NAME

DropSite - Commands set for Drop facilities

COMMAND

DropSite::include class types

DropSite::register path ?option value...?

DropSite::setcursor cursor

DropSite::setdrop path subpath dropover drop ?force?

DropSite::setoperation op

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DESCRIPTION

Commands of this namespace enable user to define a BWidget or a Tk widget as a drop site. A drop site is composed of the type of object that can be dropped and associated operation, a command called when drop occurs, and a command when an object is dragged over the widget. A drop site must have at least one type of acceptable object and a drop command.

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COMMAND

DropSite::include class types

This command provides a simple way to include options relatives to a drop site into BWidget resources definition. It includes the options needed for register, -dropovercmd and -dropcmd, initialized to empty string, and -droptypes, initialized to types, and one new option:

-dropenabled

Specifies wether or not drop is active (initialized to 0)

DropSite::register path ?option value...?

This command is used to declare path as a drop site. Options are:

-dropcmd

This command is called when user release the drag icon over a valid drop target widget. Arguments passed to the command are:

• pathname of the drop target (the widget itself),
• pathname of the drag source,
• root x-coordinate of the pointer,
• root y-coordinate of the pointer,
• operation,
• type of the dragged data,
• dragged data.

Its return values is passed as a result to the -dragendcmd command of the drag source widget.

-dropovercmd

This command can be used to provide a dynamic drag while drag-over events. While a drag occurs, events <Enter>, <Motion> and <Leave> are catched. Arguments passed to the command are:

• pathname of the drop target (the widget itself),
• pathname of the drag source,
• event over the drop target: enter, motion or leave,
• root x-coordinate of the pointer,
• root y-coordinate of the pointer,
• operation,
• type of the dragged data,
• dragged data.

Command must the new status of the drag:

• 0 if widget refuse this drag. Command will not be recalled on motion/leave event.
• 1 if widget accept this drag. Command will not be recalled on motion/leave event.
• 2 if widget refuse this drag. Command will be recalled on each motion event to reevaluate.
• 3 if widget accept this drag. Command will be recalled on each motion event to reevaluate.

Here is a list of events and associated actions on a DropSite widget. This example assumes that dragged data type is valid for the drop target. status is the status of the drag on a DropSite. Its value is:

Event	Old status	Action	New status
<Enter>	-	if DropSite has dropovercmd, call it with enter	result of dropovercmd
		else	1
<Motion>	0 or 1		unchanged
	2 or 3	call dropovercmd with motion	result of dropovercmd
<Leave>	0 or 1		-
	2 or 3	call dropovercmd with leave	-
<Drop>	0	call dragendcmd of drag source	-
	1	call dropcmd and call dragendcmd of drag source
	2	call dropovercmd with leave and call dragendcmd of drag source
	3	call dropcmd and call dragendcmd of drag source

-droptypes

Specifies a list {type oplist ?type oplist? ...} of acceptable types and associated operations for the drop target. For each type, oplist is a list {descops mod ?descops mod? ...} describing operations and modifier keys for these operations. descops describe an operation. It can be a predefined operations (copy, move or link) or a new user defined operation, of the form {subop baseop ?bitmap?}. subop is the name given to the sub operation, baseop is the name of the base operation (copy, move or link) and bitmap is a bitmap to display for the operation.
If bitmap is empty, the default bitmap of the base operation is used for the sub operation.
subop can be a base operation, in order to change the bitmap of a base operation. In this case, baseop must be empty or equal to subop.
mod is the modifer key for the operation. It can be:

• none to specify that no modifier key is pressed. This modifier can only be used with a sub operation named default (and vice versa), which has the behaviour of not display any bitmap operation. For all type, if the modifier none is not given, it is automatically associated to the default sub operation of a copy base operation.
• program to specifies a sub operation accessible only by DropSite::setoperation.
• A list combining shift, control and alt, which means their corresponding key.

DropSite::setcursor cursor

This command can be used within the script dragovercmd. It is usefull to provide visual effect about the state of the drag.

DropSite::setdrop path subpath dropover drop ?force?

This command provides a simple way to call register during a BWidget creation or configuration.

• path is the pathname of the BWidget,
• subpath is the pathname of the tk widget where drag event occurs,
• dropover is a command for drag-over event,
• drop is a command for drop event,
• force specifies wether or not to call register whenever no option value has changed (0 by default - for BWidget configuration, use 1 for BWidget creation).

setdrop verifies the modification flag of options dropenabled and droptypes and calls register if needed according to the options values and dropover and drop arguments. dropovercmd and dropcmd are not taken from options of widget because they are considered as user command, called by BWidget implementation of drag-over and drop events.

DropSite::setoperation op

Description text