/// <summary>
/// This is used to redraw only once instead of on every property change.
/// </summary>
internal void ScheduleRedraw()
{
if (!_redrawPending) // This ensures that the "BeginInvoke" method is only called once, and it is not called again until its delegate has been executed.
{
if (_isLoaded)
{
_redrawPending = true;
// We use a dispatcher to avoid redrawing every time that a dependency property is set
// (the result is as if we waited for the last property to be set). We use "INTERNAL_DispatcherHelpers.QueueAction"
// instead of "Dispatcher.BeginInvoke" because it has better performance than calling Dispatcher.BeginInvoke directly.
INTERNAL_DispatcherHelpers.QueueAction(() =>
{
_redrawPending = false;
// We check whether the Shape is visible in the HTML DOM tree, because if the HTML canvas is hidden
// (due to a "Dispay:none" on one of the ancestors), we cannot draw on it
// (this can be seen by hiding a canvas, drawing, and then showing it: it will appear empty):
if (INTERNAL_VisibilityChangedNotifier.IsElementVisible(this))
{
Redraw();
}
else
{
_redrawWhenBecomeVisible = true;
}
});
}
}
}
void ScheduleRefresh()
{
if (!_refreshPending) // This ensures that the "BeginInvoke" method is only called once, and it is not called again until its delegate has been executed.
{
_refreshPending = true;
INTERNAL_DispatcherHelpers.QueueAction(() => // We use a dispatcher to avoid refreshing every time (the result is as if we waited for the last change to be done before the thread is free). We use "INTERNAL_DispatcherHelpers.QueueAction" instead of "Dispatcher.BeginInvoke" because it has better performance than calling Dispatcher.BeginInvoke directly.
{
_refreshPending = false;
Refresh();
});
}
}
/// <summary>
/// This is used to redraw only once instead of on every property change.
/// </summary>
internal void ScheduleRedraw()
{
if (!_redrawPending) // This ensures that the "BeginInvoke" method is only called once, and it is not called again until its delegate has been executed.
{
if (INTERNAL_VisualTreeManager.IsElementInVisualTree(this))
{
_redrawPending = true;
INTERNAL_DispatcherHelpers.QueueAction(() => // We use a dispatcher to avoid redrawing every time that a dependency property is set (the result is as if we waited for the last property to be set). We use "INTERNAL_DispatcherHelpers.QueueAction" instead of "Dispatcher.BeginInvoke" because it has better performance than calling Dispatcher.BeginInvoke directly.
{
_redrawPending = false;
// We check whether the Shape is visible in the HTML DOM tree, because if the HTML canvas is hidden (due to a "Dispay:none" on one of the ancestors), we cannot draw on it (this can be seen by hiding a canvas, drawing, and then showing it: it will appear empty):
if (INTERNAL_VisibilityChangedNotifier.IsElementVisible(this))
{
Redraw();
// Stop listening to the ancestors' Visibility_Changed, if it was listening:
if (_isListeningToAncestorsVisibilityChanged)
{
INTERNAL_VisibilityChangedNotifier.StopListeningToAncestorsVisibilityChanged(this);
}
_isListeningToAncestorsVisibilityChanged = false;
}
else
{
// We listen to the Visibility_Changed event of the ancestors so as try again if a parent becomes visible:
if (!_isListeningToAncestorsVisibilityChanged)
{
_isListeningToAncestorsVisibilityChanged = true;
INTERNAL_VisibilityChangedNotifier.StartListeningToAncestorsVisibilityChanged(this,
() =>
{
// Stop listening to the ancestors' Visibility_Changed:
if (_isListeningToAncestorsVisibilityChanged)
{
INTERNAL_VisibilityChangedNotifier.StopListeningToAncestorsVisibilityChanged(this);
}
_isListeningToAncestorsVisibilityChanged = false;
// Try again:
ScheduleRedraw();
});
}
}
});
}
}
}
