Markers and Bookmarking Lines

This recipe shows how markers can be used to indicate bookmarked lines and iterate through them. Markers are symbols displayed in the left margins and are typically used for things like showing breakpoints, search results, the current line of execution, or in this case, bookmarks.

In the Form.Load event we'll prepare a margin to be used for our bookmarks and we'll configure one of the markers to use the Bookmark symbol:

private const int BOOKMARK_MARGIN = 1; // Conventionally the symbol margin
private const int BOOKMARK_MARKER = 3; // Arbitrary. Any valid index would work.

private void MainForm_Load(object sender, EventArgs e)
{
    var margin = scintilla.Margins[BOOKMARK_MARGIN];
    margin.Width = 16;
    margin.Sensitive = true;
    margin.Type = MarginType.Symbol;
    margin.Mask = Marker.MaskAll;
    margin.Cursor = MarginCursor.Arrow;

    var marker = scintilla.Markers[BOOKMARK_MARKER];
    marker.Symbol = MarkerSymbol.Bookmark;
    marker.SetBackColor(Color.DeepSkyBlue);
    marker.SetForeColor(Color.Black);

    scintilla.MarginClick += Scintilla_MarginClick;
}

The margin is flagged as Sensitive so we can receive mouse click notifications from it (and because this margin can sometimes get emotional). The margin Mask is a way of restricting which marker symbols can appear in the margin. For the purposes of this example we'll configure it so that all marker symbols assigned to any given line will be displayed.

By handling the MarginClick event we can toggle a bookmark marker for each line:

private void scintilla_MarginClick(object sender, MarginClickEventArgs e)
{
    if (e.Margin == BOOKMARK_MARGIN)
    {
        // Do we have a marker for this line?
        const uint mask = (1 << BOOKMARK_MARKER);
        var line = scintilla.Lines[scintilla.LineFromPosition(e.Position)];
        if ((line.MarkerGet() & mask) > 0)
        {
            // Remove existing bookmark
            line.MarkerDelete(BOOKMARK_MARKER);
        }
        else
        {
            // Add bookmark
            line.MarkerAdd(BOOKMARK_MARKER);
        }
    }
}

The code above makes use of the MarkerGet method to get a bitmask indicating which markers are set for the current line. This mask is a 32-bit value where each bit corresponds to one of the 32 marker indexes. If marker 0 were set, bit 0 would be set. If marker 1 where set, bit 1 would be set and so on. To determine if our maker has been set for a line we would want to check if the 1 << 3 bit is set which is what the statement (line.MarkerGet() & mask) > 0 does.

At this point, if you run the code you should be able to add and remove pretty blue bookmarks from document lines. To let a user jump between bookmarks we'll add 'Next' and 'Previous' buttons and wire-up their click events like this:

private void buttonPrevious_Click(object sender, EventArgs e)
{
    var line = scintilla.LineFromPosition(scintilla.CurrentPosition);
    var prevLine = scintilla.Lines[--line].MarkerPrevious(1 << BOOKMARK_MARKER);
    if (prevLine != -1)
        scintilla.Lines[prevLine].Goto();
}

private void buttonNext_Click(object sender, EventArgs e)
{
    var line = scintilla.LineFromPosition(scintilla.CurrentPosition);
    var nextLine = scintilla.Lines[++line].MarkerNext(1 << BOOKMARK_MARKER);
    if (nextLine != -1)
        scintilla.Lines[nextLine].Goto();
}