from palm-dev e-mail list, credit goes to Logan Shaw

typedef struct
{
    RectangleType bounds;
    WinHandle savedbits;
} ProgBar;

void OpenProgressBar (ProgBar *progbar)
{
    UInt16 savebitserror;

    progbar->savedbits = WinSaveBits (& progbar->bounds, & savebitserror);
    WinEraseRectangle (& progbar->bounds, 0);
}

void CloseProgressBar (ProgBar *progbar)
{
    if (progbar->savedbits)
    {
        WinRestoreBits (
	        progbar->bounds.topLeft.x, progbar->bounds.topLeft.y,
	        progbar->savedbits);
    }
    else
    {
	/* maybe should enqueue a frmUpdateEvent instead, maybe not */
        WinEraseRectangle (& progbar->bounds, 0);
    }
}

void UpdateProgressBar (ProgBar *progbar, Int32 numerator, Int32 denominator)
{
    RectangleType fillrect;

    RctCopyRectangle (& progbar->bounds, & fillrect);
    fillrect.extent.x = progbar->bounds.extent.x * numerator / denominator;

    WinDrawRectangle (& fillrect, 0);
}

void TestProgressBar ()
{
    Int32 i;
    const Int32 max = 25;
    ProgBar progbar;

    progbar.bounds.topLeft.x = 20;
    progbar.bounds.topLeft.y = 70;
    progbar.extent.x = 120;
    progbar.extent.y = 20;

    OpenProgressBar (& progbar);
    for (i = 0; i <= max; i++)
    {
        UpdateProgressBar (& progbar, i, max);
        SysTaskDelay (SysTicksPerSecond() / 5);
    }
    CloseProgressBar (& progbar);
}

Preferences structure definition

typedef struct {
	int skeletonData;
} Prefs;

Prefs prefs;

Open preferences

void startApp() {
	Int16 prefSize = sizeof(Prefs);
	if ((PrefGetAppPreferences (AppCreator, 
			 		1000, // pref database id
			 		&prefs, 
			 		&prefSize, 
		 	 		true) // saved during Hotsync
		== noPreferenceFound) 
		|| (prefSize != sizeof(Prefs))) {
					// default initialization, since discovered 
					// Prefs was missing or old.
		prefs.skeletonData=1;
	}
}

Write preferences

void stopApp() {
	PrefSetAppPreferences (AppCreator, 
				1000,	// pref database id
				1, 	// version of pref database
				&prefs, 
				sizeof(Prefs), 
				true);	// saved during hotsync
}

Load and initializing the library

#include 
int MathLibRef = -1;
...
// is library already loaded?
err = SysLibFind("MathLib", &MathLibRef);
if (err != 0) {
	// negative, load
	err = SysLibLoad('libr', 'MthL', &MathLibRef);
	if (err == 0) {
		err = MathLibOpen (MathLibRef, 1);
	}
}

Closing library

if (MathLibRef != -1) {
	Err err;
	UInt16 usecount;
	err = MathLibClose (MathLibRef, &usecount);
	if (usecount == 0) {
		SysLibRemove (MathLibRef);
	}
}

static Boolean frmMain_myField_OnfldEnter(EventPtr event)
{
    SysKeyboardDialog(kbdAlpha);
    return true;
}

UInt32       *ptrScreen = BmpGetBits(WinGetBitmap(WinGetDisplayWindow()));
// 8bits/color, 320x320 display.. fill entire display with black
UInt32       count = 320*320

while(count--) { ptrScreen[count] = 0; }

* since OS3.5

is neccessary to evalute number of colors used and desired resolution. Buffer is by rows from upper. 16bit (65535) means 2bytes per pixel, 256 means 1byte etc...

for PalmOS<3.5 use the following:

WindowType  *winP;
winP = WinGetWindowHandle( win );
ptr = winP->displayAddrV20;

resource - .h file:

#define CustomAlert 1000

resource - .rcp file:

ALERT ID CustomAlert
BEGIN
  TITLE "custom alert"
  MESSAGE "^1\n^2\n^3"
  BUTTONS "OK"
END

code:

    Char alertMsg[64];
    StrPrintF(alertMsg, "Your value is %d", yourValue);
    FrmCustomAlert(CustomAlert, alertMsg, "", "");

do NOT pass NULL value as param in FrmCustomAlert - always use "".

Boolean SetScreenColorDepth(int depth)
{
    UInt16 reqDepth=depth;
    Err err = WinScreenMode(winScreenModeSet,NULL,NULL,&reqDepth,NULL);
    return !err;
}

Boolean RestoreScreenColorDepth(void)
{
    Err err = WinScreenMode(winScreenModeSetToDefaults,NULL,NULL,NULL,NULL);
    return !err;
}

You must set color depth before any window is created. Check error codes for unsupported modes.