1.3. chromium源代码分析 - chromiumframe - 窗口系列

在_tWinMain中有这样两条语句：

 MainWindowDelegate delegate;
 view::Window::CreateNativeWindow(NULL, gfx::Rect(), &delegate);

从这开始窗口相关的探索，目的就是要找到WNDCLASS注册与CreateWindow的地方。
Window类顾名思义就是的窗口。chromium对原始窗口做的封装。window相关的类主要有Window / WindowDelegate / WindowWin / Widget / WidgetDelegate / WidgetWin.
我的理解，Window为有标题栏和边框的窗口，Widget则为无标题栏的HWND。Window其实是特殊的在Widget上加了标题栏和边框相关处理的类。chromium已经在Window和Widget中加入默认消息处理，以及默认的窗口属性。我们自己的程序当然要有自己窗口属性和窗口行为，这时就需要继承Window或者Widget的嵌入类Delegate。
我在学习代码的时候画了一下类图，辅助自己理解。

按图索骥，从基类开始看起。

基类:MessageMapInterface

 class MessageMapInterface
 {
 public:
     virtual BOOL ProcessWindowMessage(HWND window,
         UINT message,
         WPARAM w_param,
         LPARAM l_param,
         LRESULT& result,
         DWORD msg_mad_id = ) = ;
 };

只有一个函数，主要用于处理消息，在消息响应函数(WndProc)中会调用此函数进行消息处理。

接下来就是WindowImpl类，WindowImpl中最重要的就是WndProc，这个函数就是我们注册在WNDCLASS里的消息响应函数。

 class WindowImpl : public MessageMapInterface
 {
 private:
     static LRESULT CALLBACK WndProc(HWND window, UINT message,
         WPARAM w_param, LPARAM l_param);
 };

WndProc会使用基类指针来调用基类的ProcessWindowMessage函数，消息的控制权就交给ProcessWindowMessage，多态行为。

再下来是widget基类，我们可以理解为是HWND的属性 行为的封装。

 class Widget
 {
 public:
     // Delegate类在这被加入
     virtual WidgetDelegate* GetWidgetDelegate() = ;
     virtual void SetWidgetDelegate(WidgetDelegate* delegate) = ;

     // 这都是HWND的常规属性与行为
     virtual void GetBounds(gfx::Rect* out, bool including_frame) const = ;
     virtual void SetBounds(const gfx::Rect& bounds) = ;
     virtual void MoveAbove(Widget* widget) = ;
     virtual void SetShape(HRGN shape) = ;
     virtual void Close() = ;
     virtual void CloseNow() = ;
     virtual void Show() = ;
     virtual void Hide() = ;
     virtual void SetAlwaysOnTop(bool on_top) = ;
     virtual bool IsVisible() const = ;
     virtual bool IsActive() const = ;

     // tooltip、主题管理、焦点管理
     virtual TooltipManager* GetTooltipManager() = ;
     virtual bool GetAccelerator(int cmd_id, MenuAccelerator* accelerator) = ;
     virtual ThemeProvider* GetThemeProvider() const = ;
     virtual ThemeProvider* GetDefaultThemeProvider() const = ;
     virtual FocusManager* GetFocusManager() = ;

     // 更新界面函数
     virtual void PaintNow(const gfx::Rect& update_rect) = ;
 };

widget的实现类为WidgetWin，平台相关Win，就是windows平台的widget子类。

     class WidgetWin : public gfx::WindowImpl,
         public Widget,
         public MessageLoopForUI::Observer,
         public FocusTraversable
     {
     public:
         VIEW_BEGIN_MSG_MAP_EX(WidgetWin)
             // Range handlers must go first!
             VIEW_MESSAGE_RANGE_HANDLER_EX(WM_MOUSEFIRST, WM_MOUSELAST, OnMouseRange)
             VIEW_MESSAGE_RANGE_HANDLER_EX(WM_NCMOUSEMOVE, WM_NCMOUSEMOVE, OnMouseRange)

             // Reflected message handler
             VIEW_MESSAGE_HANDLER_EX(kReflectedMessage, OnReflectedMessage)

             // CustomFrameWindow hacks
             VIEW_MESSAGE_HANDLER_EX(WM_NCUAHDRAWCAPTION, OnNCUAHDrawCaption)
             VIEW_MESSAGE_HANDLER_EX(WM_NCUAHDRAWFRAME, OnNCUAHDrawFrame)

             // Vista and newer
             VIEW_MESSAGE_HANDLER_EX(WM_DWMCOMPOSITIONCHANGED, OnDwmCompositionChanged)

             // Non-atlcrack.h handlers
             VIEW_MESSAGE_HANDLER_EX(WM_GETOBJECT, OnGetObject)
             VIEW_MESSAGE_HANDLER_EX(WM_NCMOUSELEAVE, OnNCMouseLeave)
             VIEW_MESSAGE_HANDLER_EX(WM_MOUSELEAVE, OnMouseLeave)
             VIEW_MESSAGE_HANDLER_EX(WM_MOUSEWHEEL, OnMouseWheel)

             // This list is in _ALPHABETICAL_ order! OR I WILL HURT YOU.
             VIEW_MSG_WM_ACTIVATE(OnActivate)
             VIEW_MSG_WM_ACTIVATEAPP(OnActivateApp)
             VIEW_MSG_WM_APPCOMMAND(OnAppCommand)
             VIEW_MSG_WM_CANCELMODE(OnCancelMode)
             VIEW_MSG_WM_CAPTURECHANGED(OnCaptureChanged)
             VIEW_MSG_WM_CLOSE(OnClose)
             VIEW_MSG_WM_COMMAND(OnCommand)
             VIEW_MSG_WM_CREATE(OnCreate)
             VIEW_MSG_WM_DESTROY(OnDestroy)

             VIEW_MSG_WM_SETTEXT(OnSetText)
             VIEW_MSG_WM_SETTINGCHANGE(OnSettingChange)
             VIEW_MSG_WM_SIZE(OnSize)
             VIEW_MSG_WM_SYSCOMMAND(OnSysCommand)
             VIEW_MSG_WM_THEMECHANGED(OnThemeChanged)
             VIEW_MSG_WM_VSCROLL(OnVScroll)
             VIEW_MSG_WM_WINDOWPOSCHANGING(OnWindowPosChanging)
             VIEW_MSG_WM_WINDOWPOSCHANGED(OnWindowPosChanged)
         VIEW_END_MSG_MAP()

         // Overridden from Widget:
         // Overridden from MessageLoop::Observer:
         // Overridden from FocusTraversable:

     protected:
         virtual void OnActivate(UINT action, BOOL minimized, HWND window);
         virtual void OnActivateApp(BOOL active, DWORD thread_id);
         virtual LRESULT OnAppCommand(HWND window, short app_command, WORD device,
             int keystate);
         virtual void OnCancelMode();
         virtual void OnCaptureChanged(HWND hwnd);
         virtual void OnClose();
         virtual void OnCommand(UINT notification_code, int command_id, HWND window);
         virtual LRESULT OnCreate(CREATESTRUCT* create_struct);
         // WARNING: If you override this be sure and invoke super, otherwise we'll
         // leak a few things.
         virtual void OnDestroy();

         virtual LRESULT OnSetText(const wchar_t* text);
         virtual void OnSettingChange(UINT flags, const wchar_t* section);
         virtual void OnSize(UINT param, const gfx::Size& size);
         virtual void OnSysCommand(UINT notification_code, gfx::Point click);
         virtual void OnThemeChanged();
         virtual void OnVScroll(int scroll_type, short position, HWND scrollbar);
         virtual void OnWindowPosChanging(WINDOWPOS* window_pos);
         virtual void OnWindowPosChanged(WINDOWPOS* window_pos);

         // deletes this window as it is destroyed, override to provide different
         // behavior.
         virtual void OnFinalMessage(HWND window);
     };

从继承关系widget_win不仅实现了widget，而且还加入了消息处理相关，焦点处理等的内容。
从类的接口看，确实是在处理消息了，这就是windows消息的默认处理类了。消息是怎么传送到这里的呢？
回到祖父类，ProcessWindowMessage消息处理总函数, 再看看WidgetWin中的VIEW_BEGIN_MSG_MAP_EX宏，

 #define VIEW_BEGIN_MSG_MAP_EX(theClass) \
 public: \
     BOOL m_bMsgHandled; \
     /* "handled" management for cracked handlers */ \
     BOOL IsMsgHandled() const \
     { \
         return m_bMsgHandled; \
     } \
     void SetMsgHandled(BOOL bHandled) \
     { \
         m_bMsgHandled = bHandled; \
     } \
     BOOL ProcessWindowMessage(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam, LRESULT& lResult, DWORD dwMsgMapID = ) \
     { \
         BOOL bOldMsgHandled = m_bMsgHandled; \
         BOOL bRet = _ProcessWindowMessage(hWnd, uMsg, wParam, lParam, lResult, dwMsgMapID); \
         m_bMsgHandled = bOldMsgHandled; \
         return bRet; \
     } \
     BOOL _ProcessWindowMessage(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam, LRESULT& lResult, DWORD dwMsgMapID) \
     { \
         BOOL bHandled = TRUE; \
         hWnd; \
         uMsg; \
         wParam; \
         lParam; \
         lResult; \
         bHandled; \
         switch(dwMsgMapID) \
         { \
         case :

已经看到ProcessWindowMessage的身影了，ProcessWindowMessage是虚函数重载，WndProc实际会把消息传送到这里，ProcessWindowMessage会调用_ProcessWindowMessage接下来就是switch case处理分发了，这应该是借鉴了WTL框架，

回看1.1的win32典型程序的消息处理函数，都是switch case 来分发消息，这里只是用宏伪装，用类进行了包装而已。

window类封装了title name，最大/小化支持等等一些窗口的属性和行为，这些都是纯虚的函数，最重要的就是在main.cpp被调用的static函数。

     class Window
     {
     public:
         virtual ~Window() {}

         // Creates an instance of an object implementing this interface.
         // TODO(beng): create a version of this function that takes a HWND, for
         //             constrained windows.
         static Window* CreateNativeWindow(HWND parent,
             const gfx::Rect& bounds, WindowDelegate* window_delegate);
 };

     // static
     Window* Window::CreateNativeWindow(HWND parent,
         const gfx::Rect& bounds,
         WindowDelegate* window_delegate)
     {
         WindowWin* window = new WindowWin(window_delegate);   // 1. new出子类
         window->GetNonClientView()->SetFrameView(window->CreateFrameViewForWindow());
         window->Init(parent, bounds); //2.调用WindowWin::Init
         return window;
     }

     void WindowImpl::Init(HWND parent, const Rect& bounds)
     {
         if(window_style_ == )
         {
             window_style_ = parent ? kWindowDefaultChildStyle : kWindowDefaultStyle;
         }

         if(parent && !::IsWindow(parent))
         {
             NOTREACHED() << "invalid parent window specified.";
             parent = NULL;
         }

         int x, y, width, height;
         if(bounds.IsEmpty())
         {
             x = y = width = height = CW_USEDEFAULT;
         }
         else
         {
             x = bounds.x();
             y = bounds.y();
             width = bounds.width();
             height = bounds.height();
         }

         hwnd_ = CreateWindowEx(window_ex_style_, GetWindowClassName().c_str(), NULL,
             window_style_, x, y, width, height, parent, NULL, NULL, this);                  // 这里就是创建窗口了
         DCHECK(hwnd_);
     }

到此，窗口的创建，消息的分发都已经展现出来了，剩下的就是消息循环了。

WindowWin继承自widget，重载了NC消息的处理。又继承了window类，实现窗口的行为及属性。

WindowDelegate则是window的委派，实质上应该是Window子类WindowWin的委派。我们要修改窗口的属性行为以及如何构建窗口也只需要继承WindowDelegate，重载windowDelegate的行为函数即可。main.cpp中就是这么干的，MainWindowDelegate就是继承WindowDelegate。