Edit Box Control

The edit box provides an important approach for the application to receive the user input. Compared with the controls mentioned above, such as static control, button, list box, etc., the behaviors of edit box is relatively simple. The edit box displays a caret, and the character input by the user would be inserted at the caret position. Besides that, the edit box also provides some simple editing functions such as selecting text, deleting text, moving the caret position, etc.

MiniGUI uses the following three control classes to implement the edit box:

  • Single-line edit box: class name 'sledit', 'edit', identifier CTRL_SLEDIT, CTRL_EDIT. It can only handle single-line text, but with the help of MiniGUI logical font, it can handle arbitrary multi-byte characters, including variable-byte charset. The Control provides the functions of being Selected, Copy and Paste, etc.

  • Multiple-line edit box: class name 'textedit', 'mledit', 'medit', identifier CTRL_TEXTEDIT, CTRL_MLEDIT, or CTRL_MEDIT. It can handle arbitrary multiple-byte character input, including variable-byte charset. The Control provides the functions of being Selected, Copy and Paste, etc.

  • Single-line Double-Direction edit box: class name "bidisledit", identifier CTRL_BIDISLEDIT. It can only handle single-line text, except the functions of Single-line edit box, it can display and input Double-Direction texts, including Arabic and Hebrew. The Control provides the functions of being Selected, Copy and Paste, etc.

Except the differences described above, the styles, messages and notification codes of the three types of edit box control classes are general similar, with only a little differences. Fig 22.1 shows the running effect of the three types of edit boxes.

alt

Figure 1 MiniGUI edit boxes

Styles of Edit Box

Generally, we use the following style combination when creating an edit box:

WS_CHILD | WS_VISIBLE | WS_BORDER

Apparently, the style definition above does not use any styles specific to edit box. That is to say, we can use edit box normally without specifying any special styles of edit box. But the edit box has some special styles, mainly including:

  • ES_UPPERCASE: Make the edit box display all characters in uppercase.

  • ES_LOWERCASE: Make the edit box display all characters in lowercase.

  • ES_PASSWORD: Edit box is used for inputting the password, and displays an asterisk (*) for each character typed into the edit box.

  • ES_READONLY: Create a read-only edit box, the user cannot change the text in the edit box, but the caret is visible.

  • ES_BASELINE: Draws a base line under text of the edit box.

  • ES_AUTOWRAP: Used for a multiple-line edit box, and automatically wraps against border when the text input exceeds the control border.

  • ES_LEFT: Specify the aligning style for a single line edit box, and realizes the left-align style.

  • ES_NOHIDESEL: Remain selected for the selected text when losing focus.

  • ES_AUTOSELECT: Selects all text when getting focus (only valid for single-line edit box).

  • ES_TITLE: Shows specified title texts in the first row, and this style is only suitable for Multiple-line edit box.

  • ES_TIP: When content of edit box is NULL, shows related tip texts, and this style is only suitable for SLEDIT control.

  • ES_CENTER: Specify the aligning style for a single line edit box, and realizes the center-align style.

  • ES_RIGHT: Specify the aligning style for a single line edit box, and realizes the right-align style.

For a multiple-line edit box, if you want to use the scroll bars, you can specify the styles WS_HSCROLL and/or WS_VSCROLL.

The following styles can be used to multiple-line edit box: ES_UPPERCASE, ES_LOWERCASE, ES_READONLY, ES_BASELINE, ES_AUTOWRAP, ES_NOHIDESEL, and ES_TITLE.

The following styles can be used to single-line edit box: ES_UPPERCASE, ES_LOWERCASE, ES_READONLY, ES_BASELINE, ES_LEFT, ES_CENTER, ES_RIGHT, ES_PASSWORD, ES_NOHIDESEL, ES_AUTOSELECT, and ES_TIP.

Messages of Edit Box

You can get the current text information in the edit box by using the following messages. These messages can be used for the two types of edit box classes described above:

  • MSG_GETTEXTLENGTH: Get the length of the text with byte as unit.

