+Namespaces are important
++ The handle & body classes should have the same name but in different namespaces
++ TypeRegistry relies on this convention
++ Here our custom control requires
+ + MyControl
+ + Internal::MyControl
+
### General Guidelines:
+ Try to avoid adding C++ APIs as they become difficult to maintain.
+ Use **properties** as much as possible as Controls should be data driven.
+ These controls will be used through JavaScript and JSON files so need to be compatible.
-+ Bear in mind that the Control is required to update when the properties change, not just the first time they are set (to deal with style change).
++ Bear in mind that the Control can be updated when the properties change (e.g. style change)
+ + Ensure control deals with these property changes gracefully
+ + Not just the first time they are set
++ Use Visuals rather than creating several child Actors
+ + DALi rendering pipeline more efficient
+ Accessibility actions should be considered when designing the Control.
+ Consider using signals if the application needs to be react to changes in the control state.
++ Use of Gestures should be preferred over analysing raw touch events
++ Check if you need to chain up to base class if overriding certain methods
___________________________________________________________________________________________________
// C++
void MyUIControlImpl::OnInitialize()
{
- // Create visuals, register events etc.
+ // Create visuals using the VisualFactory, register events etc.
+ // Register any created visuals with Control base class
}
~~~
___________________________________________________________________________________________________
Dali::Toolkit::Internal::Control provides several behaviours which are specified through its constructor (@ref Dali::Toolkit::Internal::Control::Control()).
-| Behaviour | Description |
-|--------------------------------------|-------------------------------------------------------------------------|
-| ACTOR_BEHAVIOUR_NONE | No behaviour required. |
-| REQUIRES_HOVER_EVENTS | If our control requires [hover events](@ref creating-controls-events). |
-| REQUIRES_WHEEL_EVENTS | If our control requires [wheel events](@ref creating-controls-events). |
-| REQUIRES_STYLE_CHANGE_SIGNALS | True if need to monitor style change signals such as Theme/Font change. |
-| REQUIRES_KEYBOARD_NAVIGATION_SUPPORT | True if need to support keyboard navigation. |
+| Behaviour | Description |
+|--------------------------------------|----------------------------------------------------------------------------------------------------------------|
+| CONTROL_BEHAVIOUR_DEFAULT | Default behavior (size negotiation is on, style change is monitored, event callbacks are not called. |
+| DISABLE_SIZE_NEGOTIATION | If our control does not need size negotiation, i.e. control will be skipped by the size negotiation algorithm. |
+| REQUIRES_HOVER_EVENTS | If our control requires [hover events](@ref creating-controls-events). |
+| REQUIRES_WHEEL_EVENTS | If our control requires [wheel events](@ref creating-controls-events). |
+| DISABLE_STYLE_CHANGE_SIGNALS | True if control should not monitor style change signals such as Theme/Font change. |
+| REQUIRES_KEYBOARD_NAVIGATION_SUPPORT | True if need to support keyboard navigation. |
___________________________________________________________________________________________________
### Touch, Hover & Wheel Events {#creating-controls-events}
___________________________________________________________________________________________________
-### Size {#creating-controls-size}
+### Size Negotiation {#creating-controls-size-negotiation}
-Methods are provided that can be overridden if notification is required when our control's size is manipulated.
-An up call to the Control class is necessary if these methods are overridden.
+The following methods must be overridden for size negotiation to work correctly with a custom control.
~~~{.cpp}
// C++
-void MyUIControlImpl::OnSizeSet( const Vector3& targetSize )
+Vector3 MyUIControlImpl::GetNaturalSize()
+{
+ // Return the natural size of the control
+ // This depends on our layout
+ // If we have one visual, then we can return the natural size of that
+ // If we have more visuals, then we need to calculate their positions within our control and work out the overall size we would like our control to be
+
+ // After working out the natural size of visuals that belong to this control,
+ // should also chain up to ensure other visuals belonging to the base class are
+ // also taken into account:
+ Vector2 baseSize = Control::GetNaturalSize(); // returns the size of the background.
+}
+~~~
+~~~{.cpp}
+// C++
+float MyUIControlImpl::GetHeightForWidth( float width )
{
- // Up call to Control
- Control::OnSizeSet( targetSize );
+ // Called by the size negotiation algorithm if we have a fixed width
+ // We should calculate the height we would like our control to be for that width
+
+ // Should also chain up to determine the base class's preferred height:
+ float baseHeight = Control::GetHeightForWidth( width );
- // Do any other operations required upon size set
}
~~~
~~~{.cpp}
// C++
-void MyUIControlImpl::OnSizeAnimation( Animation& animation, const Vector3& targetSize )
+float MyUIControlImpl::GetWidthForHeight( float height )
{
- // Up call to Control
- Control::OnSizeAnimation( animation, targetSize );
+ // Called by the size negotiation algorithm if we have a fixed height
+ // We should calculate the width we would like our control to be for that height
- // Do any other operations required upon size animation
+ // Should also chain up to determine the base class's preferred width:
+ float baseWidth = Control::GetWidth( height );
+}
+~~~
+~~~{.cpp}
+// C++
+void MyUIControlImpl::OnRelayout( const Vector2& size, RelayoutContainer& container )
+{
+ // The size is what we have been given and what our control needs to fit into
+ // Here, we need to set the position and the size of our visuals
+ // If we have other controls/actors as children
+ // - Add the control/actor to the container paired with the size required
+ // - To ensure this works, you need to set up the control with a relayout policy of USE_ASSIGNED_SIZE
+ // - DO NOT CALL SetSize on this control: This will trigger another size negotiation calculation
+ // DO NOT chain up to base class.
}
~~~
+More information on size negotiation can be found [here](@ref size-negotiation-controls).
___________________________________________________________________________________________________
projects / platform / core / uifw / dali-toolkit.git / blobdiff