Docs » Autodocs » workbench.library » AddAppWindowDropZoneA
AddAppWindowDropZoneA -- Designate an AppWindow area as suitable for
dropping icons on. (V44)
dropZone = AddAppWindowDropZoneA(appWindow,id,userData,tags)
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struct AppWindowDropZone * AddAppWindowDropZoneA(struct AppWindow *aw,
ULONG id,ULONG userData,
struct TagItem * tags);
dropZone = AddAppWindowDropZone(appWindow,id,userData,zone,...)
struct AppWindowDropZone * AddAppWindowDropZone(struct AppWindow *aw,
ULONG id,ULONG userData,...);
Once it is created, Workbench will allow the user to drop an
icon anywhere inside an AppWindow, regardless of whether the
icon was dropped on an area designated for dropping icons on
or not. With AddAppWindowDropZoneA() you can tell Workbench
which AppWindow areas are suitable for dropping icons on.
aw -- An AppWindow data structure, as returned by
id -- This variable is strictly for your own use and is ignored by
Workbench. Typical uses in C are in switch and case statements,
and in assembly language table lookup. Later, when an icon is
dropped on the designated area, the AppMessage sent to your
port will have the am_ID member set to this value.
userData -- this variable is strictly for your own use and is ignored
by Workbench. Later, when an icon is dropped on the designated area,
the AppMessage sent to your port will have the am_UserData member
set to this value.
tags -- List of attributes to control the position and size
of the drop zone.
WBDZA_Left (WORD) -- Left edge of the drop zone; a value of
0 would create a zone located at the left corner of the
WBDZA_RelRight (WORD) -- Left edge of the drop zone, relative
to the window width; a value of -10 would create a zone located
10 pixels left of the window right edge.
WBDZA_Top (WORD) -- Top edge of the drop zone; a value of
0 would create a zone located at the top corner of the
WBDZA_RelBottom (WORD) -- Top edge of the drop zone, relative
to the window height; a value of -10 would create a zone located
10 pixels above the window bottom edge.
WBDZA_Width (WORD) -- Width of the drop zone.
WBDZA_RelWidth (WORD) -- Width of the drop zone, relative to the
width of the window; a value of -20 would create a zone that
is by 20 pixels narrower than the window.
WBDZA_Height (WORD) -- Height of the drop zone.
WBDZA_RelHeight (WORD) -- Height of the drop zone, relative to the
height of the window; a value of -20 would create a zone that
is by 20 pixels smaller than the window.
WBDZA_Box (struct IBox *) -- Position and size of the drop zone.
WBDZA_Hook (struct Hook *) -- Pointer to a hook that will be
invoked whenever the mouse enters or leaves your drop zone
area. Your hook will be called with the following parameters:
result = hookFunc(hook,reserved,arm)
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LONG hookFunc(struct Hook *hook,APTR reserved,
struct AppWindowDropZoneMsg *adzm);
The reserved parameter will be set to NULL (V44).
For future enhancement, make sure that your hook
function always returns NULL (V44).
The drop zone message contents are as follows:
A pointer to the RastPort to render into.
Typically, this is the RastPort of the window
the drop zone is attached to.
This member describes the position and size
of the drop zone. The zone is guaranteed to
be a valid area, i.e. the Width and Height
will both be greater than 0 and the Left/Top
will be well within the bounds of the window
containing the drop zone.
These two come straight from the values you passed
as the id and userData parameters to
Depending upon whether the mouse has just entered
or left the drop zone area, this variable will be
set to ADZMACTION_Enter or to ADZMACTION_Leave.
Any other values for adzm_Action should be ignored.
When the mouse enters the drop zone, do your drop
zone area highlighting. When the mouse leaves the
drop zone, remove any highlighting done in the
previous ADZMACTION_Enter pass.
Note that the mouse leaving your drop zone box
does not imply that no icons will be dropped on it.
You may still receive a notification lateron, telling
you that your drop zone had icons dropped on it.
The hook function is solely for highlighting and
unhighlighting the drop zone area.
A final word of warning: when your hook code is called, you
must limit your rendering to simple drawing operations
from graphics.library; if you do anything complex that
involves Intuition locking and unlocking the display,
such as refreshing gadgets or locking IntuitionBase,
you will deadlock the operating system. You have been
dropZone -- A newly created drop zone identifier, or NULL if
it could not be created; use dos.library/IoErr to find out
what caused it to fail.
Once an AppWindow has a drop zone installed, Workbench will senddos.library/IoErr(), workbench.library/AddAppWindowA()
a new type of AppMessage to your port if icons are dropped on
a drop zone. Instead of AMTYPE_APPWINDOW type messages you
will receive AMTYPE_APPWINDOWZONE messages. In fact, you will
no longer hear any AMTYPE_APPWINDOW type messages since Workbench
will allow users to drop icons only on drop zones. Be prepared
to handle this.
Adding a drop zone to an AppWindow does not guarantee that only
AMTYPE_APPWINDOWZONE type messages will arrive at your message
port. In fact, the user may be able to drop an icon on the window
before the first drop zone is installed. Be prepared to handle
Workbench checks drop zones in the order in which they were added
to the AppWindow. Thus, if two zones overlap, the zone that was
added first will be reported as hit.
An AppWindow starts out with its entire area available for dropping
icons on. Thus, you may receive AppMessages for icons dropped upon
your AppWindow before you have added the first drop zone to it.
Be prepared to handle this.
Drop zones must be created with a position and a size. If you omit
either one, this routine will fail.
When an icon is dropped on a drop zone, the AppMessage am_MouseX and
am_MouseY members will be relative to the window top left corner;
they WILL NOT be relative to the left/top edge of the drop zone.