Delphi 对话框实现源码分析
Delphi 对话框实现源码分析
简介
在这篇文章中，我将大概的从Delphi XE2 的Dialogs单元入手，分析ShowMessage，MessageBox等对话框运行原理，希望能帮助你理解Delphi，不求你爱上她，只求让你能快速地解决问题。
跟踪代码
为了了解这些对话框的运行原理，我们需要跟踪进源代码中去，为此，你需要做如下设置
1. 简单创建一个使用了ShowMessage的VCL应用程序
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unit
Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;
type
TForm1 =
class
(TForm)
Edit1: TEdit;
Button1: TButton;
procedure
Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end
;
var
Form1: TForm1;
implementation
{$R *.dfm}
procedure
TForm1
.
Button1Click(Sender: TObject);
begin
ShowMessage(Edit1
.
Text);
MessageBox(Self
.
Handle,
PChar
(Edit1
.
Text),
PChar
(Application
.
Title),
MB_ICONINFORMATION
or
MB_OK);
MessageDlg(Edit1
.
Text,mtInformation,[mbOK,mbCancel],
0
);
end
;
end
.
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2. 在29行里设置一个断点, 再在Edit里输入一些内容,按下Message Box按钮, 按F7跟踪到Dialogs单元, 经过一段时间的仔细跟踪, 你会发现程序运行到下面一段代码:
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function
MessageDlgPosHelp(
const
Msg:
string
; DlgType: TMsgDlgType;
Buttons: TMsgDlgButtons; HelpCtx:
Longint
; X, Y:
Integer
;
const
HelpFileName:
string
):
Integer
;
begin
if
(Win32MajorVersion >=
6
)
and
UseLatestCommonDialogs
and
ThemeServices
.
ThemesEnabled
then
Result := DoTaskMessageDlgPosHelp(
''
, Msg, DlgType, Buttons,
HelpCtx, X, Y, HelpFileName)
else
Result := DoMessageDlgPosHelp(CreateMessageDialog(Msg, DlgType, Buttons),
HelpCtx, X, Y, HelpFileName);
end
;
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函数MessageDlgPosHelp指出, 如果当前系统是Vista,sever2008或以上版本的系统,那就调用DoTaskMessageDlgPosHelp函数进行对话框显示, 否则调用DoMessageDlgPosHelp显示对话框. 继续跟踪DoTaskMessageDlgPosHelp函数, 你会发现如下一段代码:
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function
TCustomTaskDialog
.
DoExecute(ParentWnd: HWND):
Boolean
;
const
CTaskDlgFlags:
array
[TTaskDialogFlag]
of
Cardinal
= (
TDF_Enable_Hyperlinks, TDF_Use_Hicon_Main,
tdf_Use_Hicon_Footer, TDF_ALLOW_DIALOG_CANCELLATION,
TDF_USE_COMMAND_LINKS, TDF_USE_COMMAND_LINKS_NO_ICON,
TDF_EXPAND_FOOTER_AREA, TDF_EXPANDED_BY_DEFAULT,
TDF_VERIFICATION_FLAG_CHECKED, TDF_SHOW_PROGRESS_BAR,
TDF_SHOW_MARQUEE_PROGRESS_BAR, TDF_CALLBACK_TIMER,
TDF_POSITION_RELATIVE_TO_WINDOW, TDF_RTL_LAYOUT,
TDF_NO_DEFAULT_RADIO_BUTTON, TDF_CAN_BE_MINIMIZED);
CTaskDlgCommonButtons:
array
[TTaskDialogCommonButton]
of
Cardinal
= (
TDCBF_OK_BUTTON, TDCBF_YES_BUTTON, TDCBF_NO_BUTTON,
TDCBF_CANCEL_BUTTON, TDCBF_RETRY_BUTTON, TDCBF_CLOSE_BUTTON);
CTaskDlgDefaultButtons:
array
[TTaskDialogCommonButton]
of
Integer
= (
IDOK, IDYES, IDNO, IDCANCEL, IDRETRY, IDCLOSE);
var
LWindowList: TTaskWindowList;
LModalResult:
Integer
;
LRadioButton:
Integer
;
LFlag: TTaskDialogFlag;
LFocusState: TFocusState;
LVerificationChecked: LongBool;
LTaskDialog: TTaskDialogConfig;
LCommonButton: TTaskDialogCommonButton;
begin
if
Win32MajorVersion <
6
then
raise
EPlatformVersionException
.
