a ficker problem of dll embedded into web page

Hi, Graus,

thanks a lot for your reply. my situation is a little bit complex, so i didn't describe my problem clearly.

i had to override WndProc() cause i must redraw the controls, their borders at least. i have tried double buffer. but my controls still flicker and besides, the dropdown area of combobox turns transparent.
now i tried another way that is to use windows xp theme to change the appearance of controls. because i take that method on richtextbox and it does work and looks no flicker. the source code is from codeproject. so i tried to apply it on a commandbutton by myself as a test. but it failed to work. there are two ways to use windows xp theme: one is to add a manifest file, Windows will handle the controls appearance automaticlly and there are many articles discussing it in codeproject; the other way is to call the related API in uxtheme.dll manualy. i follow the latter cause my target is a .dll, manifest file only works with .exe.

did i forget something in my code? if you have any idea, pls tell me. thank you for you time. i will paste my code in the next post.

my code using uxtheme.dll in VS2003 (c#)

<br />
	using System;<br />
	using System.Collections;<br />
	using System.ComponentModel;<br />
	using System.Drawing;<br />
	using System.Data;<br />
	using System.Windows.Forms;<br />
	using System.Runtime.InteropServices;<br />
<br />
	namespace CustomControls<br />
	{<br />
		public class CustomButton : System.Windows.Forms.Button <br />
		{<br />
			private System.ComponentModel.Container components = null;<br />
<br />
			public CustomButton()<br />
			{<br />
				InitializeComponent();<br />
<br />
			}<br />
<br />
			protected override void Dispose( bool disposing )<br />
			{<br />
				if( disposing )<br />
				{<br />
					if(components != null)<br />
					{<br />
						components.Dispose();<br />
					}<br />
				}<br />
				base.Dispose( disposing );<br />
			}<br />
<br />
			private void InitializeComponent()<br />
			{<br />
				components = new System.ComponentModel.Container();<br />
			}<br />
		<br />
			private const int WM_PAINT =0x000F;<br />
			public const int WM_NCPAINT = 0x85;<br />
			public const int WM_NCCALCSIZE = 0x83;<br />
			public const int WM_THEMECHANGED = 0x031A;<br />
<br />
			private enum BUTTONPARTS:int<br />
			{<br />
				BP_UNKNOWN = 0,<br />
				BP_PUSHBUTTON = 1,<br />
				BP_RADIOBUTTON = 2,<br />
				BP_CHECKBOX = 3,<br />
				BP_GROUPBOX = 4,<br />
				BP_USERBUTTON = 5,<br />
				BP_COMMANDLINK = 6,<br />
				BP_COMMANDLINKGLYPH = 7<br />
			};<br />
<br />
			private enum PUSHBUTTONSTATES:int<br />
			{<br />
				PBS_NORMAL = 1,<br />
				PBS_HOT = 2,<br />
				PBS_PRESSED = 3,<br />
				PBS_DISABLED = 4,<br />
				PBS_DEFAULTED = 5,<br />
				PBS_DEFAULTED_ANIMATING = 6<br />
			};<br />
<br />
			public struct RECT <br />
			{<br />
				public int Left;<br />
				public int Top;<br />
				public int Right;<br />
				public int Bottom;<br />
<br />
				public RECT(int left_, int top_, int right_, int bottom_) <br />
				{<br />
					Left = left_;<br />
					Top = top_;<br />
					Right = right_;<br />
					Bottom = bottom_;<br />
				}<br />
			}<br />
<br />
			[DllImport("uxtheme.dll", ExactSpelling=true)]<br />
			public extern static bool IsThemeActive();<br />
<br />
			[DllImport("user32.dll")]<br />
			public static extern IntPtr GetWindowDC (IntPtr hWnd );<br />
<br />
			[DllImport("user32.dll")]<br />
			public static extern int ReleaseDC(IntPtr hWnd, IntPtr hDC );<br />
<br />
			[DllImport("user32.dll")]<br />
			public static extern bool GetWindowRect(IntPtr hWnd, out RECT lpRect);<br />
<br />
			[DllImport("uxtheme.dll", ExactSpelling=true, CharSet=CharSet.Unicode)]<br />
			public static extern IntPtr OpenThemeData(IntPtr hWnd, String classList);<br />
<br />
			[DllImport("uxtheme.dll", ExactSpelling=true)]<br />
			public extern static Int32 DrawThemeBackground(IntPtr hTheme, IntPtr hdc, int iPartId,<br />
				int iStateId, ref RECT pRect, IntPtr pClipRect);<br />
<br />
			[DllImport("uxtheme.dll", ExactSpelling=true)]<br />
			public extern static Int32 CloseThemeData(IntPtr hTheme);<br />
<br />
			protected override void WndProc(ref Message m)<br />
<br />
			{<br />
				switch(m.Msg)<br />
				{<br />
					case WM_NCPAINT:<br />
						WmPaint(ref m);<br />
						break;<br />
					default:<br />
						base.WndProc (ref m);<br />
						break;<br />
				}<br />
			}<br />
<br />
			public void WmPaint(ref Message m) {<br />
				try<br />
				{<br />
					base.WndProc(ref m);<br />
<br />
					if (!IsThemeActive()) {<br />
						return;<br />
					}<br />
<br />
					/////////////////////////////////////////////////////////////////////////////<br />
					// Get the DC of the window frame and paint the border using uxTheme API<br />
					/////////////////////////////////////////////////////////////////////////////<br />
<br />
					// set the part id to TextBox<br />
					int partId = (int)BUTTONPARTS.BP_PUSHBUTTON;<br />
					int stateId = (int)PUSHBUTTONSTATES.PBS_NORMAL;<br />
<br />
					// define the windows frame rectangle of the TextBox<br />
					RECT windowRect;<br />
					GetWindowRect(this.Handle, out windowRect);<br />
<br />
					// get the device context of the window frame<br />
					IntPtr hDC = GetWindowDC(this.Handle);<br />
<br />
					// open theme data<br />
					IntPtr hTheme = OpenThemeData(this.Handle, "Button");<br />
<br />
					// draw background<br />
					DrawThemeBackground(hTheme, hDC, partId, stateId, ref windowRect, IntPtr.Zero);<br />
          <br />
					// close theme data<br />
					CloseThemeData(hTheme);<br />
<br />
					// release dc<br />
					ReleaseDC(this.Handle, hDC);<br />
<br />
					// we have processed the message so set the result to zero<br />
					m.Result = IntPtr.Zero;<br />
<br />
				}<br />
				catch(Exception ex)<br />
				{<br />
					MessageBox.Show(ex.Message);<br />
				}<br />
			}<br />
		}<br />
	}<br />

