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We have updated our windows code to use Styles and since then we get a flicker in various parts of the code when using STM_SETIMAGE to update a bitmap on a window.
I have created a minimal reproducible example here. Can anyone tell me what I need to do to get rid of the flicker please ?
The code simply redraws a bitmap every 1/100 second and calls the windows function to set the image onto the window. It worked without a flicker before we added Windows Styles.
Thanks
Shaun
#include <windows.h>
#include <CommCtrl.h>
#include <math.h>
#include <objbase.h>
#pragma comment(linker,"\"/manifestdependency:type='win32' name='Microsoft.Windows.Common-Controls' version='6.0.0.0' processorArchitecture='*' publicKeyToken='6595b64144ccf1df' language='*'\"")
//--------------------------------------
#ifndef HINST_THISCOMPONENT
EXTERN_C IMAGE_DOS_HEADER __ImageBase;
#define HINST_THISCOMPONENT ((HINSTANCE)&__ImageBase)
#endif
//--------------------------------------
LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
return DefWindowProc(hwnd, message, wParam, lParam);
}
//--------------------------------------
HWND logo;
HWND m_hwnd;
HBITMAP testBitmap;
int counter=0;
typedef unsigned char u8;
typedef unsigned int u32;
//--------------------------------------
HRESULT App_Initialize()
{
HRESULT hr;
// Register the window class.
WNDCLASSEX wcex = { sizeof(WNDCLASSEX) };
wcex.style = CS_HREDRAW | CS_VREDRAW;
wcex.lpfnWndProc = WndProc;
wcex.cbClsExtra = 0;
wcex.cbWndExtra = sizeof(LONG_PTR);
wcex.hInstance = HINST_THISCOMPONENT;
wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);;
wcex.lpszMenuName = NULL;
wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
wcex.lpszClassName = TEXT("myApp");
RegisterClassEx(&wcex);
int dpiX = 0;
int dpiY = 0;
HDC hdc = GetDC(NULL);
if (hdc)
{
dpiX = GetDeviceCaps(hdc, LOGPIXELSX);
dpiY = GetDeviceCaps(hdc, LOGPIXELSY);
ReleaseDC(NULL, hdc);
}
m_hwnd = CreateWindow( TEXT("myApp"), TEXT("Simple Set image Example"), WS_OVERLAPPEDWINDOW | WS_CLIPCHILDREN, CW_USEDEFAULT, CW_USEDEFAULT, 640, 640, NULL,NULL,HINST_THISCOMPONENT,0);
hr = m_hwnd ? S_OK : E_FAIL;
if (SUCCEEDED(hr))
{
ShowWindow(m_hwnd, SW_SHOWNORMAL);
UpdateWindow(m_hwnd);
}
logo = CreateWindow("Static", NULL, SS_BITMAP | WS_CHILD | WS_VISIBLE, 40, 40,512,512, m_hwnd, NULL, NULL, NULL);
return hr;
}
//----------------------------------------------
void Redraw()
{
DeleteObject(testBitmap);
testBitmap=0;
u8 * RenderImageData=(u8*)malloc(512*512*4);
u32 * p=(u32*)RenderImageData;
for(int i=0;i<512;i++)
{
p[i+counter*512]=0xff000000;
p[i*512+counter]=0xff000000;
}
testBitmap = CreateBitmap(512,512, 4, 8, RenderImageData);
SendMessage(logo,STM_SETIMAGE, IMAGE_BITMAP, (LPARAM) testBitmap);
free(RenderImageData);
counter=(counter+1)&511;
}
//----------------------------------------------
int WINAPI WinMain(HINSTANCE hInstance ,HINSTANCE hPrevInstance ,LPSTR lpCmdLine ,int nCmdShow)
{
if (SUCCEEDED(CoInitialize(NULL)))
{
if (SUCCEEDED(App_Initialize()))
{
MSG msg;
while(1)
{
while (PeekMessage(&msg, NULL, 0,0,PM_REMOVE))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
Sleep(10);
Redraw();
}
}
CoUninitialize();
}
return 0;
}
//----------------------------------------------
I found this code which seems to work.
