HAL_VideoUpdatePointer (changes)

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Hardware Abstraction Layer

HAL entry points from RISC OS

» HAL_VideoUpdatePointer

HAL_VideoUpdatePointer

(HAL entry #46)

  void int HAL_VideoUpdatePointer(uint flags, int x, int y, const shape_t *shape)

Use

This is an internal call for OS use only and should not be used by user software. User software should use GraphicsV instead of interacting with the HAL directly.

shape points to shape_t descriptor block:

typedef struct shape_t
{
  uint8   width;      /* unpadded width in bytes (see notes) */
  uint8   height;     /* in pixels */
  uint8   padding[2]; /* 2 bytes of padding for field alignment */
  void   *buffLA;     /* logical address of buffer holding pixel data */
  void   *buffPA;     /* corresponding physical address of buffer */
}

Notes:

1. If flags bit 0 is 0 (pointer off), x, y, shape are undefined
2. The shape data from RISC OS is always padded with transparent pixels on the rhs, to a width of 32 pixels (8 bytes)
3. Pointer clipping is the responsibility of the HAL (eg. may be able to allow display of pointer in border region on some h/w)
4. Buffer for pixel data is aligned to a multiple of 256 bytes or better

The HAL may need to take note of the shape updated flag, and make its own new copies if true. This is to handle cases like dual scan LCD pointer, which typically needs two or more shape buffers for the hardware, or possibly to handle clipping properly. This work should only be done when the updated flag is true.

A simple HAL, where hardware permits, can use the shape data in the buffer directly, ignoring the updated flag. The OS guarantees that the buffer data is valid for the whole time it is to be displayed.

See also

• HAL Video API

Information source: Kernel.Docs.HAL.HAL_API in CVS