/// <summary>
/// Check if the selection direction is forward or backward.<br/>
/// Is the selection start word is before the selection end word in DFS traversal.
/// </summary>
private void CheckSelectionDirection()
{
if (_selectionStart == _selectionEnd)
{
_backwardSelection = _selectionStartIndex > _selectionEndIndex;
}
else if (DomUtils.GetCssLineBoxByWord(_selectionStart) == DomUtils.GetCssLineBoxByWord(_selectionEnd))
{
_backwardSelection = _selectionStart.Left > _selectionEnd.Left;
}
else
{
_backwardSelection = _selectionStart.Top >= _selectionEnd.Bottom;
}
}
/// <summary>
/// Calculate the charecter index and offset by charecters for the given word and given offset.
/// If the location is below the word line then set the selection to the end.<br/>
/// If the location is to the right of the word then set the selection to the end.<br/>
/// If the offset is to the left of the word set the selection to the begining.<br/>
/// Otherwise calculate the width of each substring to find the char the location is on.
/// </summary>
/// <param name="control">used to create graphics to measure string</param>
/// <param name="word">the word to calculate its index and offset</param>
/// <param name="loc">the location to calculate for</param>
/// <param name="selectionIndex">return the index of the char under the location</param>
/// <param name="selectionOffset">return the offset of the char under the location</param>
/// <param name="inclusive">is to include the first charecter in the calculation</param>
private static void CalculateWordCharIndexAndOffset(Control control, CssRect word, Point loc, bool inclusive, out int selectionIndex, out float selectionOffset)
{
selectionIndex = 0;
selectionOffset = 0.1f;
var offset = loc.X - word.Left;
if (word.Text == null)
{
// not a text word - set full selection
selectionIndex = -1;
selectionOffset = -1;
}
else if (offset > word.Width - word.OwnerBox.ActualWordSpacing || loc.Y > DomUtils.GetCssLineBoxByWord(word).LineBottom)
{
// mouse under the line, to the right of the word - set to the end of the word
selectionIndex = word.Text.Length;
selectionOffset = word.Width;
}
else if (offset > 0)
{
// calculate partial word selection
selectionIndex = word.Text.Length;
selectionOffset = word.OwnerBox.ActualWordSpacing / 2f;
using (var g = control.CreateGraphics())
{
for (int i = 1; i <= word.Text.Length; i++)
{
var sf = new StringFormat();
sf.SetMeasurableCharacterRanges(new[] { new CharacterRange(0, i) });
var regions = g.MeasureCharacterRanges(word.Text, word.OwnerBox.ActualFont, new RectangleF(0, 0, float.MaxValue, float.MaxValue), sf);
SizeF s = regions[0].GetBounds(g).Size;
if (!inclusive)
{
selectionOffset = s.Width + (s.Width / i / 15f);
}
if (s.Width > offset)
{
selectionIndex = i - (inclusive ? 1 : 0);
break;
}
selectionOffset = s.Width + (s.Width / i / 15f);
}
}
}
}