Instead of
HBITMAP hbm=(HBITMAP)SendMessage(hWndPic,STM_SETIMAGE, IMAGE_BITMAP, (LPARAM) pD->hbitmap);
I call
GDI_SetImageX(pD->hbitmap,hWndPic, xs, ys);
void GDI_SetImageX( HBITMAP hBM, HWND hCtrl , int w, int h)
{
HDC hdcSrc=CreateCompatibleDC(0);
HDC hdcDst=GetDC(hCtrl);
HGDIOBJ hbmOld=SelectObject(hdcSrc,hBM);
HGDIOBJ hbmNew=CreateBitmap(w,h,4,8,0);
HGDIOBJ hbmOld2=SelectObject(hdcDst,hbmNew);
BitBlt(hdcDst,0,0,w,h,hdcSrc,0,0,0x00cc0020);
SelectObject(hdcSrc,hbmOld);
DeleteDC(hdcSrc);
ReleaseDC(hCtrl,hdcDst);
SendMessage(hCtrl,0x0b,0,0);
LRESULT oBM=SendMessage(hCtrl,STM_SETIMAGE, IMAGE_BITMAP, (LPARAM) hBM);
SendMessage(hCtrl,0x0b,1,0);
DeleteObject(hBM);
}
I need to get the whole window's display area size, including controls that are hidden. In order to do that, I get the value from top from the very first window and the value of bottom from very last control. However, I'm getting a gap/white are in the end of the display area. See what's like in the below image. The display area is supposed to be until the Edit control's borders is seen. What am I missing?
I'm getting this size by:
int scrollHeight(void)
{
int minTop = 0;
int maxBottom = 0;
RECT rt = {0};
if(allControls_indx == 0) {
return 0;
}
#if 0
assert(allControls[0] == hMainWindow);
assert(allControls[allControls_indx - 1] == hEdit1);
#endif
if(!GetWindowRect(allControls[0], &rt)) {
ErrorExit(NAMEOF(scrollHeight), __LINE__, __FILENAME__);
}
minTop = rt.top;
if(!GetWindowRect(allControls[allControls_indx - 1], &rt)) {
ErrorExit(NAMEOF(scrollHeight), __LINE__, __FILENAME__);
}
maxBottom = rt.bottom;
return maxBottom - minTop;
}
set as scrollbar's page size like this:
setUpScrollBar(hwnd, scrollHeight());
where setUpScrollBar is defined as:
void setUpScrollBar(HWND hwnd, int h)
{
RECT rc = { 0 };
GetClientRect(hwnd, &rc);
SCROLLINFO si = { 0 };
si.cbSize = sizeof(SCROLLINFO);
si.fMask = SIF_ALL;
si.nMin = 0;
si.nMax = h;
si.nPage = (rc.bottom - rc.top);
si.nPos = 0;
si.nTrackPos = 0;
SetScrollInfo(hwnd, SB_VERT, &si, TRUE);
}
full code:
#pragma comment(lib, "user32.lib")
#pragma comment(lib, "Comctl32.lib")
#pragma comment(lib, "Gdi32.lib")
#define WIN32_LEAN_AND_MEAN
#define UNICODE
#define _UNICODE
#include <windows.h>
#include <Commctrl.h>
#include <crtdbg.h>
#include <strsafe.h>
#include <string.h>
#include <assert.h>
#ifdef UNICODE
#define STRSPLIT wcsrchr
#else
#define STRSPLIT strrchr
#endif
#define __FILENAME__ (STRSPLIT(TEXT(__FILE__), '/') ? STRSPLIT(TEXT(__FILE__), '/') + 1 : TEXT(__FILE__))
#define NAMEOF(s) TEXT(#s)
#define COUNTOF(a) (sizeof(a)/sizeof(a[0]))
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
LRESULT CALLBACK CreateTabProc(HWND, UINT, WPARAM, LPARAM);
void ErrorExit(LPWSTR lpszFunction, int line, LPWSTR filename);
void InitComControls();
