VideoOverlay_Create
VideoOverlay
» SWI Calls
» VideoOverlay_Create
VideoOverlay_Create
(SWI &59CC0)
| Entry | |
|---|---|
| R0 | Pointer to Mode Selector Block describing the required properties of the overlay |
| R1 | Aspect ratio to use when calculating returned min/max scale values |
| Top 16 bits = width | |
| Bottom 16 bits = height | |
| R2 | Flags |
| Bit 0: Overlay must support scaling | |
| Bits 1-31 reserved, should be zero | |
| R3 | Task handle |
| Exit | |
|---|---|
| R0 | Overlay ID |
| R1 | Flags: |
| Bits 0-7: Overlay type (0 = Z-Order, 1 = Basic, 2+ reserved) | |
| Bits 8-31: Reserved | |
| R2 | Minimum width overlay can be scaled to |
| R3 | Minimum height overlay can be scaled to |
| R4 | Maximum width overlay can be scaled to |
| R5 | Maximum height overlay can be scaled to |
| - | All other registers preserved |
Use
Creates a new overlay associated with the indicated Wimp task. If the task exits, the overlay will be automatically destroyed. For the overlay to become visible, it must be attached to a window via VideoOverlay_SetWindow.
Notes
See GraphicsV 20 for more details on overlay creation.
If a Mode change occurs, all Overlays will be destroyed by the GraphicsV driver. An application should watch for this occurring, reissue this call to recreate the overlay and call any additional VideoOverlay SWI’s to transform/display the overlay if required.
Mode Selector Block
The Mode Selector Block must include some additional Mode Variable Numbers. Refer to Extended Framebuffer Format Specification for ModeFlags and NColour values:
| Value | Name | Meaning |
|---|---|---|
| 0 | ModeFlags | Data format and colour space information |
| 3 | NColour | Maximum logical colour |
| 13 | MinScreenBanks | Optional. If omitted, 1 overlay bank is assumed |
See also
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