nsITreeView

Implementing a nsITreeView in lieu of DOM methods for tree creation can improve performance dramatically, and removes the need to make changes to the tree manually when changes to the database occur.

Further information about creating treeviews is given in the XUL Tutorial.

Method overview

Attributes

Constants

Methods

Methods used by the drag feedback code to determine if a drag is allowable at the current location. To get the behavior where drops are only allowed on items, such as the mailNews folder pane, always return false when the orientation is not DROP_ON.

boolean canDrop(
  in long index,
  in long orientation,
  in nsIDOMDataTransfer dataTransfer
);

Parameters

index

The index of the row.

orientation

The position around the given row. Defined in constants.

dataTransfer

This parameter, added in Gecko 1.9.2, provides the data being dragged, so that it can be examined to determine if a drop is possible.

Return value

true if a drop is allowed at the current location; otherwise false.

Method used by the drag feedback code to determine if a drag is allowable at the current location. To get the behavior where drops are only allowed on items, such as the mailNews folder pane, always return false from canDropBeforeAfter().

boolean canDropBeforeAfter(
  in long index,
  in boolean before
);

Parameters

index

The index of the item.

before

true to test drop before. false to test drop after.

Return value

true if a drop event can occur. Otherwise false.

Method used by the drag feedback code to determine if a drag is allowable at the current location. To get the behavior where drops are only allowed on items, such as the mailNews folder pane, always return false from canDropBeforeAfter().

boolean canDropOn(
  in long index
);

Parameters

index

The index of the item.

Return value

true if a drop event can occur. Otherwise false.

cycleCell()

Called on the view when a cell in a non-selectable cycling column (for example, unread/flag/and so on.) is clicked.

void cycleCell(
  in long row,
  in nsITreeColumn col
);

Parameters

row

The row of the cell.

col

The column of the cell.

cycleHeader()

Called on the view when a header is clicked.

void cycleHeader(
  in nsITreeColumn col
);

Parameters

col

The column to cycle.

drop()

Called when the user drops something on this view. The orientation paramater specifies before/on/after the given row.

void drop(
  in long row,
  in long orientation,
  in nsIDOMDataTransfer dataTransfer
);

Parameters

row

The index of the row.

orientation

The position around the given row. Defined in constants.

dataTransfer

This parameter, added in Gecko 1.9.2, provides the data that has been dropped.

getCellProperties()

An atomized list of properties for a given cell. Each property, x, that the view gives back will cause the CSS ::moz-tree-cell-*(x) pseudoelement to be matched on the treechildren element.

See getRowProperties() for an example.

AString getCellProperties(
  in long row,
  in nsITreeColumn col,
  in nsISupportsArray properties
);

Parameters

row

The index of the row.

col

The current column.

properties

An array of the cell's current properties. Obsolete since Gecko 22

Return value

A string of space-separated property names. Requires Gecko 22

getCellText()

The text for a given cell. If a column consists only of an image, then the empty string is returned.

AString getCellText(
  in long row,
  in nsITreeColumn col
);

Parameters

row

The index of the row.

col

The column of the cell. (Note that this is not the column index.)

Return value

The text of the cell.

getCellValue()

The value for a given cell. This method is only called for columns of type other than text.

AString getCellValue(
  in long row,
  in nsITreeColumn col
);

Parameters

row

The index of the row.

col

The column of the cell. (Note that this is not the column index.)

Return value

The value of the cell.

getColumnProperties()

Called to get properties to paint a column background. For shading the sort column, and so on. Each property, x, that the view gives back will cause the CSS  ::moz-tree-column(x) to be matched on the treechildren element.

See getRowProperties() for an example.

void getColumnProperties(
  in nsITreeColumn col,
  in nsISupportsArray properties
);

Parameters

col

The current column.

properties

An array of the column's current properties. Obsolete since Gecko 22

Return value

A string of space-separated property names. Requires Gecko 22

getImageSrc()

The image path for a given cell. For defining an icon for a cell. If the empty string is returned, the ::moz-tree-image pseudoelement will be used.

AString getImageSrc(
  in long row,
  in nsITreeColumn col
);

Parameters

row

The index of the row.

col

The index of the column.

Return value

The image path of the cell.

getLevel()

The level is an integer value that represents the level of indentation. It is multiplied by the width specified in the ::moz-tree-indentation pseudoelement to compute the exact indentation.

long getLevel(
  in long index
);

Parameters

index

The index of the item.

Return value

The level of indentation.

getParentIndex()

Methods used by the tree to draw thread lines in the tree. getParentIndex is used to obtain the index of a parent row. If there is no parent row, getParentIndex returns -1.

long getParentIndex(
  in long rowIndex
);

Parameters

rowIndex

The index of the row whose parent should be found.

Return value

The row index of the parent row.

getProgressMode()

The progress mode for a given cell. This method is only called for columns of type progressmeter. See the constants section for possible modes.

long getProgressMode(
  in long row,
  in nsITreeColumn col
);

Parameters

row

The index of the row.

col

The index of the column.