void ErrorExit(LPWSTR lpszFunction, int line, LPWSTR filename);
DWORD ShowLastError(LPWSTR lpszFunction, int line, LPWSTR filename);
void InitComControls();
void CreateTab(HWND hwnd);
void InsertTabItem(HWND tabHwnd, UINT id, LPWSTR text);
void CreateButtons(HWND hwnd);
RECT GetLocalCoordinates(HWND hWnd);
int scrollHeight(void);
int getHeight(HWND control);
void setUpScrollBar(HWND hwnd, int);
void pushControl(HWND);
int displayArea(void);
void setScrollBarSize(HWND hwnd, int s);
inline int my_max(int a, int b);
inline int my_min(int a, int b);
void displayText(HWND h);
HINSTANCE ghInstance;
HWND hTab;
HWND hLabel1, hLabel2;
HWND hEdit1;
HWND hRemoveButton;
enum
{
IDBUTTON_REMOVE = 50
};
#define MAX_CONTROLS 8
static const wchar_t *title[] = { L"Button A1", L"Button B2", L"Button C3",
L"Button D4", L"Button E5", L"Button F6",
L"Button G" , L"Button 001", L"Button 002",
L"Button 003", L"Button 004",
L"Button 005", L"Button 006" };
HWND hButton[sizeof(title)/sizeof(title[0])] = {0};
HWND allControls[MAX_CONTROLS];
HWND hMainWindow;
int allControls_indx = 0;
int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
PWSTR pCmdLine, int nCmdShow)
{
MSG msg = {0};
HWND hwnd;
WNDCLASSW wc = {0};
wc.lpszClassName = L"Window";
wc.hInstance = hInstance;
wc.hbrBackground = GetSysColorBrush(COLOR_3DFACE);
wc.lpfnWndProc = WndProc;
wc.hCursor = LoadCursor(0, IDC_ARROW);
InitComControls();
if(!RegisterClass(&wc)) {
ErrorExit(NAMEOF(RegisterClass), __LINE__, __FILENAME__);
}
int width = 500;
int height = 350/2; // half than the usual size, so that the scrollbar show up and we can test it
int screenWidth = GetSystemMetrics(SM_CXSCREEN);
int screenHeight = GetSystemMetrics(SM_CYSCREEN);
int cx = (screenWidth - width) / 2;
int cy = (screenHeight - height) / 2;
hwnd = CreateWindowW(wc.lpszClassName, L"main window",
WS_OVERLAPPEDWINDOW | WS_VISIBLE,
cx, cy, width, height, NULL, NULL,
hInstance, NULL);
ghInstance = hInstance;
while (GetMessage(&msg, NULL, 0, 0))
{
if (!IsDialogMessage(hwnd, &msg))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
return (int) msg.wParam;
}
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
static int g_scrollY;
switch(msg)
{
case WM_CREATE:
hMainWindow = hwnd;
pushControl(hwnd); // push main window too
hLabel1 = CreateWindowW(L"Static", L"This is label 1...",
WS_VISIBLE | WS_CHILD | WS_TABSTOP,
50, 10, 130, 25, hwnd, (HMENU) 18, NULL, NULL);
pushControl(hLabel1);
hLabel2 = CreateWindowW(L"Static", L"This is label 2...",
WS_VISIBLE | WS_CHILD | WS_TABSTOP,
50, 40, 130, 25, hwnd, (HMENU) 19, NULL, NULL);
hRemoveButton = CreateWindow(L"Button", L"Remove",
WS_VISIBLE | WS_CHILD | WS_TABSTOP,
200, 40, 80, 25,
hwnd,
(HMENU) IDBUTTON_REMOVE,
NULL,
NULL);
pushControl(hLabel2);
CreateTab(hwnd);
CreateButtons(hwnd);
setUpScrollBar(hwnd, scrollHeight());
break;
