/// <summary>
/// Draw an expand/collapse box for the given node using provided centre point.
/// </summary>
/// <param name="tc">Reference to owning TreeControl.</param>
/// <param name="n">Reference to Node instance.</param>
/// <param name="g">Reference to Graphics instance to draw into.</param>
/// <param name="x">X centre of box.</param>
/// <param name="y">Y centre of box.</param>
public virtual void DrawExpandCollapseBox(TreeControl tc, Node n, Graphics g, int x, int y)
{
bool hasChildren = (n.Nodes.VisibleCount > 0);
// Do we need to draw a box for this child node?
if (tc.BoxShownAlways || hasChildren)
{
// Create rectangle at centre of box position
Rectangle box = new Rectangle(x, y, 0, 0);
// If we theme information and the boxes need drawing themed
if (tc.IsControlThemed && (tc.BoxDrawStyle == DrawStyle.Themed))
{
// Themes cannot support the drawing of an empty expand/collapse box
if (hasChildren)
{
// Find how far to expand left and up
int halfV = tc.GlyphThemeSize.Height / 2;
int halfH = tc.GlyphThemeSize.Width / 2;
// Move box so that centre of box is centred
box.Y -= halfV;
box.X -= halfH;
// Expand it to required size
box.Size = tc.GlyphThemeSize;
// Ask the tree to draw the themed box in required state
tc.DrawThemedBox(g, box, n.IsExpanded);
}
}
else
{
// Should we draw in the gradient style?
bool gradient = (tc.BoxDrawStyle == DrawStyle.Gradient);
// Find how far to expand left and up
int half = tc.BoxLength / 2;
// Expand it to required size
box.X -= half;
box.Y -= half;
box.Width = tc.BoxLength - 1;
box.Height = tc.BoxLength - 1;
if (gradient)
{
// Modify box very slightly to make gradient look better
Rectangle boxCopy = box;
boxCopy.Inflate(1, 1);
// Create graduated brush using inside color and box size
using (Brush brush = new LinearGradientBrush(boxCopy,
tc.BoxInsideColor,
tc.BackColor,
225))
{
// Fill inside with required brush first
g.FillRectangle(brush, box);
}
// Draw the border as all except the four corner pixels
using (Pen pen = new Pen(tc.BoxBorderColor, 1),
lightPen = new Pen(ControlPaint.Light(tc.BoxBorderColor, 1)))
{
g.DrawLine(pen, box.Left + 1, box.Bottom, box.Right - 1, box.Bottom);
g.DrawLine(pen, box.Right, box.Top + 1, box.Right, box.Bottom - 1);
g.DrawLine(lightPen, box.Left + 1, box.Top, box.Right - 1, box.Top);
g.DrawLine(lightPen, box.Left, box.Top + 1, box.Left, box.Bottom - 1);
}
}
else
{
// Fill inside with required brush first
g.FillRectangle(tc.GetCacheBoxInsideBrush(), box);
// Draw border in required color around box
g.DrawRectangle(tc.GetCacheBoxBorderPen(), box);
}
// Only draw a plus/minus sign if node has children
if (hasChildren)
{
// Cannot draw a sign if the box is too small to show it
if (tc.BoxLength >= 7)
{
Pen boxSignPen = tc.GetCacheBoxSignPen();
// Find length of the line for drawing sign
int sign = (tc.BoxLength / 3) - 1;
// Always draw the minus part of sign
g.DrawLine(boxSignPen, box.X + half, box.Y + half, box.X + half - sign, box.Y + half);
g.DrawLine(boxSignPen, box.X + half, box.Y + half, box.X + half + sign, box.Y + half);
// Only draw the line to make it a plus sign, if not expanded
if (!n.IsExpanded)
{
g.DrawLine(boxSignPen, box.X + half, box.Y + half, box.X + half, box.Y + half - sign);
g.DrawLine(boxSignPen, box.X + half, box.Y + half, box.X + half, box.Y + half + sign);
}
}
}
else
{
// Otherwise we just draw a dot at the center
g.DrawLine(tc.GetCacheBoxSignPen(), new PointF(box.X + half, box.Y + half),
new PointF(box.X + half + 0.1f, box.Y + half));
}
}
}
}