a2d/MGTK.md
2018-02-04 21:05:31 -08:00

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# MGTK API
There are three distinct API classes that need to be used:
* Main MGTK API - entry point $4000 AUX, called MLI-style (JSR followed by command type and address of param block)
* DeskTop Jump Table - simple JSR calls starting at $4003 MAIN, no arguments
* DeskTop API - another MLI-style interface starting at $8E00 AUX
## Main MGTK API
### Concepts
#### GrafPort
The _port_ block is reused in several places. It has the following structure:
```
.word left pixels from screen left edge
.word top pixels from screen top edge
.addr addr screen address $2000
.word stride screen stride $80
.word hoff pixels scrolled left
.word voff pixels scrolled up
.word width pixels wide
.word height pixels tall
```
Drawing state can be set to a port (SetPort) and then subsequent operations will occur
within the port: they will be clipped to the bounds and the offset will be taken into account.
For example, if hoffset is 15 and voffset is 5 then a pixel plotted at 40, 40 will appear
at 40 - 15 = 25 pixels from the left edge and 40 - 5 = 35 pixels from the top edge.
#### Pattern
A simple repeating 8x8 _pattern_ is defined by 8 bytes. All bits of each byte are used.
#### Window Parts
Windows have a _client area_ which has the requested dimensions. Above this is an optional
_title bar_ which in turn has an optional _close box_. Within the client area are an
optional _resize box_ and optional _scroll bars_.
### Desk Accessory Lifecycle
* Loaded/invoked at $800 MAIN (have through $1FFF available)
* Save stack
* Copy DA code from MAIN to AUX (e.g. using AUXMOVE)
* Transfer control to AUX
* Turn on ALTZP and LCBANK1
* Create window (OpenWindow)
* Draw everything
* Call $2B (no idea what this does!)
* Enter [input loop](#input-loop)
* ...
* Destroy window (CloseWindow)
* Redraw desktop icons (DESKTOP_REDRAW_ICONS)
* Switch control back to MAIN (RAMRDOFF/RAMWRTOFF)
* Ensure ALTZP and LCBANK1 are on
* Restore stack
* RTS
> NOTE: Movable windows must maintain an _offscreen_flag_. If a window is moved so that the
> client area is entirely offscreen then various operations should be skipped because
> the window's box coordinates will not be set correctly.
#### Input Loop
* Call GetEvent.
* If a key, then check modifiers (Open/Solid Apple) and key code, ignore or take action.
* If a click, call FindWindow.
* If target id not the window id, ignore.
* If target element is desktop or menu then ignore.
* If target element is close box then initiate [window close](#window-close).
* If target element is title bar then initiate [window drag](#window-drag).
* If target element is resize box then initiate [window resize](#window-resize).
* Otherwise, it is client area; call FindControl.
* If client part is a scrollbar then initiate a [scroll](#window-scroll).
* Otherwise, handle a client click using custom logic (e.g. hit testing buttons, etc)
#### Window Close
* Call TrackGoAway, which enters a modal loop to handle the mouse moving out/in the box.
* Result indicates clicked or canceled; if clicked, exit the DA, otherwise ignore.
#### Window Drag
* Call DragWindow.
* Call JUMP_TABLE_REDRAW_ALL.
* If _offscreen flag_ was not set, redraw desktop icons (DESKTOP_REDRAW_ICONS).
* Set _offscreen flag_ if window's `top` is greater than or equal to the screen bottom (191), clear otherwise.
* If _offscreen flag_ is not set, redraw window.
#### Window Resize
* Call GrowWindow.
* Call JUMP_TABLE_REDRAW_ALL.
* Call DESKTOP_REDRAW_ICONS.
* Call UpdateThumb if needed to adjust scroll bar settings. (Details TBD).
* Redraw window.
#### Window Scroll
### Drawing Operations
### Commands
## DeskTop Jump Table
Call from MAIN (RAMRDOFF/RAMWRTOFF). Call style:
```
jsr $xxxx
```
> NOTE: Most of these calls have not been identified yet.
#### JUMP_TABLE_REDRAW_ALL ($4015)
Redraws all DeskTop windows. Required after a drag or resize. Follow with DESKTOP_REDRAW_ICONS call.
#### JUMP_TABLE_CLEAR_SEL ($401E)
Deselect all DeskTop icons (volumes/files).
#### JUMP_TABLE_CUR_POINTER ($4039)
Changes mouse cursor to the default pointer. Note that bitmap is in the language card memory so it must be swapped in.
#### JUMP_TABLE_CUR_WATCH ($403C)
Changes mouse cursor to a watch. Note that bitmap is in the language card memory so it must be swapped in.
## DeskTop API
Call from AUX (RAMRDON/RAMWRTON). Call style:
```
jsr $8E00
.byte command
.addr params
```
> NOTE: Only a single call has been identified so far.
Commands:
#### DESKTOP_REDRAW_ICONS ($0C)
Parameters: none (pass $0000 as address)
Redraws the icons on the desktop (mounted volumes, trash). This call is required in these cases:
* After destroying a window (CloseWindow)
* After repainting the desktop (JUMP_TABLE_REDRAW_ALL) following a drag (DragWindow)
* After repainting the desktop (JUMP_TABLE_REDRAW_ALL) following a resize (GrowWindow)