case WM_VSCROLL:
{
int action = LOWORD(wParam);
//HWND hScroll = (HWND)lParam;
int pos = -1;
if (action == SB_THUMBPOSITION || action == SB_THUMBTRACK) {
pos = HIWORD(wParam);
} else if (action == SB_LINEDOWN) {
pos = g_scrollY + 30;
} else if (action == SB_LINEUP) {
pos = g_scrollY - 30;
}
if (pos == -1)
break;
SCROLLINFO si = { 0 };
si.cbSize = sizeof(SCROLLINFO);
si.fMask = SIF_POS;
si.nPos = pos;
si.nTrackPos = 0;
SetScrollInfo(hwnd, SB_VERT, &si, TRUE);
GetScrollInfo(hwnd, SB_VERT, &si);
pos = si.nPos;
POINT pt;
pt.x = 0;
pt.y = pos - g_scrollY;
HDC hdc = GetDC(hwnd);
LPtoDP(hdc, &pt, 1);
ReleaseDC(hwnd, hdc);
ScrollWindow(hwnd, 0, -pt.y, NULL, NULL);
g_scrollY = pos;
return 0;
}
break;
case WM_COMMAND:
{
switch(LOWORD(wParam))
{
case IDBUTTON_REMOVE:
ShowWindow(hEdit1, SW_HIDE);
SetScrollRange(hwnd, SB_VERT, 0, displayArea(), TRUE);
break;
}
}
break;
case WM_DESTROY:
PostQuitMessage(0);
return 0;
}
return DefWindowProc(hwnd, msg, wParam, lParam);
}
// this is like scrollHeight but control that are hidden
// aren't considered part of the display area.
int displayArea(void)
{
int size = scrollHeight();
// start i with 1 so we skip the mainwindow.
// we are interested in the "children controls"
for(int i = 1; i < MAX_CONTROLS && allControls[i]; i++)
{
HWND h = allControls[i];
// if it not visible, remove it from display area
if(!IsWindowVisible(h)) {
size -= getHeight(h);
}
}
return size;
}
void pushControl(HWND hwnd)
{
if(allControls_indx > MAX_CONTROLS) {
assert(!"no room for extra controls");
}
allControls[allControls_indx++] = hwnd;
}
void CreateTab(HWND hwnd)
{
hTab =
CreateWindow(WC_TABCONTROLW, NULL,
WS_CHILD | WS_VISIBLE | WS_CLIPSIBLINGS | WS_TABSTOP,
100, 80, 400, 250,
hwnd,
(HMENU) 1,
NULL,
NULL);
InsertTabItem(hTab, 2, L"Tab 1");
InsertTabItem(hTab, 3, L"Tab b");
pushControl(hTab);
}
void CreateButtons(HWND hwnd)
{
RECT rt = GetLocalCoordinates(hTab);
TabCtrl_AdjustRect(hTab, FALSE, &rt);
RECT rt2 = {0};
GetWindowRect(hTab, &rt2);
int tab_width = rt2.right - rt2.left;
int tab_height = rt2.bottom - rt2.top;
int id = 4;
const int cy_breakSize = 25;
int cx_initPos = rt.left;
int cy_initPos = rt.top;
int cx = cx_initPos;
int cy = cy_initPos;
const int button_width = 80;
const int button_height = 25;
const int cx_margin = 10;
int nMaxButtonPerRow = tab_width / (button_width + cx_margin);
for(int i = 0; i < sizeof(title)/sizeof(title[0]); ++i)
{
if(i != 0 && (i % nMaxButtonPerRow) == 0) {
cy += cy_breakSize;
cx = cx_initPos;
}
hButton[i] =
CreateWindow(L"button", title[i],
WS_VISIBLE | WS_CHILD | WS_TABSTOP,
cx,
cy,
button_width,
button_height,
hwnd, (HMENU) id++, NULL, NULL);
cx += button_width;
}
const int edit_width = 180;
const int edit_height = 25;
hEdit1 = CreateWindow(L"Edit", L"Hello, world!",
WS_VISIBLE | WS_CHILD | WS_BORDER,
cx,
