GetUtf8StringWidth

Short summary

This function returns the width of a given Utf-8 string.

A width of -1 means the string contains control characters, e.g. line feed or carriage return. If a string has for example a line break, the width cannot be calculated. A width 0 means the string is either empty or consists only of combining marks.

Attention: The actual width a character needs for displaying is always dependent on the used font, the fontsize and the rendering! The width this function returns is actually an estimation.

Example:

myString :String(10) := 'Test';
myWidth, charCount :UDINT;
------------------
GetUtf8StringLength(
	stringAddress := ADR(myString),
	width => myWidth,
	visibleCharacters => charCount
);

• Return type: DINT

Parameters

Name	Type	Comment	Kind
utf8StringBuffer	PVOID	adrress of the utf-8 encoded string or byte array (must be also null terminated!)	input
width	DINT	width of the given string	output
visibleCharacters	UDINT	count of visible characters	output

Code

Declaration

FUNCTION GetUtf8StringWidth
VAR_INPUT
	(* adrress of the utf-8 encoded string or byte array (must be also null terminated!) *)
	utf8StringBuffer :PVOID;
END_VAR
VAR_OUTPUT
	(* width of the given string *)
	width :DINT := 0;
	(* count of visible characters *)
	visibleCharacters :UDINT := 0;
END_VAR
VAR
	stringBufferLength :UDINT := 0;
	codepoints :POINTER TO UnicodeCodePoint;
	codepointCount :UDINT;
END_VAR

Implementation

stringBufferLength := GetUtf8StringLength(utf8StringBuffer);
RETURN (stringBufferLength = 0);
codepoints := __NEW(UnicodeCodePoint, stringBufferLength);
RETURN(codepoints = 0);

GetCodepointsFromUtf8String(
	utf8StringAddress := utf8StringBuffer,
	utf8StringByteCount := GetUtf8StringLength(utf8StringBuffer),
	codePointBuffer := codepoints,
	bufferSize := stringBufferLength * 4,
	codePointsCount => codepointCount );
	
width := GetWidthFromCodepointSequence(
			codepoints := codepoints,
			codepointCount := codepointCount,
			visibleCharacters => visibleCharacters
);
			
__DELETE(codepoints);