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c# - RichTextBox保存 "Selection Direction"

转载 作者:太空狗 更新时间:2023-10-29 23:42:07 24 4
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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。为此,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,但我无法保持“选择方向”:如果用户从光标向前或向后突出显示。

关于如何在不更改选择的情况下保存选择方向或为文本着色的任何想法?

最佳答案

我刚刚遇到了同样的问题,现在我使用 EM_EXSETSEL 解决了这个问题。当 cpMin > cpMax 时,它的工作方式类似于“向后选择”(所选文本开头的插入符号)。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)但是在 SelectionStart/Length 变化之后......

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,但至少以下方法对我有用。

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);
}

关于c# - RichTextBox保存 "Selection Direction",我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/3801293/

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