// put below tab control's display area
getHeight(hTab) + cx,
edit_width,
edit_height,
hwnd,
(HMENU) id++,
NULL, NULL);
pushControl(hEdit1);
cx += edit_width;
}
void setUpScrollBar(HWND hwnd, int h)
{
RECT rc = { 0 };
GetClientRect(hwnd, &rc);
SCROLLINFO si = { 0 };
si.cbSize = sizeof(SCROLLINFO);
si.fMask = SIF_ALL;
si.nMin = 0;
si.nMax = h;
si.nPage = (rc.bottom - rc.top);
si.nPos = 0;
si.nTrackPos = 0;
SetScrollInfo(hwnd, SB_VERT, &si, TRUE);
}
void setScrollBarSize(HWND hwnd, int s)
{
SCROLLINFO si = { 0 };
si.cbSize = sizeof(SCROLLINFO);
si.fMask = SIF_RANGE;
si.nMin = 0;
si.nMax = s;
SetScrollInfo(hwnd, SB_VERT, &si, TRUE);
}
int getHeight(HWND control)
{
RECT rt;
if(!GetWindowRect(control, &rt)) {
ErrorExit(NAMEOF(getHeight), __LINE__, __FILENAME__);
}
return rt.bottom - rt.top;
}
void displayText(HWND h)
{
int len = GetWindowTextLength(h);
if(len == 0) {
return;
}
wchar_t buffer[len + 1];
memset(buffer, 0, sizeof(buffer));
GetWindowText(h, buffer, len+1);
MessageBox(NULL, buffer, L"control text = ", MB_OK);
}
int scrollHeight(void)
{
int minTop = 0;
int maxBottom = 0;
RECT rt = {0};
if(allControls_indx == 0) {
return 0;
}
#if 0
assert(allControls[0] == hMainWindow);
assert(allControls[allControls_indx - 1] == hEdit1);
#endif
if(!GetWindowRect(allControls[0], &rt)) {
ErrorExit(NAMEOF(scrollHeight), __LINE__, __FILENAME__);
}
minTop = rt.top;
if(!GetWindowRect(allControls[allControls_indx - 1], &rt)) {
ErrorExit(NAMEOF(scrollHeight), __LINE__, __FILENAME__);
}
maxBottom = rt.bottom;
return maxBottom - minTop;
}
RECT GetLocalCoordinates(HWND hWnd)
{
RECT Rect;
GetWindowRect(hWnd, &Rect);
MapWindowPoints(HWND_DESKTOP, GetParent(hWnd), (LPPOINT) &Rect, 2);
return Rect;
}
void InsertTabItem(HWND tabHwnd, UINT id, LPWSTR text)
{
TCITEMW tci = {0};
tci.mask = TCIF_TEXT;
tci.pszText = text;
tci.cchTextMax = lstrlenW(text);
SendMessage(tabHwnd, TCM_INSERTITEM, id, (LPARAM) &tci);
}
void InitComControls()
{
INITCOMMONCONTROLSEX icex;
/* initialize this component is required to use tab control,
it seems.
*/
icex.dwSize = sizeof(INITCOMMONCONTROLSEX);
icex.dwICC = ICC_TAB_CLASSES;
InitCommonControlsEx(&icex);
}
// display the error message from last error seen then
// exit the application, with that last error code seen.
// to test function, do something like:
// if(!GetProcessId(NULL))
// errorExit(TEXT("GetProcessId"));
// not quite a unittest but yeah.
void ErrorExit(LPWSTR lpszFunction, int line, LPWSTR filename)
{
DWORD dw = ShowLastError(lpszFunction, line, filename);
ExitProcess(dw);
}
DWORD ShowLastError(LPWSTR lpszFunction, int line, LPWSTR filename)
{
#define MAX_DIGITS 16
/*
* NOTE!!: calling GetLastError() must be done before calling
* any other function, that would reset the GetLastError(), making
* this function report error about the wrong function.