Return value

The progress mode for the cell.

getRowProperties()

An atomized list of properties for a given row. Each property, x, that the view gives back will cause the CSS ::moz-tree-row(x) pseudoelement to be matched on the treechildren element.

void getRowProperties(
  in long index,
  in nsISupportsArray properties
);

Parameters

index

The index of the row.

properties

An array of the row's current properties. Obsolete since Gecko 22

Return value

A string of space-separated property names. Requires Gecko 22

Example

getRowProperties: function(index) {
  return "dummy";
}

getRowProperties: function(index, properties) {
  var atomService = Components.classes["@mozilla.org/atom-service;1"].getService(Components.interfaces.nsIAtomService);
  var atom = atomService.getAtom("dummy");
  properties.AppendElement(atom);
}

hasNextSibling()

Used to determine if the row at rowIndex has a nextSibling that occurs after the index specified by afterIndex. Code that is forced to march down the view looking at levels can optimize the march by starting at afterIndex+1.

boolean hasNextSibling(
  in long rowIndex,
  in long afterIndex
);

Parameters

rowIndex

The index of the item.

afterIndex

The index of the item to find siblings after.

Return value

true if the row has a next sibling. Otherwise false

isContainer()

Whether the row has the potential to hold other rows within it. This does not determine whether a twisty is actually drawn; that's left up to isContainerEmpty. For very simple tree views, such as those without multi-level data, you might want to consider using something simpler than a tree view, such as a listbox.

For tree views with multi-level data, it's advisable to distinguish between a row which is an empty container (i.e., a row with the potential to hold children but that currently has none), and a non-empty container (i.e., a row that positively does currently have children). The tree frame code that handles drag and drop, for example, uses this method to determine how to interpret the drop position.

boolean isContainer(
  in long index
);

Parameters

index

The index of the row being asked about.

Return value

true if the row is a container. Otherwise false.

isContainerEmpty()

One of the methods that can be used to test whether or not a twisty should be drawn, and if so, whether an open or closed twisty should be used.

boolean isContainerEmpty(
  in long index
);

Parameters

index

The index of the item being asked about.

Return value

true if the item is an empty container. Otherwise false.

isContainerOpen()

One of the methods that can be used to test whether or not a twisty should be drawn, and if so, whether an open or closed twisty should be used.

boolean isContainerOpen(
  in long index
);

Parameters

index

The index of the item being asked about.

Return value

true if the item is an open container. Otherwise false.

isEditable()

Called to ask the view if the cell contents are editable. A value of true will result in the tree popping up a text field when the user tries to inline edit the cell.

boolean isEditable(
  in long row,
  in nsITreeColumn col
);

Parameters

row

The row of the cell.

col

The column of the cell.

Called to ask the view if the cell is selectable. This method is only called if the selection type is cell or text.

boolean isSelectable(
  in long row,
  in nsITreeColumn col
);

Parameters

row

The row of the cell.

col

The column of the cell.

Return value

true if the cell is selectable. Otherwise false.

isSeparator()

Used to determine if the row at index is a separator. A value of true will result in the tree drawing a horizontal separator. The tree uses the ::moz-tree-separator pseudoelement to draw the separator.

boolean isSeparator(
  in long index
);

Parameters

index

The index of the item being asked about.

true if the row is a separator. Otherwise false.

isSorted()

Specifies if there is currently a sort on any column. Used mostly by dragdrop to affect drop feedback.

boolean isSorted();

Parameters

None.

true if the column is sorted. Otherwise false.

performAction()

A command API that can be used to invoke commands on the selection. The tree will automatically invoke this method when certain keys are pressed. For example, when the DEL key is pressed, performAction will be called with the delete string.

void performAction(
  in wstring action
);

Parameters

action

The action to perform.

performActionOnCell()

A command API that can be used to invoke commands on a specific cell.

void performActionOnCell(
  in wstring action,
  in long row,
  in nsITreeColumn col
);

Parameters

action

The action to perform.

row

The row of the cell.

col

The column of the cell.

performActionOnRow()

A command API that can be used to invoke commands on a specific row.

void performActionOnRow(
  in wstring action,
  in long row
);

Parameters

action

The action to perform.

row

The row of the cell.

selectionChanged()

Should be called from a XUL onselect handler whenever the selection changes.

void selectionChanged();

Parameters

None.

setCellText()

setCellText is called when the contents of the cell have been edited by the user.

void setCellText(
  in long row,
  in nsITreeColumn col,
  in AString value
);

Parameters

row

The row of the cell.

col

The column of the cell.

value

The text to change the cell to.

setCellValue is called when the value of the cell has been set by the user. This method is only called for columns of type other than text.

void setCellValue(
  in long row,
  in nsITreeColumn col,
  in AString value
);

Parameters

row

The row of the cell.

col

The column of the cell.

value

The value to change the cell to.

setTree()

Called when setting or clearing the view on the tree to link the view to or disconnect the front end box object.

void setTree(
  in nsITreeBoxObject tree
);

Parameters

tree

The nsITreeBoxObject to attach this view to, or null if the view is being removed from the tree.

toggleOpenState()

Called on the view when an item is opened or closed, e.g., by clicking the twisty, keyboard access, et cetera.

void toggleOpenState(
  in long index
);

Parameters

index

The index of the row to toggle.

See also

• Tree Widget Changes (applies to Gecko 1.8 and later)
• XUL Tutorial:Tree View Details
• Sorting and filtering a custom tree view

When working with tree views, the tree box object may also be useful

• XUL Tutorial:Tree Box Objects