计算 Windows 中字形的位置

是否有任何简单且兼容的 GDI 或 .NET 可访问的 Windows 子系统可以提供字形位置字符。这里的任务是组合符号，例如阿拉伯语中的符号，有时有多个组合符号链堆叠在一起，例如阿拉伯语 Fatha + 阿拉伯字母上标 Alef + 阿拉伯语 Maddah 以上。问题在于，虽然可以使用 GDI GetCharacterPlacement 精确确定 X 位置，但无法使用从 OpenType 或 TrueType 字体表和锚点以及一组复杂规则派生的 Y 位置计算。最终，要生成阿拉伯语格式正确的 PDF，需要精确的 Y 位置。研究 Microsoft Word 2013 的另存为 PDF 功能，很明显他们有一种正确收集这些数据的方法，因为研究 PDF 详细信息表明每个字符都显示在其精确位置，包括组合符号。

WPF 可能包含一些在 GlyphRun 类属性 GlyphOffsets 中执行此操作的函数。 DirectWrite 具有 IDWriteTextAnalyzer 接口，该接口的 GetGlyphPlacements 方法可以返回 DWRITE_GLYPH_OFFSET 和许多其他复杂的脚本信息。查看 GDI 显示和打印机驱动函数，STROBJ_bEnumPositionsOnly 似乎返回一组包含此信息的 GLYPHPOS 结构。如果您发送全文进行渲染，那么 GDI 在所有情况下肯定都能正确渲染此内容，但如果您想逐个字形地进行渲染，则不会。

XPS 对象模型中的 IXpsOMGlyphs 允许 GetGlyphIndices 调用返回一组 XPS_GLYPH_INDEX 给出水平偏移和垂直偏移，尽管此库不太合适。

最后，唯一合适的库看起来是 Uniscribe，它使用起来很复杂，但自 Internet Explorer 5 和 Windows 2000 以来就受到支持，而不是 GDI 之外的所有其他讨论，这些库通常是 Vista 及更高版本或需要特殊依赖项。 ScriptItemize 返回一个 SCRIPT_STRING_ANALYSIS 数组，该数组可以传递给 ScriptShape，然后 ScriptPlace 返回一个 GOFFSETs 数组。事实上，Uniscribe 将提供有关断字、变音符号、方向流以及复杂脚本中发生的情况的许多其他方面的信息。我只是想知道是否有更简单的方法，或者这是否是此类任务所需的最低限度且完全合适，因为 Uniscribe 似乎很难直接从 .NET 使用，并且合理地需要一个 C++ 包装器，因为有一个很棒的结构和指针的处理。

更新和回答：Uniscribe 不适用于 PDF 目的，因为它在 GDI 设备单元中使用整数，因此准确性会受到很大影响。也许 Microsoft Word 2013 最终支持本机 PDF 转换支持的原因是因为最终似乎依赖于 DirectWrite。如下所述，我在 .NET 中发布了两种代码解决方案作为 CodeProject 上的提示。 DirectWrite 似乎是除了设计自定义字体成形和计算引擎之外的唯一答案。

