With this template you can add a new Toggle Item component to your project. Toggle Item is a simple widget the user can press in order to toggle a value. It is also suitable to serve as a check box item. Each time the user interacts with the Toggle Item, the component sends signals to associated slot methods where your particular implementation is executed. If the Toggle Item is focused the component can also be controlled by pressing keys on the keyboard or by using hardware buttons. Generally menu items are used within menus only. Therefore when using a Toggle Item you will also need to add at least one Menu component to your project.

Components created with this template are intended to be adapted to your particular design expectations. After adding the new Toggle Item you should edit the component, change its appearance and if desired also its behavior. Once you have adapted the component, you can embed instances of this Toggle Item wherever you need in your GUI project. Because it serves as template, it is intentionally kept very simple. Nevertheless, Toggle Items created by the template are working widgets. If desired, they can already be used as they are. The following figure demonstrates the default appearance of the Toggle Item created by using the here described component template:

The approach with component templates has two functions. Primarily the templates should simplify the development of new components. Instead of creating the Toggle Item from scratch you can use the available template. The second function is more educative. The template implements fully working Toggle Item component you can investigate and learn about the corresponding programming aspects. The template is well documented. It contains annotations and inline comments with instructions helping you to understand how the component works and how it can be adapted to your particular needs.

This chapter provides an overview how the Toggle Item component template is used within your own application and how you adapt this component according to your particular needs. You will find here also further details concerning the internal implementation of the Toggle Item component.

To create a new Toggle Item component from a template you simply Drag & Drop it between the Templates window and the Composer with an opened unit. This is important in that by using the component templates you add in fact a new class to your project. Classes, in turn, can exist within units only. The following are the typical steps to create a new Toggle Item component from a template:

The new created Toggle Item component appears accompanied by annotation providing helpful tips how to proceed. If undesired, you can select and delete the annotation.

Once you have created the Toggle Item component, you can use it to assemble menu components. Technically seen, you embed an instance of the Toggle Item class in-place within a superior Menu GUI component. At the runtime, the superior Menu GUI component takes care of the correct initialization, arrangement and the displaying of all embedded item components.

The following are the typical steps to create a new instance of an already existing Toggle Item component:

As long as the Toggle Item is selected you can inspect and modify its properties conveniently in the Inspector window as demonstrated with the property Bounds in the screenshot below. This is in so far worth mentioning as diverse features of the Toggle Item are controlled by the corresponding properties. If you are not familiar with the concept of a property and the usage of Inspector window, please read first the preceding chapter Compositing component appearance.

The Toggle Item component descends from the Mosaic class Core::Group. Consequently, most of the properties listed in the above screenshot are inherited from this base class. Particular to the Toggle Item are only few following properties:

Property	Description
Active	The property Active stores the current state of the toggle item. As long as the property is false, the widget should appear in switched-off state. As long as the property is true, the widget should appear in switched-on state.
Caption	The property Caption stores the text to display within the item.
OnToggle	The property OnToggle can refer to a slot method, which will receive a signal as soon as the user has toggled the item. Thereupon the method's logic will be executed. In the associated slot method you can evaluate the current value of the property Active.
Outlet	The property Outlet can refer to any other bool property the item should remain synchronized with. When the user toggles the item, the affected property is automatically updated to reflect the item's current state. On the other hand, when the referred property is modified by another component, the toggle item is automatically notified to remain in sync with the property. This approach follows the Model-View-Controller (MVC) programming paradigm. Here the toggle item represents the view and controller. The property referred via Outlet can be seen as a part of the model. See also Outlet properties.

The position of the Toggle Item doesn't matter. The Menu component will automatically arrange the items within its area and if necessary enlarge or reduce their size. Moreover, the size of the menu itself is adapted to the number and to the size of the enclosed items. This layout algorithm is part of the Menu component template. Consequently, when you move an item within the menu, it does not have any effect on its final position.

However, the order in which the items will be displayed at the runtime does correspond to the order in which the item objects are stored within the menu component. This is the order in which the items have been originally added. Consequently, the first added item appears at the top of the menu while the last added item is arranged at the end of the menu. See also the column Order in the members area of the Inspector window:

While the user interacts with the Toggle Item, the component sends signals to associated slot methods. Within the slot method your particular implementation can react and process the event. If the Toggle Item is controlled by keyboard events, the item can also be toggled by using the Enter key. This is the default behavior implemented in the Toggle Item template.