There is no double buffering in this code. Without it, you will get a flicker.

my code override WndProc and paint the control all by myself:

<br />
using System;<br />
using System.Windows.Forms;<br />
using System.Drawing;<br />
using System.Drawing.Drawing2D;<br />
using System.Runtime.InteropServices;<br />
<br />
namespace CustomControls<br />
{<br />
	[ToolboxBitmap(typeof(System.Windows.Forms.ComboBox))]<br />
	public class CustomComboBox: ComboBox<br />
	{	<br />
		#region ComboInfoHelper<br />
		internal class ComboInfoHelper<br />
		{<br />
			[DllImport("user32")] <br />
			private static extern bool GetComboBoxInfo(IntPtr hwndCombo, ref ComboBoxInfo info);<br />
<br />
			#region RECT struct<br />
			[StructLayout(LayoutKind.Sequential)]<br />
				private struct RECT <br />
			{<br />
				public int Left;<br />
				public int Top;<br />
				public int Right;<br />
				public int Bottom;<br />
			}<br />
			#endregion<br />
<br />
			#region ComboBoxInfo Struct<br />
			[StructLayout(LayoutKind.Sequential)]<br />
				private struct ComboBoxInfo <br />
			{<br />
				public int cbSize;<br />
				public RECT rcItem;<br />
				public RECT rcButton;<br />
				public IntPtr stateButton;<br />
				public IntPtr hwndCombo;<br />
				public IntPtr hwndEdit;<br />
				public IntPtr hwndList;<br />
			}<br />
			#endregion<br />
<br />
			public static int GetComboDropDownWidth()<br />
			{<br />
				ComboBox cb = new ComboBox();<br />
				int width = GetComboDropDownWidth(cb.Handle);<br />
				cb.Dispose();<br />
				return width;<br />
			}<br />
			public static int GetComboDropDownWidth(IntPtr handle)<br />
			{<br />
				ComboBoxInfo cbi = new ComboBoxInfo();<br />
				cbi.cbSize = Marshal.SizeOf(cbi);<br />
				GetComboBoxInfo(handle, ref cbi);<br />
				int width = cbi.rcButton.Right - cbi.rcButton.Left;<br />
				return width;<br />
			}<br />
		}<br />
		#endregion<br />
<br />
		public const int WM_ERASEBKGND = 0x14;<br />
		public const int WM_PAINT = 0xF;<br />
		public const int WM_NC_PAINT = 0x85;<br />
		public const int WM_PRINTCLIENT = 0x318;<br />
		private static int DropDownButtonWidth = 17;<br />
<br />
		[DllImport("user32.dll", EntryPoint="SendMessageA")]<br />
		public static extern int SendMessage (IntPtr hwnd, int wMsg, IntPtr wParam, object lParam);<br />
<br />
		[DllImport("user32")]<br />
		public static extern IntPtr GetWindowDC (IntPtr hWnd );<br />
<br />
		[DllImport("user32")]<br />
		public static extern int ReleaseDC(IntPtr hWnd, IntPtr hDC );<br />
<br />
		static CustomComboBox()<br />
		{<br />
			DropDownButtonWidth = ComboInfoHelper.GetComboDropDownWidth() + 2;<br />
		}<br />
<br />
		public CustomComboBox()<br />
			: base()<br />
		{<br />
			//this.SetStyle(ControlStyles.DoubleBuffer, true); //looks ok and flicker<br />
			this.SetStyle(ControlStyles.DoubleBuffer | ControlStyles.UserPaint | ControlStyles.AllPaintingInWmPaint, true); //transparent and flicker<br />
		}<br />
<br />
		protected override void OnSelectedValueChanged(EventArgs e)<br />
		{<br />
			base.OnSelectedValueChanged (e);<br />