CreateResFmt(
{$IFNDEF CLR}@{$ENDIF}
SWindowsVistaRequired, [ClassName]);
if
not
ThemeServices
.
ThemesEnabled
then
raise
Exception
.
CreateResFmt(
{$IFNDEF CLR}@{$ENDIF}
SXPThemesRequired, [ClassName]);
{$IF NOT DEFINED(CLR)}
FillChar(LTaskDialog, SizeOf(LTaskDialog),
0
);
{
$IFEND
}
with
LTaskDialog
do
begin
// Set Size, Parent window, Flags
cbSize := SizeOf(LTaskDialog);
hwndParent := ParentWnd;
dwFlags :=
0
;
for
LFlag := Low(TTaskDialogFlag)
to
High(TTaskDialogFlag)
do
if
LFlag
in
FFlags
then
dwFlags := dwFlags
or
CTaskDlgFlags[LFlag];
// Set CommonButtons
dwCommonButtons :=
0
;
for
LCommonButton := Low(TTaskDialogCommonButton)
to
High(TTaskDialogCommonButton)
do
if
LCommonButton
in
FCommonButtons
then
dwCommonButtons := dwCommonButtons
or
CTaskDlgCommonButtons[LCommonButton];
// Set Content, MainInstruction, Title, MainIcon, DefaultButton
if
FText <>
''
then
pszContent :=
{$IFNDEF CLR}PWideChar{$ENDIF}
(
WideString
(FText));
if
FTitle <>
''
then
pszMainInstruction :=
{$IFNDEF CLR}PWideChar{$ENDIF}
(
WideString
(FTitle));
if
FCaption <>
''
then
pszWindowTitle :=
{$IFNDEF CLR}PWideChar{$ENDIF}
(
WideString
(FCaption));
if
tfUseHiconMain
in
FFlags
then
hMainIcon := FCustomMainIcon
.
Handle
else
begin
if
FMainIcon
in
[tdiNone
..
tdiShield]
then
pszMainIcon := LPCWSTR(CTaskDlgIcons[FMainIcon])
else
pszMainIcon := LPCWSTR(MakeIntResourceW(
Word
(FMainIcon)));
end
;
nDefaultButton := CTaskDlgDefaultButtons[FDefaultButton];
// Set Footer, FooterIcon
if
FFooterText <>
''
then
pszFooter :=
{$IFNDEF CLR}PWideChar{$ENDIF}
(
WideString
(FFooterText));
if
tfUseHiconFooter
in
FFlags
then
hFooterIcon := FCustomFooterIcon
.
Handle
else
begin
if
FFooterIcon
in
[tdiNone
..
tdiShield]
then
pszFooterIcon := LPCWSTR(CTaskDlgIcons[FFooterIcon])
else
pszFooterIcon := LPCWSTR(MakeIntResourceW(
Word
(FFooterIcon)));
end
;
// Set VerificationText, ExpandedInformation, CollapsedControlText
if
FVerificationText <>
''
then
pszVerificationText :=
{$IFNDEF CLR}PWideChar{$ENDIF}
(
WideString
(FVerificationText));
if
FExpandedText <>
''
then
pszExpandedInformation :=
{$IFNDEF CLR}PWideChar{$ENDIF}
(
WideString
(FExpandedText));
if
FExpandButtonCaption <>
''
then
pszCollapsedControlText :=
{$IFNDEF CLR}PWideChar{$ENDIF}
(
WideString
(FExpandButtonCaption));
// Set Buttons
cButtons := FButtons
.
