最近需要在Winform項目中實現一個走馬燈的效果，一開始用了一些辦法比如移動Label控件，效果總是不太好，移動文本時總有閃爍的現象。後來找了一個國外的開源控件，應用了一下，效果還不錯。仔細閱讀了一下代碼，發現還有一些地方值得改進，現把代碼以及改動說明貼出來，和大家分享。
控件出處：http://www.codeproject.com/KB/miscctrl/ScrollingTextControlArtic.aspx
我的改動：
1、DoubleBuffer 的設置
原代碼中用的是 this.SetStyle(ControlStyles.DoubleBuffer, true); 但一些網友反映這個標志在.net 2.0 以上版本無效。說句老實話，我也不是特別確信，MSDN上也沒有說明這一點。在我的.net 2.0 系統中，兩種設置的效果似乎沒有太多區別。在一個國外網站上找到他們的區別，下面是原文：
ControlStyles == CS
AllPaintingInWMPaint == APWMP
OptimizedDoubleBuffer = ODB
DoubleBuffer = DB
An earlier permutation of the design called for ODB to simply be a combinationof DB, APWMP and UserPaint. Through several design changes, the two control styles are nearly synonymous, but they still have differences. Now that we've broken that, we may considerun-deprecating CS.DB to retain . Here is a more complete summary of the current design:
Mechanism Side effects Other flags required to work Require APWMP? Notes ControlStyle
I'm following up on the need for deprecating CS.DB and Control.DoubleBuffered's getter and will post here.
總之保險起見，還是判一下版本號，下面是判斷代碼
Version v = System.Environment.Version;
if (v.Major < 2)
{
this.SetStyle(ControlStyles.DoubleBuffer, true);
}
else
{
this.SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
}
2、刷新區域
原代碼中刷新區域是這樣設置的
private void Tick(object sender, EventArgs e)
{
//update rectangle to include where to paint for new position
//lastKnownRect.X -= 10;
//lastKnownRect.Width += 20;
lastKnownRect.Inflate(10, 5);
//create region based on updated rectangle
Region updateRegion = new Region(lastKnownRect);
//repaint the control
Invalidate(updateRegion);
Update();
}
lastKnownRect是文字的整個區域，如果文字較長，這個刷新區域就會比較大，但實際上我們只需要刷新控件顯示范圍內的區域就可以了。
所以這裡改動如下：
//Controls the animation of the text.
private void Tick(object sender, EventArgs e)
{
//update rectangle to include where to paint for new position
//lastKnownRect.X -= 10;
//lastKnownRect.Width += 20;
lastKnownRect.Inflate(10, 5);
//get the display rectangle
RectangleF refreshRect = lastKnownRect;
refreshRect.X = Math.Max(0, lastKnownRect.X);
refreshRect.Width = Math.Min(lastKnownRect.Width + lastKnownRect.X, this.Width);
refreshRect.Width = Math.Min(this.Width - lastKnownRect.X, refreshRect.Width);
//create region based on updated rectangle
//Region updateRegion = new Region(lastKnownRect);
Region updateRegion = new Region(refreshRect);
//repaint the control
Invalidate(updateRegion);
Update();
}
2、修改Enabled屬性
當Enabled設置為false時，原控件依然會滾動，覺得還是不讓它滾動更好一些。
修改代碼如下：
[
Browsable(true),
CategoryAttribute("Behavior"),
Description("Indicates whether the control is enabled")
]
new public bool Enabled
{
set
{
timer.Enabled = value;
base.Enabled = value;
}
get
{
return base.Enabled;
}
}
下面給出修改後完整的控件代碼，代碼原作者為jconwell，原始代碼見前面提到的控件出處
using System;
using System.Collections;
using System.ComponentModel;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Data;
using System.Windows.Forms;
namespace ScrollingTextControl
{
/**//// <summary>
/// Summary description for ScrollingTextControl.
/// </summary>
[
ToolboxBitmapAttribute(typeof(ScrollingTextControl.ScrollingText), "ScrollingText.bmp"),
DefaultEvent("TextClicked")
]
public class ScrollingText : System.Windows.Forms.Control
{
private Timer timer; // Timer for text animation.
private string text = "Text"; // Scrolling text
private float staticTextPos = 0; // The running x pos of the text
private float yPos = 0; // The running y pos of the text
private ScrollDirection scrollDirection = ScrollDirection.RightToLeft; // The direction the text will scroll
private ScrollDirection currentDirection = ScrollDirection.LeftToRight; // Used for text bouncing
private VerticleTextPosition verticleTextPosition = VerticleTextPosition.Center; // Where will the text be vertically placed
private int scrollPixelDistance = 2; // How far the text scrolls per timer event
private bool showBorder = true; // Show a border or not
private bool stopScrollOnMouseOver = false; // Flag to stop the scroll if the user mouses over the text
private bool scrollOn = true; // Internal flag to stop / start the scrolling of the text
private Brush foregroundBrush = null; // Allow the user to set a custom Brush to the text Font
private Brush backgroundBrush = null; // Allow the user to set a custom Brush to the background
private Color borderColor = Color.Black; // Allow the user to set the color of the control border
private RectangleF lastKnownRect; // The last known position of the text
public ScrollingText()
{
// Setup default properties for ScrollingText control
InitializeComponent();
//This turns off internal double buffering of all custom GDI+ drawing
Version v = System.Environment.Version;
if (v.Major < 2)
{
this.SetStyle(ControlStyles.DoubleBuffer, true);
}
else
{
this.SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
}
this.SetStyle(ControlStyles.AllPaintingInWmPaint, true);
this.SetStyle(ControlStyles.UserPaint, true);
this.SetStyle(ControlStyles.ResizeRedraw, true);
//setup the timer object
timer = new Timer();
timer.Interval = 25; //default timer interval
timer.Enabled = true;
timer.Tick += new EventHandler(Tick);
}
/**//// <summary>
/// Clean up any resources being used.
