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This item has no description. Showing description inherited from TCastleUserInterface.Update.
Control may do here anything that must be continuously repeated. E.g. camera handles here falling down due to gravity, rotating model in Examine mode, and many more.
This method may be used, among many other things, to continuously react to the fact that user pressed some key (or mouse button). For example, if holding some key should move some 3D object, you should do something like:
if HandleInput then
begin
if Container.Pressed[keyArrowRight] then
begin
Transform.Position := Transform.Position + Vector3(SecondsPassed * 10, 0, 0);
HandleInput := false;
end;
end;
Instead of directly using a key code, consider also using TInputShortcut that makes the input key nicely configurable. See engine tutorial about handling inputs.
Multiplying movement by SecondsPassed makes your operation frame-rate independent. Object will move by 10 units in a second, regardless of how many FPS your game has.
The code related to HandleInput is important if you write a generally-useful control that should nicely cooperate with all other controls, even when placed on top of them or under them. The correct approach is to only look at pressed keys/mouse buttons if HandleInput is True. Moreover, if you did check that HandleInput is True, and you did actually handle some keys, then you have to set HandleInput := false. This will prevent the other controls (behind the current control) from handling the keys (they will get HandleInput = False). And this is important to avoid doubly-processing the same key press, e.g. if two controls react to the same key, only the one on top should process it.
Note that to handle a single press / release (like "switch light on when pressing a key") you should rather use Press and Release methods. Use this method only for continuous handling (like "holding this key makes the light brighter and brighter").
To understand why such HandleInput approach is needed, realize that the "Update" events are called differently than simple mouse and key events like "Press" and "Release". "Press" and "Release" events return whether the event was somehow "handled", and the container passes them only to the controls under the mouse (decided by TCastleUserInterface.CapturesEventsAtPosition). And as soon as some control says it "handled" the event, other controls (even if under the mouse) will not receive the event.
This approach is not suitable for Update events. Some controls need to do the Update job all the time, regardless of whether the control is under the mouse and regardless of what other controls already did. So all controls (well, all controls that exist, in case of TCastleUserInterface, see TCastleUserInterface.Exists) receive Update calls.
So the "handled" status is passed through HandleInput. If a control is not under the mouse, it will receive HandleInput = False. If a control is under the mouse, it will receive HandleInput = True as long as no other control on top of it didn't already change it to False.
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