public void RenderIntoBatch(RenderBatchBuilder batchBuilder, RenderFragment renderFragment)
{
// A component might be in the render queue already before getting disposed by an
// earlier entry in the render queue. In that case, rendering is a no-op.
if (_componentWasDisposed)
{
return;
}
// Swap the old and new tree builders
(CurrentRenderTree, _renderTreeBuilderPrevious) = (_renderTreeBuilderPrevious, CurrentRenderTree);
CurrentRenderTree.Clear();
renderFragment(CurrentRenderTree);
var diff = RenderTreeDiffBuilder.ComputeDiff(
_renderer,
batchBuilder,
ComponentId,
_renderTreeBuilderPrevious.GetFrames(),
CurrentRenderTree.GetFrames());
batchBuilder.UpdatedComponentDiffs.Append(diff);
batchBuilder.InvalidateParameterViews();
}
public static void UpdateToMatchClientState(RenderTreeBuilder renderTreeBuilder, ulong eventHandlerId, object newFieldValue)
{
// We only allow the client to supply string or bool currently, since those are the only kinds of
// values we output on attributes that go to the client
if (!(newFieldValue is string || newFieldValue is bool))
{
return;
}
// Find the element that contains the event handler
var frames = renderTreeBuilder.GetFrames();
var framesArray = frames.Array;
var framesLength = frames.Count;
var closestElementFrameIndex = -1;
for (var frameIndex = 0; frameIndex < framesLength; frameIndex++)
{
ref var frame = ref framesArray[frameIndex];
switch (frame.FrameTypeField)
{
case RenderTreeFrameType.Element:
closestElementFrameIndex = frameIndex;
break;
case RenderTreeFrameType.Attribute:
if (frame.AttributeEventHandlerIdField == eventHandlerId)
{
if (!string.IsNullOrEmpty(frame.AttributeEventUpdatesAttributeNameField))
{
UpdateFrameToMatchClientState(
renderTreeBuilder,
framesArray,
closestElementFrameIndex,
frame.AttributeEventUpdatesAttributeNameField,
newFieldValue);
}
// Whether or not we did update the frame, that was the one that matches
// the event handler ID, so no need to look any further
return;
}
break;
}
}
public void RenderIntoBatch(RenderBatchBuilder batchBuilder, RenderFragment renderFragment, out Exception?renderFragmentException)
{
renderFragmentException = null;
// A component might be in the render queue already before getting disposed by an
// earlier entry in the render queue. In that case, rendering is a no-op.
if (_componentWasDisposed)
{
return;
}
_nextRenderTree.Clear();
try
{
renderFragment(_nextRenderTree);
}
catch (Exception ex)
{
// If an exception occurs in the render fragment delegate, we won't process the diff in any way, so child components,
// event handlers, etc., will all be left untouched as if this component didn't re-render at all. The Renderer will
// then forcibly clear the descendant subtree by rendering an empty fragment for this component.
renderFragmentException = ex;
return;
}
// We don't want to make errors from this be recoverable, because there's no legitimate reason for them to happen
_nextRenderTree.AssertTreeIsValid(Component);
// Swap the old and new tree builders
(CurrentRenderTree, _nextRenderTree) = (_nextRenderTree, CurrentRenderTree);
var diff = RenderTreeDiffBuilder.ComputeDiff(
_renderer,
batchBuilder,
ComponentId,
_nextRenderTree.GetFrames(),
CurrentRenderTree.GetFrames());
batchBuilder.UpdatedComponentDiffs.Append(diff);
batchBuilder.InvalidateParameterViews();
}