RichTextBox 保存“选择方向”

Question

我有一个 WinForms 程序，每当您更改选择时，RichTextBox 都需要更改某些其他文本的颜色。为了做到这一点，它必须选择该文本，因此我失去了当前的选择。

我可以保存和加载 SelectionStart 和 SelectionLength 属性，但无法保留“选择方向”：如果用户从光标向前或向后突出显示。

关于如何保存选择方向或为文本着色而无需更改选择的任何想法？

Answer 1

我刚刚遇到了同样的问题，现在我通过使用 EM_EXSETSEL 解决了这个问题。当cpMin>时cpMax，它的工作原理类似于“向后选择”（插入符号位于所选文本的开头）。然而我还没有找到任何其他方法来找出当前的选择方向（EM_EXGETSEL 总是返回 cpMin < cpMax），但是遵循 SelectionStart/Length 更改...

编辑：

这就是我用来解决这个问题的方法。可能有一些更简单的方法，但至少以下对我有用。

using System.Runtime.InteropServices;

//********************
//SendMessage stuff for EM_EXSETSEL
//********************

[StructLayout(LayoutKind.Sequential)]
public struct CHARRANGE
{
    public int cpMin;
    public int cpMax;
}

[DllImport("user32.dll")]
private static extern IntPtr SendMessage(IntPtr hWnd, UInt32 msg, IntPtr wParam, ref CHARRANGE lParam);

private const UInt32 WM_USER = 0x0400;
private const UInt32 EM_EXSETSEL = WM_USER + 55;
private const UInt32 EM_EXGETSEL = WM_USER + 52;

//********************
//event handlers
//********************

//locking variable to avoid stack overflow while setting selection in code
private bool richTextBox1_SelectionChanged_lock = false;

//handler for richTextBox selection change event
private void richTextBox1_SelectionChanged(object sender, EventArgs e)
{
    if (richTextBox1_SelectionChanged_lock) return;
    richTextBox1_SelectionChanged_lock = true;

    //detect selection changes and store information needed for restoring
    TrackRTBSelection(richTextBox1.SelectionStart, richTextBox1.SelectionLength);

    //here do whatever you want with selection (some analysis to show font name in font selection comboBox etc.)
    //...

    //restore selection from saved informations
    SetRTBSelectionBasedOnTracking();

    richTextBox1_SelectionChanged_lock = false;
}

//sample button click handler for changing fore color of selected text
private void buttonSetForeColor_Click(object sender, EventArgs e)
{
    if (colorDialog1.ShowDialog() == DialogResult.Cancel)
        return;

    //prevent selection change events while we are changing font colors
    if (richTextBox1_SelectionChanged_lock) return;
    richTextBox1_SelectionChanged_lock = true;

    //save selection parameters for use in loop
    int selStart = richTextBox1.SelectionStart;
    int selLength = richTextBox1.SelectionLength;

    for (int i = 0; i < selLength; i++)
    {
        richTextBox1.SelectionLength = 1;
        richTextBox1.SelectionStart = selStart + i;

        richTextBox1.SelectionColor = colorDialog1.Color;
    }

    //restore selection from saved informations
    SetRTBSelectionBasedOnTracking();

    richTextBox1_SelectionChanged_lock = false;
}

//********************
//selection tracking utilities
//********************

//false - caret at the beginning; true - caret at the end
private bool caretPosition = false;
private int lastSelectionStart = -1;
private int lastSelectionLength = -1;

//initialize selection informations. this must be called during Form_Load
private void InitRTBSelection()
{
    richTextBox1.SelectionStart = 0;
    richTextBox1.SelectionLength = 0;

    caretPosition = false;
    lastSelectionStart = 0;
    lastSelectionLength = 0;

    //force "selection changed" to detect "selection changes" for the first time
    richTextBox1_SelectionChanged(richTextBox1, new EventArgs());
}

//this method detects changes in selection, based on selection parameters received from richTextBox
private void TrackRTBSelection(int newSelectionStart, int newSelectionLength)
{
    int condition = 0;

    int s_change = (newSelectionStart - lastSelectionStart > 0) ?
                    1 :
                    (newSelectionStart - lastSelectionStart < 0) ? -1 : 0;
    int l_change = (newSelectionLength - lastSelectionLength > 0) ?
                    1 :
                    (newSelectionLength - lastSelectionLength < 0) ? -1 : 0;

    //these conditions where created over change table for all user-achievable scenarios
    condition = (newSelectionLength == 0 ||
                (l_change == 1 && s_change == -1) ||
                (l_change == -1 && s_change == 1 && caretPosition == false)) ? 1 : condition;
    condition = (s_change == 0 && (l_change == 1 || (caretPosition == true && l_change == -1))) ? 2 : condition;

    switch (condition)
    {
        case 1: caretPosition = false; break;
        case 2: caretPosition = true; break;
        default: break; //if no condition was satisfied then maintain current information
    }

    lastSelectionStart = newSelectionStart;
    lastSelectionLength = newSelectionLength;
}

//set richTextBox selection using EM_EXSETSEL
private void SetRTBSelectionBasedOnTracking()
{
    CHARRANGE chrrange = new CHARRANGE
    {
        cpMin = caretPosition ? lastSelectionStart : lastSelectionStart + lastSelectionLength,
        cpMax = caretPosition ? lastSelectionStart + lastSelectionLength : lastSelectionStart
    };
    SendMessage(richTextBox1.Handle, EM_EXSETSEL, IntPtr.Zero, ref chrrange);
}

Answer 2

哎呀，丑陋的问题。不可以，EM_SETPARAFORMAT 只能对当前选择起作用。并且 EM_EXSETSEL 始终将插入符号放在选择的末尾。您可以通过观察 SelectionStart 的变化来检测选择方向，但无法将插入符号放在正确的位置。编辑控件也有同样的问题。

这通常不是问题，因为仅当用户修改文本时才会发生重新着色，而不是在选择文本时发生。我能想到的唯一解决方法是通过注入击键来恢复选择。太丑了。

Answer 3

另一种方法是直接设置 Rtf 属性。您确实需要了解 rtf 语言的语法。

附言。这也将使选择无效。我自己进行了按键注入。