MarkerVerticalScrollBar

What it is for

It is a VerticalScrollBar in every other respect: range, position, events and themes work the same. On top of that it draws the objects in ScrollBarMarks, in the way an editor marks its scroll bar.

Marks

• ScrollBarShapeMark – a rectangle or oval, solid or gradient, centred on its ScrollBarMarkBase.Value.
• ScrollBarRangeMark – a band from ScrollBarMarkBase.Value to ScrollBarRangeMark.EndValue.
• ScrollBarImageMark – a small image, such as an icon.

A mark's value is in the bar's own range units and is placed at the same point of the track as the thumb's top would be for that position. ScrollBarMarkBase.Alignment puts it at the left, centre or right of the bar.

Using it

Turn on ShouldEnableMarkerDrawing – it is off by default – add marks to ScrollBarMarks, and call Invalidate() after changing the list. Clicking a mark scrolls to it (ShouldScrollUponBookmarkClick); hovering over one with ScrollBarMarkBase.ToolTipInfo shows its tool tip.

Marks are hit tested where they were last drawn, so they respond to the mouse only once they have been painted.

Marking the error lines of a build log shown in a list box.

using Binarymission.WinForms.Controls.MarkerScrollBar;

var logBar = new MarkerVerticalScrollBar
{
    Location = new Point(buildLog.Right, buildLog.Top),
    Height = buildLog.Height,
    MaximumScrollRange = buildLog.Items.Count,
    LargeChange = buildLog.ClientSize.Height / buildLog.ItemHeight,
    SmallChange = 1,
    ShouldEnableMarkerDrawing = true,
};

for (int line = 0; line < buildLog.Items.Count; line++)
{
    var text = (string)buildLog.Items[line];
    if (!text.Contains(": error "))
        continue;

    logBar.ScrollBarMarks.Add(new ScrollBarShapeMark
    {
        Value = line,
        Size = new SizeF(8, 4),
        Alignment = ScrollBarMarkAlignment.Center,
        StartColor = Color.Firebrick,
        ToolTipTitle = "Line " + (line + 1),
        ToolTipInfo = text,
        ToolTipIcon = ToolTipIcon.Error,
    });
}

logBar.PositionChanged += (sender, e) => buildLog.TopIndex = (int)e.NewPosition;
Controls.Add(logBar);