UserDrawCaption函数是用来实现窗口标题显示。具体代码如下：

#001 BOOL UserDrawCaption(

#002 PWINDOW_OBJECT pWnd,

#003 HDC hDc,

#004 LPCRECT lpRc,

#005 HFONT hFont,

#006 HICON hIcon,

#007 const PUNICODE_STRING str,

#008 UINT uFlags)

#009 {

#010 BOOL Ret = FALSE;

#011 HBITMAP hMemBmp = NULL,hOldBmp = NULL;

#012 HBRUSH hOldBrush = NULL;

#013 HDC hMemDc = NULL;

#014 ULONG Height;

#015 UINT VCenter = 0,Padding = 0;

#016 RECT r = *lpRc;

#017 LONG ButtonWidth,IconWidth;

#018 BOOL HasIcon;

#019 PWINDOW Wnd = NULL;

#020

#021 //ASSERT(pWnd != NULL);

#022

获取窗口句柄。

#023 if (pWnd)

#024 Wnd = pWnd->Wnd;

#025

创建兼容DC的内存位图。

#026 hMemBmp = NtGdiCreateCompatibleBitmap(hDc,

#027 lpRc->right - lpRc->left,

#028 lpRc->bottom - lpRc->top);

#029

#030 if(!hMemBmp)

#031 {

#032 DPRINT1("%s: NtGdiCreateCompatibleBitmap() Failed!/n",__FUNCTION__);

#033 return FALSE;

#034 }

#035

创建兼容的内存设备。

#036 hMemDc = NtGdiCreateCompatibleDC(hDc);

#037 if(!hMemDc)

#038 {

#039 DPRINT1("%s: NtGdiCreateCompatibleDC() Failed!/n",__FUNCTION__);

#040 goto cleanup;

#041 }

#042

关联内存设备和位图设备。

#043 hOldBmp = NtGdiSelectBitmap(hMemDc,hMemBmp);

#044 if(!hOldBmp)

#045 {

#046 DPRINT1("%s: NtGdiSelectBitmap() Failed!/n",__FUNCTION__);

#047 goto cleanup;

#048 }

#049

获取窗口标题的高度。

#050 Height = UserGetSystemMetrics(SM_CYCAPTION) - 1;

#051 VCenter = (lpRc->bottom - lpRc->top) / 2;

#052 Padding = VCenter - (Height / 2);

#053

判断窗口标题是否有图标显示。

#054 if ((!hIcon) && (Wnd != NULL))

#055 {

#056 HasIcon = (uFlags & DC_ICON) && (Wnd->Style & WS_SYSMENU)

#057 && !(uFlags & DC_SMALLCAP) && !(Wnd->ExStyle & WS_EX_DLGMODALFRAME)

#058 && !(Wnd->ExStyle & WS_EX_TOOLWINDOW);

#059 }

#060 else

#061 HasIcon = (BOOL) hIcon;

#062

获取图标的宽度。

#063 IconWidth = UserGetSystemMetrics(SM_CXSIZE) + Padding;

#064

#065 r.left = Padding;

#066 r.right = r.left + (lpRc->right - lpRc->left);

#067 r.top = Padding;

#068 r.bottom = r.top + (Height / 2);

#069

显示标题的背景。

#070 // Draw the caption background

#071 if(uFlags & DC_INBUTTON)

#072 {

#073 hOldBrush = NtGdiSelectBrush(hMemDc,

#074 IntGetSysColorBrush(COLOR_3DFACE));

#075

#076 if(!hOldBrush)

#077 {

#078 DPRINT1("%s: NtGdiSelectBrush() Failed!/n",__FUNCTION__);

#079 goto cleanup;

#080 }

#081

#082 if(!NtGdiPatBlt(hMemDc,

#083 lpRc->right - lpRc->left,

#084 lpRc->bottom - lpRc->top,

#085 PATCOPY))

#086 {

#087 DPRINT1("%s: NtGdiPatBlt() Failed!/n",__FUNCTION__);

#088 goto cleanup;

#089 }

#090

#091 if(HasIcon) r.left+=IconWidth;

#092 }

#093 else

#094 {

#095 r.right = (lpRc->right - lpRc->left);

#096 if(uFlags & DC_SMALLCAP)

#097 ButtonWidth = UserGetSystemMetrics(SM_CXSMSIZE) - 2;

#098 else ButtonWidth = UserGetSystemMetrics(SM_CXSIZE) - 2;

#099

#100 hOldBrush = NtGdiSelectBrush(hMemDc,

#101 IntGetSysColorBrush(uFlags & DC_ACTIVE ?

#102 COLOR_ACTIVECAPTION : COLOR_INACTIVECAPTION));

#103

#104 if(!hOldBrush)

#105 {

#106 DPRINT1("%s: NtGdiSelectBrush() Failed!/n",__FUNCTION__);

#107 goto cleanup;

#108 }

#109

#110 if(HasIcon && (uFlags & DC_GRADIENT))

#111 {

#112 NtGdiPatBlt(hMemDc,

#113 IconWidth+1,

#114 lpRc->bottom - lpRc->top,

#115 PATCOPY);

#116 r.left+=IconWidth;

#117 }

#118 else

#119 {

#120 NtGdiPatBlt(hMemDc,

#121 lpRc->right - lpRc->left,

#122 lpRc->bottom - lpRc->top,

#123 PATCOPY);

#124 }

#125

#126 if(uFlags & DC_GRADIENT)

#127 {

#128 static GRADIENT_RECT gcap = {0,1};

#129 TRIVERTEX vert[2];

#130 COLORREF Colors[2];

#131 PDC pMemDc;

#132

#133 if (Wnd != NULL)

#134 {

计算系统菜单显示位置。

#135 if(Wnd->Style & WS_SYSMENU)

#136 {

#137 r.right -= 3 + ButtonWidth;

#138 if(!(uFlags & DC_SMALLCAP))

#139 {

#140 if(Wnd->Style & (WS_MAXIMIZEBox | WS_MINIMIZEBox))

#141 r.right -= 2 + 2 * ButtonWidth;

#142 else r.right -= 2;

#143 r.right -= 2;

#144 }

#145

显示按钮背景颜色。

#146 //Draw buttons background

#147 if(!NtGdiSelectBrush(hMemDc,

#148 IntGetSysColorBrush(uFlags & DC_ACTIVE ?

#149 COLOR_GRADIENTACTIVECAPTION:COLOR_GRADIENTINACTIVECAPTION)))

#150 {

#151 DPRINT1("%s: NtGdiSelectBrush() Failed!/n",__FUNCTION__);

#152 goto cleanup;

#153 }

#154

#155 NtGdiPatBlt(hMemDc,

#156 r.right,

#157 0,

#158 lpRc->right - lpRc->left - r.right,

#159 lpRc->bottom - lpRc->top,

#160 PATCOPY);

#161 }

#162 }

#163

#164 Colors[0] = IntGetSysColor((uFlags & DC_ACTIVE) ?

#165 COLOR_ACTIVECAPTION : COLOR_INACTIVECAPTION);

#166

#167 Colors[1] = IntGetSysColor((uFlags & DC_ACTIVE) ?

#168 COLOR_GRADIENTACTIVECAPTION : COLOR_GRADIENTINACTIVECAPTION);

#169

#170 vert[0].x = r.left;

#171 vert[0].y = 0;

#172 vert[0].Red = (WORD)Colors[0]<<8;

#173 vert[0].Green = (WORD)Colors[0] & 0xFF00;

#174 vert[0].Blue = (WORD)(Colors[0]>>8) & 0xFF00;

#175 vert[0].Alpha = 0;

#176

#177 vert[1].x = r.right;

#178 vert[1].y = lpRc->bottom - lpRc->top;

#179 vert[1].Red = (WORD)Colors[1]<<8;

#180 vert[1].Green = (WORD)Colors[1] & 0xFF00;

#181 vert[1].Blue = (WORD)(Colors[1]>>8) & 0xFF00;

#182 vert[1].Alpha = 0;

#183

#184 pMemDc = DC_LockDc(hMemDc);

#185 if(!pMemDc)

#186 {

#187 DPRINT1("%s: Can't lock dc!/n",__FUNCTION__);

#188 goto cleanup;

#189 }

#190

#191 if(!IntGdiGradientFill(pMemDc,vert,2,&gcap,

#192 1,GRADIENT_FILL_RECT_H))

#193 {

#194 DPRINT1("%s: IntGdiGradientFill() Failed!/n",__FUNCTION__);

#195 }

#196

#197 DC_UnlockDc(pMemDc);

#198 } //if(uFlags & DC_GRADIENT)

#199 }

#200

显示系统菜单按钮。

#201 if(HasIcon)

#202 {

#203 r.top ++;

#204 r.left -= --IconWidth;

#205 /* FIXME: Draw the Icon when pWnd == NULL but hIcon is valid */

#206 if (pWnd != NULL)

#207 UserDrawSysMenuButton(pWnd,hMemDc,&r,FALSE);

#208 r.left += IconWidth;

#209 r.top --;

#210 }

#211

#212 r.top ++;

#213 r.left += 2;

#214

#215 r.bottom = r.top + Height;

#216

计算标题字符串显示位置。

#217 if((uFlags & DC_TEXT))

#218 {

#219 if(!(uFlags & DC_GRADIENT))

#220 {

#221 r.right = (lpRc->right - lpRc->left);

#222

#223 if(uFlags & DC_SMALLCAP)

#224 ButtonWidth = UserGetSystemMetrics(SM_CXSMSIZE) - 2;

#225 else ButtonWidth = UserGetSystemMetrics(SM_CXSIZE) - 2;

#226

#227 if ((Wnd != NULL) && (Wnd->Style & WS_SYSMENU))

#228 {

#229 r.right -= 3 + ButtonWidth;

#230 if(! (uFlags & DC_SMALLCAP))

#231 {

#232 if(Wnd->Style & (WS_MAXIMIZEBox | WS_MINIMIZEBox))

#233 r.right -= 2 + 2 * ButtonWidth;

#234 else r.right -= 2;

#235 r.right -= 2;

#236 }

#237 }

#238 }

#239

调用函数UserDrawCaptionText显示标题字符串。

#240 /* FIXME: hFont isn't handled */

#241 if (str)

#242 UserDrawCaptionText(hMemDc,str,uFlags);

#243 else if (pWnd != NULL)

#244 UserDrawCaptionText(hMemDc,&pWnd->Wnd->WindowName,uFlags);

#245 }

#246

从内存设备显示到实际显示设备。

#247 if(!NtGdiBitBlt(hDc,lpRc->left,lpRc->top,

#248 lpRc->right - lpRc->left,lpRc->bottom - lpRc->top,

#249 hMemDc,SRCCOPY,0))

#250 {

#251 DPRINT1("%s: NtGdiBitBlt() Failed!/n",__FUNCTION__);

#252 goto cleanup;

#253 }

#254

#255 Ret = TRUE;

#256

删除创建的DC资源。

#257 cleanup:

#258 if (hOldBrush) NtGdiSelectBrush(hMemDc,hOldBrush);

#259 if (hOldBmp) NtGdiSelectBitmap(hMemDc,hOldBmp);

#260 if (hMemBmp) NtGdiDeleteObject(hMemBmp);

#261 if (hMemDc) NtGdiDeleteObjectApp(hMemDc);

#262

#263 return Ret;

#264}