The slot methods are connected to the item by simply storing them in the for this purpose available property OnToggle. The slot method connected to property OnToggle is signaled when the user has toggled (switched on or off) the item. You can initialize the property OnToggle with already existing slot methods or you add a new one and implement it as desired. The following steps describe how to do this:

When you start the Prototyper now, you can interact with the item. Thereupon the item will trigger the associated slot method.

To simplify the development of GUI applications, the Toggle Item implements a technique permitting you to connect an item directly to a data provider. Once connected, the item will remain in sync with the value stored actually in this provider. Similarly, if the user toggles the item, the associated value changes automatically. This technique corresponds to the model-view-controller (MVC) programming paradigm, where the Toggle Item has the function of the view and controller and the associated data provider serves as model. If you associate in your application several Toggle Items to one and the same data provider value, the underlying mechanisms will ensure, that after toggling one item all other affected items do update their state automatically.

The connection between the Toggle Item and the data provider is established by assigning to the Toggle Item's property Outlet a reference to a property existing within the data provider and storing the interesting value. Since Toggle Item is a bistable widget (it can assume only the states Off or On), the property suitable to be connected via reference to the item has to be declared with bool as its data type. Accordingly, the value false of the property corresponds to the state Off of the item and the value true to the state On.

Summarized, after assigning a reference to an existing bool property to the Toggle Item's own property Outlet, the item adapts its own state to automatically correspond to the actual value of the associated property. When the user toggles the item, the associated property is modified. You don't need to write a single line of code to benefit from this mechanisms. The aspects underlying this technique are explained in the sections Outlet properties and Notifications and Observer.

Component templates are intended to create widgets which can be adapted and enhanced to your particular design expectations. For this purpose, once you have added a new Toggle Item component to your project, you can open the component class for editing. Thereupon the implementation of the component appears in a new Composer page:

Originally, if not yet modified, the Toggle Item appears composed of rectangles with a caption text and a visual toggle indicator (knob). When the user interacts with the item, it changes its appearance to provide visual feedback. Our intention is to keep the component templates as minimalistic as possible so they don't distract you with less important design details. The Toggle Item can react to touch, mouse and keyboard inputs. The color and position of the knob and the border reflect the actual state of the item.

This default functionality is implemented by following members belonging to the Toggle Item. These members are explicitly intended to be modified. Understanding this internal structure is thus the first step before you start to adapt the Toggle Item to your particular needs:

