This chapter provides information about list objects by discussing these topics:
The header file List.h
declares the API that this chapter describes. For more information on lists, see the section "Lists" in the Palm OS Programmer's Companion, vol. I.
List Data Structures
ListAttrType Struct
Purpose
The ListAttrType
bit field defines the visible characteristics of the list.
Prototype
typedef struct { UInt16 usable:1; UInt16 enabled:1; UInt16 visible:1; UInt16 poppedUp:1; UInt16 hasScrollBar:1. UInt16 search:1; UInt16 reserved:2; } ListAttrType;
Fields
-
usable
- Set to make the list usable.
- If not set, the list is not considered part of the current interface of the application, and does not appear on screen.
-
enabled
- Not used.
-
visible
- Set when the list object is drawn, and cleared when the list object is erased.
- This attribute is set and cleared internally.
-
poppedUp
- Set to indicate that the choices are displayed in a popup window.
- This attribute is set and cleared internally.
-
hasScrollBar
- Set to indicate that the list has a scroll bar.
-
search
- Set to enable incremental search. If incremental search is enabled, when the list is displayed the user can navigate the list by entering up to five characters. The list will scroll to present the first list item that matches the entered characters. This feature only works for popup lists, and only works if the list is sorted and the list items are available to the List Manager (that is, you don't pass
NULL
toLstSetListChoices()
). -
reserved
- Reserved for system use.
ListType Struct
Purpose
The ListType
structure is defined below.
WARNING! PalmSource, Inc. does not support or provide backward compatibility for the
ListType
structure. Never access its structure members directly, or your code may break in future versions. Use the information below for debugging purposes only.
Prototype
typedef struct { UInt16 id; RectangleType bounds; ListAttrType attr; Char **itemsText; Int16 numItems; Int16 currentItem; Int16 topItem; FontID font; UInt8 reserved; WinHandle popupWin; ListDrawDataFuncPtr drawItemCallback; } ListType;
Fields
-
id
- The ID value, specified by the application developer. This ID value is part of the event data of
lstEnterEvent
andlstSelectEvent
. -
bounds
- The bounds of the list, relative to the window. For example, to access the bounds of an object in a form whose ID is kObjectID:
-
{
-
RectangleType rect;
-
FormPtr formP = FrmGetActiveForm();
-
FrmGetObjectBounds(formP,
FrmGetObjectIndex(formP, kObjectID),
&rect); -
}
-
attr
- The list attributes. See
ListAttrType
. -
itemsText
- A pointer to an array of pointers to the text of the choices. Access with
LstGetSelectionText()
. - For example, to access the string specified by
itemNum
in the list whose ID iskChoiceList
use the following: -
{
-
Char *string;
-
Int16 itemNum;
-
...
-
string = LstGetSelectionText(GetObjectPtr(kChoicesList), itemNum);
-
}
- where
GetObjectPtr
is the following: -
static void *GetObjectPtr(UInt16 rsrcID){
-
FormPtr formP;
-
formP = FrmGetActiveForm();
-
return FrmGetObjectPtr(formP, FrmGetObjectIndex(formP, rsrcID));
-
}
- If you use a callback routine to draw the list items, note that the
itemsText
pointer you supply toLstSetListChoices()
is passed to your callback routine. See the comments underListDrawDataFuncType()
for tips on usingitemsText
with a callback routine. -
numItems
- The number of choices in the list. Access with
LstGetNumberOfItems()
. -
currentItem
- The currently-selected list choice (0 = first choice). Access with
LstGetSelection()
. -
topItem
- The first choice displayed in the list. Set this field with
LstSetTopItem()
. -
font
- The ID of the font used to draw all list text strings.
-
reserved
- Reserved for future use.
-
popupWin
- The handle of the window created when a list is displayed by calling
LstPopupList()
. -
drawItemCallback
- Function used to draw an item in the list. If
NULL
, the default drawing routine is used instead. Set this field withLstSetDrawFunction()
. See Application-Defined Function.
List Resources
The List Resource (tLST), and Popup Trigger Resource (tPUT) are used together to represent an active list. See Palm OS User Interface Guidelines for more information.
List Functions
LstDrawList Function
Purpose
Sets the visible attribute of the list object to true
, and draws the list object if it is usable.
Declared In
List.h
Prototype
void LstDrawList ( ListType *listP )
Parameters
-
→ listP
- Pointer to a list object (ListType).
