Tutorial 33: RichEdit Control: Basics

There are lots of request on tutorials about RichEdit controls. Finally I have played with it enough to think I can write tutorials about it. So here it is: the first RichEdit tutorial. The tutorials will describe nearly everything there is to know about RichEdit control or at least as much as I know it. The amount of information is rather large so I divide it into several parts, this tutorial being the first part. In this tutorial, you'll learn what a RichEdit control is, how to create it and how to load/save data to/from it.
 

Theory

A richedit control can be thought of as a souped-up edit control. It provides many desirable features that are lacking from the plain simple edit control, for example, the ability to use multiple font face/size, multiple-level undo/redo, search-for-text operation, OLE-embedded objects, drag-and-drop editing support, etc. Since the richedit control has so many features, it's stored in a separate DLL. This also means that, to use it, you can't just call InitCommonControls like other common controls. You have to call LoadLibrary to load the richedit DLL.

The problem is that there are three versions of richedit control up till now. Version 1,2, and 3. The table below shows you the name of the DLL for each version.
 
DLL Name RichEdit version Richedit Class Name
Riched32.dll 1.0 RICHEDIT
RichEd20.dll 2.0 RICHEDIT20A
RichEd20.dll 3.0 RICHEDIT20A

You can notice that richedit version 2 and 3 use the same DLL name. They also use the same class name! This can pose a problem if you want to use specific features of richedit 3.0. Up to now, I haven't found an official method of differentiating between version 2.0 and 3.0. However, there is a workaround which works ok, I'll show you later.

; data
   [RichEditDLL:  'RichEd20.dll',0]
      .....
; data?
     [hRichEditDLL: D§ ?]
; code
  call 'KERNEL32.LoadLibraryA'  RichEditDLL
     mov D§hRichEditDLL eax
    ......
  call 'KERNEL32.FreeLibrary'  D§hRichEditDLL
When the richedit dll is loaded, it registers the RichEdit window class. Thus it's imperative that you load the DLL before you create the control. The names of the richedit control classes are also different. Now you may have a question: how do I know which version of richedit control should I use? Using the latest version is not always appropriate if you don't require the extra features. So below is the table that shows the features provided by each version of richedit control.
 
Feature Version 1.0 Version 2.0 Version 3.0
selection bar
x
x
x
unicode editing
x
x
character/paragraph formatting
x
x
x
search for text
forward
forward/backward
forward/backward
OLE embedding
x
x
x
Drag and drop editing
x
x
x
Undo/Redo
single-level
multi-level
multi-level
automatic URL recognition
x
x
Accelerator key support
x
x
Windowless operation
x
x
Line break
CRLF
CR only
CR only (can emulate version 1.0)
Zoom
x
Paragraph numbering
x
simple table
x
normal and heading styles
x
underline coloring
x
hidden text
x
font binding
x

The above table is by no means comprehensive: I only list the important features.

Creating the richedit control

After loading the richedit dll, you can call CreateWindowEx to create the control. You can use edit control styles and common window styles in CreateWindowEx except ES_LOWERCASE, ES_UPPERCASE and ES_OEMCONVERT.
; const
        [RichEditID 300]
; data
        [RichEditDLL: B§ 'RichEd20.dll',0
         RichEditClass: 'RichEdit20A',0]
        ...
.data?
       [hRichEditDLL: D§ ?
        hwndRichEdit: D§ ?]
.code
        .....
        call 'KERNEL32.LoadLibraryA' RichEditDLL
        mov D§hRichEditDLL eax
    call 'USER32.CreateWindowExA' 0 RichEditClass,
        &WS_VISIBLE__&ES_MULTILINE__&WS_CHILD__&WS_VSCROLL__&WS_HSCROLL,
        &CW_USEDEFAULT,&CW_USEDEFAULT,&CW_USEDEFAULT,&CW_USEDEFAULT,
        D§hWnd,RichEditID,D§hInstance,0
        mov D§hwndRichEdit,eax

Setting default text and background color

You may have the problem with setting text color and the background color of the edit control. But this problem has been remedy in richedit control. To set the background color of the richedit control, you send EM_SETBKGNDCOLOR to the richedit control. This message has the following syntax.

wParam == color option. The value of 0 in this parameter specifies that Windows uses the color value in lParam as the background color. If this value is nonzero, Windows uses the Windows system background color. Since we send this message to change the background color, we must pass 0 in wParam.
lParam == specifies the COLORREF structure of the color you want to set if wParam is 0.

For example, if I want to set the background color to pure blue, I would issue this following line:

        call 'USER32.SendMessageA' D§hwndRichEdit &EM_SETBKGNDCOLOR 0 0FF0000
To set the text color, richedit control provides another new message, EM_SETCHARFORMAT, for the job. This message controls the text formatting of a range to characters in selection or all text in the control. This message has the following syntax:

wParam == formatting options:
 
SCF_ALL The operation affects all text in the control.
SCF_SELECTION The operation affects only the text in selection
SCF_WORD or SCF_SELECTION Affects the word in selection. If the selection is empy, ie, only the caret is in the word, the operation affects that word. SCF_WORD flag must be used with SCF_SELECTION.

lParam == pointer to a CHARFORMAT or CHARFORMAT2 structure that specifies the text formatting to be applied. CHARFORMAT2 is available for richedit 2.0 and above only. This doesn't mean that you must use CHARFORMAT2 with RichEdit 2.0 or above. You can still use CHARFORMAT if the added features in CHARFORMAT2 are not necessary for your need.

[CHARFORMATA:
        cbSize: D§ ?
        dwMask: D§ ?
        dwEffects: D§ ?
        yHeight: D§ ?
        yOffset: D§ ?
        crTextColor: D§ ?
        bCharSet: D§ ?
        bPitchAndFamily: D§ ?]
       [szFaceName: B§ ?  # (BYTE LF_FACESIZE) ]
       [wPad2: W§ ? ]
Field Name Description
cbSize The size of the structure. RichEdit control uses this field to determine the version of the structure whether it is CHARFORMAT or CHARFORMAT2
dwMask Bit flags that determine which of the following members are valid.
 