.NET 中的示例 Uniscribe 代码，因为当前在 Web 上不可用：

     _
    Public Structure GCP_RESULTS
        Public StructSize As UInteger
         _
        Public OutString As String
        Public Order As IntPtr
        Public Dx As IntPtr
        Public CaretPos As IntPtr
        Public [Class] As IntPtr
        Public Glyphs As IntPtr
        Public GlyphCount As UInteger
        Public MaxFit As Integer
    End Structure
     _
    Public Structure SCRIPT_CONTROL
        Public ScriptControlFlags As UInteger
    End Structure
     _
    Public Structure SCRIPT_STATE
        Public ScriptStateFlags As UShort
    End Structure
     _
    Public Structure SCRIPT_ANALYSIS
        Public ScriptAnalysisFlags As UShort
        Public s As SCRIPT_STATE
    End Structure
     _
    Public Structure SCRIPT_VISATTR
        Public ScriptVisAttrFlags As UShort
    End Structure
     _
    Public Structure SCRIPT_ITEM
        Public iCharPos As Integer
        Public a As SCRIPT_ANALYSIS
    End Structure
     _
    Public Structure GOFFSET
        Public du As Integer
        Public dv As Integer
    End Structure
     _
    Public Structure ABC
        Public abcA As Integer
        Public abcB As UInteger
        Public abcC As Integer
    End Structure
    Public Const E_OUTOFMEMORY As Integer = &H8007000E;
    Public Const E_PENDING As Integer = &H8000000A;
    Public Const USP_E_SCRIPT_NOT_IN_FONT As Integer = &H80040200;
     _
    Public Shared Function GetCharacterPlacement(hdc As IntPtr,  lpString As String, nCount As Integer, nMaxExtent As Integer,  ByRef lpResults As GCP_RESULTS, dwFlags As UInteger) As UInteger
    End Function
     _
    Public Shared Function ScriptItemize( wcInChars As String, cInChars As Integer, cMaxItems As Integer, psControl As SCRIPT_CONTROL, psState As SCRIPT_STATE,  pItems() As SCRIPT_ITEM,  ByRef pcItems As Integer) As Integer
    End Function
     _
    Public Shared Function ScriptShape(hdc As IntPtr, ByRef psc As IntPtr,  wcChars As String, cChars As Integer, cMaxGlyphs As Integer, ByRef psa As SCRIPT_ANALYSIS,  wOutGlyphs() As UShort,  wLogClust() As UShort,  psva() As SCRIPT_VISATTR,  ByRef cGlyphs As Integer) As Integer
    End Function
     _
    Public Shared Function ScriptPlace(hdc As IntPtr, ByRef psc As IntPtr, wGlyphs() As UShort, cGlyphs As Integer, psva() As SCRIPT_VISATTR, ByRef psa As SCRIPT_ANALYSIS,  iAdvance() As Integer,  pGoffset() As GOFFSET,  ByRef pABC As ABC) As Integer
    End Function
     _
    Public Shared Function ScriptFreeCache(ByRef psc As IntPtr) As Integer
    End Function
     _
    Public Shared Function GetDC(hWnd As IntPtr) As IntPtr
    End Function
     _
    Public Shared Function ReleaseDC(hWnd As IntPtr, hdc As IntPtr) As Integer
    End Function
     _
    Private Shared Function SelectObject(ByVal hdc As IntPtr, ByVal hObject As IntPtr) As IntPtr
    End Function
    Structure CharPosInfo
        Public Index As Integer
        Public Width As Integer
        Public PriorWidth As Integer
        Public X As Integer
        Public Y As Integer
    End Structure
    Public Shared Function GetWordDiacriticPositions(Str As String, useFont As Font) As CharPosInfo()
        Dim hdc As IntPtr
        Dim CharPosInfos As New List(Of CharPosInfo)
        hdc = GetDC(IntPtr.Zero) 'desktop device context
        Dim oldFont As IntPtr = SelectObject(hdc, useFont.ToHfont())
        Dim MaxItems As Integer = 16
        Dim Control As New SCRIPT_CONTROL With {.ScriptControlFlags = 0}
        Dim State As New SCRIPT_STATE With {.ScriptStateFlags = 1} '0 LTR, 1 RTL
        Dim Items() As SCRIPT_ITEM = Nothing
        Dim ItemCount As Integer
        Dim Result As Integer
        Do
            ReDim Items(MaxItems - 1)
            Result = ScriptItemize(Str, Str.Length, MaxItems, Control, State, Items, ItemCount)
            If Result = 0 Then
                ReDim Preserve Items(ItemCount) 'there is a dummy last item so adding one here