Count;
if
cButtons >
0
then
pButtons := FButtons
.
Buttons;
if
FButtons
.
DefaultButton <>
nil
then
nDefaultButton := FButtons
.
DefaultButton
.
ModalResult;
// Set RadioButtons
cRadioButtons := FRadioButtons
.
Count;
if
cRadioButtons >
0
then
pRadioButtons := FRadioButtons
.
Buttons;
if
not
(tfNoDefaultRadioButton
in
FFlags)
and
(FRadioButtons
.
DefaultButton <>
nil
)
then
nDefaultRadioButton := FRadioButtons
.
DefaultButton
.
ModalResult;
// Prepare callback
{$IF DEFINED(CLR)}
pfCallBack := @CallbackProc;
{
$ELSE
}
lpCallbackData := LONG_PTR(Self);
pfCallback := @TaskDialogCallbackProc;
{
$IFEND
}
end
;
LWindowList := DisableTaskWindows(ParentWnd);
LFocusState := SaveFocusState;
try
Result := TaskDialogIndirect(LTaskDialog,
{$IFNDEF CLR}@{$ENDIF}
LModalResult,
{$IFNDEF CLR}@{$ENDIF}LRadioButton, {$IFNDEF CLR}@{$ENDIF}
LVerificationChecked) = S_OK;
FModalResult := LModalResult;
if
Result
then
begin
FButton := TTaskDialogButtonItem(FButtons
.
FindButton(FModalResult));
FRadioButton := TTaskDialogRadioButtonItem(FRadioButtons
.
FindButton(LRadioButton));
if
LVerificationChecked
then
Include(FFlags, tfVerificationFlagChecked)
else
Exclude(FFlags, tfVerificationFlagChecked);
end
;
finally
EnableTaskWindows(LWindowList);
SetActiveWindow(ParentWnd);
RestoreFocusState(LFocusState);
end
;
end
;
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上面这段代码在Dialogs单元的第5407行, 该函数先进行可用性判断, 然后填充
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LTaskDialog: TTaskDialogConfig;
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一个TTaskDialogConfig的结构体, 该结构体定义在CommCtrl单元第9550行, 其定义如下:
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type
{ $EXTERNALSYM TASKDIALOGCONFIG}
TASKDIALOGCONFIG =
packed
record
cbSize: UINT;
hwndParent: HWND;
hInstance: HINST;
// used for MAKEINTRESOURCE() strings
dwFlags: DWORD;
// TASKDIALOG_FLAGS (TDF_XXX) flags
dwCommonButtons: DWORD;
// TASKDIALOG_COMMON_BUTTON (TDCBF_XXX) flags
pszWindowTitle: LPCWSTR;
// string or MAKEINTRESOURCE()
case
Integer
of
0
: (hMainIcon: HICON);
1
: (pszMainIcon: LPCWSTR;
pszMainInstruction: LPCWSTR;
pszContent: LPCWSTR;
cButtons: UINT;
pButtons: PTaskDialogButton;
nDefaultButton:
Integer
;
cRadioButtons: UINT;
pRadioButtons: PTaskDialogButton;
nDefaultRadioButton:
Integer
;
pszVerificationText: LPCWSTR;
pszExpandedInformation: LPCWSTR;
pszExpandedControlText: LPCWSTR;
pszCollapsedControlText: LPCWSTR;
case
Integer
of
0
: (hFooterIcon: HICON);
1
: (pszFooterIcon: LPCWSTR;
pszFooter: LPCWSTR;
pfCallback: TFTaskDialogCallback;
lpCallbackData: LONG_PTR;
cxWidth: UINT
// width of the Task Dialog's client area in DLU's.
// If 0, Task Dialog will calculate the ideal width.