Returns
Comments
If there are more choices than can be displayed, this function ensures that the current selection is visible. The current selection is highlighted. Note that this function does not ensure the current selection is visible; if you need to do this, call the LstMakeItemVisible()
function.
If the list is disabled, it's drawn grayed-out (strongly discouraged). If it's empty, nothing is drawn. If it's not usable, nothing is drawn.
See Also
FrmGetObjectPtr()
, LstPopupList()
, LstEraseList()
LstEraseList Function
Purpose
Declared In
List.h
Prototype
void LstEraseList ( ListType *listP )
Parameters
-
→ listP
- Pointer to a list object (ListType).
Returns
Comments
The visible
attribute is set to false by this function.
See Also
FrmGetObjectPtr()
, LstDrawList()
LstGetNumberOfItems Function
Purpose
Return the number of items in a list.
Declared In
List.h
Prototype
Int16 LstGetNumberOfItems ( const ListType *listP )
Parameters
-
→ listP
- Pointer to a list object (ListType).
Returns
Returns the number of items in a list.
See Also
FrmGetObjectPtr()
, LstSetListChoices()
LstGetSelection Function
Purpose
Return the currently selected choice in the list.
Declared In
List.h
Prototype
Int16 LstGetSelection ( const ListType *listP )
Parameters
Returns
Returns the item number of the current list choice. The list choices are numbered sequentially, starting with 0; Returns noListSelection
if none of the items are selected.
See Also
FrmGetObjectPtr()
, LstSetListChoices()
, LstSetSelection()
, LstGetSelectionText()
LstGetSelectionText Function
Purpose
Return a pointer to the text of the specified item in the list, or NULL
if no such item exists.
Declared In
List.h
Prototype
Char *LstGetSelectionText ( const ListType *listP, Int16 itemNum )
Parameters
Returns
Returns a pointer to the text of the current selection, or NULL
if out of bounds.
Comments
This is a pointer within ListType, not a copy. This function is only usable if you supplied an array of strings and a count to LstSetListChoices()
; if your application uses a callback function that dynamically generates the list text, this function returns NULL
.
See Also
LstGetTopItem Function
Purpose
Returns the topmost visible item.
Declared In
List.h
Prototype
Int16 LstGetTopItem ( const ListType *listP )
Parameters
Returns
Returns the item number of the top item visible.
Compatibility
Implemented only if 4.0 New Feature Set is present.
See Also
LstGetSelection()
, LstSetTopItem()
LstGetVisibleItems Function
Purpose
Return the number of visible items.
Declared In
List.h
Prototype
Int16 LstGetVisibleItems ( const ListType *listP )
Parameters
Returns
Compatibility
Implemented only if 2.0 New Feature Set is present.
LstHandleEvent Function
Purpose
Handle event in the specified list; the list object must have its usable
and visible
attribute set to true
.This routine handles two type of events, penDownEvent
and lstEnterEvent
; see Comments.
Declared In
List.h
Prototype
Boolean LstHandleEvent ( ListType *listP, const EventType *eventP )
Parameters
-
→ listP
- Pointer to a list object (ListType).
-
→ eventP
- Pointer to an EventType structure.
Returns
Return true if the event was handled. The following cases will result in a return value of true:
- A
penDownEvent
within the bounds of the list - A
lstEnterEvent
with a list ID value that matches the list ID in the list data structure
Comments
When this routine receives a penDownEvent
, it checks if the pen position is within the bounds of the list object. If it is, this routine tracks the pen until the pen comes up. If the pen comes up within the bounds of the list, a lstEnterEvent
is added to the event queue, and the routine is exited.
When this routine receives a lstEnterEvent
, it checks that the list ID in the event record matches the ID of the specified list. If there is a match, this routine creates and displays a popup window containing the list's choices and the routine is exited.
If a penDownEvent
is received while the list's popup window is displayed and the pen position is outside the bounds of the popup window, the window is dismissed. If the pen position is within the bounds of the window, this routine tracks the pen until it comes up. If the pen comes up outside the list object, a lstEnterEvent
is added to the event queue.
LstMakeItemVisible Function
Purpose
Make an item visible, preferably at the top. If the item is already visible, make no changes.
Declared In
List.h
Prototype
void LstMakeItemVisible ( ListType *listP, Int16 itemNum )
Parameters
-
→ listP
- Pointer to a list object (ListType).
-
→ itemNum
- Item to select (0 = first item in list).
Returns
Comments
Does not visually update the list. You must call LstDrawList()
to update it.
See Also
FrmGetObjectPtr()
, LstSetSelection()
, LstSetTopItem()
, LstDrawList()
LstNewList Function
Purpose
Create a new list object dynamically and install it in the specified form. This function can be used to create a new popup trigger and its associated list.
Declared In
List.h
Prototype
Err LstNewList ( void **formPP, UInt16 id, Coord x, Coord y, Coord width, Coord height, FontID font, Int16 visibleItems, Int16 triggerId )
Parameters
-
↔ formPP
- Pointer to the pointer to the form in which the new list is installed. This value is not a handle; that is, the old
formPP
value is not necessarily valid after this function returns. In subsequent calls, always use the newformPP
value returned by this function. -
→ id
- Symbolic ID of the list, specified by the developer. By convention, this ID should match the resource ID (not mandatory).
-
→ x
- Horizontal coordinate of the upper-left corner of the list's boundaries, relative to the window in which it appears.
-
→ y
- Vertical coordinate of the upper-left corner of the list's boundaries, relative to the window in which it appears.
-
→ width
- Width of the list, expressed in pixels. Valid values are 1 – 160.
-
→ height
- Height of the list, expressed in pixels.Valid values are 1 – 160.
-
→ visibleItems
- Number of list items that can be viewed together.
-
→ triggerId
- Symbolic ID of the popup trigger associated with the new list (this ID is specified by the developer). A nonzero value for
triggerID
causes this function to create both the list and its associated popup trigger. If the list isn't a popup list, pass 0 fortriggerId
.
Returns
Compatibility
Implemented only if 3.0 New Feature Set is present.
See Also
LstDrawList()
, FrmRemoveObject()
LstPopupList Function
Purpose
Display a modal window that contains the items in the list.
Declared In
List.h
Prototype
Int16 LstPopupList ( ListType *listP )
Parameters
Returns
Returns the list item selected, or -1 if no item was selected.
Comments
Saves the previously active window. Creates and deletes the new popup window.
See Also
LstScrollList Function
Purpose
Scroll the list up or down a number of times.
Declared In
List.h
Prototype
Boolean LstScrollList ( ListType *listP, WinDirectionType direction, Int16 itemCount )
Parameters
-
→
listP
- Pointer to a list object.
-
→
direction
- Direction to scroll.
-
→
itemCount
- Items to scroll in direction.
Returns
Returns true
when the list is actually scrolled, false
otherwise. May return false
if a scroll past the end of the list is requested.
Compatibility
Implemented only if 2.0 New Feature Set is present.
LstSetDrawFunction Function
Purpose
Set a callback function to draw each item instead of drawing the item's text string.
Declared In
List.h
Prototype
void LstSetDrawFunction ( ListType *listP, ListDrawDataFuncPtr func )
Parameters
Returns
Comments
This function also adjusts topItem to prevent a shrunken list from being scrolled down too far. Use this function for custom draw functionality.
See Also
FrmGetObjectPtr()
, LstGlueGetDrawFunction()
, LstSetListChoices()
, ListDrawDataFuncType()
LstSetHeight Function
Purpose
Set the number of items visible in a list.
Declared In
List.h
Prototype
void LstSetHeight ( ListType *listP, Int16 visibleItems )
Parameters
Returns
Comments
This function doesn't redraw the list if it's already visible.
See Also
LstSetListChoices Function
Purpose
Set the items of a list to the array of text string pointers passed to this function. This functions erases the old list items.
Declared In
List.h
Prototype
void LstSetListChoices ( ListType *listP, Char **itemsText, Int16 numItems )
Parameters
-
→ listP
- Pointer to a list object.
-
→ itemsText
- Pointer to an array of text strings. See
SysFormPointerArrayToStrings()
for one way to create this array of strings. -
→ numItems
- Number of choices in the list.
Returns
Comments
You need to call the LstDrawList
function to update the list if it is displayed when you call this function.
NOTE: This function does not copy the strings in the
itemsText
array, which means that you need to ensure that the array is not moved or deallocated until after you are done with the list.
If you use a callback routine to draw the items in your list, the itemsText
pointer is simply passed to that callback routine and is not otherwise used by the List Manager code. See the comments under ListDrawDataFuncType()
for tips on using the itemsText
parameter with a callback routine.
See Also
FrmGetObjectPtr()
, LstGlueGetItemsText()
, LstSetSelection()
, LstSetTopItem()
, LstDrawList()
, LstSetHeight()
, LstSetDrawFunction()
LstSetPosition Function
Purpose
Declared In
List.h
Prototype
void LstSetPosition ( ListType *listP, Coord x, Coord y )
Parameters
Returns
Comments
The list is not redrawn. Don't call this function when the list is visible.
See Also
LstSetSelection Function
Purpose
Declared In
List.h
Prototype
void LstSetSelection ( ListType *listP, Int16 itemNum )
Parameters
-
→ listP
- Pointer to a list object.
-
→ itemNum
- Item to select (0 = first item in list,
noListSelection
= none).
Returns
Comments
The old selection, if any, is unselected. If the list is visible, the selected item is visually updated. The list is scrolled to the selection, if necessary, as long as the list object is both visible and usable.
See Also
FrmGetObjectPtr()
, LstSetTopItem()
LstSetTopItem Function
Purpose
Set the item visible. The item cannot become the top item if it's on the last page.
Declared In
List.h
Prototype
void LstSetTopItem ( ListType *listP, Int16 itemNum )
Parameters
-
→ listP
- Pointer to a list object.
-
→ itemNum
- Item to select (0 = first item in list). This must be a valid item number.
Returns
Comments
See Also
FrmGetObjectPtr()
, LstGlueGetTopItem
, LstSetSelection()
, LstGetTopItem()
, LstMakeItemVisible()
, LstDrawList()
, LstEraseList()
Application-Defined Function
If you need to perform special drawing for items in the list, call LstSetDrawFunction()
to set the list drawing callback function. The ListDrawDataFuncType()
section documents the prototype for the callback function you provide for drawing list items.
ListDrawDataFuncType Function
Purpose
Callback function that you provide for drawing items in a list. This function is called whenever the Palm OS needs to draw an element in the list. Your callback function declaration must match the prototype shown here.
Declared In
List.h
Prototype
void ListDrawDataFuncType( Int16 itemNum, RectangleType *bounds, Char **itemsText )
Parameters
-
→
itemNum
- The number of the item to draw.
-
→
bounds
- The bounds of the list, relative to the window.
-
→
itemsText
- A pointer to an array of pointers to the text of the list items. This is the pointer that you supplied when calling
LstSetListChoices()
.
Returns
Comments
You can call LstSetDrawFunction()
to register your callback function for the list, which means that your function will be called to draw the list items, rather than using the built-in draw functionality, which displays each item's text string.
Your callback function is called whenever an item in the list needs to be drawn. When it is called, the value of the itemNum
parameter specifies which item the function is to draw. The itemsText
parameter, which is what was supplied to LstSetListChoices
, doesn't actually need to point to a list of strings: you can pass NULL
, or you can pass a pointer to anything that will be useful to your drawing function. Note, however, that if you pass anything other than a pointer to a list of strings when you call LstSetListChoices,
you must ensure that LstGetSelectionText()
is never called since it assumes that this pointer indicates an array of text items. In particular, if your list is associated with a pop-up trigger you must handle the popSelectEvent
yourself before FrmHandleEvent()
gets a chance at it since FrmHandleEvent
calls LstGetSelectionText
.
WARNING! If the list is a popup list, the form that owns the list is not active while the list is in a window. This means that you cannot call the
FrmGetActiveForm()
function. Instead, use itemsText pointer to access any information that you need for drawing. If you must access the form, use the FrmGetFormPtr()
function.
Note that the list object manages which colors are used to draw the items and how to draw selected versus unselected items. In almost all circumstances, your drawing function does not have to be concerned with these details.
However, if you do need to determine if the item is selected, you can rely on the fact that the system has set the pen color to one of two colors prior to calling your draw function:
- If the item is selected, the foreground color is
UIObjectSelectedForeground
. - If the item is not selected, the foreground color is
UIObjectForeground
.
You can determine the foreground color that is in effect for the list item by calling the WinSetForeColor()
function, which returns the previous value of the foreground color. Remember to call WinSetForeColor
again to reset the foreground color to what it was. For example:
itemColor = WinSetForeColor(myColor) WinSetForeColor(itemColor) selectColor = UiColorGetTableEntryIndex( UIObjectSelectedForeground) if itemColor == selectColor ...
See Also
LstSetDrawFunction()
, UIColorGetTableEntryIndex()
, WinSetForeColor()