeType = LayoutTimeSizeType.Star;
userSize = double.PositiveInfinity;
}
break;
default:
Debug.Assert(false);
break;
}
definitions[i].UpdateMinSize(userMinSize);
definitions[i].MeasureSize = Math.Max(userMinSize, Math.Min(userSize, userMaxSize));
}
}
/// <summary>
/// Calculates one dimensional measure size for given definitions' range.
/// </summary>
/// <param name="definitions">Source array of definitions to read values from.</param>
/// <param name="start">Starting index of the range.</param>
/// <param name="count">Number of definitions included in the range.</param>
/// <returns>Calculated measure size.</returns>
/// <remarks>
/// For "Auto" definitions MinWidth is used in place of PreferredSize.
/// </remarks>
private double GetMeasureSizeForRange(
DefinitionBase[] definitions,
int start,
int count)
{
Debug.Assert(0 < count && 0 <= start && (start + count) <= definitions.Length);
double measureSize = 0;
int i = start + count - 1;
do
{
measureSize += (definitions[i].SizeType == LayoutTimeSizeType.Auto)
? definitions[i].MinSize
: definitions[i].MeasureSize;
} while (--i >= start);
return (measureSize);
}
// Gets Column or Row definition at index from grid based on resize direction
private static void SetDefinitionLength(DefinitionBase definition, GridLength length)
{
definition.SetValue(definition is ColumnDefinition ? ColumnDefinition.WidthProperty : RowDefinition.HeightProperty, length);
}
// Retrieves the ActualWidth or ActualHeight of the definition depending on its type Column or Row
private double GetActualLength(DefinitionBase definition)
{
ColumnDefinition column = definition as ColumnDefinition;
return column == null ? ((RowDefinition)definition).ActualHeight : column.ActualWidth;
}
// These methods are to help abstract dealing with rows and columns.
// DefinitionBase already has internal helpers for getting Width/Height, MinWidth/MinHeight, and MaxWidth/MaxHeight
// Returns true if the row/column has a Star length
private static bool IsStar(DefinitionBase definition)
{
return definition.UserSizeValueCache.IsStar;
}
/// <summary>
/// OnLayoutUpdated handler. Validates that all participating definitions
/// have updated min size value. Forces another layout update cycle if needed.
/// </summary>
private void OnLayoutUpdated(object sender, EventArgs e)
{
double sharedMinSize = 0;
// accumulate min size of all participating definitions
for (int i = 0, count = _registry.Count; i < count; ++i)
{
sharedMinSize = Math.Max(sharedMinSize, _registry[i]._minSize);
}
bool sharedMinSizeChanged = !DoubleUtil.AreClose(_minSize, sharedMinSize);
// compare accumulated min size with min sizes of the individual definitions
for (int i = 0, count = _registry.Count; i < count; ++i)
{
DefinitionBase definitionBase = _registry[i];
// we'll set d.UseSharedMinimum to maintain the invariant:
// d.UseSharedMinimum iff d._minSize < this.MinSize
// i.e. iff d is not a "long-pole" definition.
//
// Measure/Arrange of d's Grid uses d._minSize for long-pole
// definitions, and max(d._minSize, shared size) for
// short-pole definitions. This distinction allows us to react
// to changes in "long-pole-ness" more efficiently and correctly,
// by avoiding remeasures when a long-pole definition changes.
bool useSharedMinimum = !DoubleUtil.AreClose(definitionBase._minSize, sharedMinSize);
// before doing that, determine whether d's Grid needs to be remeasured.
// It's important _not_ to remeasure if the last measure is still
// valid, otherwise infinite loops are possible
bool measureIsValid;
if (!definitionBase.UseSharedMinimum)
{
// d was a long-pole. measure is valid iff it's still a long-pole,
// since previous measure didn't use shared size.
measureIsValid = !useSharedMinimum;
}
else if (useSharedMinimum)
{
// d was a short-pole, and still is. measure is valid
// iff the shared size didn't change
measureIsValid = !sharedMinSizeChanged;
}
else
{
// d was a short-pole, but is now a long-pole. This can
// happen in several ways:
// a. d's minSize increased to or past the old shared size
// b. other long-pole definitions decreased, leaving
// d as the new winner
// In the former case, the measure is valid - it used
// d's new larger minSize. In the latter case, the
// measure is invalid - it used the old shared size,
// which is larger than d's (possibly changed) minSize
measureIsValid = (definitionBase.LayoutWasUpdated &&
DoubleUtil.GreaterThanOrClose(definitionBase._minSize, this.MinSize));
}
if (!measureIsValid)
{
Grid parentGrid = (Grid)definitionBase.Parent;
parentGrid.InvalidateMeasure();
}
else if (!DoubleUtil.AreClose(sharedMinSize, definitionBase.SizeCache))
{
// if measure is valid then also need to check arrange.
// Note: definitionBase.SizeCache is volatile but at this point
// it contains up-to-date final size
Grid parentGrid = (Grid)definitionBase.Parent;
parentGrid.InvalidateArrange();
}
// now we can restore the invariant, and clear the layout flag
definitionBase.UseSharedMinimum = useSharedMinimum;
definitionBase.LayoutWasUpdated = false;
}
_minSize = sharedMinSize;
_layoutUpdatedHost.LayoutUpdated -= _layoutUpdated;
_layoutUpdatedHost = null;
_broadcastInvalidation = true;
}
/// <summary>
/// Adds / registers a definition instance.
/// </summary>
internal void AddMember(DefinitionBase member)
{
Debug.Assert(!_registry.Contains(member));
_registry.Add(member);
Invalidate();
}