C# MDI application: how to scale child windows when main window is re-sized?

Question

Hi,
I have an MDI application that have several child forms.  Users can view several forms at one time, and users also are given the options to arrange the child forms anyway they want:  cascade or tile.  What I want to achieve is that if the
parent window is re-sized, all child forms should also be re-sized proportionally.   The code that I have only work if the child forms are tiled horizontally, AND that I only make the main window wider.  Otherwise, all forms are scaled (but not perfect),
however, the location is not scaled; therefore, they are overlapping each other.   I greatly appreciate any help from you.  
Size m_preSize;
private void MainForm_ResizeBegin(object sender, EventArgs e)
m_prevSize = this.ClientRectangle.Size;
private void MainForm_ResizeEnd(object sender, EventArgs e)
int iWidth = m_prevSize.Width;
int iHeight = m_prevSize.Height;
double dXFactor = (double)(this.ClientRectangle.Width) / (double)iWidth;
double dYFactor = (double)(this.ClientRectangle.Height) / (double)iHeight;
foreach (Form c in this.MdiChildren)
if (!c.Visible)
continue;
if (c.WindowState == System.Windows.Forms.FormWindowState.Maximized ||
c.WindowState == System.Windows.Forms.FormWindowState.Minimized)
// DO not ajust on resize if a child window is at its Maximized state
return;
c.Scale(new SizeF((float)dXFactor, (float)dYFactor));
Best Regards,
Emily

Answer 1

Hi Badidea,
Once again, I did not explain my idea clearly.  I am sorry about that.  I only wanted to scale the child-windows as the parent re-sized.  And yes, if the child-windows fill up the view-able area of the parent's window, I would like them to
also fill up the  view-able area of parent's window once again after re-size of parent window.  No scroll should be involved.
Regards,
Emily
Hello,
It depends on how you cascade or tile these forms.
In this case, I would recommend you use this way below.
1. Layout with splitContainers.
2. Set each child form's toplevel to false, then add them to the panels of splitContainers.
3. Resize these form to fit the panels.
4. repeat #3 inside the main form's resize event.
Here is a simple sample.
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace _150313AutoSizeMdiChiledForm
public partial class MainForm : Form
public MainForm()
InitializeComponent();
Form1 f1 = new Form1();
Form2 f2 = new Form2();
Form3 f3 = new Form3();
private void MainForm_Load(object sender, EventArgs e)
f1.TopLevel = false;
this.splitContainer2.Panel1.Controls.Add(f1);
f1.Size = this.splitContainer2.Panel1.ClientSize;
f1.Show();
f2.TopLevel = false;
this.splitContainer2.Panel2.Controls.Add(f2);
f2.Size = this.splitContainer2.Panel2.ClientSize;
f2.Show();
f3.TopLevel = false;
this.splitContainer1.Panel2.Controls.Add(f3);
f3.Size = this.splitContainer1.Panel2.ClientSize;
f3.Show();
private void MainForm_Resize(object sender, EventArgs e)
f1.Size = this.splitContainer2.Panel1.ClientSize;
f2.Size = this.splitContainer2.Panel2.ClientSize;
f3.Size = this.splitContainer1.Panel2.ClientSize;
Designer code.
namespace _150313AutoSizeMdiChiledForm
partial class MainForm
/// <summary>
/// Required designer variable.
/// </summary>
private System.ComponentModel.IContainer components = null;
/// <summary>
/// Clean up any resources being used.
/// </summary>
/// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
protected override void Dispose(bool disposing)
if (disposing && (components != null))
components.Dispose();
base.Dispose(disposing);
#region Windows Form Designer generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
private void InitializeComponent()
this.splitContainer1 = new System.Windows.Forms.SplitContainer();
this.splitContainer2 = new System.Windows.Forms.SplitContainer();
((System.ComponentModel.ISupportInitialize)(this.splitContainer1)).BeginInit();
this.splitContainer1.Panel1.SuspendLayout();
this.splitContainer1.SuspendLayout();
((System.ComponentModel.ISupportInitialize)(this.splitContainer2)).BeginInit();
this.splitContainer2.SuspendLayout();
this.SuspendLayout();
// splitContainer1
this.splitContainer1.Dock = System.Windows.Forms.DockStyle.Fill;
this.splitContainer1.Location = new System.Drawing.Point(0, 0);
this.splitContainer1.Name = "splitContainer1";
this.splitContainer1.Orientation = System.Windows.Forms.Orientation.Horizontal;
// splitContainer1.Panel1
this.splitContainer1.Panel1.Controls.Add(this.splitContainer2);
this.splitContainer1.Size = new System.Drawing.Size(607, 411);
this.splitContainer1.SplitterDistance = 198;
this.splitContainer1.TabIndex = 0;
// splitContainer2
this.splitContainer2.Dock = System.Windows.Forms.DockStyle.Fill;
this.splitContainer2.Location = new System.Drawing.Point(0, 0);
this.splitContainer2.Name = "splitContainer2";
this.splitContainer2.Size = new System.Drawing.Size(607, 198);
this.splitContainer2.SplitterDistance = 294;
this.splitContainer2.TabIndex = 0;
// MainForm
this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
this.ClientSize = new System.Drawing.Size(607, 411);
this.Controls.Add(this.splitContainer1);
this.Name = "MainForm";
this.Text = "MainForm";
this.Load += new System.EventHandler(this.MainForm_Load);
this.Resize += new System.EventHandler(this.MainForm_Resize);
this.splitContainer1.Panel1.ResumeLayout(false);
((System.ComponentModel.ISupportInitialize)(this.splitContainer1)).EndInit();
this.splitContainer1.ResumeLayout(false);
((System.ComponentModel.ISupportInitialize)(this.splitContainer2)).EndInit();
this.splitContainer2.ResumeLayout(false);
this.ResumeLayout(false);
#endregion
private System.Windows.Forms.SplitContainer splitContainer1;
private System.Windows.Forms.SplitContainer splitContainer2;
Result.
You could download it form http://1drv.ms/1Mwwibp.
It is quite similar with the one for tiling, you could edit it to fit your requirements.
Regards,
Carl
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