internal void Push(IScreen source, IScreen newScreen)
{
if (stack.Contains(newScreen))
{
throw new ScreenAlreadyEnteredException();
}
if (source == null && stack.Count > 0)
{
throw new InvalidOperationException($"A source must be provided when pushing to a non-empty {nameof(ScreenStack)}");
}
if (newScreen.AsDrawable().RemoveWhenNotAlive)
{
throw new ScreenWillBeRemovedOnPushException(newScreen.GetType());
}
// Suspend the current screen, if there is one
if (source != null && source != stack.Peek())
{
throw new ScreenNotCurrentException(nameof(Push));
}
var newScreenDrawable = newScreen.AsDrawable();
if (newScreenDrawable.IsLoaded)
{
throw new InvalidOperationException("A screen should not be loaded before being pushed.");
}
if (suspendImmediately)
{
suspend(source, newScreen);
}
stack.Push(newScreen);
ScreenPushed?.Invoke(source, newScreen);
// this needs to be queued here before the load is begun so it preceed any potential OnSuspending event (also attached to OnLoadComplete).
newScreenDrawable.OnLoadComplete += _ => newScreen.OnEntering(new ScreenTransitionEvent(source, newScreen));
if (source == null)
{
// this is the first screen to be loaded.
if (LoadState >= LoadState.Ready)
{
LoadScreen(this, newScreenDrawable, () => finishPush(null, newScreen));
}
else
{
log($"scheduling push {getTypeString(newScreen)}");
Schedule(() => finishPush(null, newScreen));
}
}
else
{
LoadScreen((CompositeDrawable)source, newScreenDrawable, () => finishPush(source, newScreen));
}
}
internal void Push(IScreen source, IScreen newScreen)
{
if (stack.Contains(newScreen))
{
throw new ScreenAlreadyEnteredException();
}
if (source == null && stack.Count > 0)
{
throw new InvalidOperationException($"A source must be provided when pushing to a non-empty {nameof(ScreenStack)}");
}
if (newScreen.AsDrawable().RemoveWhenNotAlive)
{
throw new ScreenWillBeRemovedOnPushException(newScreen.GetType());
}
// Suspend the current screen, if there is one
if (source != null)
{
if (source != stack.Peek())
{
throw new ScreenNotCurrentException(nameof(Push));
}
source.OnSuspending(newScreen);
source.AsDrawable().Expire();
}
// Push the new screen
stack.Push(newScreen);
ScreenPushed?.Invoke(source, newScreen);
void finishLoad()
{
if (!newScreen.ValidForPush)
{
exitFrom(null);
return;
}
AddInternal(newScreen.AsDrawable());
newScreen.OnEntering(source);
}
if (source != null)
{
LoadScreen((CompositeDrawable)source, newScreen.AsDrawable(), finishLoad);
}
else if (LoadState >= LoadState.Ready)
{
LoadScreen(this, newScreen.AsDrawable(), finishLoad);
}
else
{
Schedule(finishLoad);
}
}
internal void Push(IScreen source, IScreen newScreen)
{
if (stack.Contains(newScreen))
{
throw new ScreenAlreadyEnteredException();
}
if (source == null && stack.Count > 0)
{
throw new InvalidOperationException($"A source must be provided when pushing to a non-empty {nameof(ScreenStack)}");
}
if (newScreen.AsDrawable().RemoveWhenNotAlive)
{
throw new ScreenWillBeRemovedOnPushException(newScreen.GetType());
}
// Suspend the current screen, if there is one
if (source != null && source != stack.Peek())
{
throw new ScreenNotCurrentException(nameof(Push));
}
if (suspendImmediately)
{
suspend(source, newScreen);
}
stack.Push(newScreen);
ScreenPushed?.Invoke(source, newScreen);
var newScreenDrawable = newScreen.AsDrawable();
if (source == null)
{
// this is the first screen to be loaded.
if (LoadState >= LoadState.Ready)
{
LoadScreen(this, newScreenDrawable, () => finishPush(null, newScreen));
}
else
{
Schedule(() => finishPush(null, newScreen));
}
}
else
{
LoadScreen((CompositeDrawable)source, newScreenDrawable, () => finishPush(source, newScreen));
}
}
/// <summary>
/// Complete suspend of a screen in the stack.
/// </summary>
/// <param name="from">The screen being suspended.</param>
/// <param name="to">The screen being entered.</param>
private void suspend(IScreen from, IScreen to)
{
var sourceDrawable = from?.AsDrawable();
if (sourceDrawable == null)
{
return;
}
if (sourceDrawable.IsLoaded)
{
performSuspend();
}
else
{
// Screens only receive OnEntering() upon load completion, so OnSuspending() should be delayed until after that
sourceDrawable.OnLoadComplete += _ => performSuspend();
}
void performSuspend()
{
from.OnSuspending(to);
sourceDrawable.Expire();
}
}
private void suspend(IScreen from, IScreen to)
{
var sourceDrawable = from.AsDrawable();
if (sourceDrawable == null)
{
return;
}
if (sourceDrawable.IsLoaded)
{
performSuspend();
}
else
{
// Screens only receive OnEntering() upon load completion, so OnSuspending() should be delayed until after that
sourceDrawable.OnLoadComplete += _ => performSuspend();
}
void performSuspend()
{
log($"suspended {getTypeString(from)} (waiting on {getTypeString(to)})");
from.OnSuspending(new ScreenTransitionEvent(from, to));
sourceDrawable.Expire();
}
}
/// <summary>
/// Complete push of a loaded screen.
/// </summary>
/// <param name="from">The screen to push to.</param>
/// <param name="to">The new screen being pushed.</param>
private void push(IScreen from, IScreen to)
{
if (!suspendImmediately)
{
suspend(from, to);
}
if (!to.ValidForPush)
{
exitFrom(null, shouldFireEvent: false);
return;
}
AddInternal(to.AsDrawable());
to.OnEntering(from);
}
/// <summary>
/// Complete push of a loaded screen.
/// </summary>
/// <param name="parent">The screen to push to.</param>
/// <param name="child">The new screen being pushed.</param>
private void finishPush(IScreen parent, IScreen child)
{
if (!child.ValidForPush)
{
if (child == CurrentScreen)
{
exitFrom(null, shouldFireExitEvent: false, shouldFireResumeEvent: suspendImmediately);
}
return;
}
if (!suspendImmediately)
{
suspend(parent, child);
}
AddInternal(child.AsDrawable());
}
private void finishPush(IScreen parent, IScreen child)
{
if (!child.ValidForPush)
{
if (child == CurrentScreen)
{
exitFrom(null, shouldFireExitEvent: false, shouldFireResumeEvent: suspendImmediately);
}
log($"push of {getTypeString(child)} cancelled due to {nameof(child.ValidForPush)} becoming false");
return;
}
if (!suspendImmediately)
{
suspend(parent, child);
}
AddInternal(child.AsDrawable());
log($"entered {getTypeString(child)}");
}