RichTextBox保存“选择方向”

Question

我有一个WinForms程序其中，无论何时更改您的选择，RichTextBox都需要更改某些其他文本的颜色。为了做到这一点，它必须选择文本，因此我失去了我目前的选择。

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

有关如何保存选择方向或为文本上色而不必更改选区的任何想法？

Answer 1

Yu，，丑陋的问题。不，EM_SETPARAFORMAT只能用于当前选择。 EM_EXSETSEL总是将插入符号放在选择的末尾。您可以通过观察SelectionStart中的更改来检测选择方向，但是无法在正确的位置获取插入符号。编辑控件有同样的问题。

这通常不是问题，因为重新着色只在用户修改文本时发生，而不是在她选择文本时发生。我能想到的唯一解决方法是通过注入击键恢复选择。真让人难过。

Answer 2

另一种方法可以直接设置Rtf属性。你确实需要知道rtf语言的语法。

PS。这也会使选择无效。我自己做了按键注射。

Answer 3

我刚刚遇到同样的问题，现在我通过使用EM_EXSETSEL解决了这个问题。当cpMin> cpMax时，它就像“向后选择”（选定文本的开头处的插入符号）一样工作。然而，我还没有发现任何其他方式找出当前选择方向（EM_EXGETSEL总是返回cpMin < cpMax则），但以下SelectionStart /长度变化......

编辑：

这是我使用的解决一下这个。可能有一些更简单的方法，但至少以下适用于我。

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); 
}