/// <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);
}
}
}
}
/// <summary>
/// Handle html text selection by mouse move over the html with left mouse button pressed.<br/>
/// Calculate the words in the selected range and set their selected property.
/// </summary>
/// <param name="control">the control hosting the html to invalidate</param>
/// <param name="loc">the mouse location</param>
/// <param name="allowPartialSelect">true - partial word selection allowed, false - only full words selection</param>
private void HandleSelection(Control control, Point loc, bool allowPartialSelect)
{
// get the line under the mouse or nearest from the top
var lineBox = DomUtils.GetCssLineBox(_root, loc);
if (lineBox != null)
{
// get the word under the mouse
var word = DomUtils.GetCssBoxWord(lineBox, loc);
// if no word found uner the mouse use the last or the first word in the line
if (word == null && lineBox.Words.Count > 0)
{
if (loc.Y > lineBox.LineBottom)
{
// under the line
word = lineBox.Words[lineBox.Words.Count - 1];
}
else if (loc.X < lineBox.Words[0].Left)
{
// before the line
word = lineBox.Words[0];
}
else if (loc.X > lineBox.Words[lineBox.Words.Count - 1].Right)
{
// at the end of the line
word = lineBox.Words[lineBox.Words.Count - 1];
}
}
// if there is matching word
if (word != null)
{
if (_selectionStart == null)
{
// on start set the selection start word
_selectionStartPoint = loc;
_selectionStart = word;
if (allowPartialSelect)
{
CalculateWordCharIndexAndOffset(control, word, loc, true);
}
}
// always set selection end word
_selectionEnd = word;
if (allowPartialSelect)
{
CalculateWordCharIndexAndOffset(control, word, loc, false);
}
ClearSelection(_root);
if (CheckNonEmptySelection(loc, allowPartialSelect))
{
CheckSelectionDirection();
SelectWordsInRange(_root, _backwardSelection ? _selectionEnd : _selectionStart, _backwardSelection ? _selectionStart : _selectionEnd);
}
else
{
_selectionEnd = null;
}
_cursorChanged = true;
control.Cursor = Cursors.IBeam;
control.Invalidate();
}
}
}