Icon	Member	Description
	Caption	The property Caption stores the text to display within the item.
	OnSetCaption	The onset method belongs to the property Caption. Each time the value of the property is changed, the code implemented in the method is executed to update the caption text view and trigger layout recalculation in the owner menu.
	Active	The property Active stores the current state of the toggle item. As long as the property is false, the widget should appear in switched-off state. As long as the property is true, the widget should appear in switched-on state.
	OnSetActive	The onset method belongs to the property Active. Each time the value of the property is changed, the code implemented in the method is executed to reflect the new state in item's appearance.
	Outlet	The property Outlet can refer to any other bool property the widget should remain synchronized with. When the user toggles the item, the affected property is automatically updated to reflect the item's current state. On the other hand, when the referred property is modified by another one, the toggle item is automatically notified to remain in sync with the property. This approach follows the model-view-controller (MVC) programming paradigm, where the Toggle Item has the function of the view and controller and the property referred via Outlet serves as model. See also Outlet properties.
	OnSetOutlet	The onset method belongs to the property Outlet. Each time a new property reference is assigned to Outlet, the code implemented in the method is executed to register the item as observer for the referred property.
	OnToggle	The property OnToggle can refer to a slot method, which will receive a signal as soon as the user has toggled the item. Wherever an instance of the Toggle Item is used, you can assign a slot method to this property. Thereupon the method's logic will be executed. In the associated slot method you can evaluate the current value of the property Active.
	onPressTouch	This internal slot method is called when the user touches the item's toggle area (when the interaction begins). This slot method is connected to the member TouchHandler. The method focuses the item and handles the feedback flash effect.
	onReleaseTouch	This internal slot method is called when the user releases the touch screen after touching the item's toggle area (when the interaction ends). This slot method is connected to the member TouchHandler. The method toggles the item if the touch ended inside the toggle area.
	onEnterLeaveTouch	This internal slot method is called when the user drags the finger/mouse while pressing the toggle area and enters or leaves the area. The method updates the item's appearance to show pressed or released state.
	KeyHandler	This key handler reacts to key press events. When the user presses the key specified in the property Filter of the key handler (per default Enter), the handler is activated and the method onPressKey is called.
	onPressKey	This internal slot method is called when the KeyHandler has been activated (when the user has pressed the Enter key). Thereupon, the method flashes the item briefly and toggles it.
	FlashTimer	This Timer object is used to flash the item when the user has tapped it very quickly or the item has been toggled with the keyboard. This is just a visual feedback effect. The timer's Begin property defines the flash duration (50 milliseconds per default).
	onFlashTimer	This internal slot method is called when the FlashTimer expires. The method ends the flash feedback effect and toggles the item by sending a signal to the slot method stored in the property OnToggle.
	onOutlet	This internal slot method will receive a signal, if the value of the property referred by Outlet has been changed by another widget or by the application logic. In response to this notification, the Toggle Item will update its own Active property to reflect the new value of the referred property.
	Background	This Filled Rectangle view displays in the template the background of the item. The background is white per default.
	Border	This Border view displays in the template the border of the item. The border appears only when the item is selected (focused) or pressed. Depending on the item's actual state variables enabled, selected and pressed the border's visibility and color changes.
	CaptionText	This Text view displays the caption text of the item. The text content is determined by the property Caption. Depending on the item's actual state, the text color changes. The text view is configured with ellipsis mode to truncate long text with [...] sign.
	KnobBorder	This Border view displays in the template the border around the toggle knob area. It visually separates the toggle control from the caption text.
	Knob	This Filled Rectangle view represents the toggle indicator (knob). Depending on the item's actual state variables enabled, pressed and checked the rectangle moves left or right and its color changes between red and green to indicate the off/on state.
	TouchHandler	This Simple Touch Handler reacts to touch and mouse events within the toggle area and invokes the associated slot methods: onPressTouch, onReleaseTouch and onEnterLeaveTouch. Note that the touch handler covers only the toggle knob area, not the entire item.
	UpdateViewState	This method is invoked automatically after the state of the component has been changed. In case of the Toggle Item, the method updates the views Background, Border, CaptionText, Knob and KnobBorder so they reflect the item's current state.
	GetMinimalSize	This method is invoked by the owner menu to determine the minimum width required by this item. The method calculates the width based on the caption text length plus the toggle knob area width plus margins. This information is used by the menu for automatic size adjustment.
	enabled	This variable stores the current state of the item. It is true if the item is allowed to handle user inputs (the component is enabled). See also Control the Enabled state of nested components. If the item is actually disabled, the variable is consequently false.
	selected	This variable stores the current state of the item. It is true if the item is actually focused for keyboard inputs (more precisely, the item is selected within its owner menu component). The user can thereupon control the item via keyboard.
	pressed	This variable stores the current state of the item. It is true if the item should appear pressed. This is usually the case when the user touches the toggle area actively or presses a key intended to toggle the item (the user is pressing the item or the flash effect is active).
	checked	This variable stores the current state of the item. It is true if the item is actually in the On state and false if it is in the Off state.

During its lifetime, the Toggle Item will assume different states as direct effect of user interactions and as result of other superior state alternations within the GUI application. To track its current state the Toggle Item manages the above mentioned state variables: enabled, selected, pressed and checked. The variables are evaluated and updated within the implementation of the method UpdateViewState. This method evaluates the common component states (Enabled and Selected) and verifies whether the user is actually interacting with the item via touch screen or keyboard (the user is pressing the item) and whether the item is in its on or off state. At the end of the method the estimated states are stored in the state variables:

For example, the local variable isPressed will become true if the user is actually touching within the toggle area of the item AND the finger/mouse is still inside this area (the variables Down and Inside of the TouchHandler are both true) or the feedback flash timer is active (the variable Enabled of the FlashTimer is true). Being in this state, the item should assume the appearance indicating that the user is actively pressing it.

The variable isChecked reflects the actual On or Off state of the toggle item by evaluating the property Active. This allows the item to display different visual representations (e.g., knob position, knob color) depending on whether it is switched on or off.

