textbox: add clear() function

Origin commit data
------------------
Commit: 0b504f8c60
Author: vanhofen <vanhofen@gmx.de>
Date: 2016-10-31 (Mon, 31 Oct 2016)

Origin message was:
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- textbox: add clear() function

src/gui/widget/textbox.cpp

@@ -836,6 +836,16 @@ void CTextBox::hide (void)
 	frameBuffer = NULL;
 }
 
+void CTextBox::clear(void)
+{
+	//TRACE("[CTextBox] %s Line %d\r\n", __FUNCTION__, __LINE__);
+	if (frameBuffer == NULL)
+		return;
+
+	std::string clear(" ");
+	setText(&clear);
+}
+
 bool CTextBox::clearScreenBuffer()
 {
 	if(m_bgpixbuf){

src/gui/widget/textbox.h

@@ -210,6 +210,7 @@ class CTextBox : public sigc::trackable
 		inline int	getTextMode()			{return m_nMode;};
 		void paint (void);
 		void hide (void);
+		void clear(void);
 		bool clearScreenBuffer();
 		sigc::signal<void> OnAfterRefresh;
 		sigc::signal<void> OnAfterScrollPage;