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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
#nullable disable
using System;
using System.Diagnostics;
using System.Text;
using System.Xaml;
namespace MS.Internal.Xaml.Parser
{
[DebuggerDisplay("{Text}")]
internal class XamlText
{
private const Char SPACE = ' ';
private const Char NEWLINE = '\n';
private const Char RETURN = '\r';
private const Char TAB = '\t';
private const Char OPENCURLIE = '{';
private const Char CLOSECURLIE = '}';
private const String ME_ESCAPE = "{}";
private const string RETURN_STRING = "\r";
private StringBuilder _sb;
private readonly bool _isSpacePreserve; // should space be preserved or collapsed?
private bool _isWhiteSpaceOnly; // is the whole thing whitespace.
public XamlText(bool spacePreserve)
{
// The majority of TEXT found in a XamlParse results in a single string call to Paste().
// A possible perf improvement might be to hold the first string and
// put off allocating the StringBuilder until a second string is Paste()ed.
_sb = new StringBuilder();
_isSpacePreserve = spacePreserve;
_isWhiteSpaceOnly = true;
}
public bool IsEmpty
{
get { return _sb.Length==0; }
}
public string Text
{
get
{
return _sb.ToString();
}
}
public string AttributeText
{
get
{
String text = Text;
if (text.StartsWith(ME_ESCAPE, false, TypeConverterHelper.InvariantEnglishUS))
{
return text.Remove(0, ME_ESCAPE.Length);
}
return text;
}
}
public bool IsSpacePreserved
{
get { return _isSpacePreserve; }
}
public bool IsWhiteSpaceOnly
{
get { return _isWhiteSpaceOnly; }
}
public void Paste(string text, bool trimLeadingWhitespace, bool convertCRLFtoLF=true)
{
bool newTextIsWhitespace = IsWhitespace(text);
if (_isSpacePreserve)
{
if (convertCRLFtoLF)
{
// (GetFixedDocumentSequence raises Exception "UnicodeString property does not contain
// enough characters to correspond to the contents of Indices property.")
//
// Convert CRLF into just LF. Including attribute text values.
// Attribute text is internal set to "preserve" to prevent (other) processing.
// We processing attribute values in this way because 3.x did it.
// Normally new lines are converted to SPACE by the XML reader.
//
// Note that the code actually just removes CR. Thus it affects
// attribute values that contain CR without LF, which can
// arise by explicit user declaration: <Element Prop="a b" />
// This is the root cause of the GetFixedDocumentSequence bug. I'm leaving it as-is, in
// case there are compat issues, but if the intent was to convert
// CRLF to LF, it should really say Replace("\r\n", "\n")
//
// To fix the GetFixedDocumentSequence bug, we don't do any substitutions if the
// property is Glyphs.UnicodeString, which should never be changed
// without changing the corresponding Glyphs.Indices property.
// See XamlScanner.EnqueueAnotherAttribute for the fixed call.
text = text.Replace(RETURN_STRING, "");
}
_sb.Append(text);
}
else if (newTextIsWhitespace)
{
if (IsEmpty && !trimLeadingWhitespace)
{
_sb.Append(SPACE);
}
}
else
{
bool textHadLeadingWhitespace = IsWhitespaceChar(text[0]);
bool textHadTrailingWhitespace = IsWhitespaceChar(text[text.Length - 1]);
bool existingTextHasTrailingWhitespace = false;
string trimmed = CollapseWhitespace(text);
// When Text is split by a Comment (or other non-Element/PropElement) we will paste
// two pieces of Text together.
// This ensures that the spacing between them is correct.
if (_sb.Length > 0)
{
// If the existing text is WS then just strike it!
if (_isWhiteSpaceOnly)
{
_sb = new StringBuilder();
}
else
{
// Notice if it ends in WS
if (IsWhitespaceChar(_sb[_sb.Length-1]))
{
existingTextHasTrailingWhitespace = true;
}
}
}
// If the new text item had leading whitespace
// AND we were not asked to trim it off
// AND there isn't existing text that ends in whitespace.
// THEN put a space before the trimmed Text.
if (textHadLeadingWhitespace && !trimLeadingWhitespace && !existingTextHasTrailingWhitespace)
{
_sb.Append(SPACE);
}
_sb.Append(trimmed);
// Always leave trailing WS, if it was present.
// Trimming trailing WS can only be figured out from higher level context.
//
if (textHadTrailingWhitespace)
{
_sb.Append(SPACE);
}
}
_isWhiteSpaceOnly = _isWhiteSpaceOnly && newTextIsWhitespace;
}
public bool LooksLikeAMarkupExtension
{
get
{
int length = _sb.Length;
if (length > 0 && _sb[0] == OPENCURLIE)
{
if (length > 1 && _sb[1] == CLOSECURLIE)
return false;
return true;
}
return false;
}
}
// ===========================================================
static bool IsWhitespace(string text)
{
for (int i=0; i<text.Length; i++)
{
if (!IsWhitespaceChar(text[i]))
return false;
}
return true;
}
static bool IsWhitespaceChar(Char ch)
{
return (ch == SPACE || ch == TAB || ch == NEWLINE || ch == RETURN);
}
// This removes all leading and trailing whitespace, and it
// collapses any internal runs of whitespace to a single space.