CFM_BOLD The CFE_BOLD value of the dwEffects member is valid
CFM_CHARSET The bCharSet member is valid.
CFM_COLOR The crTextColor member and the CFE_AUTOCOLOR value of the dwEffects member are valid
CFM_FACE The szFaceName member is valid.
CFM_ITALIC The CFE_ITALIC value of the dwEffects member is valid
CFM_OFFSET The yOffset member is valid
CFM_PROTECTED The CFE_PROTECTED value of the dwEffects member is valid
CFM_SIZE The yHeight member is valid
CFM_STRIKEOUT The CFE_STRIKEOUT value of the dwEffects member is valid.
CFM_UNDERLINE The CFE_UNDERLINE value of the dwEffects member is valid
dwEffects The character effects. Can be the combination of the following values
 
CFE_AUTOCOLOR Use the system text color
CFE_BOLD Characters are bold
CFE_ITALIC Characters are italic
CFE_STRIKEOUT Characters are struck.
CFE_UNDERLINE Characters are underlined
CFE_PROTECTED Characters are protected; an attempt to modify them will cause an EN_PROTECTED notification message. 
yHeight Character height, in twips (1/1440 of an inch or 1/20 of a printer's point). 
yOffset Character offset, in twips, from the baseline. If the value of this member is positive, the character is a superscript; if it is negative, the character is a subscript. 
crTextColor  Text color. This member is ignored if the CFE_AUTOCOLOR character effect is specified. 
bCharSet Character set value
bPitchAndFamily Font family and pitch. 
szFaceName  Null-terminated character array specifying the font name
_wPad2 Padding

From examination of the structure, you'll see that we can change the text effects (bold,italic, strikeout,underline), text color (crTextColor) and font face/size/character set. A notable flag is CFE_RPOTECTED. The text with this flag is marked as protected which means that when the user tries to modify it, EN_PROTECTED notification message will be sent to the parent window. And you can allow the change to happen or not.

CHARFORMAT2 adds more text styles such as font weight, spacing,text background color, kerning, etc. If you don't need these extra features, simply use CHARFORMAT.

To set text formatting, you have to think about the range of text you want to apply to. Richedit control introduces the notion of character text range. Richedit control gives each character a number starting from 0: the first characterin the control has Id of 0, the second character 1 and so on. To specify a text range, you must give the richedit control two numbers: the IDs of the first and the last character of the range. To apply the text formatting with EM_SETCHARFORMAT, you have at most three choices:

  1. Apply to all text in the control (SCF_ALL)
  2. Apply to the text currently in selection (SCF_SELECTION)
  3. Apply to the whole word currently in selection (SCF_WORD or SCF_SELECTION)
The first and the second choices are straightforward. The last choice requires a little explanation. If the current selection only covers one or more of the characters in the word but not the whole word, specifying the flag SCF_WORD+SCF_SELECTION applies the text formatting to the whole word. Even if there is no current selection, ie, only the caret is positioned in the word, the third choice also applies the text formatting to the whole word.
 

Setting the text/saving the text

For those of you who are used to edit control, you'll surely be familiar with WM_GETTEXT/WM_SETTEXT as the means to set the text/get the text to/from the control. This method still works with richedit control but may not be efficient if the file is large. Edit control limits the text that can be entered into it to 64K but richedit control can accept text much larger than that. It would be very cumbersome to allocate a very large block of memory (such as 10 MB or so) to receive the text from WM_GETTEXT. Richedit control offers a new approach to this method, ie. text streaming.

To put it simply, you provide the address of a callback function to the richedit control. And richedit control will call that callback, passing the address of the buffer to it, when it's ready. The callback will fill the buffer with the data it wants to send to the control or read the data from the buffer and then waits for the next call until the operation is finished. This paradigm is used for both streaming in (setting the text) and streaming out (getting the text out of the control). You'll see that this method is more efficient: the buffer is provided by the richedit control itself so the data are divided into chunks. The operations involve two messages: EM_STREAMIN and EM_STREAMOUT

Both EM_STREAMIN and EM_STREAMOUT use the same syntax:

wParam == formatting options.
 
SF_RTF The data is in the rich-text format (RTF) 
SF_TEXT The data is in the plain text format
SFF_PLAINRTF Only the keywords common to all languages are streamed in.
SFF_SELECTION If specified, the target of the operation is the text currently in selection. If you stream the text in, the text replaces the current selection. If you stream the text out, only the text currently in selection is streamed out. If this flag is not specified, the operation affects the whole text in the control.
SF_UNICODE (Available on RichEdit 2.0 or later) Specify the unicode text.

lParam == point to an EDITSTREAM structure which has the following definition:

 [EDITSTREAM:
        dwCookie: D§ ?
        dwError: D§ ?
        pfnCallback: D§ ?]
dwCookie application-defined value that will be passed to the callback function speficied in pfnCallback member below. We normally pass some important value to the callback function such as the file handle to use in the stream-in/out procedure.
dwError Indicates the results of the stream-in (read) or stream-out (write) operation. A value of zero indicates no error. A nonzero value can be the return value of the EditStreamCallback function or a code indicating that the control encountered an error. 
pfnCallback Pointer to an EditStreamCallback function, which is an application-defined function that the control calls to transfer data. The control calls the callback function repeatedly, transferring a portion of the data with each call

The editstream callback function has the following definition:

        EditStreamCallback proto dwCookie:DWORD,
                                 pBuffer:DWORD,
                                 NumBytes:DWORD,
                                 pBytesTransferred:DWORD
You have to create a function with the above prototype in your program. And then pass its address to EM_STREAMIN or EM_STREAMOUT via EDITSTREAM structure.