When common component states (Enabled or Selected) have changed, the method UpdateViewState is invoked automatically. You don't need to worry about it. Any other state alternations need to explicitly request an invocation of the UpdateViewState method. This is especially true for state alternations caused by touch handlers, keyboard handlers or timer objects. When you modify the Toggle Item to handle other user inputs or perform other animations always ensure that each state alternation (each event) does request an invocation of UpdateViewState. In your implementation you use for this purpose the method InvalidateViewState.

For example, the slot method onEnterLeaveTouch is associated to the TouchHandler and it is invoked when the user drags the finger while touching the toggle area and enters or leaves this area. In response to this, the pressed state of the item might change. The method onEnterLeaveTouch requests thus the invocation of UpdateViewState:

Depending on your design expectations the default state management may require adaptations. Generally, you are free to modify the method UpdateViewState, add further state variables to your Toggle Item or even remove the existing functionality if it is not needed in your case.

For example, the default implementation of the Toggle Item template manages the state selected. This state indicates that the item is actually selected within the superior menu. The item could thus receive keyboard events. However, whether the item is really able to receive events does depend on the selection status of its owner menu and all other superior components. Only when the item lies on the focus path, the item will receive keyboard events. If your application case requires the item to distinguish this additional state, you can add a variable focused similar to the approach described in the Horizontal Slider template.

Originally, if not yet modified, the Toggle Item appears composed of rectangles with a caption text and a toggle indicator (knob). Our intention is to keep the component templates as minimalistic as possible so they don't distract you with less important design details. It's up to you to adapt the item to have the expected appearance. The available possibilities are explained in the following sections. Please note, that you can combine the different approaches according to your application case:

The Toggle Item template contains per default the views Background, Border, CaptionText, KnobBorder and Knob. If desired, you can modify the views. For example, you can display them with other colors depending on the actual state of the item. For this purpose you change the implementation of the above explained method UpdateViewState responsible for tracking the state alternations within the Toggle Item.

When you open the method UpdateViewState you will see that it does not only update the state variables but also updates the views existing within the component. Accordingly, depending on the actual state of the item the views Background, Border, CaptionText and Knob are displayed with different colors and the border's visibility changes. Furthermore, the position of the view Knob changes according to whether the item is actually in Off or On state. By simply modifying this implementation you change the appearance. For example, you change the knob color from green to blue when the item is in On position:

If not needed, you can delete the per default existing views Background, Border, CaptionText, KnobBorder or Knob. Doing this, please don't forget to also remove all references to the deleted views from the implementation of the UpdateViewState and GetMinimalSize method. Otherwise you will get error messages next time the Composer contents is reloaded. To avoid this error message we recommend to perform the steps in following order:

You can add further views to your Toggle Item. For example, you can add an Image view to display an icon within the item. Or you add additional decoration elements like status indicators or separators. The appearance of the views (e.g. colors) can be fixed, predetermined at the design time. Or it can change according to the actual state of the item. Following steps explain the workflow:

Also possible, you can replace the existing views by other views. For example, in the original version, the Toggle Item displays the knob as an ordinary filled rectangle. To make the component more sophisticated, you could replace the here used Filled Rectangle view by e.g. Image view showing different bitmaps for on/off states. For this purpose:

The initial size of the Toggle Item is determined by the thick blue border surrounding the Canvas area. It corresponds to the default size that all instances of this Toggle Item component will have. However, when toggle items are embedded within a menu, the Menu component will automatically adjust the size of items according to:

If desired, you can adjust the Canvas area of the item component itself. This affects the default height and visual proportions of the item during editing. For this purpose you click and drag the edges of the surrounding border (see also Resize the Canvas area). Once the size is changed, you can then adapt (move, resize) the views existing within the component.

The views existing per default in the Toggle Item template (Background, Border and CaptionText) are configured to automatically adjust to fill the area of the item. The KnobBorder, Knob and TouchHandler are configured to remain aligned at the right edge of the item. All other views you have eventually added later to the Toggle Item are not adjusted automatically.