                Exit Do
            ElseIf Result = E_OUTOFMEMORY Then
            End If
            MaxItems *= 2
        Loop While True
        If Result = 0 Then
            'last item is dummy item pointing to end of string
            Dim Cache As IntPtr = IntPtr.Zero
            For Count = 0 To ItemCount - 2
                Dim Logs() As UShort = Nothing
                Dim Glyphs() As UShort = Nothing
                Dim VisAttrs() As SCRIPT_VISATTR = Nothing
                ReDim Glyphs((Items(Count + 1).iCharPos - Items(Count).iCharPos) * 3 \ 2 + 16 - 1)
                ReDim VisAttrs((Items(Count + 1).iCharPos - Items(Count).iCharPos) * 3 \ 2 + 16 - 1)
                ReDim Logs(Items(Count + 1).iCharPos - Items(Count).iCharPos - 1)
                Dim dc As IntPtr = IntPtr.Zero
                Do
                    Dim GlyphsUsed As Integer
                    Result = ScriptShape(dc, Cache, Str.Substring(Items(Count).iCharPos), Items(Count + 1).iCharPos - Items(Count).iCharPos, Glyphs.Length, Items(Count).a, Glyphs, Logs, VisAttrs, GlyphsUsed)
                    If Result = 0 Then
                        ReDim Preserve Glyphs(GlyphsUsed - 1)
                        ReDim Preserve VisAttrs(GlyphsUsed - 1)
                        Exit Do
                    ElseIf Result = E_PENDING Then
                        dc = hdc
                    ElseIf Result = E_OUTOFMEMORY Then
                        ReDim Glyphs(Glyphs.Length * 2 - 1)
                        ReDim VisAttrs(VisAttrs.Length * 2 - 1)
                    ElseIf Result = USP_E_SCRIPT_NOT_IN_FONT Then
                    Else
                    End If
                Loop While True
                If Result = 0 Then
                    Dim Advances(Glyphs.Length - 1) As Integer
                    Dim Offsets(Glyphs.Length - 1) As GOFFSET
                    Dim abc As New ABC With {.abcA = 0, .abcB = 0, .abcC = 0}
                    dc = IntPtr.Zero
                    Do
                        Result = ScriptPlace(dc, Cache, Glyphs, Glyphs.Length, VisAttrs, Items(Count).a, Advances, Offsets, abc)
                        If Result  E_PENDING Then Exit Do
                        dc = hdc
                    Loop While True
                    If Result = 0 Then
                        Dim LastPriorWidth As Integer = 0
                        Dim RunStart As Integer = 0
                        For CharCount = 0 To Logs.Length - 1
                            Dim PriorWidth As Integer = 0
                            Dim RunCount As Integer = 0
                            For ResCount As Integer = Logs(CharCount) To If(CharCount = Logs.Length - 1, 0, Logs(CharCount + 1)) Step -1
                                'fDiacritic or fZeroWidth
                                If (VisAttrs(ResCount).ScriptVisAttrFlags And (32 Or 64))  0 Then
                                    CharPosInfos.Add(New CharPosInfo With {.Index = RunStart + RunCount, .PriorWidth = LastPriorWidth, .Width = Advances(ResCount), .X = Offsets(ResCount).du, .Y = Offsets(ResCount).dv})
                                End If
                                If CharCount = Logs.Length - 1 OrElse Logs(CharCount)  Logs(CharCount + 1) Then
                                    PriorWidth += Advances(ResCount)
                                    RunCount += 1
                                End If
                            Next
                            LastPriorWidth += PriorWidth
                            If CharCount = Logs.Length - 1 OrElse Logs(CharCount)  Logs(CharCount + 1) Then
                                RunStart = CharCount + 1
                            End If
                        Next
                    End If
                End If
            Next
            ScriptFreeCache(Cache)
        End If
        SelectObject(hdc, oldFont)
        ReleaseDC(IntPtr.Zero, hdc)
        Return CharPosInfos.ToArray()
    End Function