);
);
end
;
{$EXTERNALSYM _TASKDIALOGCONFIG}
_TASKDIALOGCONFIG = TASKDIALOGCONFIG;
PTaskDialogConfig = ^TTaskDialogConfig;
TTaskDialogConfig = TASKDIALOGCONFIG;
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该结构体其实是从MSDN里翻译过来的, 定义在CommCtrl.h 头文件里(需要Windows Vista, Windows Server 2008及以上版本, 我是用Windows 7 64位进行的测试), 详细说明可以查看MSDN.
TCustomTaskDialog.DoExecute 填充完LTaskDialog结构体后, 直接调用:
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Result := TaskDialogIndirect(LTaskDialog,
{$IFNDEF CLR}@{$ENDIF}
LModalResult,
{$IFNDEF CLR}@{$ENDIF}LRadioButton, {$IFNDEF CLR}@{$ENDIF}
LVerificationChecked) = S_OK;
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TaskDialogIndirect显示对话框, TaskDialogIndirect定义在CommCtrl单元, 其代码如下:
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{ Task Dialog }
var
_TaskDialogIndirect:
function
(
const
pTaskConfig: TTaskDialogConfig;
pnButton: PInteger; pnRadioButton: PInteger;
pfVerificationFlagChecked: PBOOL): HRESULT; stdcall;
_TaskDialog:
function
(hwndParent: HWND; hInstance: HINST;
pszWindowTitle: LPCWSTR; pszMainInstruction: LPCWSTR; pszContent: LPCWSTR;
dwCommonButtons: DWORD; pszIcon: LPCWSTR; pnButton: PInteger): HRESULT; stdcall;
function
TaskDialogIndirect(
const
pTaskConfig: TTaskDialogConfig;
pnButton: PInteger; pnRadioButton: PInteger; pfVerificationFlagChecked: PBOOL): HRESULT;
begin
if
Assigned(_TaskDialogIndirect)
then
Result := _TaskDialogIndirect(pTaskConfig, pnButton, pnRadioButton,
pfVerificationFlagChecked)
else
begin
InitComCtl;
Result := E_NOTIMPL;
if
ComCtl32DLL <>
0
then
begin
@_TaskDialogIndirect := GetProcAddress(ComCtl32DLL,
'TaskDialogIndirect'
);
if
Assigned(_TaskDialogIndirect)
then
Result := _TaskDialogIndirect(pTaskConfig, pnButton, pnRadioButton,
pfVerificationFlagChecked)
end
;
end
;
end
;
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查看代码知道, TaskDialogIndirect 直接调用ComCtrl32.Dll里的函数:TaskDialogIndirect 显示对话框. 通过查询MSDN了解TaskDialogIndirect API的用途与用法:
The TaskDialogIndirect function creates, displays, and operates a task dialog. The task dialog contains application-defined icons, messages, title, verification check box, command links, push buttons, and radio buttons. This function can register a callback function to receive notification messages.
函数TaskDialogIndirect 用于创建, 显示, 运行一个任务对话框, 这个任务对话框可以包括由应用程序定义的图标,消息,标题,复选框,按钮,单选框. 该函数还可以接收一个回调函数用于接收通知信息
看到这里你或许会问:
如果我的系统是xp或其他低于Vista, server2008的系统呢? 由上文中可知, 如果是低版本的系统, 则调用DoMessageDlgPosHelp 函数进行对话框显示, 调用代码如下:
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Result := DoMessageDlgPosHelp(CreateMessageDialog(Msg, DlgType, Buttons),
HelpCtx, X, Y, HelpFileName);
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DoMessageDlgPosHelp代码:
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function
DoMessageDlgPosHelp(MessageDialog: TForm; HelpCtx:
Longint
; X, Y:
Integer
;
const
HelpFileName:
string
):
Integer
;
begin
with
MessageDialog
do
try
HelpContext := HelpCtx;
HelpFile := HelpFileName;
if
X >=
0
then
Left := X;
if
Y >=
0
then
Top := Y;
if
(Y <
0
)
and
(X <
0
)
then
Position := poScreenCenter;
Result := ShowModal;
finally
Free;
end
;
end
;
|
从DoMessageDlgPosHelp代码中可见, 该函数只是简单的将传递进来的TForm以模式窗口的形式显示在指定的位置.
