GetTextExtentExPointA function (wingdi.h)

Article
02/09/2023

The GetTextExtentExPoint function retrieves the number of characters in a specified string that will fit within a specified space and fills an array with the text extent for each of those characters. (A text extent is the distance between the beginning of the space and a character that will fit in the space.) This information is useful for word-wrapping calculations.

Syntax

BOOL GetTextExtentExPointA(
  [in]  HDC    hdc,
  [in]  LPCSTR lpszString,
  [in]  int    cchString,
  [in]  int    nMaxExtent,
  [out] LPINT  lpnFit,
  [out] LPINT  lpnDx,
  [out] LPSIZE lpSize
);

Parameters

[in] hdc

A handle to the device context.

[in] lpszString

A pointer to the null-terminated string for which extents are to be retrieved.

[in] cchString

The number of characters in the string pointed to by the lpszStr parameter. For an ANSI call it specifies the string length in bytes and for a Unicode it specifies the string length in WORDs. Note that for the ANSI function, characters in SBCS code pages take one byte each, while most characters in DBCS code pages take two bytes; for the Unicode function, most currently defined Unicode characters (those in the Basic Multilingual Plane (BMP)) are one WORD while Unicode surrogates are two WORDs.

[in] nMaxExtent

The maximum allowable width, in logical units, of the formatted string.

[out] lpnFit

A pointer to an integer that receives a count of the maximum number of characters that will fit in the space specified by the nMaxExtent parameter. When the lpnFit parameter is NULL, the nMaxExtent parameter is ignored.

[out] lpnDx

A pointer to an array of integers that receives partial string extents. Each element in the array gives the distance, in logical units, between the beginning of the string and one of the characters that fits in the space specified by the nMaxExtent parameter. This array must have at least as many elements as characters specified by the cchString parameter because the entire array is used internally. The function fills the array with valid extents for as many characters as are specified by the lpnFit parameter. Any values in the rest of the array should be ignored. If alpDx is NULL, the function does not compute partial string widths.

For complex scripts, where a sequence of characters may be represented by any number of glyphs, the values in the alpDx array up to the number specified by the lpnFit parameter match one-to-one with code points. Again, you should ignore the rest of the values in the alpDx array.

[out] lpSize

A pointer to a SIZE structure that receives the dimensions of the string, in logical units. This parameter cannot be NULL.

Return value

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero.

Remarks

If both the lpnFit and alpDx parameters are NULL, calling the GetTextExtentExPoint function is equivalent to calling the GetTextExtentPoint function.

For the ANSI version of GetTextExtentExPoint, the lpDx array has the same number of INT values as there are bytes in lpString. The INT values that correspond to the two bytes of a DBCS character are each the extent of the entire composite character.

Note, the alpDx values for GetTextExtentExPoint are not the same as the lpDx values for ExtTextOut. To use the alpDx values in lpDx, you must first process them.

When this function returns the text extent, it assumes that the text is horizontal, that is, that the escapement is always 0. This is true for both the horizontal and vertical measurements of the text. Even if you use a font that specifies a nonzero escapement, this function doesn't use the angle while it computes the text extent. The app must convert it explicitly. However, when the graphics mode is set to GM_ADVANCED and the character orientation is 90 degrees from the print orientation, the values that this function return do not follow this rule. When the character orientation and the print orientation match for a given string, this function returns the dimensions of the string in the SIZE structure as { cx : 116, cy : 18 }. When the character orientation and the print orientation are 90 degrees apart for the same string, this function returns the dimensions of the string in the SIZE structure as { cx : 18, cy : 116 }.

This function returns the extent of each successive character in a string. When these are rounded to logical units, you get different results than what is returned from the GetCharWidth, which returns the width of each individual character rounded to logical units.

Note

The wingdi.h header defines GetTextExtentExPoint as an alias which automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	wingdi.h (include Windows.h)
Library	Gdi32.lib
DLL	Gdi32.dll