Class TInputListener

Container sizes.

Warning: this symbol is deprecated: better override VisibleChange and watch for chCursor in Changes

Called when Cursor changed. In TCastleUserInterface class, just calls OnCursorChange.

Handle press or release of a key, mouse button or mouse wheel. Return True if the event was somehow handled, which prevents from passing this event to other UI controls.

When implementing in descendants it is best to override it like this:

function TMyControl.Press(const Event: TInputPressRelease): boolean;
begin
  Result := inherited;
  if Result then Exit; // exit if ancestor already handled event

  if Event.IsKey(keyEnter) then
  begin
    // do something in reaction on Enter
    Exit(ExclusiveEvents); // ExclusiveEvents is true by default
  end;

  if Event.IsMouseButton(buttonLeft) then
  begin
    // do something in reaction on Enter
    Exit(ExclusiveEvents); // ExclusiveEvents is true by default
  end;
end;

Note that releasing of the mouse wheel is not implemented for now, neither by CastleWindow or Lazarus CastleControl.

The events PreviewPress and PreviewRelease are passed first to the parent control, before children have a chance to process this event. Overriding them makes sense if you draw something in TCastleUserInterface.RenderOverChildren.

The events Press and Release are passed to the parent only after the children had a chance to process this event. Overriding them makes sense if you draw something in TCastleUserInterface.Render. This is usually more natural, and adviced.

Motion of mouse or touch.

Rotation detected by sensor. Used for example by 3Dconnexion devices or touch controls.

Parameters

X

X axis (tilt forward/backwards)

Y

Y axis (rotate)

Z

Z axis (tilt sidewards)

Angle

Angle of rotation (in radians)

SecondsPassed

The time passed since last SensorRotation call. This is necessary because some sensors, e.g. 3Dconnexion, may *not* reported as often as normal Update calls.

Translation detected by sensor. Used for example by 3Dconnexion devices or touch controls.

Parameters

X

X axis (move left/right)

Y

Y axis (move up/down)

Z

Z axis (move forward/backwards)

Length

Length of the vector consisting of the above

SecondsPassed

The time passed since last SensorRotation call. This is necessary because some sensors, e.g. 3Dconnexion, may *not* reported as often as normal Update calls.

Axis movement detected by joystick

Parameters

JoyID

ID of joystick with pressed button

Axis

Number of moved axis

Joystick button pressed.

Parameters

JoyID

ID of joystick with pressed button

Button

Number of pressed button

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
    Transform.Position := Transform.Position + Vector3(SecondsPassed * 10, 0, 0);
  HandleInput := not ExclusiveEvents;
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 := not ExclusiveEvents. As ExclusiveEvents is True in normal circumstances, 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.GetExists) 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.

Parameters

SecondsPassed

Should be calculated like TFramesPerSecond.SecondsPassed, and usually it's in fact just taken from TCastleWindowBase.Fps.SecondsPassed.

Called always when something important inside this control (or it's children) changed. To be more precise, this is called when something mentioned among the TCastleUserInterfaceChange enumerated items changed.

This is always called with Changes <> [] (non-empty set).

Warning: this symbol is deprecated: use VisibleChange overload with (TCastleUserInterfaceChanges,boolean) parameters

Allow window containing this control to suspend waiting for user input. Typically you want to override this to return False when you do something in the overridden Update method.

In this class, this simply returns always True.

See also

TCastleWindowBase.AllowSuspendForInput

Is it allowed to suspend (for an indefinite amount of time) waiting for user input.

Event called when the container (component or window with OpenGL context) size changes.

You can resize/reposition your component here, for example set TCastleUserInterface.Left or TCastleUserInterface.Bottom, to react to parent size changes. This is called only when the OpenGL context of the container is initialized, so you can be sure that this is called only between GLContextOpen and GLContextClose.

We also call this once when inserting into the controls list (like TCastleWindowBase.Controls or TCastleControlBase.Controls or inside parent TCastleUserInterface), if inserting into the container/parent with already initialized OpenGL context. If inserting into the container/parent without OpenGL context initialized, it will be called later, when OpenGL context will get initialized, right after GLContextOpen.

In other words, this is always called to let the control know the size of the container, if and only if the OpenGL context is initialized.

Warning: this symbol is deprecated: use Resize

Called always when something important inside this control (or it's children) changed. See VisibleChange for details about when and how this is called.

Be careful when handling this event. Various changes may cause this, so be prepared to handle it at any moment, even in the middle when UI control is changing. It may also occur very often. It's usually safest to only set a boolean flag like "something should be recalculated" when this event happens, and do the actual recalculation later.

Container of this control. When adding control to container's Controls list (like TCastleWindowBase.Controls) container will automatically set itself here, and when removing from container this will be changed back to Nil.

May be Nil if this control is not yet inserted into any container.

Warning: this symbol is deprecated: use OnVisibleChange (or override VisibleChange) and watch for Changes that include chCursor

Event called when the Cursor property changes. This event is, in normal circumstances, used by the Container, so you should not use it in your own programs.

Should we disable further mouse / keys handling for events that we already handled in this control. If True, then our events will return True for mouse and key events handled.

This means that events will not be simultaneously handled by both this control and some other (or camera or normal window callbacks), which is usually more sensible, but sometimes somewhat limiting.

Mouse cursor over this control. When user moves mouse over the Container, the currently focused (topmost under the cursor) control determines the mouse cursor look.

Event that occurs continuously on each control. See Update for details.

An input (key, mouse button, mouse wheel) was pressed. See Press for details.

An input (key, mouse button, mouse wheel) was released. See Release for details.

Pointer (mouse or finger) moved. See Motion for details.