  • MSG_GETTEXT: Copy the text in the edit box.

  • MSG_SETTEXT: Set the text in the edit box.

The application can also call the following three functions to complete corresponding work:

  • GetWindowTextLength

  • GetWindowText

  • SetWindowText

In fact, the three functions above are the simple wraps of the three messages mentioned above. As we have seen in the foregoing chapters, the same messages and functions can also be used for controls such as static control and button control.

The messages to be introduced in the following sections are special for edit box.

Getting/Setting Caret Position

Sending EM_GETCARETPOS message to the edit box will get the current caret position:

int line_pos;
int char_pos;

SendMessage (hwndEdit, EM_GETCARETPOS, (WPARAM) &line_pos, (LPARAM) &char_pos);

After the message returns, line_pos and char_pos include the line number and the position in that line of the caret. For a single-line edit box, line_pos is always zero, so you can pass NULL value for the argument wParam of the message.

It should be noted that, for multi-line edit box, one lines means a character string line ended with a linefeed (carriage return), instead of a line in a paragraph when displayed with ES_AUTOWRAP style. Character position in edit box of MiniGUI takes multiple byte character (such as Chinese characters) as unit when displaying multiple byte text, instead of byte. This definition works for other messages of edit box.

The application can also set the caret position through EM_SETCARETPOS message:

int line_pos;
int char_pos;

SendMessage (hwndEdit, EM_SETCARETPOS, line_pos, char_pos);

wParam and IParam argument specify line position and character position respectively.

Setting/Getting Selection of Text

EM_GETSEL message is used to get the currently selected text:

char buffer[buf_len];

SendMessage (hwndEdit, EM_GETSEL, buf_len, (LPARAM) buffer);

Here, lParam argument specifies the character buffer for saving the gotten text; wParam argument specifies the size of the buffer. If the specified buffer is small, then excrescent text will be cut off.

EM_SETSEL message is used to set the currently selected text:

int line_pos, char_pos;

SendMessage (hwndEdit, EM_SETSEL, line_pos, char_pos);

Here, lParam argument specifies the row index of selected point; wParam specifies the character position in line of selected point. After this message is sent, text between the current insertion point and the selected point will be selected.

EM_GETSELPOS message is used to get the position of currently selected point:

int line_pos;
int char_pos;

SendMessage (hwndEdit, EM_GETCARETPOS, (WPARAM) &line_pos, (LPARAM) &char_pos);

The use of EM_GETSELPOS message is similar to that of EM_GETCARETPOS message.

EM_SELECTALL message is used to make all the text in edit box selected, as CTRL+A operation:

SendMessage (hwndEdit, EM_SELECTALL, 0, 0);

Copy, Cut, and Past

You can perform edit operations on an edit box control, for example, copy, cut, and paste, by key operations or sending corresponding messages. Keyboard operations of edit box control, such as copy:

  • CTRL+C: Copy text from edit box to clipboard

  • CTRL+V: Copy text from clipboard to edit box

  • CTRL+X: Cut text of edit box to clipboard

EM_COPYTOCB message is used to copy the currently selected text of an edit box control to the clipboard, as <CTRL+C> operation:

SendMessage (hwndEdit, EM_COPYTOCB, 0, 0);

EM_CUTTOCB message is used to cut the currently selected text of an edit box control to the clipboard, as <CTRL+X> operation:

SendMessage (hwndEdit, EM_CUTTOCB, 0, 0);

EM_INSERTCBTEXT message is used to copy the text on the clipboard to an edit box, as <CTRL+V> operation:

SendMessage (hwndEdit, EM_INSERTCBTEXT, 0, 0);

Setting/Getting Properties of Line Height and Others

Row height here represents the height of single line in wrapped display style.

