Windows API controls III

In this chapter, we will finish talking about Windows API controls. We will mention radio buttons, radio box, combo box, and a progress bar.

Radio buttons and GroupBox

Here we introduce two controls. A group box is a rectangle that surrounds a set of controls. These are often radio buttons. A group box has a label that describes the control. The purpose of this control is to group controls that are somehow related. A radio button is a special kind of button that can be selected by the user, but not cleared. It allows the user to select a single exclusive choice from a group of options.

radio_buttons.c
#include <windows.h>

#define ID_BLUE 1
#define ID_YELLOW 2
#define ID_ORANGE 3

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

HINSTANCE g_hinst;
COLORREF g_color;

int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PWSTR lpCmdLine, int nCmdShow) {

    HWND hwnd;
    MSG  msg ;    
    WNDCLASSW wc = {0};
    wc.lpszClassName = L"GroupBox";
    wc.hInstance     = hInstance;
    wc.hbrBackground = GetSysColorBrush(COLOR_3DFACE);
    wc.lpfnWndProc   = WndProc;
    wc.hCursor       = LoadCursor(0, IDC_ARROW);

    g_hinst = hInstance;
  
    RegisterClassW(&wc);
    hwnd = CreateWindowW(wc.lpszClassName, L"GroupBox",
                  WS_OVERLAPPEDWINDOW | WS_VISIBLE,
                  100, 100, 300, 170, 0, 0, hInstance, 0);  


    while (GetMessage(&msg, NULL, 0, 0)) {
            
        DispatchMessage(&msg);
    }

    return (int) msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, 
    WPARAM wParam, LPARAM lParam) {

    HDC hdc;
    PAINTSTRUCT ps;
    HBRUSH hBrush, holdBrush;
    HPEN hPen, holdPen;

    switch(msg) {

        case WM_CREATE:

            CreateWindowW(L"Button", L"Choose colour", 
                  WS_CHILD | WS_VISIBLE | BS_GROUPBOX,
                  10, 10, 120, 110, hwnd, (HMENU) 0, g_hinst, NULL);
            CreateWindowW(L"Button", L"Blue",
                  WS_CHILD | WS_VISIBLE | BS_AUTORADIOBUTTON,
                  20, 30, 100, 30, hwnd, (HMENU) ID_BLUE , g_hinst, NULL);
            CreateWindowW(L"Button", L"Yellow",
                  WS_CHILD | WS_VISIBLE | BS_AUTORADIOBUTTON,
                  20, 55, 100, 30, hwnd, (HMENU) ID_YELLOW , g_hinst, NULL);
            CreateWindowW(L"Button", L"Orange",
                  WS_CHILD | WS_VISIBLE | BS_AUTORADIOBUTTON,
                  20, 80, 100, 30, hwnd, (HMENU) ID_ORANGE , g_hinst, NULL);      
            break;

        case WM_COMMAND:

            if (HIWORD(wParam) == BN_CLICKED) {
            
                switch (LOWORD(wParam)) {
                
                    case ID_BLUE:
                        g_color = RGB(0, 76, 255);
                        break;
                    case ID_YELLOW:
                        g_color = RGB(255, 255, 0);
                        break;
                    case ID_ORANGE:
                        g_color = RGB(255, 123, 0);
                        break;
                }                    
                InvalidateRect(hwnd, NULL, TRUE);
            }
            break;

        case WM_PAINT:

            hdc = BeginPaint(hwnd, &ps);
            hBrush = CreateSolidBrush(g_color);
            hPen = CreatePen(PS_NULL, 1, RGB(0, 0, 0));
            holdPen = SelectObject(hdc, hPen);
            holdBrush = (HBRUSH) SelectObject(hdc, hBrush);

            Rectangle(hdc, 160, 20, 260, 120);

            SelectObject(hdc, holdBrush);
            SelectObject(hdc, holdPen);
            DeleteObject(hPen);
            DeleteObject(hBrush);
            EndPaint(hwnd, &ps);
            break;

        case WM_DESTROY:
            PostQuitMessage(0);
            break; 
    }

    return DefWindowProcW(hwnd, msg, wParam, lParam);
}

In our example, we have a group box with three radio buttons. By clicking on the radio button, we select a background colour for the rectangle on the right.

CreateWindowW(L"Button", L"Choose colour", 
        WS_CHILD | WS_VISIBLE | BS_GROUPBOX,
        10, 10, 120, 110, hwnd, (HMENU) 0, g_hinst, NULL);

A group box is a special kind of a button created with the BS_GROUPBOX style.

CreateWindowW(L"Button", L"Blue",
        WS_CHILD | WS_VISIBLE | BS_AUTORADIOBUTTON,
        20, 30, 100, 30, hwnd, (HMENU) ID_BLUE , g_hinst, NULL);

A radio button is also a special kind of a button with BS_AUTORADIOBUTTON style.

case ID_BLUE:
    g_color = RGB(0, 76, 255);
    break;

If we click on the radio button, a global variable is filled with selected colour. This variable is used to create a brush that fills the rectangle.

