Bir Windows API programında, bir ComboBox kontrolunu CBS_OWNERDRAWFIXED özelliği ile tanımlayarak, ComboBox'ın içinde yer aldığı pencere fonksiyonu içinde WM_DRAWITEM mesajına işlem yaparak, ComboBox'ın elemanlarını kendi belirlediğimiz görünümlere göre çizebiliriz.
Programda yer alacak main.c dosya içeriği aşağıdaki şekilde olacaktır:
main.c
#if defined(UNICODE) && !defined(_UNICODE)
#define _UNICODE
#elif defined(_UNICODE) && !defined(UNICODE)
#define UNICODE
#endif
#define _WIN32_WINNT 0x0501
#define _WIN32_IE 0x0501
#include <tchar.h>
#include <windows.h>
#define IDC_COMBOBOX 1001
/* Declare Windows procedure */
LRESULT CALLBACK WindowProcedure (HWND, UINT, WPARAM, LPARAM);
/* Make the class name into a global variable */
TCHAR szClassName[ ] = _T("CodeBlocksWindowsApp");
HWND hwndComboBox;
int WINAPI WinMain (HINSTANCE hThisInstance,
HINSTANCE hPrevInstance,
LPSTR lpszArgument,
int nCmdShow)
{
HWND hwnd; /* This is the handle for our window */
MSG messages; /* Here messages to the application are saved */
WNDCLASSEX wincl; /* Data structure for the windowclass */
/* The Window structure */
wincl.hInstance = hThisInstance;
wincl.lpszClassName = szClassName;
wincl.lpfnWndProc = WindowProcedure; /* This function is called by windows */
wincl.style = CS_DBLCLKS; /* Catch double-clicks */
wincl.cbSize = sizeof (WNDCLASSEX);
/* Use default icon and mouse-pointer */
wincl.hIcon = LoadIcon (NULL, IDI_APPLICATION);
wincl.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
wincl.hCursor = LoadCursor (NULL, IDC_ARROW);
wincl.lpszMenuName = NULL; /* No menu */
wincl.cbClsExtra = 0; /* No extra bytes after the window class */
wincl.cbWndExtra = 0; /* structure or the window instance */
/* Use Windows's default colour as the background of the window */
wincl.hbrBackground = (HBRUSH) COLOR_BACKGROUND;
/* Register the window class, and if it fails quit the program */
if (!RegisterClassEx (&wincl))
return 0;
/* The class is registered, let's create the program*/
hwnd = CreateWindowEx (
0, /* Extended possibilites for variation */
szClassName, /* Classname */
_T("ComboBox Renkli"), /* Title Text */
WS_OVERLAPPEDWINDOW, /* default window */
CW_USEDEFAULT, /* Windows decides the position */
CW_USEDEFAULT, /* where the window ends up on the screen */
400, /* The programs width */
300, /* and height in pixels */
HWND_DESKTOP, /* The window is a child-window to desktop */
NULL, /* No menu */
hThisInstance, /* Program Instance handler */
NULL /* No Window Creation data */
);
/* Make the window visible on the screen */
ShowWindow (hwnd, nCmdShow);
/* Run the message loop. It will run until GetMessage() returns 0 */
while (GetMessage (&messages, NULL, 0, 0))
{
/* Translate virtual-key messages into character messages */
TranslateMessage(&messages);
/* Send message to WindowProcedure */
DispatchMessage(&messages);
}
/* The program return-value is 0 - The value that PostQuitMessage() gave */
return messages.wParam;
}
/* This function is called by the Windows function DispatchMessage() */
LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
switch (message) /* handle the messages */
{
case WM_CREATE:
{
hwndComboBox = CreateWindowEx(0, "COMBOBOX", NULL,
WS_CHILD | WS_VISIBLE | CBS_DROPDOWNLIST | WS_TABSTOP | CBS_HASSTRINGS | WS_VSCROLL | CBS_OWNERDRAWFIXED,
20, 20, 180, 200,
hwnd, (HMENU)(IDC_COMBOBOX), NULL, NULL);
SendMessage(hwndComboBox, CB_ADDSTRING, 0, (LPARAM) "Karakter dizisi 01");
SendMessage(hwndComboBox, CB_ADDSTRING, 0, (LPARAM) "Karakter dizisi 02");
SendMessage(hwndComboBox, CB_ADDSTRING, 0, (LPARAM) "Karakter dizisi 03");
SendMessage(hwndComboBox, CB_ADDSTRING, 0, (LPARAM) "Karakter dizisi 04");
SendMessage(hwndComboBox, CB_ADDSTRING, 0, (LPARAM) "Karakter dizisi 05");
SendMessage(hwndComboBox, CB_ADDSTRING, 0, (LPARAM) "Karakter dizisi 06");
SendMessage(hwndComboBox, CB_ADDSTRING, 0, (LPARAM) "Karakter dizisi 07");
SendMessage(hwndComboBox, CB_ADDSTRING, 0, (LPARAM) "Karakter dizisi 08");
SendMessage(hwndComboBox, CB_ADDSTRING, 0, (LPARAM) "Karakter dizisi 09");
SendMessage(hwndComboBox, CB_ADDSTRING, 0, (LPARAM) "Karakter dizisi 10");
SendMessage(hwndComboBox, CB_SETCURSEL, 0, 0);
}
break;
case WM_DRAWITEM:
{
COLORREF backgr=0;
TEXTMETRIC tm;
int x, y;
TCHAR achTemp[256];
LPDRAWITEMSTRUCT lpDrawItem = (LPDRAWITEMSTRUCT) lParam;
if (lpDrawItem->CtlType==ODT_COMBOBOX) {
if (wParam == IDC_COMBOBOX) {
if (lpDrawItem->itemID == -1) break; // ComboBox boş ise
switch ((lpDrawItem->itemID)%5) {
case 0: backgr = RGB(200, 100, 245); break;
case 1: backgr = RGB(200, 220, 50); break;
case 2: backgr = RGB(255, 210, 50); break;
case 3: backgr = RGB(252, 170, 255); break;
case 4: backgr = RGB(220, 180, 140); break;
}
SetTextColor(lpDrawItem->hDC, RGB(50, 50, 50));
SetBkColor(lpDrawItem->hDC, backgr);
// Yatay ve dikey pozisyonu hesaplama
GetTextMetrics(lpDrawItem->hDC, &tm);
y = (lpDrawItem->rcItem.bottom + lpDrawItem->rcItem.top - tm.tmHeight) / 2;
x = LOWORD(GetDialogBaseUnits()) / 4;
// Listedeki satırı alma ve yazma
SendMessage(lpDrawItem->hwndItem, CB_GETLBTEXT, lpDrawItem->itemID, (LPARAM) achTemp);
ExtTextOut(lpDrawItem->hDC, x+4, y, ETO_CLIPPED | ETO_OPAQUE, &lpDrawItem->rcItem, achTemp, (UINT)strlen(achTemp), NULL);
if ((lpDrawItem->itemState & ODS_FOCUS) && !(lpDrawItem->itemState & ODS_COMBOBOXEDIT)) {
FrameRect(lpDrawItem->hDC, &lpDrawItem->rcItem, CreateSolidBrush(RGB(200, 255, 200)));
}
}
}
}
break;
case WM_DESTROY:
PostQuitMessage (0); /* send a WM_QUIT to the message queue */
break;
default: /* for messages that we don't deal with */
return DefWindowProc (hwnd, message, wParam, lParam);
}
return 0;
}
Program derleyip çalıştırdığımızda aşağıdakine benzer bir ekran görüntüsü karşımıza gelecektir: