在Windows窗体上拖动时调整矩形大小 [英] Resizing a Rectangle while dragging on Windows Form

问题描述

我在Windows窗体的顶部绘制了一个矩形，我想使用提供的其中一个手柄来调整它的大小！

I have a Rectangle Drawn on top of my Windows Form and I want to resize it using one of the handles provided !

Rectangle areaRect = new Rectangle(100,100, 300, 300);
Bool dragging = false;
Point ptOld = new Point(0, 0);

protected override void OnPaint(PaintEventArgs e)
{
  Graphics dcPaint = e.Graphics;
  dcPaint.DrawRectangle(rectPen, areaRect);
}

protected override void OnMouseDown(MouseEventArgs e)
{
  ptOld = new Point(e.X, e.Y);
  dragging = true;
}

protected override void OnMouseMove(MouseEventArgs e)
{
  if(dragging = true) 
  {
    Point ptNew = new Point(e.X, e.Y);
    Int32 handleSelected = GetSelectedHandle(ptNew);

   // Lets say I want to resize this rectangle using Handle 2 now.
    if(handleSelected == 2) 
    {
      // I am resizing this rectangle Width
      areaRect.X += ptNew.X - ptOld.X;
      areaRect.Width -= ptNew .X - ptOld.X;

      this.Invalidate();
    }
  }
}

protected override void OnMouseUp(MouseEventArgs e)
{
  dragging = false;
}

它将给我这样的效果.哪个是正确的，

It will give me an effect like this. Which is correct,

不过，我想对此做些微调整，我也想更改此矩形的高度，当我移动第2点时，我的第7点应该保持原样，就像这样. . 类似地，当我移动第4点时，我的第5点应该完整，依此类推，第7点和第2点也是如此.

How ever I want to have a small tweak in this, I would like to change the height of this rectangle as well, When I am moving point 2, my point 7 should remain exactly as it is, Something like this... Similarly when I moving point 4, my point 5 should intact and so on for point 7 and 2 also.

任何想法，如何进行，因为如果我更改高度，我的第7点位置也会更改?

Any idea, how to proceed, because if I change the height, my point 7 location also gets changed ?

推荐答案

在WinForms中像这样在MouseMove上绘制不会很平滑.

Drawing on a MouseMove like this is not going to be very smooth in WinForms.

在调整矩形大小之前，您基本上需要引用该矩形.

You basically need a reference to the rectangle before you resize it.

我添加了以下代码来跟踪矩形和8个可拖动点:

I added the following code to keep track of the rectangle and the 8 draggable points:

private Point GetHandlePoint(int value) {
  Point result = Point.Empty;

  if (value == 1)
    result = new Point(areaRect.Left, areaRect.Top);
  else if (value == 2)
    result = new Point(areaRect.Left, areaRect.Top + (areaRect.Height / 2));
  else if (value == 3)
    result = new Point(areaRect.Left, areaRect.Bottom);
  else if (value == 4)
    result = new Point(areaRect.Left + (areaRect.Width / 2), areaRect.Top);
  else if (value == 5)
    result = new Point(areaRect.Left + (areaRect.Width / 2), areaRect.Bottom);
  else if (value == 6)
    result = new Point(areaRect.Right, areaRect.Top);
  else if (value == 7)
    result = new Point(areaRect.Right, areaRect.Top + (areaRect.Height / 2));
  else if (value == 8)
    result = new Point(areaRect.Right, areaRect.Bottom);

  return result;
}

private Rectangle GetHandleRect(int value) {
  Point p = GetHandlePoint(value);
  p.Offset(-2, -2);
  return new Rectangle(p, new Size(5, 5));
}

这是我修改您的表单代码的方式:

Here is how I reworked your form code:

private Rectangle areaRect = new Rectangle(100, 100, 300, 300);
private Rectangle oldRect;
private int dragHandle = 0;
private Point dragPoint;

public Form1() {
  InitializeComponent();
  this.DoubleBuffered = true;
}

protected override void OnMouseDown(MouseEventArgs e) {
  for (int i = 1; i < 9; i++) {
    if (GetHandleRect(i).Contains(e.Location)) {
      dragHandle = i;
      oldRect = areaRect;
      dragPoint = GetHandlePoint(i);
    }
  }
  base.OnMouseDown(e);
}

protected override void OnMouseMove(MouseEventArgs e) {
  if (dragHandle == 1) {
    // to do
  } else if (dragHandle == 2) {
    int diff = dragPoint.X - e.Location.X;
    areaRect = new Rectangle(oldRect.Left - diff, oldRect.Top, oldRect.Width + diff, oldRect.Height);
  } else if (dragHandle == 7) {
    int diff = dragPoint.X - e.Location.X;
    areaRect = new Rectangle(oldRect.Left, oldRect.Top, oldRect.Width - diff, oldRect.Height);
  }

  if (dragHandle > 0)
    this.Invalidate();

  base.OnMouseMove(e);
}

protected override void OnMouseUp(MouseEventArgs e) {
  dragHandle = 0;
  base.OnMouseUp(e);
}

protected override void OnPaint(PaintEventArgs e) {
  e.Graphics.DrawRectangle(Pens.Red, areaRect);
  for (int i = 1; i < 9; i++) {
    e.Graphics.FillRectangle(Brushes.DarkRed, GetHandleRect(i));
  }
  base.OnPaint(e);
}

发布的代码仅执行第2点和第7点，但这应该给您一些逻辑.我确信可以改进此代码，这只是一个有效的示例.

The posted code only does Points #2 and #7, but that should give you some logic to work with. I'm sure this code can be improved, it's just a working example.

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