class HT_Update

class HT_Update_Status

HT_Update_Status is an abstract base class defining the interface to support update progress or cancel functionality. It provides a mechanism to monitor the progress of potentially lengthy update() operations and to cancel update(), if necessary to save time.

See Also

For more information, see the virtual function update in the section, "Life Cycle of a Driver," chapter 2, "Heidi Architecture," and HT_Renderer::update.

Synopsis

class HT_Update_Status {

    public:

        virtual void        request_cancel (void) = 0;
        virtual HT_Boolean  cancel_requested (void) = 0;
        virtual int         percentage (void) = 0;
        virtual void        set_percentage (int percent) = 0;
};

Details
No mechanism is provided for the draw calls. It is assumed that each draw call will be relatively short¾precluding the need for cancel. Also, within the draw call, there is no notion of "overall" progress.

The application subclasses off of HT_Update_Status to create "real" update objects. Following is an example class defined for testing:

class My_Update_Status : public HT_Update_Status {
    private:
        HT_Boolean  m_cancel;
        int         m_percentage;

    public:
        My_Update_Status (void) : m_cancel (HK_False), m_percentage (0) {}
        void        request_cancel (void) {m_cancel = HK_False;}
        HT_Boolean  cancel_requested (void) {return m_cancel;}
        int         percentage (void) {return m_percentage;}
        void        set_percentage (int percentage) {m_percentage = percentage;}
};

Currently, only the EOV (elimination of overlapping vectors) renderer supports the update status interface. The update object gets passed to the EOV renderer as a configuration parameter as exemplified in the following code snippets from ad hoc testing:

    pUS = new My_Update_Status ();
        ....

    // get the EOV renderer going
    m_render = (*mx_render) (m_device);
    HD_Assert (m_render != null);
    m_render.set_configure ("Process Diagonals", HT_Option_Value(HK_True));
    m_render.set_configure ("Update Monitor", HT_Option_Value((void *) pUS));

    m_render.establish ();

The EOV renderer update() checks for a cancel request and updates progress approximately every second.