			this.Invalidate();<br />
		}<br />
<br />
		protected override void WndProc(ref Message m)<br />
		{<br />
			if (this.DropDownStyle == ComboBoxStyle.Simple)<br />
			{<br />
				base.WndProc(ref m);<br />
				return;<br />
			}<br />
<br />
			IntPtr hDC = IntPtr.Zero;<br />
			Graphics gdc = null;<br />
			switch (m.Msg)<br />
			{<br />
				case WM_NC_PAINT:	<br />
					hDC = GetWindowDC(this.Handle);<br />
					gdc = Graphics.FromHdc(hDC);<br />
					SendMessage(this.Handle, WM_ERASEBKGND, hDC, 0);<br />
					SendPrintClientMsg();	// send to draw client area<br />
					PaintFlatControlBorder(this, gdc);<br />
					m.Result = (IntPtr) 1;	// indicate msg has been processed			<br />
					ReleaseDC(m.HWnd, hDC);<br />
					gdc.Dispose();	<br />
<br />
					break;<br />
				case WM_PAINT:	<br />
					base.WndProc(ref m);<br />
					// flatten the border area again<br />
					hDC = GetWindowDC(this.Handle);<br />
					gdc = Graphics.FromHdc(hDC);<br />
					Pen p = new Pen((this.Enabled? BackColor:SystemColors.Control), 2);	<br />
					gdc.DrawRectangle(p, new Rectangle(2, 2, this.Width-3, this.Height-3));<br />
					PaintFlatDropDown(this, gdc);<br />
					PaintFlatControlBorder(this, gdc);<br />
					ReleaseDC(m.HWnd, hDC);<br />
					gdc.Dispose();	<br />
<br />
					break;<br />
				default:<br />
					base.WndProc(ref m);<br />
					break;<br />
			}<br />
		}<br />
		private void SendPrintClientMsg()<br />
		{<br />
			// We send this message for the control to redraw the client area<br />
			Graphics gClient = this.CreateGraphics();<br />
			IntPtr ptrClientDC = gClient.GetHdc();<br />
			SendMessage(this.Handle, WM_PRINTCLIENT, ptrClientDC, 0);<br />
			gClient.ReleaseHdc(ptrClientDC);<br />
			gClient.Dispose();<br />
		}<br />
<br />
		private void PaintFlatControlBorder(Control ctrl, Graphics g)<br />
		{<br />
			Rectangle rect = new Rectangle(0, 0, ctrl.Width, ctrl.Height);<br />
			if (ctrl.Focused == false || ctrl.Enabled == false )<br />
				ControlPaint.DrawBorder(g, rect, SystemColors.ControlDark, ButtonBorderStyle.Solid);<br />
			else<br />
				ControlPaint.DrawBorder(g, rect, Color.Black, ButtonBorderStyle.Solid);<br />
			Color borderColor = Color.LightBlue;<br />
			ControlPaint.DrawBorder(g, rect, borderColor, ButtonBorderStyle.Solid);<br />
		}<br />
		public static void PaintFlatDropDown(Control ctrl, Graphics g)<br />
		{<br />
			Rectangle rect = new Rectangle(ctrl.Width-DropDownButtonWidth, 0, DropDownButtonWidth, ctrl.Height);<br />
			ControlPaint.DrawComboButton(g, rect, ButtonState.Flat);<br />
		}<br />
<br />
		protected override void OnLostFocus(System.EventArgs e)<br />
		{<br />
			base.OnLostFocus(e);<br />
			this.Invalidate();<br />
		}<br />
<br />
		protected override void OnGotFocus(System.EventArgs e)<br />
		{<br />
			base.OnGotFocus(e);<br />
			this.Invalidate();<br />
		}		<br />
		protected override void OnResize(EventArgs e)<br />
		{<br />
			base.OnResize (e);<br />
			this.Invalidate();<br />
		}<br />
<br />
	}<br />
}<br />
<br />

the former code using uxtheme.dll doesn't work. the latter does work but flicker.