最佳的自动换行的算法？ [英] Best word wrap algorithm?
问题描述
自动换行是一个必须具备的现代文本编辑器的功能。
Word wrap is one of must-have features in modern text editor.
你知道如何处理自动换行？ 什么是自动换行的最佳算法？
Do you know how to handle word wrap? What is the best algorithm for word-wrap?
更新： 如果文字是几百万行，我怎样才能使自动换行非常之快？
updated: If text is several million lines, how can I make word-wrap very fast?
更新：为什么我需要的解决方案？因为我的项目必须绘制文本的各种缩放级别，同时外形美观。
updated: Why I need the solution? Because my projects must draw text with various zoom level and simultaneously beautiful appearance.
更新：运行环境是Windows Mobile设备。最高600MHz的速度非常小的内存大小。
updated: Running environment is Windows Mobile devices. Maximum 600MHz speed with very small memory size.
更新：我应该如何处理行信息？让我们假设原始数据有三条线。
updated: How should I handle line information? Let's assume original data has three lines.
THIS IS LINE 1.
THIS IS LINE 2.
THIS IS LINE 3.
在断字的文字会显示像这样：
After word break text will be shown like this:
THIS IS
LINE 1.
THIS IS
LINE 2.
THIS IS
LINE 3.
我应该拨出3线多吗？或者有什么其他的建议？
Should I allocate 3 lines more? Or any other suggestions?
推荐答案
下面是我写在C＃中自动换算法。它应该很容易翻译成其他语言（也许除了 IndexOfAny ）。
Here is a word-wrap algorithm I've written in C#. It should be fairly easy to translate into other languages (except perhaps for IndexOfAny).
static char[] splitChars = new char[] { ' ', '-', '\t' };
private static string WordWrap(string str, int width)
{
string[] words = Explode(str, splitChars);
int curLineLength = 0;
StringBuilder strBuilder = new StringBuilder();
for(int i = 0; i < words.Length; i += 1)
{
string word = words[i];
// If adding the new word to the current line would be too long,
// then put it on a new line (and split it up if it's too long).
if (curLineLength + word.Length > width)
{
// Only move down to a new line if we have text on the current line.
// Avoids situation where wrapped whitespace causes emptylines in text.
if (curLineLength > 0)
{
strBuilder.Append(Environment.NewLine);
curLineLength = 0;
}
// If the current word is too long to fit on a line even on it's own then
// split the word up.
while (word.Length > width)
{
strBuilder.Append(word.Substring(0, width - 1) + "-");
word = word.Substring(width - 1);
strBuilder.Append(Environment.NewLine);
}
// Remove leading whitespace from the word so the new line starts flush to the left.
word = word.TrimStart();
}
strBuilder.Append(word);
curLineLength += word.Length;
}
return strBuilder.ToString();
}
private static string[] Explode(string str, char[] splitChars)
{
List<string> parts = new List<string>();
int startIndex = 0;
while (true)
{
int index = str.IndexOfAny(splitChars, startIndex);
if (index == -1)
{
parts.Add(str.Substring(startIndex));
return parts.ToArray();
}
string word = str.Substring(startIndex, index - startIndex);
char nextChar = str.Substring(index, 1)[0];
// Dashes and the likes should stick to the word occuring before it. Whitespace doesn't have to.
if (char.IsWhiteSpace(nextChar))
{
parts.Add(word);
parts.Add(nextChar.ToString());
}
else
{
parts.Add(word + nextChar);
}
startIndex = index + 1;
}
}
这是相当原始 - 它分裂的空格，制表符和破折号。它确保破折号坚持到它之前的单词（这样你就不会结束与堆栈\正溢出），尽管它不利于移动的小连字符的话换行，而不是分裂他们。它拆分的话，如果他们太久了一条线。
It's fairly primitive - it splits on spaces, tabs and dashes. It does make sure that dashes stick to the word before it (so you don't end up with stack\n-overflow) though it doesn't favour moving small hyphenated words to a newline rather than splitting them. It does split up words if they are too long for a line.
这也是非常特定的文化，因为我不知道很多关于其他文化的自动换行规则。
It's also fairly culturally specific, as I don't know much about the word-wrapping rules of other cultures.
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