InvalidateRect(hwnd, NULL, TRUE);

We invalidate the rectangle (in this case whole window), which will cause the client area to be redrawn. This will launch a WM_PAINT message. During the WM_PAINT message, we draw the rectangle. Drawing is explained in GDI chapter in more detail.

Radio buttons in a GroupBox
Figure: Radio buttons in a GroupBox

Combo box

A combo box is a combination of an edit box or static text and a list. A combo box is used when we need to select an item from a list of available options.

combobox.c
#include <windows.h>

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

HINSTANCE g_hinst;

int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PWSTR lpCmdLine, int nCmdShow) {

    HWND hwnd;
    MSG  msg ;    
    WNDCLASSW wc = {0};
    wc.lpszClassName = L"Application";
    wc.hInstance     = hInstance ;
    wc.hbrBackground = GetSysColorBrush(COLOR_3DFACE);
    wc.lpfnWndProc   = WndProc ;
    wc.hCursor       = LoadCursor(0,IDC_ARROW);

    g_hinst = hInstance;
  
    RegisterClassW(&wc);
    hwnd = CreateWindowW(wc.lpszClassName, L"Combo box",
                  WS_OVERLAPPEDWINDOW | WS_VISIBLE,
                  100, 100, 270, 170, 0, 0, hInstance, 0);  


    while (GetMessage(&msg, NULL, 0, 0)) {
    
        DispatchMessage(&msg);
    }

    return (int) msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, 
        WPARAM wParam, LPARAM lParam) {

    static HWND hwndCombo, hwndStatic;
    const wchar_t *items[] = { L"FreeBSD", L"OpenBSD", 
        L"NetBSD", L"Solaris", L"Arch" };

    switch(msg) {
    
        case WM_CREATE:
        
              hwndCombo = CreateWindowW(L"Combobox", NULL, 
                    WS_CHILD | WS_VISIBLE | CBS_DROPDOWN,
                    10, 10, 120, 110, hwnd, NULL, g_hinst, NULL);   

              CreateWindowW(L"Button", L"Drop down", 
                    WS_CHILD | WS_VISIBLE,
                    150, 10, 90, 25, hwnd, (HMENU) 1, g_hinst, NULL); 

              hwndStatic = CreateWindowW(L"Static", L"", 
                    WS_CHILD | WS_VISIBLE,
                    150, 80, 90, 25, hwnd, NULL, g_hinst, NULL); 

              for (int i = 0; i < 4; i++ ) {
              
                  SendMessageW(hwndCombo, CB_ADDSTRING, 0, (LPARAM) items[i]);
              }

              break;

        case WM_COMMAND:
        
             if (HIWORD(wParam) == BN_CLICKED) {
             
                  SendMessage(hwndCombo, CB_SHOWDROPDOWN, (WPARAM) TRUE, 0);
             }
             
             if (HIWORD(wParam) == CBN_SELCHANGE) {      
             
                  LRESULT sel = SendMessage(hwndCombo, CB_GETCURSEL, 0, 0);
                  SetWindowTextW(hwndStatic, items[sel]);
             }
             break;

        case WM_DESTROY:
        
            PostQuitMessage(0);
            break; 
    }
  
    return DefWindowProcW(hwnd, msg, wParam, lParam);
}

In our example, we put three controls on the window: a combo box, a button, and a static text. The static text displays the currently selected item from the combo box. It is used to demonstrate the CBN_SELCHANGE combo box message. The button programatically opens the combo box.

hwndCombo = CreateWindowW(L"Combobox", NULL, 
    WS_CHILD | WS_VISIBLE | CBS_DROPDOWN,
    10, 10, 120, 110, hwnd, NULL, g_hinst, NULL); 

To create a combo box, we use the L"Combobox" window class. The CBS_DROPDOWN flag creates a drop-down list.

for (int i = 0; i < 4; i++ ) {

    SendMessageW(hwndCombo, CB_ADDSTRING, 0, (LPARAM) items[i]);
}

We fill the combo box with items. To add a string to the combo box, we send a CB_ADDSTRING message.

if (HIWORD(wParam) == BN_CLICKED) {

    SendMessage(hwndCombo, CB_SHOWDROPDOWN, (WPARAM) TRUE, 0);
}

Clicking on the button causes a CB_SHOWDROPDOWN message to be send, which programmatically invokes a drop down of the combo box.

If we select an item from the combo box, the window procedure receives the WM_COMMAND message with the notification message CBN_SELCHANGE in the high-order word of the wParam parameter.

if (HIWORD(wParam) == CBN_SELCHANGE) {      

    LRESULT sel = SendMessage(hwndCombo, CB_GETCURSEL, 0, 0);
    SetWindowTextW(hwndStatic, items[sel]);
}

We figure out the currently selected item. We send a CB_GETCURSEL message to the combo box. The function returns the index of the currently selected item. We set the static text to the currently selected string.