For stream-in operation (settting the text in the richedit control):

        dwCookie: the application-defined value you pass to EM_STREAMIN via EDITSTREAM structure. We almost always 
                pass the file handle of the file we want to set its content to the control here.
        pBuffer: points to the buffer provided by the richedit control that will receive the text from your callback function.
        NumBytes: the maximum number of bytes you can write the the buffer (pBuffer) in this call. You MUST always obey this limit, ie, you can send
                less data than the value in NumBytes but must not send more data than this value. You can think of this value as the size
                of the buffer in pBuffer.
   pBytesTransferred: points to a dword that you must set the value indicating the number of bytes you actually transferred to the buffer.
                This value is usually identical to the value in NumBytes. The exception is when the data is to send is less than
                the size of the buffer provided such as when the end of file is reached.
For stream-out operation (getting the text out of the richedit control):
        dwCookie: Same as the stream-in operation. We usually pass the file handle we want to write the data to in this parameter. 
        pBuffer: points to the buffer provided by the richedit control that is filled with the data from the richedit control. 
                To obtain its size, you must examine the value of NumBytes        NumBytes: the size of the data in the buffer pointed to by pBuffer. 
        pBytesTransferred: points to a dword that you must set the value indicating the number of bytes you actually read from the buffer.
The callback function returns 0 to indicate success and richedit control will continue calling the callback function if there is still data left to read/write. If some error occurs during the process and you want to stop the operation, returns a non-zero value and the richedit control will discard the data pointed to by pBuffer. The error/success value will be filled in the dwError field of EDITSTREAM so you can examine the error/success status of the stream operation after SendMessage returns.

Example:

The example below is a simple editor which you can open an asm source code file, edit and save it. It uses RichEdit control version 2.0 or above.
____________________________________________________________________________________________

[IDD_OPTIONDLG                  1000
 IDC_BACKCOLORBOX               1001
 IDC_TEXTCOLORBOX               1002]

[RichEditID 300]

[ClassName:         B§ 'IczEditClass',0
 AppName :          B§ 'IczEdit version 1.0',0
 RichEditDLL:       B§ 'riched20.dll',0
 RichEditClass:     B§ 'RichEdit20A',0
 NoRichEdit:        B§ 'Cannot find riched20.dll',0
 ASMFilterString:   B§ 'ASM Source code (*.asm)',0,'*.asm',0
                    B§ 'All Files (*.*)',0,'*.*',0,0
 OpenFileFail:      B§ 'Cannot open the file',0
 WannaSave:         B§ 'The data in the control is modified. Want to save it?',0]
 
[FileOpened:        D§ &FALSE
 BackgroundColor:   D§ 0FFFFFF          ; default to white
 TextColor:         D§ 0]               ; default to black

[hInstance:         D§ ?
 hRichEdit:         D§ ?
 hwndRichEdit:      D§ ?]
[FileName:          B§ ? #260]
[AlternateFileName: B§ ? #260]
[CustomColors:      D§ ? #16]

____________________________________________________________________________________________
____________________________________________________________________________________________

[WNDCLASSEX:
 @cbSize: D§ len
 @style: D§ &CS_HREDRAW__&CS_VREDRAW
 @lpfnWndProc: D§ MainWindowProc
 @cbClsExtra: D§ 0
 @cbWndExtra: D§ 0
 @hInstance: D§ 0
 @hIcon: D§ 0
 @hCursor: D§ 0
 @hbrBackground: D§ &COLOR_WINDOW+1
 @lpszMenuName: D§ M00_Menu
 @lpszClassName: D§ ClassName
 @hIconSm: D§ 0]

[MSG:
 @hwnd: D§ 0
 @message: D§ 0
 @wParam: D§ 0
 @lParam: D§ 0
 @time: D§ 0
 @MSG@pt: @MSG@pt@x: D§ 0
          @MSG@pt@y: D§ 0]

[hwnd: D§ 0]

[M00_Menu  1000                  M00_Open  1001                  M00_Close  1002
 M00_Save  1003                  M00_save_As  1004               M00_Exit  1005
 M00_Undo  1006                  M00_Redo  1007                  M00_Copy  1008
 M00_Cut  1009                   M00_Paste  1010                 M00_Delete  1011
 M00_select_All  1012            M00_Options  1013]
____________________________________________________________________________________________
____________________________________________________________________________________________

[&SCF_ALL 4]

____________________________________________________________________________________________
____________________________________________________________________________________________

 
Main:
    call 'KERNEL32.GetModuleHandleA'  &NULL
    mov D§hInstance eax, D§WNDCLASSEX@hInstance eax
    
    call 'KERNEL32.LoadLibraryA' RichEditDLL
    .If eax <> 0
        mov D§hRichEdit eax
    .Else
        call 'USER32.MessageBoxA' 0 NoRichEdit AppName &MB_OK__&MB_ICONERROR | jmp L9>>
    .End_If
    
    call 'USER32.LoadIconA' &NULL &IDI_APPLICATION
    mov D§WNDCLASSEX@hIcon eax, D§WNDCLASSEX@hIconSm eax
    call 'USER32.LoadCursorA' &NULL &IDC_ARROW
    mov D§WNDCLASSEX@hCursor eax
    
    call 'USER32.RegisterClassExA' WNDCLASSEX
    call 'USER32.CreateWindowExA' &NULL ClassName AppName,
                                  &WS_OVERLAPPEDWINDOW  &CW_USEDEFAULT,
                                  &CW_USEDEFAULT &CW_USEDEFAULT &CW_USEDEFAULT &NULL &NULL,
                                  D§hInstance &NULL
    mov   D§hwnd eax
    
    call 'USER32.ShowWindow' D§hwnd &SW_SHOWNORMAL
    call 'USER32.UpdateWindow' D§hwnd
 
L1: call 'USER32.GetMessageA' MSG  0 0 0 | On eax = 0, jmp L8>

        call 'USER32.TranslateMessage' MSG
        call 'USER32.DispatchMessageA' MSG | jmp L1<
        
L8: call 'KERNEL32.FreeLibrary' D§hRichEdit
 
L9: call 'KERNEL32.ExitProcess' 0

____________________________________________________________________________________________
____________________________________________________________________________________________

Proc StreamInProc:
    arguments @hFile @pBuffer @NumBytes @pBytesRead

        call 'KERNEL32.ReadFile' D@hFile D@pBuffer D@NumBytes D@pBytesRead 0
        xor eax 1
EndP


Proc StreamOutProc:
    Arguments @hFile @pBuffer @NumBytes @pBytesWritten
    
        call 'KERNEL32.WriteFile' D@hFile D@pBuffer D@NumBytes D@pBytesWritten 0
        xor eax 1
EndP


