Method DrawChildren

Source/Editor/GUI/Tree/TreeNode.cs:820–891

()

        /// <inheritdoc />
        protected override void DrawChildren()
        {
            // Draw all visible child controls
            var children = _children;
            if (children.Count == 0)
                return;
            var last = children.Count - 1;

            if (CullChildren)
            {
                Render2D.PeekClip(out var globalClipping);
                Render2D.PeekTransform(out var globalTransform);

                // Try to estimate the rough location of the first and the last nodes, assuming the node height is constant
                var firstChildGlobalRect = GetChildGlobalRectangle(children[0], ref globalTransform);
                var firstVisibleChild = Math.Clamp((int)Math.Floor((globalClipping.Top - firstChildGlobalRect.Top) / _headerHeight) + 1, 0, last);
                if (GetChildGlobalRectangle(children[firstVisibleChild], ref globalTransform).Top > globalClipping.Top || !children[firstVisibleChild].Visible)
                {
                    // Estimate overshoot, either it's partially visible or hidden in the tree
                    for (; firstVisibleChild > 0; firstVisibleChild--)
                    {
                        var child = children[firstVisibleChild];
                        if (!child.Visible)
                            continue;
                        if (GetChildGlobalRectangle(child, ref globalTransform).Top < globalClipping.Top)
                            break;
                    }
                }
                var lastVisibleChild = Math.Clamp((int)Math.Ceiling((globalClipping.Bottom - firstChildGlobalRect.Top) / _headerHeight) + 1, firstVisibleChild, last);
                if (GetChildGlobalRectangle(children[lastVisibleChild], ref globalTransform).Top < globalClipping.Bottom || !children[lastVisibleChild].Visible)
                {
                    // Estimate overshoot, either it's partially visible or hidden in the tree
                    for (; lastVisibleChild < last; lastVisibleChild++)
                    {
                        var child = children[lastVisibleChild];
                        if (!child.Visible)
                            continue;
                        if (GetChildGlobalRectangle(child, ref globalTransform).Top > globalClipping.Bottom)
                            break;
                    }
                }

                for (int i = firstVisibleChild; i <= lastVisibleChild; i++)
                {
                    var child = children[i];
                    if (!child.Visible)
                        continue;
                    Render2D.PushTransform(ref child._cachedTransform);
                    child.Draw();
                    Render2D.PopTransform();
                }

                static Rectangle GetChildGlobalRectangle(Control control, ref Matrix3x3 globalTransform)
                {
                    Matrix3x3.Multiply(ref control._cachedTransform, ref globalTransform, out var globalChildTransform);
                    return new Rectangle(globalChildTransform.M31, globalChildTransform.M32, control.Width * globalChildTransform.M11, control.Height * globalChildTransform.M22);
                }
            }