To control the adjustment you have to explicitly configure for each view its Layout property. (see also Configure component layout). Let's assume, in order to display an icon you have added an Image view to the Toggle Item. Then you have arranged the view within the Canvas area according to your design expectation. If you want now that the view is centered vertically and remains aligned at the left side when the item width changes, you enable in the property Layout of this view following settings:

When creating your own Toggle Item component you should ensure that instances of the item can be configured to control all the features implemented in it. For example, if you have enhanced the item to display some icon, you should allow this icon to be specified individually for each item instance. In this way several item instances can exist at the same time, each displaying another icon.

To control the features in your item you use properties. A property can be understood as variable where the corresponding setting is stored, e.g. the icon bitmap to display in the item. When the value of the property changes, the item can react to it and update its appearance accordingly. The properties reflect thus the settings within your item. Together they form the interface of the component.

Usually, each particular setting within a component is represented by the corresponding property. Thus, an item where icon and text color can be configured will require two properties: one for the icon and one for the color. In its original version, the Toggle Item contains already four properties Caption, Active, Outlet and OnToggle. These allow the item instance to display text, control and reflect its toggle state, synchronize with data providers, and execute custom logic when toggled. In order to enhance this interface by your own properties, following steps are necessary:

That is all. Now when you deal with instances of the Toggle Item component, you can evaluate and modify the properties similarly to how you access variables. Especially, when the item instance is selected, you see in Inspector window the property and can change it there. The modification is immediately visible in the Composer window.

If desired, the properties can also be modified at the runtime of your application. For example, the item caption can be adapted to reflect the current context or the toggle state can be changed programmatically. For this purpose you access and modify the affected property directly within Chora code:

The Toggle Item is an interactive component. It can be controlled via touch screen or by the mouse device. For this purpose the template contains the Simple Touch Handler object named TouchHandler. Per default, this handler covers only the toggle knob area on the right side of the item - this is thus the touch sensitive area. To this handler are associated three slot methods: onPressTouch, onReleaseTouch and onEnterLeaveTouch. As their names imply the methods are invoked at the beginning of the interaction (press), at its end (release) and when the user drags the finger and enters or leaves the toggle area:

The methods take care of two tasks. As first they request an invocation of the UpdateViewState method if due to the performed touch (mouse) interaction the visual appearance of the item does need the update. The second task is the toggling of the item when the user successfully touches and releases within the toggle area.

The toggle item uses a feedback flash effect to provide visual feedback when the user taps the toggle area very quickly. If the user holds the finger pressed for a short moment (at least 50 milliseconds per default), the item is toggled immediately when released. If the user taps very quickly (less than 50 milliseconds), a short flash effect is shown first before the item is toggled. This ensures the user always gets visual feedback.

The slot method onPressTouch is invoked when the user touches the toggle area:

Later, when the user finalizes the touch (mouse) interaction, the item is toggled depending on whether the finger/mouse is still inside the toggle area and how long the user held the area pressed. This functionality is implemented in the slot method onReleaseTouch:

The slot method onEnterLeaveTouch is invoked when the user drags the finger while touching the toggle area and enters or leaves this area. This method is also invoked at the beginning and at the end of the touch interaction. The method simply requests a visual update to show the item as pressed or released:

Usually you will not need to edit the implementation of these methods. It corresponds already to whatever typical toggle items do. Nevertheless, you are free to change this default functionality if you want some particular behavior to be implemented in your item. For example, you can modify the flash duration by changing the Begin property of the FlashTimer object. A shorter duration (e.g. 25 milliseconds) makes the flash faster, a longer duration (e.g. 100 milliseconds) makes it slower.

Per default the TouchHandler is configured to handle all touch events within the toggle knob area. The handler is also configured to allow vertical wipe gestures (up/down) to pass through to the menu's scroll handler via its RetargetCondition property. This ensures users can scroll the menu even when starting the gesture on a toggle item. If necessary you can change this behavior and restrict the item to react only when the user performs a particular touch interaction. The TouchHandler provides for this purpose diverse configuration properties like MinStrikeCount, MaxStrikeCount, NoOfFingers or LimitToFinger. For more details, see Configure the filter condition.

