How do I get a control's position and size from the original designer settings?

Question

Windows (depending font/zoom/scaling) is resizing my form. I'd like to programmatically find the original position and size of the form and controls (which were set in the designer. At runtime, these sizes and positions change as the form is created.

Answer 1

Windows (depending font/zoom/scaling) is resizing my form.

Windows is not resizing your form. Your form is configured to auto-scale. This is controlled by the AutoScaleMode Property. The designer default value is System.Windows.Forms.AutoScaleMode.Font (the true default is Inherit). A high-level overview of the WinForm auto-scaling can be found in the documentation Current support for automatic scaling. A common alternative value to use is System.Windows.Forms.AutoScaleMode.DPI. When auto-scaling is enabled, a scaling factor computed using the value of AutoScaleDimensions and a value evaluated at runtime using the DPI reported to the application. AutoScaleDimensions is set in designer genearated code.

If the application is declared to be DPI-aware, the true DPI value is used. If it is not DPI-aware, Windows tells that application that it is running at 96 dpi. The reported DPI value also affects the metrics used in Font-based scaling.

I'd like to programmatically find the original position and size of the form and controls (which were set in the designer. At runtime, these sizes and positions change as the form is created.

This can be accomplished by intercepting the point before auto-scaling is applied. There is not a direct way to do this as you are dealing with auto-generated code (the Form.designer.cs file's InitializeComponent method). It is in this method that AutoScaleDimensions and AutoScaleMode are set.

When you create a new form, and this method looks like the following.

private void InitializeComponent()
{
    this.components = new System.ComponentModel.Container();
    this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
    this.ClientSize = new System.Drawing.Size(800, 450);
    this.Text = "Form1";
}

Notice that the AutoScaleDimensions property is not yet declared in the method; it will be added once you make some change to form (change a property or add a control) and the new information is written to the file. The AutoScaleDimensions property will only be written if AutoScaleMode is set to either DPI or Font.

The following is the result of changing the form's Size.

private void InitializeComponent()
{
    this.SuspendLayout();
    // 
    // Form1
    // 
    this.AutoScaleDimensions = new System.Drawing.SizeF(8F, 16F);
    this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
    this.ClientSize = new System.Drawing.Size(782, 453);
    this.Name = "Form1";
    this.Text = "Form1";
    this.ResumeLayout(false);
}

The purpose for showing the above is show you how to obtain the value for setting the AutoScaleDimensions property in the following proposed solution.

Proposed Solution:

In the designer, set the form's AutoScaleMode property to either Inherit or None. Then modify the form's constructor code to reflect the following:

SizeF scalingFactor;
public Form1()
{
    InitializeComponent();

    SuspendLayout();
    AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
    AutoScaleDimensions = new System.Drawing.SizeF(8.0F, 16.0F);

    // at this point you can obtain the scaling factor that will
    // be applied on ResumeLayout
    scalingFactor = AutoScaleFactor;

    // store the design-time bounds in the control's Tag property
    RecursivelyRecordBounds(this);
    ResumeLayout(true);
}

Also add this method to the form's code.

private static void RecursivelyRecordBounds(Control c)
{
    c.Tag = c.Bounds;
    foreach (Control cc in c.Controls)
    {
        cc.Tag = cc.Bounds;
        if (cc.Controls.Count > 0)
        {
            RecursivelyRecordBounds(cc);
        }
    }
}

For the purposes of this example, each control's design-time Bounds is stored in its Tag property. Note that setting the two auto scaling properties must be wrapped in a SupendLayout/ResumeLayout region. Also it is important to first set the AutoScaleMode property before setting the AutoScaleDimensions property.

An alternative solution (hack) would be leave the AutoScaleMode property set to either Font or DPI and to rely on the observed pattern of the Initialize method. In this method, the form's Text property is always set after the two scaling properties. This allows using the TextChanged event to be used to signal the proper time to retrieve the design-time Bounds.

public Form1()
{
    EventHandler eh = (s,e) => RecursivelyRecordBounds(this);;
    TextChanged += eh;
    InitializeComponent();
    TextChanged -= eh;
}