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26    Progress Manager Reference

User Interface

Exploring Palm OS®

This chapter provides reference material for the Progress Manager.

Progress Manager Structures and Types
Progress Manager Constants
Progress Manager Events
Progress Manager Functions and Macros
Application-Defined Functions

The header file Progress.h declares the API that this chapter describes. For more information on the Progress Manager, see the section "Progress Dialogs."

Progress Manager Structures and Types ^TOP^

PrgCallbackData Struct ^TOP^

Purpose

Structure used to share information between the Progress Manager and the PrgCallbackFunc() callback function.

Declared In

Progress.h

Prototype

typedef struct {
   uint16_t stage;
   uint16_t bitmapId;
   DmOpenRef bitmapDatabase;
   uint32_t textLen;
   char *textP;
   char *message;
   status_t error;
   uint16_t canceled:1;
   uint16_t showDetails:1;
   uint16_t textChanged:1;
   uint16_t timedOut:1;
   uint16_t displaySkipBtn:1;
   uint16_t skipped:1;
   uint16_t spareBits1:10;
   uint16_t padding1;
   uint32_t timeout;
   uint32_t padding2;
   uint32_t barMaxValue;
   uint32_t barCurValue;
   char *barMessage;
   uint16_t barFlags;
   uint16_t delay:1;
   uint16_t spareBits2:15;
   void *userDataP;
} PrgCallbackData, *PrgCallbackDataPtr

Fields

→ stage
Current stage passed from PrgUpdateDialog().
↔ bitmapId
Resource ID of the bitmap to display in the progress dialog, if any.
↔ bitmapDatabase
Open database containing bitmapId.
→ textLen
Size in bytes of the text buffer textP. Note that this value is defined by the system, not by your callback function. Be careful not to exceed this length in textP.
↔ textP
Buffer to hold the text to display in the updated dialog. You might want to look up a message in a resource file, based on the value in the stage field. Also, you should append the additional text in the message field, to form the full string to display. Be sure to include a null terminator at the end of the string you return, and don't exceed the length in textLen.
→ message
Additional text to display in the dialog (from the messageP parameter to PrgUpdateDialog()). This string is no longer than progressMaxMessage.
↔ error
Current error (passed from the err parameter to PrgUpdateDialog()).
↔ canceled
true if user has pressed the Cancel button.
→ showDetails
true if user pressed the down arrow button on the device for more details. (Because this is a non-standard user interface technique, you shouldn't use this feature to display details that users need under normal conditions. It's more for debugging purposes.)
← textChanged
If true, then the system should update text (defaults to true). You can set this to false to avoid an update to the text.
→ timedOut
true if and only if the update was caused by a timeout. If an application calls PrgUpdateDialog() and a timeout occurs before the callback is called, this field is false.
← displaySkipBtn
If true, the progress dialog displays a skip button, which allows the user to skip the current stage.
↔ skipped
If true, the user tapped the skip button to skip the current stage.
spareBits1
Not used.
padding1
Not used.
↔ timeout
Timeout in ticks to force next update. After this number of ticks, an update is automatically triggered (which sets the timedOut flag). You can use this feature to do a simple animation effect. Note that you must set the timeout for EvtGetEvent() to a value that is equal to or less than this value, otherwise you won't get update events as frequently as you expect.
padding2
Not used.
↔ barMaxValue
The maximum value for the progress bar.
↔ barCurValue
The current value that the progress bar should display.
barMessage
Not used.
barFlags
Not used.
↔ delay
If true, delay for one second after updating the dialog. Use this value when you are displaying the final progress message so that users have a chance to see the message before the dialog closes.
spareBits2
Not used.
→ userDataP
A pointer to any application-defined data that the function needs to access. You specify this pointer as a parameter to PrgStartDialog() if the callback function needs to access some application data but does not have access to the application's global variables.

ProgressType Struct ^TOP^

Purpose

Internal structure that identifies the current progress. This structure is created with PrgStartDialog() and passed to all other Progress Manager functions. A ProgressPtr defines a pointer to a ProgressType structure.

Declared In

Progress.h

Prototype

typedef struct ProgressType ProgressType, 
*ProgressPtr

Fields

None.

Progress Manager Constants ^TOP^

Progress Manager String Length Constants ^TOP^

Purpose

Specify the maximum sizes of the strings that are displayed in the progress dialog.

Declared In

Progress.h

Constants

#define progressMaxButtonText 7
Maximum length of the text in the OK or Cancel button.
#define progressMaxMessage 128
Maximum length of the message field in PrgCallbackData.
#define progressMaxTitle 31
Maximum length in bytes for a title to a progress dialog.

Progress Manager Events ^TOP^

prgUpdateEvent ^TOP^

Purpose

Sent when another thread has updated the progress.

Declared In

EventCodes.h

Prototype

None.

Progress Manager Functions and Macros ^TOP^

PrgGetError Function ^TOP^

Purpose

Returns the current error, if any.

Declared In

Progress.h

Prototype

status_t PrgGetError (
   const ProgressType *prgP
)

Parameters

prgP
Pointer to a progress structure created by PrgStartDialog() or PrgStartDialogWithFlags().

Returns

The value of the error field in PrgCallbackData.

PrgHandleEvent Function ^TOP^

Purpose

Handles events related to the active progress dialog.

Declared In

Progress.h

Prototype

Boolean PrgHandleEvent (
   ProgressPtr prgGP,
   EventType *eventP
)

Parameters

prgGP
Pointer to a progress structure created by PrgStartDialog() or PrgStartDialogWithFlags().
eventP
Pointer to an event. You can pass a NULL event to cause this function to immediately call your PrgCallbackFunc() function and then update the dialog (for example, after you call PrgUpdateDialog()).

Returns

true if the system handled the event. If it returns false, you should check if the user cancelled the dialog by calling PrgUserCancel().

Comments

Use this function instead of SysHandleEvent() when you have a progress dialog. PrgHandleEvent() internally calls SysHandleEvent() as needed.

If an update to the dialog is pending (from a call to PrgUpdateDialog(), for example) this function handles that event and causes the dialog to be updated. As part of this process, the PrgCallbackFunc() function you specified in your call to PrgStartDialog() is called. Your PrgCallbackFunc() function should set the textP buffer in the PrgCallbackData structure with the new message to be displayed in the progress dialog. Optionally, you can also set the bitmapId and bitmapDatabase fields to include an icon in the update dialog.

See Also

PrgStartDialog(), PrgStopDialog(), PrgUpdateDialog(), PrgUserCancel()

PrgStartDialog Function ^TOP^

Purpose

Displays a progress dialog that can be updated.

Declared In

Progress.h

Prototype

ProgressPtr PrgStartDialog (
   const char *title,
   PrgCallbackFunc textCallback,
   void *userDataP
)

Parameters

title
Pointer to a title for the progress dialog. Must be a null-terminated string that is no longer than progressMaxTitle.
textCallback
Pointer to a callback function that supplies the text and icons for the current progress state. See PrgCallbackFunc().
userDataP
A pointer to data that you need to access in the callback function. This address gets passed directly to your function.

Returns

A pointer to a progress structure. This pointer must be passed to other Progress Manager functions and must be released by calling PrgStopDialog(). NULL is returned if the system is unable to allocate the progress structure.

Comments

The dialog created by this function can be updated by another thread using the PrgUpdateDialog() function. The dialog can contain a Cancel or OK button. The initial dialog defaults to stage 0 and calls the textCallback function to get the initial text and icon data for the progress dialog.

Progress dialogs cannot be associated with window constraints resources, and usually one is not necessary. The UI Library makes sure that the dialog is always the same size and snaps to the bottom of the application area. If you need to set window creation attributes that you would normally set in a constraints resource, use PrgStartDialogWithFlags().

See Also

PrgHandleEvent(), PrgStopDialog(), PrgUpdateDialog(), PrgUserCancel()

PrgStartDialogWithFlags Function ^TOP^

Purpose

Displays a progress dialog that can be updated. Uses the specified window flags to create the dialog.

Declared In

Progress.h

Prototype

ProgressPtr PrgStartDialogWithFlags (
   const char *title,
   PrgCallbackFunc textCallback,
   void *userDataP,
   WinFlagsType flags
)

Parameters

title
Pointer to a title for the progress dialog. Must be a null-terminated string that is no longer than progressMaxTitle.
textCallback
Pointer to a callback function that supplies the text and icons for the current progress state. See PrgCallbackFunc().
userDataP
A pointer to data that you need to access in the callback function. This address gets passed directly to your function.
flags
Window attributes to use when creating the dialog. See WinFlagsType. The attribute winFlagModal is set for you.

Returns

A pointer to a progress structure. This pointer must be passed to other Progress Manager functions and must be released by calling PrgStopDialog(). NULL is returned if the system is unable to allocate the progress structure.

Comments

Use this function instead of PrgStartDialog() in one of two circumstances:

  • You need the window created for the progress dialog to be a transitional window so that you can draw to it outside of frmUpdateEvents. In this case set the winFlagBackBuffer bit in flags.
  • You are displaying a progress dialog outside of the application process and it should appear in the same window layer as all of the other windows in that process.

See Also

PrgHandleEvent(), PrgStopDialog(), PrgUpdateDialog(), PrgUserCancel()

PrgStopDialog Function ^TOP^

Purpose

Releases memory used by the progress dialog and restores the screen to its initial state.

Declared In

Progress.h

Prototype

void PrgStopDialog (
   ProgressPtr prgP,
   Boolean force
)

Parameters

prgP
Pointer to a progress structure created by PrgStartDialog() or PrgStartDialogWithFlags().
force
true removes the progress dialog immediately, false causes the system to wait until the user confirms an error, if one is displayed.

Returns

Nothing.

Comments

If the progress dialog is in a state where it is displaying an error message to the user, this function normally waits for the user to confirm the dialog before it removes the dialog. If you specify true for the force parameter, this causes the system to remove the dialog immediately.

See Also

PrgHandleEvent(), PrgStartDialog(), PrgUpdateDialog(), PrgUserCancel()

PrgUpdateDialog Function ^TOP^

Purpose

Updates the status of the current progress dialog.

Declared In

Progress.h

Prototype

void PrgUpdateDialog (
   ProgressPtr prgGP,
   status_t err,
   uint16_t stage,
   const char *messageP,
   Boolean updateNow
)

Parameters

prgGP
Pointer to a progress structure created by PrgStartDialog() or PrgStartDialogWithFlags().
err
If nonzero, causes the dialog to go into error mode, to display an error message with only an OK button.
stage
Current stage of progress. The callback function can use this to determine the correct string to display in the updated dialog.
messageP
Extra text that may be useful in displaying the progress for this stage. Used by the callback function, which can append it to the base message that is based on the stage.
updateNow
If true, the dialog is immediately updated. If false, sends a prgUpdateEvent, which causes the dialog to be updated on the next call to PrgHandleEvent().

Returns

Nothing.

Comments

This function can be called from a background thread to update the dialog in the application thread. The updateNow parameter must be false in this situation.

For more information about how the parameters are used and the callback function, see the section "Application-Defined Functions."

See Also

PrgHandleEvent(), PrgStartDialog(), PrgStopDialog(), PrgUserCancel()

PrgUserCancel Function ^TOP^

Purpose

Returns true if the user cancelled the process using the progress dialog.

Declared In

Progress.h

Prototype

Boolean PrgUserCancel (
   const ProgressType *prgP
)

Parameters

prgP
Pointer to a progress structure created by PrgStartDialog() or PrgStartDialogWithFlags().

Returns

true if the user tapped the Cancel button; false otherwise.

Comments

This is a function you can use to check if the user cancelled the process. If the user did cancel, you can change the progress dialog text to something like "Cancelling," or "Disconnecting," or whatever is appropriate for your application. Then you should cancel the process, end the communication session, or do whatever processing is necessary.

See Also

PrgHandleEvent(), PrgStartDialog(), PrgStopDialog(), PrgUpdateDialog()

PrgUserSkip Function ^TOP^

Purpose

Returns true if the user skipped the current stage of the process using the progress dialog.

Declared In

Progress.h

Prototype

Boolean PrgUserSkip (
   const ProgressType *prgP
)

Parameters

prgP
Pointer to a progress structure created by PrgStartDialog() or PrgStartDialogWithFlags().

Returns

true if the user tapped the Skip button; false otherwise.

Comments

This is a function you can use to check if the user skipped the current stage of the process. If the user did skip, you can change the progress dialog text to something like "Skipping," or whatever is appropriate for your application. Then you should move on to the next stage of the process, or do whatever processing is necessary.

The progress dialog only has a skip button if you specifically enable it by setting displaySkipBtn to true in the PrgCallbackData structure.

Application-Defined Functions ^TOP^

PrgCallbackFunc Function ^TOP^

Purpose

Supplies the text and icons for the current progress state.

Declared In

Progress.h

Prototype

Boolean (
   *PrgCallbackFunc
) (
   PrgCallbackDataPtr cbP
)

Parameters

cbP
A pointer to a PrgCallbackData structure.

Returns

true if the progress dialog should be updated using the values you specified in the PrgCallbackData structure. If you return false, the dialog is still updated, but with default status messages. (Returning false is not recommended.)

Comments

This is a callback function that you specify when you call PrgStartDialog(). The callback function is called by PrgHandleEvent() when it needs current progress information to display in the progress dialog.

In this function, you should set the value of the textP buffer to the string you want to display in the progress dialog when it is updated. You can use the value in the stage field to look up a message in a string resource. You also might want to append the text in the message field to your base string. Typically, the message field would contain more dynamic information that depends on a user selection, such as a phone number, device name, or network identifier, etc.

For example, the PrgUpdateDialog() function might have been called with a stage of 1 and a message parameter value of a phone number string, "555-1212". Based on the stage, you might find the string "Dialing" in a string resource, and append the phone number, to form the final text "Dialing 555-1212" that you place in the text buffer textP.

Keeping the static strings corresponding to various stages in a resource makes it easier to localize your application. More dynamic information can be passed in by calling PrgUpdateDialog() with a messageP parameter.


NOTE: This function is called only if the parameters passed to PrgUpdateDialog() have changed from the last time it was called. If PrgUpdateDialog() is called twice with exactly the same parameters, the callback function is called only once.