Proc CheckModifyState:
    Argument @hWnd
    
        call 'USER32.SendMessageA' D§hwndRichEdit &EM_GETMODIFY 0 0
        .If eax <> 0
            call 'USER32.MessageBoxA' D§hWnd WannaSave AppName &MB_YESNOCANCEL
            If eax = &IDYES
                call 'USER32.SendMessageA' D@hWnd &WM_COMMAND M00_SAVE 0
            Else _If eax = &IDCANCEL
                mov eax &FALSE | Exit
            End_If
        .Endif
        mov eax &TRUE
EndP


[CHARFORMAT:
 @cbSize:           D§ 60
 @dwMask:           D§ &CFM_COLOR
 @dwEffects:        D§ 0  ; &CFE_AUTOCOLOR ; ?
 @yHeight:          D§ 0
 @yOffset:          D§ 0
 @crTextColor:      D§ 0
 @bCharSet:         B§ 0
 @bPitchAndFamily:  B§ 0]
[@szFaceName:       B§ 0 #32] ; &LF_FACESIZE
[wPad2:             W§ 0]


SetColor:
    call 'USER32.SendMessageA' D§hwndRichEdit &EM_SETBKGNDCOLOR 0 D§BackgroundColor

    move D§CHARFORMAT@crTextColor D§TextColor
    call 'USER32.SendMessageA' D§hwndRichEdit &EM_SETCHARFORMAT &SCF_ALL CHARFORMAT
ret


[CHOOSECOLOR:
 @lStructSize:      D§ len
 @hwndOwner:        D§ 0
 @hInstance:        D§ 0
 @rgbResult:        D§ 0
 @lpCustColors:     D§ CustomColors
 @Flags:            D§ &CC_RGBINIT
 @lCustData:        D§ 0
 @lpfnHook:         D§ 0
 @lpTemplateName:   D§ 0]

Proc OptionProc:
    Arguments @hWnd @uMsg @wParam @lParam
    
    pushad
    
        ...If D@uMsg = &WM_INITDIALOG
            ; returns &TRUE
        ...Else_If D@uMsg = &WM_COMMAND
            mov eax D@wParam | shr eax 16
            ..If ax = &BN_CLICKED
                mov eax D@wParam
                .If ax = &IDCANCEL
                    call 'USER32.SendMessageA' D@hWnd &WM_CLOSE 0 0
                    
                .Else_If ax = IDC_BACKCOLORBOX
                    move D§CHOOSECOLOR@hwndOwner D@hwnd
                    move D§ CHOOSECOLOR@hInstance D§hInstance
                    Move D§CHOOSECOLOR@rgbResult D§BackgroundColor
                    call 'COMDLG32.ChooseColorA' CHOOSECOLOR
                    If eax <> 0
                        move D§BackgroundColor D§CHOOSECOLOR@rgbResult
                        call 'USER32.GetDlgItem' D@hWnd IDC_BACKCOLORBOX
                        call 'USER32.InvalidateRect' eax 0 &TRUE
                    End_If
                    
                .Else_If ax = IDC_TEXTCOLORBOX
                    move D§CHOOSECOLOR@hwndOwner D@hwnd
                    move D§ CHOOSECOLOR@hInstance D§hInstance
                    move D§CHOOSECOLOR@rgbResult D§TextColor
                    call 'COMDLG32.ChooseColorA' CHOOSECOLOR
                    If eax <> 0
                        move D§TextColor D§CHOOSECOLOR@rgbResult
                        call 'USER32.GetDlgItem' D@hWnd IDC_TEXTCOLORBOX
                        call 'USER32.InvalidateRect' eax 0 &TRUE
                    End_If
                    
                .Else_If ax = &IDOK
    ;================================================================================
    ; Save the modify state of the richedit control because changing the text color changes the
    ; modify state of the richedit control.
    ;==================================================================================
                    call 'USER32.SendMessageA' D§hwndRichEdit &EM_GETMODIFY 0 0
                    push eax
                        call SetColor
                    pop eax
                    call 'USER32.SendMessageA' D§hwndRichEdit &EM_SETMODIFY eax 0
                    call 'USER32.EndDialog' D@hWnd 0
                .End_If
                
            ..End_If
                
        ...Else_If D@uMsg = &WM_CTLCOLORSTATIC
            call 'USER32.GetDlgItem' D@hWnd IDC_BACKCOLORBOX
            .If eax = D@lParam
                popad
                call 'GDI32.CreateSolidBrush' D§BackgroundColor 
                Exit
            .Else
                call 'USER32.GetDlgItem' D@hWnd IDC_TEXTCOLORBOX
                If eax = D@lParam
                    popad
                    call 'GDI32.CreateSolidBrush' D§TextColor
                    Exit
                End_If
            .End_If
            popad | mov eax &FALSE | Exit
            
        ...Else_If D@uMsg = &WM_CLOSE
            call 'USER32.EndDialog' D@hWnd 0
        ...Else
            popad | mov eax &FALSE | Exit
        ...End_If
        popad | mov eax &TRUE
EndP

____________________________________________________________________________________________
____________________________________________________________________________________________

[CHARRANGE:
 @cpMin: D§ 0
 @cpMax: D§ 0]

[OPENFILENAME:
 @lStructSize: D§ Len
 @hWndOwner: D§ 0
 @hInstance: D§ 0
 @lpstrFilter: D§ ASMFilterString
 @lpstrCustomFilter: D§ 0
 @nMaxCustFilter: D§ 0
 @nFilterIndex: D§ 0
 @lpstrFile: D§ FileName
 @nMaxFile: D§ 260
 @lpstrFileTitle: D§ 0
 @nMaxFileTitle: D§ 260
 @lpstrInitialDir: D§ 0
 @lpstrTitle: D§ 0
 @Flags: D§ 0
 @nFileOffset: W§ 0
 @nFileExtension: W§ 0
 @lpstrDefExt: D§ 0
 @lCustData: D§ 0
 @lpfnHook: D§ 0
 @lpTemplateName: D§ 0]

[Buffer: B§ ? #256]

