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33 lines
1.1 KiB
Markdown
33 lines
1.1 KiB
Markdown
# Desk Accessory API
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Desk Accessories for DeskTop have general access to the Mouse Graphics
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Tool Kit MLI, ProDOS MLI, and DeskTop APIs. Special considerations for
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DAs are documented here.
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### Desk Accessory Lifecycle
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* DAs are loaded/invoked at $800 MAIN
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* Up to $1C00 MAIN is available
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* But AUX $1B00 and on must be preserved.
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* Save stack pointer
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* Copy DA code from MAIN to AUX (e.g. using `AUXMOVE`) at same address.
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* Transfer control to the AUX copy
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* This allows direct access to MGTK/DeskTop MLI
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* Retaining a copy in MAIN allows easy access to ProDOS MLI
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* Turn on ALTZP and LCBANK1
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* Create window (`OpenWindow`)
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* Draw everything
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* Flush event queue (`FlushEvents`)
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* Run an event Loop (`GetEvent`, and subsequent processing, per MGTK)
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* Normal event processing per MGTK
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* In addition, following a window drag/resize, DeskTop calls must be made:
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* `JUMP_TABLE_REDRAW_ALL`
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* `DESKTOP_REDRAW_ICONS`
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* ...
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* Destroy window (`CloseWindow`)
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* Tell DeskTop to redraw desktop icons (`DESKTOP_REDRAW_ICONS`)
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* Switch control back to MAIN (`RAMRDOFF`/`RAMWRTOFF`)
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* Ensure ALTZP and LCBANK1 are still on
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* Restore stack pointer
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* `rts`
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