Winforms - click / drag anywhere on the form to move it as if it clicked on the form header

Question

I am creating a small modal form that is used in a Winforms application. This is basically an indicator of progress. But I would like the user to be able to click anywhere on the form and drag it to move it to the desktop while it is still displayed.

How can I implement this behavior?

Answer 1

Microsoft KB Article 320687 provides a detailed answer to this question.

Basically, you override the WndProc method to return HTCAPTION to the WM_NCHITTEST message when the test point is in the client area of ​​the form, which in fact means that Windows processes the click just as if it happened on the form header.

private const int WM_NCHITTEST = 0x84; private const int HTCLIENT = 0x1; private const int HTCAPTION = 0x2; protected override void WndProc(ref Message m) { switch(m.Msg) { case WM_NCHITTEST: base.WndProc(ref m); if ((int)m.Result == HTCLIENT) { m.Result = (IntPtr)HTCAPTION; } return; } base.WndProc(ref m); } 

Answer 2

Here's how to do it using P / Invoke.

 public const int WM_NCLBUTTONDOWN = 0xA1; public const int HTCAPTION = 0x2; [DllImport("User32.dll")] public static extern bool ReleaseCapture(); [DllImport("User32.dll")] public static extern int SendMessage(IntPtr hWnd, int Msg, int wParam, int lParam); void Form_Load(object sender, EventArgs e) { this.MouseDown += new MouseEventHandler(Form_MouseDown); } void Form_MouseDown(object sender, MouseEventArgs e) { if (e.Button == MouseButtons.Left) { ReleaseCapture(); SendMessage(Handle, WM_NCLBUTTONDOWN, HTCAPTION, 0); } } 

Answer 3

The following code assumes that the ProgressBarForm form has a ProgressBar control with the Dock property set to Fill

 public partial class ProgressBarForm : Form { private bool mouseDown; private Point lastPos; public ProgressBarForm() { InitializeComponent(); } private void progressBar1_MouseMove(object sender, MouseEventArgs e) { if (mouseDown) { int xoffset = MousePosition.X - lastPos.X; int yoffset = MousePosition.Y - lastPos.Y; Left += xoffset; Top += yoffset; lastPos = MousePosition; } } private void progressBar1_MouseDown(object sender, MouseEventArgs e) { mouseDown = true; lastPos = MousePosition; } private void progressBar1_MouseUp(object sender, MouseEventArgs e) { mouseDown = false; } } 

Answer 4

The accepted answer is a cool trick, but it doesn’t always work if the form is covered by a Fill-docked child, such as Panel (or derivatives), because this control will use all the majority of Windows messages.

Here is a simple approach that works in this case too: output the appropriate control (use this class instead of the standard one) for a mouse message like this:

  private class MyTableLayoutPanel : Panel // or TableLayoutPanel, etc. { private Point _mouseDown; private Point _formLocation; private bool _capture; // NOTE: we cannot use the WM_NCHITTEST / HTCAPTION trick because the table is in control, not the owning form... protected override void OnMouseDown(MouseEventArgs e) { _capture = true; _mouseDown = e.Location; _formLocation = ((Form)TopLevelControl).Location; } protected override void OnMouseUp(MouseEventArgs e) { _capture = false; } protected override void OnMouseMove(MouseEventArgs e) { if (_capture) { int dx = e.Location.X - _mouseDown.X; int dy = e.Location.Y - _mouseDown.Y; Point newLocation = new Point(_formLocation.X + dx, _formLocation.Y + dy); ((Form)TopLevelControl).Location = newLocation; _formLocation = newLocation; } } } 

Answer 5

Version VC ++ 2010 (from FlySwat's):

 #include <Windows.h> namespace DragWithoutTitleBar { using namespace System; using namespace System::Windows::Forms; using namespace System::ComponentModel; using namespace System::Collections; using namespace System::Data; using namespace System::Drawing; public ref class Form1 : public System::Windows::Forms::Form { public: Form1(void) { InitializeComponent(); } protected: ~Form1() { if (components) { delete components; } } private: System::ComponentModel::Container ^components; HWND hWnd; #pragma region Windows Form Designer generated code void InitializeComponent(void) { this->SuspendLayout(); this->AutoScaleDimensions = System::Drawing::SizeF(6, 13); this->AutoScaleMode = System::Windows::Forms::AutoScaleMode::Font; this->ClientSize = System::Drawing::Size(640, 480); this->FormBorderStyle = System::Windows::Forms::FormBorderStyle::None; this->Name = L"Form1"; this->Text = L"Form1"; this->Load += gcnew EventHandler(this, &Form1::Form1_Load); this->MouseDown += gcnew System::Windows::Forms::MouseEventHandler(this, &Form1::Form1_MouseDown); this->ResumeLayout(false); } #pragma endregion private: System::Void Form1_Load(Object^ sender, EventArgs^ e) { hWnd = static_cast<HWND>(Handle.ToPointer()); } private: System::Void Form1_MouseDown(Object^ sender, System::Windows::Forms::MouseEventArgs^ e) { if (e->Button == System::Windows::Forms::MouseButtons::Left) { ::ReleaseCapture(); ::SendMessage(hWnd, /*WM_NCLBUTTONDOWN*/ 0xA1, /*HT_CAPTION*/ 0x2, 0); } } }; }