EM_GETLINEHEIGHT message is used to get the row height of an edit box:

int line_height;
line_height = SendMessage (hwndEdit, EM_GETLINEHEIGHT, 0, 0);

EM_SETLINEHEIGHT message is used to set the row height, If success, return old line height value, otherwise return –1:

int line_height;
SendMessage (hwndEdit, EM_SETLINEHEIGHT, line_height, 0);

NOTE It should be noted that it is preferred to use EM_SETLINEHEIGHT message before setting text of an edit box, because reset row height will redraw the whole content of the edit box.

EM_GETLINECOUNT message is used to get the number of rows:

int line_count;
line_count = SendMessage (hwndEdit, EM_GETLINECOUNT, 0, 0);

Row herein represents a single line in wrapped display style.

Setting Limit of Text

Sending EM_LIMITTEXT to an edit box can set the text upper limit in bytes of an edit box:

SendMessage (hwndEdit, EM_LIMITTEXT, 10, 0L);

The message above will make that only 10 bytes of characters can be input to the edit box.

Setting or Canceling Read-only Status

Using EM_SETREADONLY message and passing TRUE for wParam, the edit box will be set in read-only status, and passing FALSE for wParam will make the edit box be set in normal editable status.

Setting/Getting Password Character

By default, MiniGUI uses asterisks (*) to display the characters input in a password edit box. However, we can use the EM_SETPASSWORDCHAR message to change the password character:

SendMessage (hwndEdit, EM_SETPASSWORDCHAR, ‘%’, 0L);

The message above will change the password character to be ‘%’.

Using EM_GETPASSWORDCHAR message would get the current password character.

PROMPT Password character only can be set ASCII code which can be displayed.

Note that TEXTEDIT control does not carry out EM_SETPASSWORDCHAR and EM_GETPASSWORDCHAR messages.

Setting Title and Tip Text

When SLEDIT has ES_TIP styles, you can set tip text of the edit box using EM_SETTIPTEXT message, and get tip text of edit box using EM_GETTIPTEXT message.

int len;
char *tip_text;
SendMessage (hwndEdit, EM_SETTIPTEXT, len, (LPARAM)tip_text);

Here lParam parameter specifies tip text string, wParam parameter specifies the length of the string; if tip_text is ended with ’\0’, wParam can be set to -1, if wParam is 0, tip_text can be NULL. EM_GETTIPTEXT message will return the current tip text string:

int len;
char tip_text[len+1];
SendMessage (hwndEdit, EM_GETTIPTEXT, len, (LPARAM)tip_text);

Here lParam specifies the buffer to store the tip text string; wParam specifies the length of the string that can be stored in buffer (not including ’\0’).

When TEXTEDIT control has ES_TITLE style, you can use EM_SETTITLETEXT message to set the title text of the edit box, and use EM_GETTITLETEXT message to get title text of edit box:

int len;
char *title_text;
SendMessage (hwndEdit, EM_SETTITLETEXT, len, (LPARAM)title_text);

Here lParam parameter specifies title text string, wParam parameter specifies the length of the string; if tip_text is ended with ’\0’, wParam can be set as -1, if wParam is 0, tip_text can be NULL. EM_GETTIPTEXT message will return current title text string.

int len;
char title_text[len+1];
SendMessage (hwndEdit, EM_GETTITLETEXT, len, (LPARAM)title_text);

Here lParam parameter specifies the buffer to store the title text string; wParam parameter specifies the length of string that can be stored in the buffer (not including ’\0’).

Setting End of Line Symbol

In normal situation, TEXTEDIT edit box will not display linefeed symbol. If using EM_SETLFDISPCHAR message sets the display symbol for line feeds, then edit box will display linefeed as the set display symbol.

char disp_char;
SendMessage (hwndEdit, EM_SETLFDISPCHAR, 0, disp_char);

Here lParam parameter is the display symbol to be set for linefeed.

For example, if you want to display linefeed with *, you can set as follows:

SendMessage (hwndEdit, EM_SETLFDISPCHAR, 0, '*');

Setting End of Line

In default situation, linefeed symbol of TEXTEDIT edit box is ’\n’. You can use EM_SETLINESEP message to change the line feed used by edit box.

char sep_char;
SendMessage (hwndEdit, EM_SETLINESEP, 0, sep_char);

Here lParam parameter is the linefeed symbol to be set.