[EDITSTREAM:
 @dwCookie: D§ 0
 @dwError: D§ 0
 @pfnCallback: D§ 0]

[hFile: 0]

Proc MainWindowProc:
    Arguments @hWnd @uMsg @wParam @lParam
    
    pushad

    ...If D@uMsg = &WM_CREATE
        call 'USER32.CreateWindowExA' &WS_EX_CLIENTEDGE RichEditClass 0,
               &WS_CHILD__&WS_VISIBLE__&ES_MULTILINE__&WS_VSCROLL__&WS_HSCROLL__&ES_NOHIDESEL,
               &CW_USEDEFAULT &CW_USEDEFAULT &CW_USEDEFAULT &CW_USEDEFAULT D@hWnd,
               RichEditID D§hInstance 0
        mov D§hwndRichEdit eax
  ;=============================================================
  ; Set the text limit. The default is 64K
  ;=============================================================
        call 'USER32.SendMessageA' D§hwndRichEdit &EM_LIMITTEXT 0-1 0
  ;=============================================================
  ; Set the default text/background color
  ;=============================================================
        call SetColor
        call 'USER32.SendMessageA' D§hwndRichEdit &EM_SETMODIFY &FALSE 0
        call 'USER32.SendMessageA' D§hwndRichEdit &EM_EMPTYUNDOBUFFER 0 0
    ...Else_If D@uMsg = &WM_INITMENUPOPUP
        mov eax D@lParam
        ..If ax = 0  ; file menu   
            .If D§FileOpened = &TRUE ; a file is already opened
                call 'USER32.EnableMenuItem' D@wParam M00_OPEN &MF_GRAYED
                call 'USER32.EnableMenuItem' D@wParam M00_CLOSE &MF_ENABLED
                call 'USER32.EnableMenuItem' D@wParam M00_SAVE &MF_ENABLED
                call 'USER32.EnableMenuItem' D@wParam M00_SAVEAS &MF_ENABLED
            .Else
                call 'USER32.EnableMenuItem' D@wParam M00_OPEN &MF_ENABLED
                call 'USER32.EnableMenuItem' D@wParam M00_CLOSE &MF_GRAYED
                call 'USER32.EnableMenuItem' D@wParam M00_SAVE &MF_GRAYED
                call 'USER32.EnableMenuItem' D@wParam M00_SAVEAS &MF_GRAYED
            .End_If
            
        ..Else_If ax = 1 ; edit menu
   ;=============================================================================
   ; Check whether there is some text in the clipboard. If so, we enable the paste menuitem
   ;=============================================================================
            call 'USER32.SendMessageA' D§hwndRichEdit &EM_CANPASTE &CF_TEXT,0
            If eax = 0  ; no text in the clipboard
                call 'USER32.EnableMenuItem' D@wParam M00_PASTE &MF_GRAYED
            Else
                call 'USER32.EnableMenuItem' D@wParam M00_PASTE &MF_ENABLED
            End_If
   _______________________________________
   ; check whether the undo queue is empty
   _______________________________________
            call 'USER32.SendMessageA' D§hwndRichEdit &EM_CANUNDO 0 0
            If eax = 0
                call 'USER32.EnableMenuItem' D@wParam M00_UNDO &MF_GRAYED
            Else
                call 'USER32.EnableMenuItem' D@wParam M00_UNDO &MF_ENABLED
            End_If
   _______________________________________
   ; check whether the redo queue is empty
   _______________________________________
            call 'USER32.SendMessageA' D§hwndRichEdit &EM_CANREDO 0 0
            If eax = 0
                call 'USER32.EnableMenuItem' D@wParam M00_REDO &MF_GRAYED
            Else
                call 'USER32.EnableMenuItem' D@wParam M00_REDO &MF_ENABLED
            End_If
   _____________________________________________________________________
   ; check whether there is a current selection in the richedit control.
   ; If there is, we enable the cut/copy/delete menuitem
   _____________________________________________________________________
            call 'USER32.SendMessageA' D§hwndRichEdit &EM_EXGETSEL 0 CHARRANGE
            mov eax D§CHARRANGE@cpMin
            If eax = D§CHARRANGE@cpMax  ; no current selection
                call 'USER32.EnableMenuItem' D@wParam M00_COPY &MF_GRAYED
                call 'USER32.EnableMenuItem' D@wParam M00_CUT &MF_GRAYED
                call 'USER32.EnableMenuItem' D@wParam M00_DELETE &MF_GRAYED
            Else
                call 'USER32.EnableMenuItem' D@wParam M00_COPY &MF_ENABLED
                call 'USER32.EnableMenuItem' D@wParam M00_CUT &MF_ENABLED
                call 'USER32.EnableMenuItem' D@wParam M00_DELETE &MF_ENABLED
            End_If
        ..End_If
        
    ...Else_If D@uMsg = &WM_COMMAND
    
        ..If D@lParam = 0  ; menu commands
            mov eax D@wParam
            .If ax = M00_OPEN
                call OpenCommand D@hWnd

            .Else_If ax = M00_CLOSE
                call CheckModifyState D@hWnd
                If eax = &TRUE
                    call 'USER32.SetWindowTextA' D§hwndRichEdit 0
                    mov D§FileOpened &FALSE
                End_If
            .Else_If ax = M00_SAVE
                call 'KERNEL32.CreateFileA' FileName &GENERIC_WRITE &FILE_SHARE_READ,
                                           &NULL &CREATE_ALWAYS &FILE_ATTRIBUTE_NORMAL 0
                If eax <> &INVALID_HANDLE_VALUE
                    call InvalidFile

