/// <summary>
/// Precalculates and caches line segments that the form can snap onto.
/// </summary>
private SnapGrid PrepareSizeMove(Control.ControlCollection mdiChildren)
{
// Ignore the possibility that the MDI client rectangle is empty.
// Create a list of MDI child rectangles sorted by their z-order. (MDI child on top has index 0.)
List <Rectangle> mdiChildRectangles = new List <Rectangle>();
int mdiChildCount = mdiChildren.Count;
for (int mdiChildIndex = 0; mdiChildIndex < mdiChildCount; ++mdiChildIndex)
{
if (mdiChildren[mdiChildIndex] is Form mdiChildForm && mdiChildForm.Visible && mdiChildForm.WindowState == FormWindowState.Normal)
{
// Convert the bounds of this MDI child to screen coordinates.
Rectangle mdiChildRectangle = mdiChildForm.Bounds;
mdiChildRectangle.Offset(m_currentMdiClientScreenRectangle.Left, m_currentMdiClientScreenRectangle.Top);
if (Form != mdiChildForm)
{
// Intersect the MDI child rectangle with the MDI client rectangle, so the form does not snap to edges outside of the visible MDI client rectangle.
mdiChildRectangle = Rectangle.Intersect(mdiChildRectangle, m_currentMdiClientScreenRectangle);
// Only add non-empty rectangles.
if (mdiChildRectangle.Left < mdiChildRectangle.Right && mdiChildRectangle.Top < mdiChildRectangle.Bottom)
{
mdiChildRectangles.Add(mdiChildRectangle);
}
}
else
{
// Save original rectangle, so its properties can be used to keep positions or sizes constant during sizing and/or moving.
m_rectangleBeforeSizeMove = mdiChildRectangle;
}
}
}
// Calculate snappable segments and save them to arrays which can be used efficiently from within the event handlers.
List <LineSegment> verticalSegments = SnapGrid.GetVerticalEdges(ref m_currentMdiClientScreenRectangle, 0);
List <LineSegment> horizontalSegments = SnapGrid.GetHorizontalEdges(ref m_currentMdiClientScreenRectangle, 0);
return(new SnapGrid(verticalSegments, horizontalSegments, mdiChildRectangles, InsensitiveBorderEndLength));
}
/// <summary>
/// Checks if line segments that the form can snap onto should be precalculated (again).
/// </summary>
private void CheckUpdateSizeMove()
{
Form parentForm = Form.MdiParent;
if (parentForm != null)
{
foreach (Control c in parentForm.Controls)
{
if (c is MdiClient)
{
// Get the bounds of the MDI client relative to the screen coordinates, because that is also how the size/move rectangles will be passed into WndProc().
Rectangle currentMdiClientScreenRectangle = c.RectangleToScreen(c.ClientRectangle);
if (m_snapGrid == null || currentMdiClientScreenRectangle != m_currentMdiClientScreenRectangle)
{
m_currentMdiClientScreenRectangle = currentMdiClientScreenRectangle;
m_snapGrid = PrepareSizeMove(c.Controls);
}
// No need to check 'other' MdiClients, so stop looping.
return;
}
}
}
}
private void OwnedForm_ResizeBegin(object sender, EventArgs e)
{
// Precalculate size/move line segments.
Form parentForm = Form.Owner;
if (parentForm != null)
{
m_rectangleBeforeSizeMove = Form.Bounds;
// Enumerate all siblings and the parent form in z-order.
Form[] snapTargetForms = parentForm.OwnedForms.Union(new SingleElementEnumerable <Form>(parentForm)).ToArray();
IntPtr[] handles = snapTargetForms.Where(x => x.IsHandleCreated).Select(x => x.Handle).ToArray();
int handleCount = handles.Length;
List <Form> formsInZOrder = new List <Form>(handleCount);
NativeMethods.EnumWindows(
new EnumThreadWindowsCallback((handle, lParam) =>
{
int handleIndex = Array.IndexOf(handles, handle);
if (handleIndex >= 0)
{
formsInZOrder.Add(snapTargetForms[handleIndex]);
handles[handleIndex] = IntPtr.Zero;
handleCount--;
}
return(handleCount > 0);
}), IntPtr.Zero);
// Now build the snap grid from all working areas edges, then the sibling rectangles.
var verticalSegments = new List <LineSegment>();
var horizontalSegments = new List <LineSegment>();
foreach (Screen screen in Screen.AllScreens)
{
Rectangle workingArea = screen.WorkingArea;
verticalSegments.AddRange(SnapGrid.GetVerticalEdges(ref workingArea, InsensitiveBorderEndLength));
horizontalSegments.AddRange(SnapGrid.GetHorizontalEdges(ref workingArea, InsensitiveBorderEndLength));
}
// Add snap line segments for each sibling.
List <Rectangle> siblingRectangles = new List <Rectangle>();
foreach (Form form in formsInZOrder)
{
if (form != Form && form.Visible && form.WindowState == FormWindowState.Normal)
{
Rectangle bounds = form.Bounds;
// Only add non-empty rectangles.
if (bounds.Left < bounds.Right && bounds.Top < bounds.Bottom)
{
siblingRectangles.Add(bounds);
}
}
}
m_snapGrid = new SnapGrid(verticalSegments, horizontalSegments, siblingRectangles, InsensitiveBorderEndLength);
if (SnapWhileMoving)
{
Form.Moving += OwnedForm_Moving;
}
if (SnapWhileResizing)
{
Form.Resizing += OwnedForm_Resizing;
}
}
}
private void OwnedForm_ResizeEnd(object sender, EventArgs e)
{
Form.Moving -= OwnedForm_Moving;
Form.Resizing -= OwnedForm_Resizing;
m_snapGrid = null;
}
private void MdiChild_ResizeEnd(object sender, EventArgs e)
{
Form.Moving -= MdiChild_Moving;
Form.Resizing -= MdiChild_Resizing;
m_snapGrid = null;
}
