淺談Winform控制元件開發（一）：使用GDI+美化基礎視窗-有解無憂

寫在前面：
本系列第一篇內容將僅包含對于Winform基礎視窗也就是System.Windows.Forms.Form的美化，后續將對一些常用控制元件如Button、ComboBox、CheckBox、TextBox等進行修改，并提供一些其他如Loading遮罩層等常見控制元件，
對于基礎視窗的美化，首要的任務就是先把基礎標題欄干掉，這個程序中會涉及一些Windows訊息機制，

首先，我們新建一個類XForm，派生自System.Windows.Forms.Form，

1 /// <summary>
2 /// 表示組成應用程式的用戶界面的視窗或對話框，
3 /// </summary>
4 [ToolboxItem(false)]
5 public class XForm : Form
6 ...

隨后，我們定義一些常量

 1 /// <summary>
 2 /// 標題欄高度
 3 /// </summary>
 4 public const int TitleBarHeight = 30;
 5 
 6 // 邊框寬度
 7 private const int BorderWidth = 4;
 8 // 標題欄圖示大小
 9 private const int IconSize = 16;
10 // 標題欄按鈕大小
11 private const int ButtonWidth = 30;
12 private const int ButtonHeight = 30;

覆寫基類屬性FormBorderStyle使base.FormBorderStyle保持None，覆寫基類屬性Padding回傳或設定正確的內邊距

 1 /// <summary>
 2 /// 獲取或設定表單的邊框樣式，
 3 /// </summary>
 4 [Browsable(true)]
 5 [Category("Appearance")]
 6 [Description("獲取或設定表單的邊框樣式，")]
 7 [DefaultValue(FormBorderStyle.Sizable)]
 8 public new FormBorderStyle FormBorderStyle
 9 {
10     get => _formBorderStyle;
11     set
12     {
13         _formBorderStyle = value;
14         UpdateStyles();
15         DrawTitleBar();
16     }
17 }
18 
19 /// <summary>
20 /// 獲取或設定表單的內邊距，
21 /// </summary>
22 [Browsable(true)]
23 [Category("Appearance")]
24 [Description("獲取或設定表單的內邊距，")]
25 public new Padding Padding
26 {
27     get => new Padding(base.Padding.Left, base.Padding.Top, base.Padding.Right, base.Padding.Bottom - TitleBarHeight);
28     set => base.Padding = new Padding(value.Left, value.Top, value.Right, value.Bottom + TitleBarHeight);
29 }

※最后一步也是最關鍵的一步：重新定義視窗客戶區邊界，重寫WndProc并處理WM_NCCALCSIZE訊息，

 1 protected override void WndProc(ref Message m)
 2 {
 3     switch (m.Msg)
 4     {
 5             case WM_NCCALCSIZE:
 6             {
 7                 // 自定義客戶區
 8                 if (m.WParam != IntPtr.Zero && _formBorderStyle != FormBorderStyle.None)
 9                 {
10                     NCCALCSIZE_PARAMS @params = (NCCALCSIZE_PARAMS)
11                         Marshal.PtrToStructure(m.LParam, typeof(NCCALCSIZE_PARAMS));
12                     @params.rgrc[0].Top += TitleBarHeight;
13                     @params.rgrc[0].Bottom += TitleBarHeight;
14                     Marshal.StructureToPtr(@params, m.LParam, false);
15                     m.Result = (IntPtr)(WVR_ALIGNTOP | WVR_ALIGNBOTTOM | WVR_REDRAW);
16                 }
17 
18                 base.WndProc(ref m);
19                 break;
20             }
21 ……

相關常量以及P/Invoke相關方法已在我的庫中定義，詳見MSDN，也可從http://pinvoke.net/查詢，
同樣在WndProc中處理WM_NCPAINT訊息

1 case WM_NCPAINT:
2 {
3     DrawTitleBar();
4     m.Result = (IntPtr)1;
5     break;
6 }

DrawTitleBar()方法定義如下：

 1 /// <summary>
 2 /// 繪制標題欄
 3 /// </summary>
 4 private void DrawTitleBar()
 5 {
 6     if (_formBorderStyle == FormBorderStyle.None)
 7         return;
 8 
 9     DrawTitleBackgroundTextIcon();
10     CreateButtonImages();
11     DrawTitleButtons();
12 }

首先使用線性漸變畫刷繪制標題欄背景、圖示、標題文字：

 1 /// <summary>
 2 /// 繪制標題欄背景、文字、圖示
 3 /// </summary>
 4 private void DrawTitleBackgroundTextIcon()
 5 {
 6     IntPtr hdc = GetWindowDC(Handle);
 7     Graphics g = Graphics.FromHdc(hdc);
 8 
 9     // 標題欄背景
10     using (Brush brsTitleBar = new LinearGradientBrush(TitleBarRectangle,
11         _titleBarStartColor, _titleBarEndColor, LinearGradientMode.Horizontal))
12         g.FillRectangle(brsTitleBar, TitleBarRectangle);
13 
14     // 標題欄圖示
15     if (ShowIcon)
16         g.DrawIcon(Icon, new Rectangle(
17             BorderWidth, TitleBarRectangle.Top + (TitleBarRectangle.Height - IconSize) / 2,
18             IconSize, IconSize));
19 
20     // 標題文本
21     const int txtX = BorderWidth + IconSize;
22     SizeF szText = g.MeasureString(Text, SystemFonts.CaptionFont, Width, StringFormat.GenericDefault);
23     using Brush brsText = new SolidBrush(_titleBarForeColor);
24     g.DrawString(Text,
25         SystemFonts.CaptionFont,
26         brsText,
27         new RectangleF(txtX,
28             TitleBarRectangle.Top + (TitleBarRectangle.Bottom - szText.Height) / 2,
29             Width - BorderWidth * 2,
30             TitleBarHeight),
31         StringFormat.GenericDefault);
32 
33     g.Dispose();
34     ReleaseDC(Handle, hdc);
35 }

隨后繪制標題欄按鈕，猶豫篇幅限制，在此不多贅述，詳見原始碼中CreateButtonImages()與DrawTitleButtons()，

至此，表面作業基本做完了，但這個視窗還不像個視窗，因為最小化、最大化、關閉以及調整視窗大小都不好用，

為什么？因為還有很多作業要做，首先，同樣在WndProc中處理WM_NCHITTEST訊息，通過m.Result指定當前滑鼠位置位于標題欄、最小化按鈕、最大化按鈕、關閉按鈕或上下左右邊框

 1 case WM_NCHITTEST:
 2     {
 3         base.WndProc(ref m);
 4 
 5         Point pt = PointToClient(new Point((int)m.LParam & 0xFFFF, (int)m.LParam >> 16 & 0xFFFF));
 6 
 7         _userSizedOrMoved = true;
 8 
 9         switch (_formBorderStyle)
10         {
11             case FormBorderStyle.None:
12                 break;
13             case FormBorderStyle.FixedSingle:
14             case FormBorderStyle.Fixed3D:
15             case FormBorderStyle.FixedDialog:
16             case FormBorderStyle.FixedToolWindow:
17                 if (pt.Y < 0)
18                 {
19                     _userSizedOrMoved = false;
20                     m.Result = (IntPtr)HTCAPTION;
21                 }
22 
23                 if (CorrectToLogical(CloseButtonRectangle).Contains(pt))
24                     m.Result = (IntPtr)HTCLOSE;
25                 if (CorrectToLogical(MaximizeButtonRectangle).Contains(pt))
26                     m.Result = (IntPtr)HTMAXBUTTON;
27                 if (CorrectToLogical(MinimizeButtonRectangle).Contains(pt))
28                     m.Result = (IntPtr)HTMINBUTTON;
29 
30                 break;
31             case FormBorderStyle.Sizable:
32             case FormBorderStyle.SizableToolWindow:
33                 if (pt.Y < 0)
34                 {
35                     _userSizedOrMoved = false;
36                     m.Result = (IntPtr)HTCAPTION;
37                 }
38 
39                 if (CorrectToLogical(CloseButtonRectangle).Contains(pt))
40                     m.Result = (IntPtr)HTCLOSE;
41                 if (CorrectToLogical(MaximizeButtonRectangle).Contains(pt))
42                     m.Result = (IntPtr)HTMAXBUTTON;
43                 if (CorrectToLogical(MinimizeButtonRectangle).Contains(pt))
44                     m.Result = (IntPtr)HTMINBUTTON;
45 
46                 if (WindowState == FormWindowState.Maximized)
47                     break;
48 
49                 bool bTop = pt.Y <= -TitleBarHeight + BorderWidth;
50                 bool bBottom = pt.Y >= Height - TitleBarHeight - BorderWidth;
51                 bool bLeft = pt.X <= BorderWidth;
52                 bool bRight = pt.X >= Width - BorderWidth;
53 
54                 if (bLeft)
55                 {
56                     _userSizedOrMoved = true;
57                     if (bTop)
58                         m.Result = (IntPtr)HTTOPLEFT;
59                     else if (bBottom)
60                         m.Result = (IntPtr)HTBOTTOMLEFT;
61                     else
62                         m.Result = (IntPtr)HTLEFT;
63                 }
64                 else if (bRight)
65                 {
66                     _userSizedOrMoved = true;
67                     if (bTop)
68                         m.Result = (IntPtr)HTTOPRIGHT;
69                     else if (bBottom)
70                         m.Result = (IntPtr)HTBOTTOMRIGHT;
71                     else
72                         m.Result = (IntPtr)HTRIGHT;
73                 }
74                 else if (bTop)
75                 {
76                     _userSizedOrMoved = true;
77                     m.Result = (IntPtr)HTTOP;
78                 }
79                 else if (bBottom)
80                 {
81                     _userSizedOrMoved = true;
82                     m.Result = (IntPtr)HTBOTTOM;
83                 }
84                 break;
85             default:
86                 throw new ArgumentOutOfRangeException();
87         }
88         break;
89     }

隨后以同樣的方式處理WM_NCLBUTTONDBLCLK、WM_NCLBUTTONDOWN、WM_NCLBUTTONUP、WM_NCMOUSEMOVE等訊息，進行標題欄按鈕等元素重繪，不多贅述，

現在視窗進行正常的單擊、雙擊、調整尺寸，我們在最后為視窗添加陰影

首先定義一個可以承載32位位圖的分層視窗(Layered Window)來負責主視窗陰影的呈現，詳見原始碼中XFormShadow類，此處僅列出用于創建分層視窗的核心代碼：

 1 private void UpdateBmp(Bitmap bmp)
 2 {
 3     if (!IsHandleCreated) return;
 4 
 5     if (!Image.IsCanonicalPixelFormat(bmp.PixelFormat) || !Image.IsAlphaPixelFormat(bmp.PixelFormat))
 6         throw new ArgumentException(@"位圖格式不正確", nameof(bmp));
 7 
 8     IntPtr oldBits = IntPtr.Zero;
 9     IntPtr screenDC = GetDC(IntPtr.Zero);
10     IntPtr hBmp = IntPtr.Zero;
11     IntPtr memDc = CreateCompatibleDC(screenDC);
12 
13     try
14     {
15         POINT formLocation = new POINT(Left, Top);
16         SIZE bitmapSize = new SIZE(bmp.Width, bmp.Height);
17         BLENDFUNCTION blendFunc = new BLENDFUNCTION(
18             AC_SRC_OVER,
19             0,
20             255,
21             AC_SRC_ALPHA);
22 
23         POINT srcLoc = new POINT(0, 0);
24 
25         hBmp = bmp.GetHbitmap(Color.FromArgb(0));
26         oldBits = SelectObject(memDc, hBmp);
27 
28         UpdateLayeredWindow(
29             Handle,
30             screenDC,
31             ref formLocation,
32             ref bitmapSize,
33             memDc,
34             ref srcLoc,
35             0,
36             ref blendFunc,
37             ULW_ALPHA);
38     }
39     finally
40     {
41         if (hBmp != IntPtr.Zero)
42         {
43             SelectObject(memDc, oldBits);
44             DeleteObject(hBmp);
45         }
46 
47         ReleaseDC(IntPtr.Zero, screenDC);
48         DeleteDC(memDc);
49     }
50 }

最后通過路徑漸變畫刷創建陰影位圖，通過位圖構建分層視窗，并與主視窗建立父子關系：

 1 /// <summary>
 2 /// 構建陰影
 3 /// </summary>
 4 private void BuildShadow()
 5 {
 6     lock (this)
 7     {
 8         _buildingShadow = true;
 9 
10         if (_shadow != null && !_shadow.IsDisposed && !_shadow.Disposing)
11         {
12             // 解除父子視窗關系
13             SetWindowLong(
14                 Handle,
15                 GWL_HWNDPARENT,
16                 0);
17 
18             _shadow.Dispose();
19         }
20 
21         Bitmap bmpBackground = new Bitmap(Width + BorderWidth * 4, Height + BorderWidth * 4);
22 
23         GraphicsPath gp = new GraphicsPath();
24         gp.AddRectangle(new Rectangle(0, 0, bmpBackground.Width, bmpBackground.Height));
25 
26         using (Graphics g = Graphics.FromImage(bmpBackground))
27         using (PathGradientBrush brs = new PathGradientBrush(gp))
28         {
29             g.CompositingMode = CompositingMode.SourceCopy;
30             g.InterpolationMode = InterpolationMode.HighQualityBicubic;
31             g.PixelOffsetMode = PixelOffsetMode.HighQuality;
32             g.SmoothingMode = SmoothingMode.AntiAlias;
33 
34             // 中心顏色
35             brs.CenterColor = Color.FromArgb(100, Color.Black);
36             // 指定從實際陰影邊界到視窗邊框邊界的漸變
37             brs.FocusScales = new PointF(1 - BorderWidth * 4F / Width, 1 - BorderWidth * 4F / Height);
38             // 邊框環繞顏色
39             brs.SurroundColors = new[] { Color.FromArgb(0, 0, 0, 0) };
40             // 掏空視窗實際區域
41             gp.AddRectangle(new Rectangle(BorderWidth * 2, BorderWidth * 2, Width, Height));
42             g.FillPath(brs, gp);
43         }
44 
45         gp.Dispose();
46 
47         _shadow = new XFormShadow(bmpBackground);
48 
49         _buildingShadow = false;
50 
51         AlignShadow();
52         _shadow.Show();
53 
54         // 設定父子視窗關系
55         SetWindowLong(
56             Handle,
57             GWL_HWNDPARENT,
58             _shadow.Handle.ToInt32());
59 
60         Activate();
61     }//end of lock(this)
62 }

感謝大家能讀到這里，代碼中如有錯誤，或存在其它建議，歡迎在評論區或Github指正，

如果覺得本文對你有幫助，還請點個推薦或Github上點個星星，謝謝大家，

轉載請注明原作者，謝謝，

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標籤：WinForm

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