                Else
                    call 'USER32.MessageBoxA' D@hWnd OpenFileFail AppName,
                                              &MB_OK__&MB_ICONERROR
                End_If
            .Else_If ax = M00_COPY
                call 'USER32.SendMessageA' D§hwndRichEdit &WM_COPY 0 0
            .Else_If ax = M00_CUT
                call 'USER32.SendMessageA' D§hwndRichEdit &WM_CUT 0 0
            .Else_If ax = M00_PASTE
                call 'USER32.SendMessageA' D§hwndRichEdit &WM_PASTE 0 0
            .Else_If ax = M00_DELETE
                call 'USER32.SendMessageA' D§hwndRichEdit &EM_REPLACESEL &TRUE 0
            .Else_If ax = M00_SELECTALL
                mov D§CHARRANGE@cpMin 0
                mov D§CHARRANGE@cpMax 0-1
                call 'USER32.SendMessageA' D§hwndRichEdit &EM_EXSETSEL 0 CHARRANGE
            .Else_If ax = M00_UNDO
                call 'USER32.SendMessageA' D§hwndRichEdit &EM_UNDO 0 0
            .Else_If ax = M00_REDO
                call 'USER32.SendMessageA' D§hwndRichEdit &EM_REDO 0 0
            .Else_If ax = M00_OPTIONS
                call 'USER32.DialogBoxParamA' D§hInstance IDD_OPTIONDLG D@hWnd OptionProc 0
            .Else_If ax = M00_SAVEAS
                move D§OPENFILENAME@hwndOwner D@hwnd
                move D§OPENFILENAME@hInstance D§hInstance
                mov D§OPENFILENAME@lpstrFilter ASMFilterString
                mov D§OPENFILENAME@lpstrFile AlternateFileName
                mov D§AlternateFileName 0
                mov D§OPENFILENAME@Flags &OFN_FILEMUSTEXIST__&OFN_HIDEREADONLY__&OFN_PATHMUSTEXIST
                call 'COMDLG32.GetSaveFileNameA' OPENFILENAME
                If eax <> 0
                    call 'KERNEL32.CreateFileA' AlternateFileName &GENERIC_WRITE,
                                               &FILE_SHARE_READ &NULL &CREATE_ALWAYS,
                                               &FILE_ATTRIBUTE_NORMAL 0
                    On eax <> &INVALID_HANDLE_VALUE, call InvalidFile
                End_If
            .Else_If ax = M00_EXIT
                call 'USER32.SendMessageA' D@hWnd &WM_CLOSE 0 0
            .End_If
        ..End_If
        
    ...Else_If D@uMsg = &WM_CLOSE
        call CheckModifyState D@hWnd
        If eax = &TRUE
            call 'USER32.DestroyWindow' D@hWnd
        End_If
        
    ...Else_If D@uMsg = &WM_SIZE
        mov eax D@lParam, edx eax
        and eax 0FFFF | shr edx 16
        call 'USER32.MoveWindow' D§hwndRichEdit 0 0 eax edx &TRUE  
        
    ...Else_If D@uMsg = &WM_DESTROY
        call 'USER32.PostQuitMessage' &NULL
        
    ...Else
        popad
        
        call 'USER32.DefWindowProcA' D@hWnd D@uMsg D@wParam D@lParam  
        Exit
        
    ...End_If
    
    popad | mov eax &FALSE
EndP


InvalidFile:
    mov D§hFile eax
     _____________________________
     ; stream the text to the file
     _____________________________
    mov D§EDITSTREAM@dwCookie eax
    mov D§EDITSTREAM@pfnCallback StreamOutProc
    call 'USER32.SendMessageA' D§hwndRichEdit &EM_STREAMOUT &SF_TEXT EDITSTREAM
     ______________________________________
     ; Initialize the modify state to false
     ______________________________________
    call 'USER32.SendMessageA' D§hwndRichEdit &EM_SETMODIFY &FALSE 0
    call 'KERNEL32.CloseHandle' D§hFile
ret


Proc OpenCommand:
    Argument @hWnd

    move D§OPENFILENAME@hwndOwner D@hWnd
    move D§OPENFILENAME@hInstance D§hInstance
    mov D§FileName 0
    mov D§OPENFILENAME@Flags &OFN_FILEMUSTEXIST__&OFN_HIDEREADONLY__&OFN_PATHMUSTEXIST
    call 'COMDLG32.GetOpenFileNameA' OPENFILENAME
    
    ...If eax <> 0
        call 'KERNEL32.CreateFileA' FileName &GENERIC_READ,
                                    &FILE_SHARE_READ &NULL,                                    
                                    &OPEN_EXISTING  &FILE_ATTRIBUTE_NORMAL 0
        .If eax <> &INVALID_HANDLE_VALUE
            mov D§hFile eax
      ___________________________________________
      ; stream the text into the richedit control
      ___________________________________________
            mov D§EDITSTREAM@dwCookie eax
            mov D§EDITSTREAM@pfnCallback StreamInProc
            call 'USER32.SendMessageA' D§hwndRichEdit &EM_STREAMIN,
                                       &SF_TEXT EDITSTREAM
      ______________________________________
      ; Initialize the modify state to false
      ______________________________________
            call 'USER32.SendMessageA' D§hwndRichEdit &EM_SETMODIFY &FALSE 0
            call 'KERNEL32.CloseHandle' D§hFile
            mov B§FileOpened &TRUE
            
        .Else
            call 'USER32.MessageBoxA' D@hWnd OpenFileFail AppName,
                                      &MB_OK__&MB_ICONERROR
                                      
        .End_If
    ...End_If
EndP

Analysis:

The program first loads the richedit dll, which in this case is riched20.dll. If the dll cannot be loaded, it exits to Windows.
    call 'KERNEL32.LoadLibraryA' RichEditDLL
    .If eax <> 0
        mov D§hRichEdit eax
    .Else
        call 'USER32.MessageBoxA' 0 NoRichEdit AppName &MB_OK__&MB_ICONERROR | jmp L9>>
    .End_If
After the dll is loaded successfully, we proceed to create a normal window which will be the parent of the richedit control. Within the WM_CREATE handler, we create the richedit control:
    ...If D@uMsg = &WM_CREATE
        call 'USER32.CreateWindowExA' &WS_EX_CLIENTEDGE RichEditClass 0,
               &WS_CHILD__&WS_VISIBLE__&ES_MULTILINE__&WS_VSCROLL__&WS_HSCROLL__&ES_NOHIDESEL,
               &CW_USEDEFAULT &CW_USEDEFAULT &CW_USEDEFAULT &CW_USEDEFAULT D@hWnd,
               RichEditID D§hInstance 0
        mov D§hwndRichEdit eax
Note that we specify ES_MULTILINE style else the control will be a single-lined one.
        call 'USER32.SendMessageA' D§hwndRichEdit &EM_LIMITTEXT 0-1 0
After the richedit control is created, we must set the new text limit on it. By default, the richedit control has 64K text limit, the same as a simple multi-line edit control. We must extend this limit to allow it to operate with larger files. In the above line, I specify -1 which amounts to 0FFFFFFFFh, a very large value.
        call SetColor
Next, we set the text/background color. Since this operation can be performed in other part of the program, I put the code in a function named SetColor.
SetColor:
    call 'USER32.SendMessageA' D§hwndRichEdit &EM_SETBKGNDCOLOR 0 D§BackgroundColor
Setting the background color of the richedit control is a straightforward operation: just send EM_SETBKGNDCOLOR message to the richedit control. (If you use a multi-line edit control, you have to process WM_CTLCOLOREDIT). The default background color is white.
    move D§CHARFORMAT@crTextColor D§TextColor
After the background color is set, we fill in the members of CHARFORMAT in order to set the text color. Note that we fill cbSize with the size of the structure so the richedit control knows we are sending it CHARFORMAT, not CHARFORMAT2. dwMask has only one flag, CFM_COLOR, because we only want to set the text color and crTextColor is filled with the value of the desired text color.
    call 'USER32.SendMessageA' D§hwndRichEdit &EM_SETCHARFORMAT &SCF_ALL CHARFORMAT
 ret
After settting the color, you have to empty undo buffer simply because the act of changing text/background color is undo-able. We send EM_EMPTYUNDOBUFFER message to achieve this.
        call 'USER32.SendMessageA' D§hwndRichEdit  &EM_EMPTYUNDOBUFFER,0,0
After filling the CHARFORMAT structure, we send EM_SETCHARFORMAT to the richedit control, specifying SCF_ALL flag in wParam to indicate that we want the text formatting to be applied to all text in the control.

Note that when we first created the richedit control, we didn't specify its size/position at that time. That's because we want it to cover the whole client area of the parent window. We resize it whenever the size of the parent window changes.

    ...Else_If D@uMsg = &WM_SIZE
        mov eax D@lParam, edx eax
        and eax 0FFFF | shr edx 16
        call 'USER32.MoveWindow' D§hwndRichEdit 0 0 eax edx &TRUE
In the above code snippet, we use the new dimension of the client area passed in lParam to resize the richedit control with MoveWindow.

When the user clicks on the File/Edit menu bar, we process WM_INITPOPUPMENU so that we can prepare the states of the menuitems in the submenu before displaying it to the user. For example, if a file is already opened in the richedit control, we want to disable the open menuitem and enable all the remaining menuitems.

In the case of the File menu bar, we use the variable FileOpened as the flag to determine whether a file is already opened. If the value in this variable is TRUE, we know that a file is already opened.

    ...Else_If D@uMsg = &WM_INITMENUPOPUP
        mov eax D@lParam
        ..If ax = 0  ; file menu   
            .If D§FileOpened = &TRUE ; a file is already opened
                call 'USER32.EnableMenuItem' D@wParam M00_OPEN &MF_GRAYED
                call 'USER32.EnableMenuItem' D@wParam M00_CLOSE &MF_ENABLED
                call 'USER32.EnableMenuItem' D@wParam M00_SAVE &MF_ENABLED
                call 'USER32.EnableMenuItem' D@wParam M00_SAVEAS &MF_ENABLED
            .Else
                call 'USER32.EnableMenuItem' D@wParam M00_OPEN &MF_ENABLED
                call 'USER32.EnableMenuItem' D@wParam M00_CLOSE &MF_GRAYED
                call 'USER32.EnableMenuItem' D@wParam M00_SAVE &MF_GRAYED
                call 'USER32.EnableMenuItem' D@wParam M00_SAVEAS &MF_GRAYED
            .End_If
As you can see, if a file is already opened, we gray out the open menuitem and enable the remaining menuitems. The reverse is true of FileOpened is false.

In the case of the edit menu bar, we need to check the state of the richedit control/clipboard first.

            call 'USER32.SendMessageA' D§hwndRichEdit &EM_CANPASTE &CF_TEXT,0
            If eax = 0  ; no text in the clipboard
                call 'USER32.EnableMenuItem' D@wParam M00_PASTE &MF_GRAYED
            Else
                call 'USER32.EnableMenuItem' D@wParam M00_PASTE &MF_ENABLED
            End_If
We first check whether some text is available in the clipboard by sending EM_CANPASTE message. If some text is available, SendMessage returns TRUE and we enable the paste menuitem. If not, we gray out the menuitem.
            call 'USER32.SendMessageA' D§hwndRichEdit &EM_CANUNDO 0 0
            If eax = 0
                call 'USER32.EnableMenuItem' D@wParam M00_UNDO &MF_GRAYED
            Else
                call 'USER32.EnableMenuItem' D@wParam M00_UNDO &MF_ENABLED
            End_If
Next, we check whether the undo buffer is empty by sending EM_CANUNDO message. If it's not empty, SendMessage returns TRUE and we enable the undo menuitem.
           call 'USER32.SendMessageA' D§hwndRichEdit &EM_CANREDO 0 0
            If eax = 0
                call 'USER32.EnableMenuItem' D@wParam M00_REDO &MF_GRAYED
            Else
                call 'USER32.EnableMenuItem' D@wParam M00_REDO &MF_ENABLED
            End_If
We check the redo buffer by sending EM_CANREDO message to the richedit control. If it's not empty, SendMessage returns TRUE and we enable the redo menuitem.
            call 'USER32.SendMessageA' D§hwndRichEdit &EM_EXGETSEL 0 CHARRANGE
            mov eax D§CHARRANGE@cpMin
            If eax = D§CHARRANGE@cpMax  ; no current selection
                call 'USER32.EnableMenuItem' D@wParam M00_COPY &MF_GRAYED
                call 'USER32.EnableMenuItem' D@wParam M00_CUT &MF_GRAYED
                call 'USER32.EnableMenuItem' D@wParam M00_DELETE &MF_GRAYED
            Else
                call 'USER32.EnableMenuItem' D@wParam M00_COPY &MF_ENABLED
                call 'USER32.EnableMenuItem' D@wParam M00_CUT &MF_ENABLED
                call 'USER32.EnableMenuItem' D@wParam M00_DELETE &MF_ENABLED
            End_If
        ..End_If
Lastly, we check whether a current selection exists by sending EM_EXGETSEL message. This message uses a CHARRANGE structure which is defined as follows:
[CHARRANGE:
  cpMin: D§      ?
  cpMax: D§      ?]
cpMin contains the character position index immediately preceding the first character in the range.
cpMax contains the character position immediately following the last character in the range.