下面是CreateMessageDialog代码:
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function
CreateMessageDialog(
const
Msg:
string
; DlgType: TMsgDlgType;
Buttons: TMsgDlgButtons; DefaultButton: TMsgDlgBtn): TForm;
const
mcHorzMargin =
8
;
mcVertMargin =
8
;
mcHorzSpacing =
10
;
mcVertSpacing =
10
;
mcButtonWidth =
50
;
mcButtonHeight =
14
;
mcButtonSpacing =
4
;
var
DialogUnits: TPoint;
HorzMargin, VertMargin, HorzSpacing, VertSpacing, ButtonWidth,
ButtonHeight, ButtonSpacing, ButtonCount, ButtonGroupWidth,
IconTextWidth, IconTextHeight, X, ALeft:
Integer
;
B, CancelButton: TMsgDlgBtn;
{$IF DEFINED(CLR)}
IconID:
Integer
;
{
$ELSE
}
IconID:
PChar
;
{
$IFEND
}
TextRect: TRect;
LButton: TButton;
begin
Result := TMessageForm
.
CreateNew(Application);
with
Result
do
begin
BiDiMode := Application
.
BiDiMode;
BorderStyle := bsDialog;
Canvas
.
Font := Font;
KeyPreview :=
True
;
PopupMode := pmAuto;
Position := poDesigned;
OnKeyDown := TMessageForm(Result).CustomKeyDown;
DialogUnits := GetAveCharSize(Canvas);
HorzMargin := MulDiv(mcHorzMargin, DialogUnits
.
X,
4
);
VertMargin := MulDiv(mcVertMargin, DialogUnits
.
Y,
8
);
HorzSpacing := MulDiv(mcHorzSpacing, DialogUnits
.
X,
4
);
VertSpacing := MulDiv(mcVertSpacing, DialogUnits
.
Y,
8
);
ButtonWidth := MulDiv(mcButtonWidth, DialogUnits
.
X,
4
);
for
B := Low(TMsgDlgBtn)
to
High(TMsgDlgBtn)
do
begin
if
B
in
Buttons
then
begin
if
ButtonWidths[B] =
0
then
begin
TextRect := Rect(
0
,
0
,
0
,
0
);
Windows
.
DrawText( canvas
.
handle,
{$IF DEFINED(CLR)}
ButtonCaptions[B], -
1
,
{
$ELSE
}
PChar
(LoadResString(ButtonCaptions[B])), -
1
,
{
$IFEND
}
TextRect, DT_CALCRECT
or
DT_LEFT
or
DT_SINGLELINE
or
DrawTextBiDiModeFlagsReadingOnly);
with
TextRect
do
ButtonWidths[B] := Right - Left +
8
;
end
;
if
ButtonWidths[B] > ButtonWidth
then
ButtonWidth := ButtonWidths[B];
end
;
end
;
ButtonHeight := MulDiv(mcButtonHeight, DialogUnits
.
Y,
8
);
ButtonSpacing := MulDiv(mcButtonSpacing, DialogUnits
.
X,
4
);
SetRect(TextRect,
0
,
0
, Screen
.
Width
div
2
,
0
);
DrawText(Canvas
.
Handle, Msg, Length(Msg)+
1
, TextRect,
DT_EXPANDTABS
or
DT_CALCRECT
or
DT_WORDBREAK
or
DrawTextBiDiModeFlagsReadingOnly);
IconID := IconIDs[DlgType];
IconTextWidth := TextRect
.
Right;
IconTextHeight := TextRect
.
