Add gwinPrintg() and fix null pointer handling in sprintg()

docs/releases.txt

@@ -7,6 +7,8 @@ FIX:		Fixing bug where the list item count wasn't decremented when an item was r
 FEATURE:	Add options GFILE_FATFS_EXTERNAL_LIB and GFILE_PETITFSFS_EXTERNAL_LIB
 FEATURE:	Added FT6x06 driver
 FIX:		Fixing issue in STM32F746G-Discovery board file that resulted in bad color reproduction
+FEATURE:	Added gwinPrintg()
+FIX:		Fix sprintg and related functions handling of NULL pointers.
 
 
 *** Release 2.5 ***

src/gfile/gfile_fs_strings.c

@@ -22,12 +22,18 @@ static int StringRead(GFILE *f, void *buf, int size) {
 	int		res;
 	char	*p;
 
+	if (!f->obj)
+		return 0;
+	
 	p = ((char *)f->obj) + f->pos;
 	for(res = 0; res < size && *p; res++, p++, buf = ((char *)buf)+1)
 		((char *)buf)[0] = *p;
 	return res;
 }
 static int StringWrite(GFILE *f, const void *buf, int size) {
+	if (!f->obj)
+		return 0;
+	
 	if ((f->flags & GFILEFLG_APPEND)) {
 		while(((char *)f->obj)[f->pos])
 			f->pos++;
@@ -50,7 +56,7 @@ static const GFILEVMT StringVMT = {
 };
 
 static void gfileOpenStringFromStaticGFILE(GFILE *f, char *str) {
-	if ((f->flags & GFILEFLG_TRUNC))
+	if ((f->flags & GFILEFLG_TRUNC) && str)
 		str[0] = 0;
 	f->vmt = &StringVMT;
 	f->obj = str;
@@ -62,7 +68,7 @@ GFILE *gfileOpenString(char *str, const char *mode) {
 	GFILE	*f;
 
 	// Get an empty file and set the flags
-	if (!(f = _gfileFindSlot(mode)))
+	if (!str || !(f = _gfileFindSlot(mode)))
 		return 0;
 
 	// File is open - fill in all the details

src/gwin/gwin_widget.c

@@ -530,6 +530,44 @@ void gwinSetText(GHandle gh, const char *text, bool_t useAlloc) {
 	_gwinUpdate(gh);
 }
 
+#if GFX_USE_GFILE && GFILE_NEED_PRINTG && GFILE_NEED_STRINGS
+	#include <stdarg.h>
+
+	void gwinPrintg(GHandle gh, const char * fmt, ...) {
+		char *str;
+		va_list va;
+		int size;
+		
+		if (!(gh->flags & GWIN_FLG_WIDGET))
+			return;
+
+		// Dispose of the old string
+		if ((gh->flags & GWIN_FLG_ALLOCTXT)) {
+			gh->flags &= ~GWIN_FLG_ALLOCTXT;
+			if (gw->text) {
+				gfxFree((void *)gw->text);
+				gw->text = "";
+			}
+		}
+
+		// Alloc the new text
+		va_start (va, fmt);
+
+		size = vsnprintg(0, 0, fmt, va) + 1;		//determine the buffer size required
+
+		if ((str = gfxAlloc(size))) {
+			gh->flags |= GWIN_FLG_ALLOCTXT;
+			vsnprintg(str, size, fmt, va);
+			gw->text = (const char *)str;
+		} else
+			gw->text = "";
+		
+		va_end (va);
+
+		_gwinUpdate(gh);
+	}
+#endif
+
 const char *gwinGetText(GHandle gh) {
 	if (!(gh->flags & GWIN_FLG_WIDGET))
 		return 0;

src/gwin/gwin_widget.h

@@ -231,6 +231,24 @@ void gwinSetText(GHandle gh, const char *text, bool_t useAlloc);
  */
 const char *gwinGetText(GHandle gh);
 
+#if (GFX_USE_GFILE && GFILE_NEED_PRINTG && GFILE_NEED_STRINGS) || defined(__DOXYGEN__)
+	/**
+	 * @brief   Set the text of a widget using a printf style format.
+	 * @pre		GFX_USE_GFILE, GFILE_NEED_PRINTG and GFILE_NEED_STRINGS must all be TRUE
+	 *
+	 * @param[in] gh		The widget handle
+	 * @param[in] fmt		The format string using a printf/g syntax. See @p vsnprintg()
+	 * @param[in] ...		The printg paramters.
+	 *
+	 * @note				The widget is automatically redrawn
+	 * @note				Non-widgets will ignore this call.
+	 * @note				The memory for the text is always allocated by this function.
+	 *
+	 * @api
+	 */
+	void gwinPrintg(GHandle gh, const char * fmt,...);
+#endif
+
 /**
  * @brief	Check whether a handles is a widget handle or not
  *