如何对字符串中的位置执行命中测试

Question

我正在使用Graphics.DrawString 写出一个字符串，并且需要在给定鼠标位置的字符串中获取字符索引。

这看起来应该很简单，但我真的很难找到一种可行的方法。

我找到了e.Graphics.MeasureString，它返回了它设法写入的字符数，但它有一些issues。

目前我唯一的工作方法是测量a，然后是ab，然后是abc，直到我超过我的x位置，但这是一个糟糕的解决方案......

Answer 1

您可以在编写字符串时计算占用字符串中每个字符的矩形的坐标。之后你可以扫描这个列表，看看鼠标坐标是否在这个矩形内。

Answer 2

正如一条评论告诉您的，您可以使用MeasureCharacterRanges 来实现此目的。我必须首先说我编辑并删除了我以前的答案，因为它太长了。其次，所有这些代码都改编自here。

这个解决方案远非完美，但它可能会引导您实现您想要的。首先，我们有一个方法可以测量最长 32 个字符的字符串的字符：

// Measure the characters in a string with
// no more than 32 characters.
private List<RectangleF> MeasureCharactersInWord(
    Graphics gr, Font font, string text)
{
    List<RectangleF> result = new List<RectangleF>();

    using (StringFormat string_format = new StringFormat())
    {
        string_format.Alignment = StringAlignment.Near;
        string_format.LineAlignment = StringAlignment.Near;
        string_format.Trimming = StringTrimming.None;
        string_format.FormatFlags =
            StringFormatFlags.MeasureTrailingSpaces;

        CharacterRange[] ranges = new CharacterRange[text.Length];
        for (int i = 0; i < text.Length; i++)
        {
            ranges[i] = new CharacterRange(i, 1);
        }
        string_format.SetMeasurableCharacterRanges(ranges);

        RectangleF rect = new RectangleF(0, 0, 10000, 100);
        Region[] regions =
            gr.MeasureCharacterRanges(
                text, font, this.ClientRectangle,
                string_format);

        foreach (Region region in regions)
            result.Add(region.GetBounds(gr));
    }

    return result;
}

在这之后，我们现在需要一个方法来测量整个字符串，不管多长：

private List<RectangleF> MeasureCharacters(Graphics gr,Font font, int      
                                           posY,string text)
{
    List<RectangleF> results = new List<RectangleF>();

    // The X location for the next character.
    float x = 0;

    // Get the character sizes 31 characters at a time.
    for (int start = 0; start < text.Length; start += 32)
    {
        // Get the substring.
        int len = 32;
        if (start + len >= text.Length) len = text.Length - start;
        string substring = text.Substring(start, len);

        // Measure the characters.
        List<RectangleF> rects =
            MeasureCharactersInWord(gr, font, substring);

        // Remove lead-in for the first character.
        if (start == 0) x += rects[0].Left;

        // Save all but the last rectangle.
        for (int i = 0; i < rects.Count + 1 - 1; i++)
        {
            RectangleF new_rect = new RectangleF(
                x, posY,
                rects[i].Width, rects[i].Height);
            results.Add(new_rect);

            // Move to the next character's X position.
            x += rects[i].Width;
        }
    }

    // Return the results.
    return results;
}

这是绘制字符串并将所有字符位置存储在 2 行中的方法：

List<List<RectangleF>> linesCharactersPositions = new List<List<RectangleF>>();
private void Form3_Paint(object sender, PaintEventArgs e)
{
    linesCharactersPositions = new List<List<RectangleF>>();
    string[] lines = new string[] { "12345678  0234567890123456789012asdjkhfkjasdhfklhasdlkfjhlasdkjhfasdlfhlasdc",
                                        "vm,xv,cxznvrtrutyquiortorutoqwruyoiurweyoquitiqwrtiqwetryqweiufhsduafh" };
    Font f = new Font("Arial", 18);

    int lineY = 10;
    foreach (string line in lines)
    {
        DrawLongStringWithCharacterBounds(e.Graphics, line, new Font("Arial", 18), new PointF(10, lineY));
        linesCharactersPositions.Add(MeasureCharacters(e.Graphics, f,lineY, line));
        lineY += 20;
    }


}

最后，MouseMove 事件：

private void Form_MouseMove(object sender, MouseEventArgs e)
{
    Graphics g = this.CreateGraphics();
    int characterCount = 0;
    foreach(var linePositions in linesCharactersPositions)
    {
        for (int i = 0; i < linePositions.Count; i++)
        {
            if (linePositions[i].Contains(e.Location))
            {

                label1.Text = "Index: " + (i+characterCount);
            }
        }
        characterCount += linePositions.Count;
    }

}