For example, if you want to indicate the line is end with TAB character, you can set as follows:

SendMessage (hwndEdit, EM_SETLINESEP, 0, ‘\t’);

Getting Paragraphs Information

EM_GETNUMOFPARAGRAPHS message is used to get the number of paragraphs.

int num;
num = SendMessage (hwnd, EM_GETNUMOFPARAGRAPHS, 0, 0);

EM_GETPARAGRAPHLENGTH message is used to get the length of a specified paragraph。If success, return the length of a specified paragraph, otherwise return –1.

int len;
len = SendMessage (hwnd, EM_GETPARAGRAPHLENGTH, idx, 0);

Here, wParam argument specifies the paragraph index.

EM_GETPARAGRAPHTEXT message is used to get the text of a specified paragraph. To show correct characters, it might adjust the number of characters can be copied appropriately.

TEXTPOSINFO info;
unsigned char buff [32];

info.start_pos = 5;
info.copy_len = 10;
info.buff = buff;
info.paragraph_index = -1;

SendMessage (hwnd, EM_GETPARAGRAPHTEXT, &info, 0);

Here, info is a structure of TEXTPOSINFO type, and specifies the related information for the copied text, as follows:

typedef struct _TEXTPOSINFO {
    /*The index of paragraph, if value is -1,
     *it will take effect on the whole text.*/
    int paragraph_index;
     /*The beginning byte position can be copied to the buffer.*/
    int start_pos;
     /*The maximal number of bytes can be copied to the buffer.*/
    int copy_len;
    /*The pointer to a buffer receives the text.
     *Please make sure buffer size is more than the value of copy_len.*/
    char *buff;
}TEXTPOSINFO;

The member start_pos is the beginning byte position can be copied to the buffer. The member copy_len is the maximal number of bytes can be copied to the buffer. The member paragraph_index is the index of paragraph, if value is -1, it will take effect on the whole text. The member buff is the character buffer for saving the gotten text.

Notification Codes of Edit Box

The edit box has not ES_NOTIFY style, so any edit box can generate notification messages, as listed below:

  • EN_SETFOCUS: The edit box has received the input focus.

  • EN_KILLFOCUS: The edit box has lost the input focus.

  • EN_CHANGE: The content in the edit box has been altered.

  • EN_UPDATE: The content in the edit box has been altered after edit box received MSG_SETTEXT, EM_RESETCONTENT, or EM_SETLINEHEIGHT message.

  • EN_ENTER: The user has pressed the ENTER key in the edit box.

  • EN_MAXTEXT: The inserting text exceeds the maximum limitation of the edit box.

  • EN_DBLCLK: The edit control is double clicked with the left button of the mouse.

  • EN_CLICKED: The edit control is clicked with the left button of the mouse.

Sample Program

In the foregoing chapters, we have already seen the use of edit boxes. List 1 gives another example of edit boxes, this program copy the input of a single-line edit box to an automatic wrapped multiple-line edit box. Please refer to edit.c file of the demo program package mg-samples of this guide for the complete source code. Effect of running the program is shown in Figure 2.

List 1 Example for using edit boxes

#include <stdio.h>
#include <stdlib.h>

#include <minigui/common.h>
#include <minigui/minigui.h>
#include <minigui/gdi.h>
#include <minigui/window.h>
#include <minigui/control.h>

/* Define dialg template */
static DLGTEMPLATE DlgBoxInputChar =
{
    WS_BORDER | WS_CAPTION,
    WS_EX_NONE,
    0, 0, 400, 220,
#ifdef _LANG_ZHCN
    "请键入字母",
#else
    "Please input letters",
#endif
    0, 0,
    4, NULL,
    0
};