/// </summary>
protected override void Dispose( bool disposing )
{
if( disposing )
{
//Make sure our brushes are cleaned up
if (foregroundBrush != null)
foregroundBrush.Dispose();
//Make sure our brushes are cleaned up
if (backgroundBrush != null)
backgroundBrush.Dispose();
//Make sure our timer is cleaned up
if (timer != null)
timer.Dispose();
}
base.Dispose( disposing );
}
Component Designer generated code#region Component 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()
{
//ScrollingText
this.Name = "ScrollingText";
this.Size = new System.Drawing.Size(216, 40);
this.Click += new System.EventHandler(this.ScrollingText_Click);
}
#endregion
//Controls the animation of the text.
private void Tick(object sender, EventArgs e)
{
//update rectangle to include where to paint for new position
//lastKnownRect.X -= 10;
//lastKnownRect.Width += 20;
lastKnownRect.Inflate(10, 5);
//get the display rectangle
RectangleF refreshRect = lastKnownRect;
refreshRect.X = Math.Max(0, lastKnownRect.X);
refreshRect.Width = Math.Min(lastKnownRect.Width + lastKnownRect.X, this.Width);
refreshRect.Width = Math.Min(this.Width - lastKnownRect.X, refreshRect.Width);
//create region based on updated rectangle
//Region updateRegion = new Region(lastKnownRect);
Region updateRegion = new Region(refreshRect);
//repaint the control
Invalidate(updateRegion);
Update();
}
//Paint the ScrollingTextCtrl.
protected override void OnPaint(PaintEventArgs pe)
{
//Console.WriteLine(pe.ClipRectangle.X + ", " + pe.ClipRectangle.Y + ", " + pe.ClipRectangle.Width + ", " + pe.ClipRectangle.Height);
//Paint the text to its new position
DrawScrollingText(pe.Graphics);
//pass on the graphics obj to the base Control class
base.OnPaint(pe);
}
//Draw the scrolling text on the control
public void DrawScrollingText(Graphics canvas)
{
canvas.SmoothingMode = SmoothingMode.HighQuality;
canvas.PixelOffsetMode = PixelOffsetMode.HighQuality;
//measure the size of the string for placement calculation
SizeF stringSize = canvas.MeasureString(this.text, this.Font);
//Calculate the begining x position of where to paint the text
if (scrollOn)
{
CalcTextPosition(stringSize);
}
//Clear the control with user set BackColor
if (backgroundBrush != null)
{
canvas.FillRectangle(backgroundBrush, 0, 0, this.ClientSize.Width, this.ClientSize.Height);
}
else
{
canvas.Clear(this.BackColor);
}
// Draw the border
if (showBorder)
{
using (Pen borderPen = new Pen(borderColor))
canvas.DrawRectangle(borderPen, 0, 0, this.ClientSize.Width - 1, this.ClientSize.Height - 1);
}
// Draw the text string in the bitmap in memory
if (foregroundBrush == null)
{
using (Brush tempForeBrush = new System.Drawing.SolidBrush(this.ForeColor))
canvas.DrawString(this.text, this.Font, tempForeBrush, staticTextPos, yPos);
}
else
{
canvas.DrawString(this.text, this.Font, foregroundBrush, staticTextPos, yPos);
}
lastKnownRect = new RectangleF(staticTextPos, yPos, stringSize.Width, stringSize.Height);
EnableTextLink(lastKnownRect);
}
private void CalcTextPosition(SizeF stringSize)
{
switch (scrollDirection)
{
case ScrollDirection.RightToLeft:
if (staticTextPos < (-1 * (stringSize.Width)))
staticTextPos = this.ClientSize.Width - 1;
else
staticTextPos -= scrollPixelDistance;
break;
case ScrollDirection.LeftToRight:
if (staticTextPos > this.ClientSize.Width)
staticTextPos = -1 * stringSize.Width;
else
staticTextPos += scrollPixelDistance;
break;
case ScrollDirection.Bouncing:
if (currentDirection == ScrollDirection.RightToLeft)
{
if (staticTextPos < 0)
currentDirection = ScrollDirection.LeftToRight;
else
staticTextPos -= scrollPixelDistance;
}
else if (currentDirection == ScrollDirection.LeftToRight)
{
if (staticTextPos > this.ClientSize.Width - stringSize.Width)
currentDirection = ScrollDirection.RightToLeft;
else
staticTextPos += scrollPixelDistance;
}
break;
}
//Calculate the vertical position for the scrolling text
switch (verticleTextPosition)
{
case VerticleTextPosition.Top:
yPos = 2;
break;
case VerticleTextPosition.Center:
yPos = (this.ClientSize.Height / 2) - (stringSize.Height / 2);
break;
case VerticleTextPosition.Botom:
yPos = this.ClientSize.Height - stringSize.Height;
break;
}
}
Mouse over, text link logic#region Mouse over, text link logic
private void EnableTextLink(RectangleF textRect)
{
Point curPt = this.PointToClient(Cursor.Position);
//if (curPt.X > textRect.Left && curPt.X < textRect.Right
// && curPt.Y > textRect.Top && curPt.Y < textRect.Bottom)
if (textRect.Contains(curPt))
{
//Stop the text of the user mouse's over the text
if (stopScrollOnMouseOver)
scrollOn = false;
this.Cursor = Cursors.Hand;
}
else
{
//Make sure the text is scrolling if user's mouse is not over the text
scrollOn = true;
this.Cursor = Cursors.Default;
}
}
private void ScrollingText_Click(object sender, System.EventArgs e)
{
//Trigger the text clicked event if the user clicks while the mouse
//is over the text. This allows the text to act like a hyperlink
if (this.Cursor == Cursors.Hand)
OnTextClicked(this, new EventArgs());
}
public delegate void TextClickEventHandler(object sender, EventArgs args);
public event TextClickEventHandler TextClicked;
private void OnTextClicked(object sender, EventArgs args)
{
//Call the delegate
if (TextClicked != null)
TextClicked(sender, args);
}
#endregion
Properties#region Properties
[
Browsable(true),
CategoryAttribute("Scrolling Text"),
Description("The timer interval that determines how often the control is repainted")
]
public int TextScrollSpeed
{
set
{
timer.Interval = value;
}
get
{
return timer.Interval;
}
}
[
Browsable(true),
CategoryAttribute("Scrolling Text"),
Description("How many pixels will the text be moved per Paint")
]
public int TextScrollDistance
{
set
{
scrollPixelDistance = value;
}
get
{
return scrollPixelDistance;
}
}
[
Browsable(true),
CategoryAttribute("Scrolling Text"),
Description("The text that will scroll accros the control")
]
public string ScrollText
{
set
{
text = value;
this.Invalidate();
this.Update();
}
get
{
return text;
}
}
[
Browsable(true),
CategoryAttribute("Scrolling Text"),
Description("What direction the text will scroll: Left to Right, Right to Left, or Bouncing")
]
public ScrollDirection ScrollDirection
{
set
{
scrollDirection = value;
}
get
{
return scrollDirection;
}
}
[
Browsable(true),
CategoryAttribute("Scrolling Text"),
Description("The verticle alignment of the text")
]
public VerticleTextPosition VerticleTextPosition
{
set
{
verticleTextPosition = value;
}
get
{
return verticleTextPosition;
}
}
[
Browsable(true),
CategoryAttribute("Scrolling Text"),
Description("Turns the border on or off")
]
public bool ShowBorder
{
set
{
showBorder = value;
}
get
{
return showBorder;
}
}
[
Browsable(true),
CategoryAttribute("Scrolling Text"),
Description("The color of the border")
]
public Color BorderColor
{
set
{
borderColor = value;
}
get
{
return borderColor;
}
}
[
Browsable(true),
CategoryAttribute("Scrolling Text"),
Description("Determines if the text will stop scrolling if the user's mouse moves over the text")
]
public bool StopScrollOnMouseOver
{
set
{
stopScrollOnMouseOver = value;
}
get
{
return stopScrollOnMouseOver;
}
}
[
Browsable(true),
CategoryAttribute("Behavior"),
Description("Indicates whether the control is enabled")
]
new public bool Enabled
{
set
{
timer.Enabled = value;
base.Enabled = value;
}
get
{
return base.Enabled;
}
}
[
Browsable(false)
]
public Brush ForegroundBrush
{
set
{
foregroundBrush = value;
}
get
{
return foregroundBrush;
}
}
[
ReadOnly(true)
]
public Brush BackgroundBrush
{
set
{
backgroundBrush = value;
}
get
{
return backgroundBrush;
}
}
#endregion
}
public enum ScrollDirection
{
RightToLeft,
LeftToRight,
Bouncing
}
public enum VerticleTextPosition
{
Top,
Center,
Botom
}
}
注意事項
如果要調整滾動速度，可以通過設置以下兩個屬性的值來實現
TextScrollSpeed 和 TextScrollDistance
TextScrollSpeed 其實是設置刷新頻率，單位是毫秒，這個值越小，滾動速度越快。但刷新頻率越高，CPU占用率越高。
TextScrollDistance 是指每次刷新移動的像素點，這個值越大，速度越快，但如果太大，文字滾動看起來就不是特別連貫。
所以在實際應用中我們需要同時調整這兩個值，以找到最佳的平衡點