Bottom;
{$IF DEFINED(CLR)}
if
DlgType <> mtCustom
then
{
$ELSE
}
if
IconID <>
nil
then
{
$IFEND
}
begin
Inc(IconTextWidth,
32
+ HorzSpacing);
if
IconTextHeight <
32
then
IconTextHeight :=
32
;
end
;
ButtonCount :=
0
;
for
B := Low(TMsgDlgBtn)
to
High(TMsgDlgBtn)
do
if
B
in
Buttons
then
Inc(ButtonCount);
ButtonGroupWidth :=
0
;
if
ButtonCount <>
0
then
ButtonGroupWidth := ButtonWidth * ButtonCount +
ButtonSpacing * (ButtonCount -
1
);
ClientWidth := Max(IconTextWidth, ButtonGroupWidth) + HorzMargin *
2
;
ClientHeight := IconTextHeight + ButtonHeight + VertSpacing +
VertMargin *
2
;
Left := (Screen
.
Width
div
2
) - (Width
div
2
);
Top := (Screen
.
Height
div
2
) - (Height
div
2
);
if
DlgType <> mtCustom
then
{$IF DEFINED(CLR)}
Caption := Captions[DlgType]
else
Caption := Application
.
Title;
if
DlgType <> mtCustom
then
{
$ELSE
}
Caption := LoadResString(Captions[DlgType])
else
Caption := Application
.
Title;
if
IconID <>
nil
then
{
$IFEND
}
with
TImage
.
Create(Result)
do
begin
Name :=
'Image'
;
Parent := Result;
Picture
.
Icon
.
Handle := LoadIcon(
0
, IconID);
SetBounds(HorzMargin, VertMargin,
32
,
32
);
end
;
TMessageForm(Result).Message := TLabel
.
Create(Result);
with
TMessageForm(Result).Message
do
begin
Name :=
'Message'
;
Parent := Result;
WordWrap :=
True
;
Caption := Msg;
BoundsRect := TextRect;
BiDiMode := Result
.
BiDiMode;
ALeft := IconTextWidth - TextRect
.
Right + HorzMargin;
if
UseRightToLeftAlignment
then
ALeft := Result
.
ClientWidth - ALeft - Width;
SetBounds(ALeft, VertMargin,
TextRect
.
Right, TextRect
.
Bottom);
end
;
if
mbCancel
in
Buttons
then
CancelButton := mbCancel
else
if
mbNo
in
Buttons
then
CancelButton := mbNo
else
CancelButton := mbOk;
X := (ClientWidth - ButtonGroupWidth)
div
2
;
for
B := Low(TMsgDlgBtn)
to
High(TMsgDlgBtn)
do
if
B
in
Buttons
then
begin
LButton := TButton
.
Create(Result);
with
LButton
do
begin
Name := ButtonNames[B];
Parent := Result;
{$IF DEFINED(CLR)}
Caption := ButtonCaptions[B];
{
$ELSE
}
Caption := LoadResString(ButtonCaptions[B]);
{
$IFEND
}
ModalResult := ModalResults[B];
if
B = DefaultButton
then
begin
Default :=
True
;
ActiveControl := LButton;
end
;
if
B = CancelButton
then
Cancel :=
True
;
SetBounds(X, IconTextHeight + VertMargin + VertSpacing,
ButtonWidth, ButtonHeight);
Inc(X, ButtonWidth + ButtonSpacing);
if
B = mbHelp
then
OnClick := TMessageForm(Result).HelpButtonClick;
end
;
end
;
end
;
end
;
|
由代码可见, CreateMessageDialog只是创建了一个TMessageForm, 然后动态地添加了一些设置. 写到这里或许可以解答一些人的问题: 对话框是不是一个窗口? 答案是:是.
你还可能会问: 为什么对话框可以停留在那一行代码直到用户操作完毕后再往下执行, 这里就需要了解一下模态窗口的知识: 请参见这篇文章 Delphi ShowModal解析
参考：
http://www.cnblogs.com/neugls/archive/2011/09/14/2176733.html