After EM_EXGETSEL returns, the CHARRANGE structure is filled with the starting-ending character position indices of the selection range. If there is no current selection, cpMin and cpMax are identical and we gray out the cut/copy/delete menuitems.

When the user clicks the Open menuitem, we display an open file dialog box and if the user selects a file, we open the file and stream its content to the richedit control.

    ...If eax <> 0
        call 'KERNEL32.CreateFileA' FileName &GENERIC_READ,
                                    &FILE_SHARE_READ &NULL,                                    
                                    &OPEN_EXISTING  &FILE_ATTRIBUTE_NORMAL 0
        .If eax <> &INVALID_HANDLE_VALUE
            mov D§hFile eax
      ___________________________________________
      ; stream the text into the richedit control
      ___________________________________________
            mov D§EDITSTREAM@dwCookie eax
            mov D§EDITSTREAM@pfnCallback StreamInProc
            call 'USER32.SendMessageA' D§hwndRichEdit &EM_STREAMIN,
                                       &SF_TEXT EDITSTREAM
After the file is successfully opened with CreateFile, we fill the EDITSTREAM structure in preparation for EM_STREAMIN message. We choose to send the handle to the opened file via dwCookie member and pass the address of the stream callback function in pfnCallback.

The stream callback procedure itself is the essence of simplicity.

Proc StreamInProc:
    arguments @hFile @pBuffer @NumBytes @pBytesRead

        call 'KERNEL32.ReadFile' D@hFile D@pBuffer D@NumBytes D@pBytesRead 0
        xor eax 1
EndP
You can see that all parameters of the stream callback procedure fit perfectly with ReadFile. And the return value of ReadFile is xor-ed with 1 so that if it returns 1 (success), the actual value returned in eax is 0 and vice versa.
            call 'USER32.SendMessageA' D§hwndRichEdit &EM_SETMODIFY &FALSE 0
            call 'KERNEL32.CloseHandle' D§hFile
            mov B§FileOpened &TRUE
After EM_STREAMIN returns, it means the stream operation is completed. In reality, we must check the value of dwError member of the EDITSTREAM structure.

Richedit (and edit) control supports a flag to indicate whether its content is modified. We can obtain the value of this flag by sending EM_GETMODIFY message to the control. SendMessage returns TRUE if the content of the control was modified. Since we stream the text into the control, it's a kind of a modification. We must set the modify flag to FALSE by sending EM_SETMODIFY with wParam==FALSE to the control to start anew after the stream-in opertion is finished. We immediately close the file and set FileOpened to TRUE to indicate that a file was opened.

When the user clicks on save/saveas menuitem, we use EM_STREAMOUT message to output the content of the richedit control to a file. As with the streamin callback function, the stream-out callback function is simplicity in itself. It fits perfectly with WriteFile.

The text operations such as cut/copy/paste/redo/undo are easily implemented by sending single message to the richedit control, WM_CUT/WM_COPY/WM_PASTE/WM_REDO/WM_UNDO respectively.

The delete/select all operations are done as follows:

            .Else_If ax = M00_DELETE
                call 'USER32.SendMessageA' D§hwndRichEdit &EM_REPLACESEL &TRUE 0
            .Else_If ax = M00_SELECTALL
                mov D§CHARRANGE@cpMin 0
                mov D§CHARRANGE@cpMax 0-1
                call 'USER32.SendMessageA' D§hwndRichEdit &EM_EXSETSEL 0 CHARRANGE
The delete operation affects the currently selection. I send EM_REPLACESEL message with NULL string so the richedit control will replace the currently selected text with the null string.

The select-all operation is done by sending EM_EXSETSEL message, specifying cpMin==0 and cpMax==-1 which amounts to selecting all the text.

When the user selects Option menu bar, we display a dialog box presenting the current background/text colors.

When the user clicks on one of the color boxes, it displays the choose-color dialog box. The "color box" is in fact a static control with SS_NOTIFY and WS_BORDER flag. A static control with SS_NOTIFY flag will notify its parent window with mouse actions on it, such as BN_CLICKED (STN_CLICKED). That's the trick.

                .Else_If ax = IDC_BACKCOLORBOX
                    move D§CHOOSECOLOR@hwndOwner D@hwnd
                    move D§ CHOOSECOLOR@hInstance D§hInstance
                    Move D§CHOOSECOLOR@rgbResult D§BackgroundColor
                    call 'COMDLG32.ChooseColorA' CHOOSECOLOR
                    If eax <> 0
                        move D§BackgroundColor D§CHOOSECOLOR@rgbResult
                        call 'USER32.GetDlgItem' D@hWnd IDC_BACKCOLORBOX
                        call 'USER32.InvalidateRect' eax 0 &TRUE
                    End_If
When the user clicks on one of the color box, we fill the members of the CHOOSECOLOR structure and call ChooseColor to display the choose-color dialog box. If the user selects a color, the colorref value is returned in rgbResult member and we store that value in BackgroundColor variable. After that, we force a repaint on the color box by calling InvalidateRect on the handle to the color box. The color box sends WM_CTLCOLORSTATIC message to its parent window.
                call 'USER32.GetDlgItem' D@hWnd IDC_TEXTCOLORBOX
                If eax = D@lParam
                    popad
                    call 'GDI32.CreateSolidBrush' D§TextColor
                    Exit
                End_If
Within the WM_CTLCOLORSTATIC handler, we compare the handle of the static control passed in lParam to that of both the color boxes. If the values match, we create a new brush using the color in the variable and immediately return. The static control will use the newly created brush to paint its background.

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