//
static string CollapseWhitespace(string text)
{
StringBuilder sb = new StringBuilder(text.Length);
int firstIdx=0;
while (firstIdx < text.Length)
{
// If it is not whitespace copy it to the destination.
char ch = text[firstIdx];
if (!IsWhitespaceChar(ch))
{
sb.Append(ch);
++firstIdx;
continue;
}
// Skip any runs of whitespace.
int advancingIdx = firstIdx;
while (++advancingIdx < text.Length)
{
if (!IsWhitespaceChar(text[advancingIdx]))
break;
}
// If the spacing is in the middle. (not at the ends)
if (firstIdx != 0 && advancingIdx != text.Length)
{
bool skipSpace = false;
// check some easy things before digging deep
// for Asian chars. (only process a single newline)
if (ch == NEWLINE)
{
if ((advancingIdx - firstIdx == 2) && text[firstIdx - 1] >= 0x1100)
{
if (HasSurroundingEastAsianChars(firstIdx, advancingIdx, text))
{
skipSpace = true;
}
}
}
if (!skipSpace)
{
sb.Append(SPACE);
}
}
firstIdx = advancingIdx;
}
return sb.ToString();
}
public static string TrimLeadingWhitespace(string source)
{
string result = source.TrimStart(SPACE, TAB, NEWLINE);
return result;
}
public static string TrimTrailingWhitespace(string source)
{
string result = source.TrimEnd(SPACE, TAB, NEWLINE);
return result;
}
// ---- Asian newline suppression code ------
// this code was modeled from the 3.5 XamlReaderHelper.cs
static bool HasSurroundingEastAsianChars(int start, int end, string text)
{
Debug.Assert(start > 0);
Debug.Assert(end < text.Length);
int beforeValue;
if (start - 2 < 0)
{
beforeValue = text[0];
}
else
{
beforeValue = ComputeUnicodeScalarValue(start - 1, start - 2, text);
}
if (IsEastAsianCodePoint(beforeValue))
{
int afterValue;
if (end + 1 >= text.Length)
{
afterValue = text[end];
}
else
{
afterValue = ComputeUnicodeScalarValue(end, end, text);
}
if (IsEastAsianCodePoint(afterValue))
{
return true;
}
}
return false;
}
static int ComputeUnicodeScalarValue(int takeOneIdx, int takeTwoIdx, string text)
{
int unicodeScalarValue=0;
bool isSurrogate = false;
Char highChar = text[takeTwoIdx];
if (Char.IsHighSurrogate(highChar))
{
Char lowChar = text[takeTwoIdx + 1];
if (Char.IsLowSurrogate(lowChar))
{
isSurrogate = true;
unicodeScalarValue = (((highChar & 0x03FF) << 10) | (lowChar & 0x3FF)) + 0x1000;
}
}
if (!isSurrogate)
{
unicodeScalarValue = text[takeOneIdx];
}
return unicodeScalarValue;
}
struct CodePointRange
{
public readonly int Min;
public readonly int Max;
public CodePointRange(int min, int max)
{
Min = min;
Max = max;
}
}
static CodePointRange[] EastAsianCodePointRanges = new CodePointRange[]
{
new CodePointRange ( 0x1100, 0x11FF ), // Hangul
new CodePointRange ( 0x2E80, 0x2FD5 ), // CJK and KangXi Radicals
new CodePointRange ( 0x2FF0, 0x2FFB ), // Ideographic Description
#if NICE_COMMENTED_RANGES
new CodePointRange ( 0x3040, 0x309F ), // Hiragana
new CodePointRange ( 0x30A0, 0x30FF ), // Katakana
new CodePointRange ( 0x3100, 0x312F ), // Bopomofo
new CodePointRange ( 0x3130, 0x318F ), // Hangul Compatibility Jamo
new CodePointRange ( 0x3190, 0x319F ), // Kanbun
new CodePointRange ( 0x31F0, 0x31FF ), // Katakana Phonetic Extensions
new CodePointRange ( 0x3400, 0x4DFF ), // CJK Unified Ideographs Extension A
new CodePointRange ( 0x4E00, 0x9FFF ), // CJK Unified Ideographs
new CodePointRange ( 0xA000, 0xA4CF ), // Yi
#else
new CodePointRange ( 0x3040, 0x319F ),
new CodePointRange ( 0x31F0, 0xA4CF ),
#endif
new CodePointRange ( 0xAC00, 0xD7A3 ), // Hangul Syllables
new CodePointRange ( 0xF900, 0xFAFF ), // CJK Compatibility
new CodePointRange ( 0xFF00, 0xFFEF ), // Halfwidth and Fullwidth forms
// surrogates
new CodePointRange ( 0x20000, 0x2a6d6 ), // CJK Unified Ext. B
new CodePointRange ( 0x2F800, 0x2FA1D ), // CJK Compatibility Supplement
};
// taken directly from WPF 3.5
static bool IsEastAsianCodePoint(int unicodeScalarValue)
{
for (int i = 0; i < EastAsianCodePointRanges.Length; i++)
{
if (unicodeScalarValue >= EastAsianCodePointRanges[i].Min)
{
if (unicodeScalarValue <= EastAsianCodePointRanges[i].Max)
return true;
}
}
return false;
}
}
}
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