IDWriteFontFace::TryGetFontTable method

Finds the specified OpenType font table if it exists and returns a pointer to it. The function accesses the underlying font data through the IDWriteFontFileStream interface implemented by the font file loader.

Syntax

virtual HRESULT TryGetFontTable(
  [in]        UINT32  openTypeTableTag,
  [out] const void   ** tableData,
  [out]       UINT32 * tableSize,
  [out]       void   ** tableContext,
  [out]       BOOL   * exists
) = 0;

Parameters

openTypeTableTag [in]

Type: UINT32

The four-character tag of a OpenType font table to find. Use the DWRITE_MAKE_OPENTYPE_TAG macro to create it as an UINT32. Unlike GDI, it does not support the special TTCF and null tags to access the whole font.

tableData [out]

Type: const void**

When this method returns, contains the address of a pointer to the base of the table in memory. The pointer is valid only as long as the font face used to get the font table still exists; (not any other font face, even if it actually refers to the same physical font). This parameter is passed uninitialized.

tableSize [out]

Type: UINT32*

When this method returns, contains a pointer to the size, in bytes, of the font table.

tableContext [out]

Type: void**

When this method returns, the address of a pointer to the opaque context, which must be freed by calling ReleaseFontTable. The context actually comes from the lower-level IDWriteFontFileStream, which may be implemented by the application or DWrite itself. It is possible for a NULL tableContext to be returned, especially if the implementation performs direct memory mapping on the whole file. Nevertheless, always release it later, and do not use it as a test for function success. The same table can be queried multiple times, but because each returned context can be different, you must release each context separately.

exists [out]

Type: BOOL*

When this method returns, TRUE if the font table exists; otherwise, FALSE.

Return value

Type: HRESULT

If this method succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.

Remarks

The context for the same tag may be different for each call, so each one must be held and released separately.

Requirements

See also

IDWriteFontFace