ExtTextOutW function (wingdi.h)

Bài viết
02/09/2023

The ExtTextOut function draws text using the currently selected font, background color, and text color. You can optionally provide dimensions to be used for clipping, opaquing, or both.

Syntax

BOOL ExtTextOutW(
  [in] HDC        hdc,
  [in] int        x,
  [in] int        y,
  [in] UINT       options,
  [in] const RECT *lprect,
  [in] LPCWSTR    lpString,
  [in] UINT       c,
  [in] const INT  *lpDx
);

Parameters

[in] hdc

A handle to the device context.

[in] x

The x-coordinate, in logical coordinates, of the reference point used to position the string.

[in] y

The y-coordinate, in logical coordinates, of the reference point used to position the string.

[in] options

Specifies how to use the application-defined rectangle. This parameter can be one or more of the following values.

Value	Meaning
ETO_CLIPPED	The text will be clipped to the rectangle.
ETO_GLYPH_INDEX	The lpString array refers to an array returned from GetCharacterPlacement and should be parsed directly by GDI as no further language-specific processing is required. Glyph indexing only applies to TrueType fonts, but the flag can be used for bitmap and vector fonts to indicate that no further language processing is necessary and GDI should process the string directly. Note that all glyph indexes are 16-bit values even though the string is assumed to be an array of 8-bit values for raster fonts. For ExtTextOutW, the glyph indexes are saved to a metafile. However, to display the correct characters the metafile must be played back using the same font. For ExtTextOutA, the glyph indexes are not saved.
ETO_IGNORELANGUAGE	Reserved for system use. If an application sets this flag, it loses international scripting support and in some cases it may display no text at all.
ETO_NUMERICSLATIN	To display numbers, use European digits.
ETO_NUMERICSLOCAL	To display numbers, use digits appropriate to the locale.
ETO_OPAQUE	The current background color should be used to fill the rectangle.
ETO_PDY	When this is set, the array pointed to by lpDx contains pairs of values. The first value of each pair is, as usual, the distance between origins of adjacent character cells, but the second value is the displacement along the vertical direction of the font.
ETO_RTLREADING	Middle East language edition of Windows: If this value is specified and a Hebrew or Arabic font is selected into the device context, the string is output using right-to-left reading order. If this value is not specified, the string is output in left-to-right order. The same effect can be achieved by setting the TA_RTLREADING value in SetTextAlign. This value is preserved for backward compatibility.

The ETO_GLYPH_INDEX and ETO_RTLREADING values cannot be used together. Because ETO_GLYPH_INDEX implies that all language processing has been completed, the function ignores the ETO_RTLREADING flag if also specified.

[in] lprect

A pointer to an optional RECT structure that specifies the dimensions, in logical coordinates, of a rectangle that is used for clipping, opaquing, or both.

[in] lpString

A pointer to a string that specifies the text to be drawn. The string does not need to be zero-terminated, since cbCount specifies the length of the string.

[in] c

The length of the string pointed to by lpString.

This value may not exceed 8192.

[in] lpDx

A pointer to an optional array of values that indicate the distance between origins of adjacent character cells. For example, lpDx[i] logical units separate the origins of character cell i and character cell i + 1.

Return value

If the string is drawn, the return value is nonzero. However, if the ANSI version of ExtTextOut is called with ETO_GLYPH_INDEX, the function returns TRUE even though the function does nothing.

If the function fails, the return value is zero.

Remarks

The current text-alignment settings for the specified device context determine how the reference point is used to position the text. The text-alignment settings are retrieved by calling the GetTextAlign function. The text-alignment settings are altered by calling the SetTextAlign function. You can use the following values for text alignment. Only one flag can be chosen from those that affect horizontal and vertical alignment. In addition, only one of the two flags that alter the current position can be chosen.

Term	Description
TA_BASELINE	The reference point will be on the base line of the text.
TA_BOTTOM	The reference point will be on the bottom edge of the bounding rectangle.
TA_TOP	The reference point will be on the top edge of the bounding rectangle.
TA_CENTER	The reference point will be aligned horizontally with the center of the bounding rectangle.
TA_LEFT	The reference point will be on the left edge of the bounding rectangle.
TA_RIGHT	The reference point will be on the right edge of the bounding rectangle.
TA_NOUPDATECP	The current position is not updated after each text output call. The reference point is passed to the text output function.
TA_RTLREADING	Middle East language edition of Windows: The text is laid out in right to left reading order, as opposed to the default left to right order. This applies only when the font selected into the device context is either Hebrew or Arabic.
TA_UPDATECP	The current position is updated after each text output call. The current position is used as the reference point.

If the lpDx parameter is NULL, the ExtTextOut function uses the default spacing between characters. The character-cell origins and the contents of the array pointed to by the lpDx parameter are specified in logical units. A character-cell origin is defined as the upper-left corner of the character cell.

By default, the current position is not used or updated by this function. However, an application can call the SetTextAlign function with the fMode parameter set to TA_UPDATECP to permit the system to use and update the current position each time the application calls ExtTextOut for a specified device context. When this flag is set, the system ignores the X and Y parameters on subsequent ExtTextOut calls.

For the ANSI version of ExtTextOut, the lpDx array has the same number of INT values as there are bytes in lpString. For DBCS characters, you can apportion the dx in the lpDx entries between the lead byte and the trail byte, as long as the sum of the two bytes adds up to the desired dx. For DBCS characters with the Unicode version of ExtTextOut, each Unicode glyph gets a single pdx entry.

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

ExtTextOut will use Uniscribe when necessary resulting in font fallback. The ETO_IGNORELANGUAGE flag will inhibit this behavior and should not be passed.

Additionally, ExtTextOut will perform internal batching of calls before transitioning to kernel mode, mitigating some of the performance concerns when weighing usage of PolyTextOut versus ExtTextOut.

Tip

ExtTextOut is strongly recommended over PolyTextOut for modern development due to its ability to handle display of different languages.

Examples

For an example, see "Setting Fonts for Menu-Item Text Strings" in Using Menus.

Note

The wingdi.h header defines ExtTextOut 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

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