If your device does not contain any touch screen nor mouse, the per default existing TouchHandler and its associated slot methods are unnecessary ballast. You can remove them in such case. We recommend to do this in following order to avoid eventual error message because of broken references between still existing and the already removed members:

The Toggle Item is an interactive component. It can be controlled via keyboard or hardware buttons. For this purpose the template contains the Key Press Handler object named KeyHandler. To this handler is associated the slot methodonPressKey. The method is thus invoked when the user presses the key matching the filter condition specified in the handler object. This is per default the Enter key:

The method takes care of toggling the item and showing the feedback flash effect. Similar to the touch handling, the method ensures that the user always gets visual feedback by showing a flash effect before toggling the item:

Usually you will not need to edit the implementation of this method. It corresponds already to whatever typical toggle items do. Nevertheless, you are free to change this default functionality if you want some particular behavior to be implemented in your item.

Per default the key handler is configured to accept the Enter key. If necessary you can change this behavior and adapt the item to react to other keys. The key handler provides for this purpose the configuration property Filter. For example, if you want the item to be toggled with the Space key, set the property Filter of the object KeyHandler to the value Core::KeyCode.Space. For more details, see Configure the filter condition.

If your device does not contain any keyboard nor hardware buttons, the per default existing key handler and its associated slot method are unnecessary ballast. You can remove them in such case. We recommend to do this in following order to avoid eventual error messages because of broken references between still existing and the already removed members:

The Toggle Item uses a feedback flash effect to provide visual feedback when the user interacts with the item very quickly. This ensures that the user always sees a visible response to their action, even for very brief taps or key presses.

The flash effect is implemented using the Timer object named FlashTimer. This timer is configured with a duration (50 milliseconds per default) that determines how long the item should appear in the pressed state:

The timer is started in two situations:

When the timer expires, the slot method onFlashTimer is called, which ends the flash effect and toggles the item:

The flash duration can be adjusted by modifying the Begin property of the FlashTimer object:

If you don't want the flash effect at all, you can simplify the touch and keyboard handling by removing the timer and directly toggling the item in the touch/keyboard handlers. However, this is not recommended as users expect visual feedback for their interactions.

The GetMinimalSize method plays a crucial role in the automatic layout system of menus. This method is called by the owner menu to determine how much horizontal space the item requires at minimum. The menu uses this information to:

The default implementation calculates the minimum width based on the caption text length, margins, and the toggle knob area width:

Please note that the calculation temporarily disables the ellipsis mode of the text view to get the full text width without truncation. This ensures that the menu knows how much space is really needed to display the complete caption.

If you have modified the item appearance by adding icons, checkmarks, or other decorations, you must adapt this method to include the additional space needed. For example, if you added an icon on the left side, take its width as well as an additional margin into account:

The Toggle Item can be connected via its property Outlet with any other bool property the widget should remain synchronized with. When the user toggles the item, the affected property is automatically updated to reflect the item's current state. On the other hand, when the referred property is modified by another one, the item is automatically notified to remain in sync with the property. This approach follows the model-view-controller (MVC) programming paradigm, where the Toggle Item has the function of the view and controller and the property referred via Outlet serves as model. See also Outlet properties.

When the state of the item changes due to a user interaction, the item updates the value of the referred property. This is, for example, the case in the slot method onReleaseTouch. The implementation found there simply assigns the actual state of the Toggle Item's Active property to the property referred via Outlet and broadcasts a notification to all other widgets connected to the same property so they also can update their state accordingly:

In order to react to alternations of the referred property (to receive notifications broadcasted by other widgets connected with the same property), the Toggle Item implements the method onOutlet. Each time the referred property is notified, this slot method is automatically invoked and following code is executed:

In order to be invoked, the method onOutlet needs to be registered with the referred property as so-called observer. The corresponding code is implemented in the onset method OnSetOutlet. Thus, just in the moment when a property reference is assigned to the Toggle Item's Outlet property, following code is executed:

In the section Adapt the appearance of the component you learned how state alternations within the Toggle Item are processed and how views existing in the component are updated in order to reflect the actual state. Accordingly, when the user touches the toggle area (starts pressing it), the item does appear pressed. When the user releases it again (ends pressing it), the item restores its released appearance. When the item is toggled, the knob position changes. The default implementation performs such appearance updates instantly, just in the moment when the respective interaction took place.

If desired, you can modify the Toggle Item to update its appearance with animations. For example, instead of instantly switching the knob position between the off and on states, such item can smoothly slide the knob with an animation effect. You could also fade-in/out colors, scale elements, or show other animated transitions. For this purpose you use the Animation Effects. With an Animation Effect you can animate a property of a view existing in the item. Following are the steps how to do this: