Delphi 组件开发教程指南（4）组件生成过程（针对TWinControl继承而来的组件）

  
  

   
   procedure
    TControl.SetVisible(Value: Boolean);


   begin
   


   if
    FVisible 
   <>
    Value 
   then
   


   begin
   

VisibleChanging;

FVisible :
   =
    Value;

Perform(CM_VISIBLECHANGED, Ord(Value), 
   0
   );

RequestAlign;


   end
   ;


   end
   ;
  
  

  
  

   
   procedure
    TWinControl.CMVisibleChanged(
   var
    Message: TMessage);


   begin
   


   if
    
   not
    FVisible 
   and
    (Parent 
   <>
    
   nil
   ) 
   then
    RemoveFocus(False);


   if
    
   not
    (csDesigning 
   in
    ComponentState) 
   or
   

(csNoDesignVisible 
   in
    ControlStyle) 
   then
    UpdateControlState;


   end
   ;
  
  

  
  

   
   procedure
    TWinControl.UpdateShowing;


   var
   

ShowControl: Boolean;

I: Integer;


   begin
   

ShowControl :
   =
    (FVisible 
   and
    (
   not
    (csDesigning 
   in
    ComponentState) 
   or
    
   not
    (csDesignerHide 
   in
    ControlState)) 
   or
   

((csDesigning 
   in
    ComponentState) 
   and
    
   not
    (csDesignerHide 
   in
    ControlState)) 
   and
   


   not
    (csNoDesignVisible 
   in
    ControlStyle)) 
   and
   


   not
    (csReadingState 
   in
    ControlState) 
   and
    
   not
    (csDestroying 
   in
    ComponentState);


   if
    ShowControl 
   then
   


   begin
    //这个时候如果是第一次显示，FHandle为0，就会调用CreateHandle来创建一个窗口句柄了，也就是说

//在这个时候才真真实实的创建Windows的标准控件！


   if
    FHandle 
   =
    
   0
    
   then
    CreateHandle;


   if
    FWinControls 
   <>
    
   nil
    
   then
   


   for
    I :
   =
    
   0
    
   to
    FWinControls.Count 
   -
    
   1
    
   do
   

TWinControl(FWinControls[I]).UpdateShowing;//之后会更新属于这个控件容器的所有子控件显示


   end
   ;


   if
    FHandle 
   <>
    
   0
    
   then
   


   if
    FShowing 
   <>
    ShowControl 
   then
   


   begin
   

FShowing :
   =
    ShowControl;


   try
   

SetPerformingShowingChanged(Self);


   try
   

Perform(CM_SHOWINGCHANGED, 
   0
   , 
   0
   );


   finally
   

ClearPerformingShowingChanged(Self);


   end
   ;


   except
   

FShowing :
   =
    
   not
    ShowControl;


   raise
   ;


   end
   ;


   end
   ;


   end
   ;
  
  

  
  

   
   procedure
    TWinControl.CMRecreateWnd(
   var
    Message: TMessage);


   var
   

WasFocused: Boolean;


   begin
   

WasFocused :
   =
    Focused;//先保存控件是否是焦点状态

UpdateRecreatingFlag(True);//这个函数，我就不贴他的代码了，从他的代码中，我们可以看出来，这个函数

//的目的是为所有的子控件打上重建的标记


   try
   

DestroyHandle;//释放句柄，同时释放所有子控件的句柄

UpdateControlState;//更新控件状态，这个函数上面已经分析，会建立句柄，同时子控件句柄。


   finally
   

UpdateRecreatingFlag(False);//重建状态完成


   end
   ;


   if
    WasFocused 
   and
    (FHandle 
   <>
    
   0
   ) 
   then
   

Windows.SetFocus(FHandle);//如果重建成功，并且原先有焦点，就恢复原先的焦点状态


   end
   ;