#define IDC_CHAR        100
#define IDC_CHARS       110

static CTRLDATA CtrlInputChar [] =
{
    {
        CTRL_STATIC,
        WS_VISIBLE ,
        10, 10, 380, 18,
        IDC_STATIC,
#ifdef _LANG_ZHCN
        "请输入一个字母:",
#else
        "Please input a letter:",
#endif
        0
    },
    {
        CTRL_SLEDIT,
        WS_VISIBLE | WS_TABSTOP | WS_BORDER | ES_CENTER,
        10, 40, 80, 25,
        IDC_CHAR,
        NULL,
        0
    },
    {
        CTRL_MLEDIT,
        WS_VISIBLE | WS_BORDER | WS_VSCROLL | ES_BASELINE | ES_AUTOWRAP,
        10, 80, 380, 70,
        IDC_CHARS,
        NULL,
        0
    },
    {
        CTRL_BUTTON,
        WS_TABSTOP | WS_VISIBLE | BS_DEFPUSHBUTTON,
        170, 160, 60, 25,
        IDOK,
#ifdef _LANG_ZHCN
        "确定",
#else
        "OK",
#endif
        0
    }
};

static void my_notif_proc (HWND hwnd, int id, int nc, DWORD add_data)
{
    unsigned char buff [256] = {0};
    if (id == IDC_CHAR && nc == EN_CHANGE) {
        /* Get the user input(the first character) of the single-line
         * edit box, and insert it to the multiple-line edit box
         */
        GetWindowText (hwnd, buff, 4);
        /* Place the caret postion of the single-line edit box in front,
         *thus to overlap the old character
         */
        SendMessage (hwnd, EM_SETCARETPOS, 0, 0);
        SendMessage (GetDlgItem (GetParent (hwnd), IDC_CHARS), MSG_CHAR, buff[0], 0L);
    }
    else if (id == IDC_CHARS && nc == EN_CHANGE) {
        GetWindowText (hwnd, buff, 255);
        printf ("String: %s\n", buff);
    }
}

static int InputCharDialogBoxProc (HWND hDlg, int message, WPARAM wParam, LPARAM lParam)
{
    static PLOGFONT my_font;
    HWND hwnd;

    switch (message) {
    case MSG_INITDIALOG:
        my_font = CreateLogFont (NULL, "fmhei", "ISO8859-1",
                        FONT_WEIGHT_REGULAR, FONT_SLANT_ROMAN, FONT_FLIP_NIL,
                        FONT_OTHER_NIL, FONT_UNDERLINE_NONE, FONT_STRUCKOUT_NONE,
                        20, 0);
        hwnd = GetDlgItem (hDlg, IDC_CHAR);
        /* Set the font of the single-line edit box to be a big font */
        SetNotificationCallback (hwnd, my_notif_proc);
        /* Simulate the press of INSERT key, and set the edit mode to be overlap mode */
        SendMessage (hwnd, MSG_KEYDOWN, SCANCODE_INSERT, 0L);
        return 1;

    case MSG_CLOSE:
        EndDialog (hDlg, IDCANCEL);
        break;

    case MSG_COMMAND:
        switch (wParam) {
        case IDOK:
        case IDCANCEL:
            DestroyLogFont (my_font);
            EndDialog (hDlg, wParam);
            break;
        }
        break;
    }

    return DefaultDialogProc (hDlg, message, wParam, lParam);
}

int MiniGUIMain (int argc, const char* argv[])
{

#ifdef _MGRM_PROCESSES
    JoinLayer(NAME_DEF_LAYER , "edit" , 0 , 0);
#endif

#ifdef _LITE_VERSION
    if (!InitVectorialFonts ()) {
        printf ("InitVectorialFonts: error.\n");
        return 1;
    }
#endif

    DlgBoxInputChar.controls = CtrlInputChar;
    DialogBoxIndirectParam (&DlgBoxInputChar, HWND_DESKTOP, InputCharDialogBoxProc, 0L);

#ifdef _LITE_VERSION
    TermVectorialFonts ();
#endif
    return 0;
}

#ifndef _LITE_VERSION
#include <minigui/dti.c>
#endif
alt

Figure 2 Effect of running the edit box example program

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