Combo box
Figure: Combo box

Progress bar

A progress bar is a control that is used when we process lengthy tasks. It is animated so that the user knows that our task is progressing.

progressbar.c
#include <windows.h>
#include <commctrl.h>

#define ID_BUTTON 1
#define ID_TIMER 2

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
void CreateControls(HWND);

HWND hwndPrgBar;
HWND hbtn;

int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PWSTR lpCmdLine, int nCmdShow) {

    HWND hwnd;
    MSG  msg ;    
    WNDCLASSW wc = {0};
    wc.lpszClassName = L"Application";
    wc.hInstance     = hInstance;
    wc.hbrBackground = GetSysColorBrush(COLOR_3DFACE);
    wc.lpfnWndProc   = WndProc;
    wc.hCursor       = LoadCursor(0, IDC_ARROW);
  
    RegisterClassW(&wc);
    hwnd = CreateWindowW(wc.lpszClassName, L"Progress bar",
                WS_OVERLAPPEDWINDOW | WS_VISIBLE,
                100, 100, 260, 170, 0, 0, hInstance, 0);  

    while (GetMessage(&msg, NULL, 0, 0)) {
        
        DispatchMessage(&msg);
    }

    return (int) msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, 
        WPARAM wParam, LPARAM lParam) {

    static int i = 0;
 
    switch(msg) {

        case WM_CREATE:

            CreateControls(hwnd);
            break;

        case WM_TIMER:

            SendMessage(hwndPrgBar, PBM_STEPIT, 0, 0);
            i++;

            if (i == 150) {

                KillTimer(hwnd, ID_TIMER);
                SendMessageW(hbtn, WM_SETTEXT, (WPARAM) NULL, (LPARAM) L"Start");
                i = 0;
            }

            break;
              
        case WM_COMMAND:
          
            if (i == 0) {  

                i = 1;
                SendMessage(hwndPrgBar, PBM_SETPOS, 0, 0);
                SetTimer(hwnd, ID_TIMER, 5, NULL);
                SendMessageW(hbtn, WM_SETTEXT, (WPARAM) NULL, (LPARAM) L"In progress");
            }

          break;

        case WM_DESTROY:

            KillTimer(hwnd, ID_TIMER);
            PostQuitMessage(0);
            break; 
    }

    return DefWindowProcW(hwnd, msg, wParam, lParam);
}

void CreateControls(HWND hwnd) {

    INITCOMMONCONTROLSEX icex;

    icex.dwSize = sizeof(INITCOMMONCONTROLSEX);
    icex.dwICC  = ICC_PROGRESS_CLASS;
    InitCommonControlsEx(&icex);

    hwndPrgBar = CreateWindowEx(0, PROGRESS_CLASS, NULL, 
          WS_CHILD | WS_VISIBLE | PBS_SMOOTH,
          30, 20, 190, 25, hwnd, NULL, NULL, NULL);   

    hbtn = CreateWindowW(L"Button", L"Start", 
          WS_CHILD | WS_VISIBLE,
          85, 90, 85, 25, hwnd, (HMENU) 1, NULL, NULL);  

    SendMessage(hwndPrgBar, PBM_SETRANGE, 0, MAKELPARAM(0, 150));
    SendMessage(hwndPrgBar, PBM_SETSTEP, 1, 0);
}

In our example, we have a progress bar and a button. The button starts a timer which updates the progress bar.

hwndPrgBar = CreateWindowEx(0, PROGRESS_CLASS, NULL, 
      WS_CHILD | WS_VISIBLE | PBS_SMOOTH,
      30, 20, 190, 25, hwnd, NULL, NULL, NULL);  

We create a progress bar control with PROGRESS_CLASS class name and PBS_SMOOTH style.

SendMessage(hwndPrgBar, PBM_SETRANGE, 0, MAKELPARAM(0, 150));
SendMessage(hwndPrgBar, PBM_SETSTEP, 1, 0);

We set the range of the progress bar and its step.

i = 1;
SendMessage(hwndPrgBar, PBM_SETPOS, 0, 0);
SetTimer(hwnd, ID_TIMER, 5, NULL);

When we press the Start button, we set the i value to 1, set the initial position of the progress bar, and start the timer. The timer will periodically send a WM_TIMER message to the window procedure, until it is killed.

SendMessageW(hbtn, WM_SETTEXT, (WPARAM) NULL, (LPARAM) L"In progress"); 

When the timer is in progress, we change the label of the button.

case WM_TIMER:

    SendMessage(hwndPrgBar, PBM_STEPIT, 0, 0);
    i++;

    if (i == 150) {

        KillTimer(hwnd, ID_TIMER);
        SendMessageW(hbtn, WM_SETTEXT, (WPARAM) NULL, (LPARAM) L"Start");
        i = 0;
    }

    break;

When we receive the WM_TIMER message, we update the progress bar by one step sending the PBM_STEPIT message. The timer is killed when the i variable reaches the upper limit of the progress bar.

Progress bar
Figure: Progress bar

In this part of the Windows API tutorial, we have finished covering Windows controls.