API Reference


Brew Release
Brew MP 1.0.2
ScrollTC is an implementation of IController that can be used by ScrollbarWidget and ScrollIndicatorWidget to handle pointer events provided to the widget by BREW.

ScrollTC handles BREW pointer events for these widgets and responds by

    - Sending scroll events to the child widget
        ScrollTC sends EVT_WDG_SCROLL to the widget it decorates, with different 
        wParam and dwParam based on the location of the pointer events.
        For example, when the pointer event is located on scroll arrows, the 
        corresponding parameter for EVT_WDG_SCROLL is WSCROLL_LEFT or WSCROLL_RIGHT 
        for a horizontal scrollbar while WSCROLL_UP or WSCROLL_DOWN for a vertical 
        scrollbar. (Similar parameters are used for ScrollIndicator Widget). 
        If the pointer event is for the scrollbar handle, then on EVT_POINTER_DOWN, 
        ScrollTC sets capture mode on and starts a drag operation. Subsequent pointer 
        move events result in EVT_WDG_SCROLL sent to the child widget with wParam 
        being WSCROLL_VPOSITION (for vertical scrollbar) or WSCROLL_HPOSITION ( for 
        horizontal scrollbar). The capture mode gets released on EVT_POINTER_UP.
        If the pointer event is located between the scrollbar handle and arrows(but
        within scrollbar), then ScrollTC starts sending EVT_WDG_SCROLL with wParam
        being WETYPE_SCROLL_PAGExx. In this case as well, on EVT_POINTER_DOWN,
        the capture mode is set on.
        ScrollTC also keeps an internal timer to repeat these scroll events when
        clicked on arrows on region between the handle and the arrows.
        When pointer events happen in the content region of the scrollbar, then
        the events are propogated to the child widget.
        Note that ScrollTC itself can not handle the scrolling by itself. It 
        needs to co-ordinate this with the child widget.  As explained above, 
        ScrollTC sends EVT_WDG_SCROLL events to the child widget which in turn
        has to respond to these events and change its view correspondingly. This
        re-layout from the childwidget will result in a viewmodel notification
        that ScrollbarWidget listens to, causing its own view to be updated.
        Thus, its ChildWidget's responsibility to respond to the scroll event
        based in wParam and dwParam specified in the event.
    - Setting the element states
        Apart from sending EVT_WDG_SCROLL events to the child widget, ScrollTC
        also sets element states for the elements of the ScrollWidget by calling
        IWIDGET_SetElementState(). On EVT_POINTER_DOWN, it sets the element state 
        to WESTATE_PRESSED for the element located by pointer event ( e.g. 
        WETYPE_LEFT_ARROW). On EVT_POINTER_UP, the state is reset to WESTATE_NORMAL.

Using ScrollTC from your application:
Applications do not need to deal with ScrollTC directly if they want to have the default behavior as described above. If the application needs to customize the behavior of this touch controller, it can do so by overriding handler for the touchcontroller.
If the application wants to have a custom scrolling behavior - then it should set a hander on the CHILD WIDGET that is decorated by ScrollWidget and handle EVT_WDG_SCROLL. The wParam and dwParam will determine the direction and amount by which to scroll.
Note that ListWidget, TextWidget , Viewport widget and HTMLWidget provided with BUIW respond to EVT_WDG_SCROLL events and no special handling is required for these widgets.
The scroll touch controller is instantiated by passing AEECLSID_ScrollTC into ISHELL_CreateInstance.
The scroll touch controller is reference counted. When you are done with your reference to the scroll touch controller, you should Release that reference. Any scroll touch controller specific cleanup will be handled for you when all references are released.
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