*/
DWORD dw = GetLastError();
LPVOID lpMsgBuf;
LPVOID lpDisplayBuf;
FormatMessage(
FORMAT_MESSAGE_ALLOCATE_BUFFER |
FORMAT_MESSAGE_FROM_SYSTEM |
FORMAT_MESSAGE_IGNORE_INSERTS,
NULL,
dw,
MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
(LPTSTR) &lpMsgBuf,
0,
NULL
);
lpDisplayBuf = (LPVOID) LocalAlloc(LMEM_ZEROINIT,
(lstrlen((LPCTSTR)lpMsgBuf) +
lstrlen((LPCTSTR)lpszFunction) + 40 +
(line > 0 ? MAX_DIGITS : 0) +
(filename != NULL ? lstrlen(filename) : 0)) *
sizeof(TCHAR)
);
StringCchPrintf((LPTSTR)lpDisplayBuf,
LocalSize(lpDisplayBuf) / sizeof(TCHAR),
TEXT("%s failed with %d: %s"),
lpszFunction, dw, lpMsgBuf
);
MessageBox(NULL, (LPCTSTR)lpDisplayBuf, TEXT("Error"), MB_OK);
LocalFree(lpMsgBuf);
LocalFree(lpDisplayBuf);
return dw;
}
I think there is no problem with your calculation method. But you added the handle of the main window hwnd for the first time, which leads to the fact that the minTop you get in GetWindowRect(allControls[0], &rt) is the top coordinate of the main window, which caused a gap at the end of the display area.
However, you should actually get the coordinates of minTop from hLabel1 so that you won't attend the question.
In addition, you forgot to add hRemoveButton to the allControls array.
Solution: You can choose not to add the main window to the allControls array, or use GetWindowRect(allControls[1], &rt) to get the coordinates of minTop.
if (!GetWindowRect(allControls[1], &rt)) {
ErrorExit((LPWSTR)NAMEOF(scrollHeight), __LINE__, (LPWSTR)__FILENAME__);
}
minTop = rt.top;
Edit:
The reason why part of the edit box is cropped is that your hLabel1 is set to a height of 10 compared to the top, so when the top of hLabel1 is used as minTop, the length of the bottom is reduced by 10 units.
You need to add the y size of the topmost control:
return maxBottom - minTop + y; //The y size of the topmost control.
How do I calculate the value to set into SCROLLINFO.nMax to my window? currently I'm looping over all the controls in the window, keeping track of the smallest top and highest bottom values, so that I could get the size of the whole window, including those out of display area, not currently being show but still there. But something is wrong, I'm getting a big empty area in the end of scrollbar, it seems nMax is too large. what am I missing? once you scroll down entirely, it's supposed the window until the edit box show up. What the gab looks like now:
I'm getting this size like this:
int scrollHeight(void)
{
int mTop = 0;
int mBottom = 0;
RECT rt = {0};
for(int i = 0; i < MAX_CONTROLS; i++)
{
HWND h = allControls[i];
if(h == NULL) break;
memset(&rt, 0, sizeof(RECT));
if(!GetWindowRect(h, &rt))
{
ErrorExit(NAMEOF(scrollHeight), __LINE__, __FILENAME__);
}
mBottom = my_max(mBottom, rt.bottom);
mTop = my_min(mTop, rt.top);
}
return mBottom - mTop;
}
setting the scrollbar like this:
void setUpScrollBar(HWND hwnd)
{
RECT rc = { 0 };
GetClientRect(hwnd, &rc);
SCROLLINFO si = { 0 };
si.cbSize = sizeof(SCROLLINFO);
si.fMask = SIF_ALL;
si.nMin = 0;
si.nMax = scrollHeight();
si.nPage = (rc.bottom - rc.top);
si.nPos = 0;
si.nTrackPos = 0;
SetScrollInfo(hwnd, SB_VERT, &si, TRUE);
}
full code:
#pragma comment(lib, "user32.lib")
#pragma comment(lib, "Comctl32.lib")
#pragma comment(lib, "Gdi32.lib")
#define WIN32_LEAN_AND_MEAN
#define UNICODE
#define _UNICODE
#include <windows.h>
#include <Commctrl.h>
#include <crtdbg.h>
#include <strsafe.h>
#include <string.h>
#include <assert.h>
#ifdef UNICODE
#define STRSPLIT wcsrchr
#else
#define STRSPLIT strrchr
#endif
#define __FILENAME__ (STRSPLIT(TEXT(__FILE__), '/') ? STRSPLIT(TEXT(__FILE__), '/') + 1 : TEXT(__FILE__))
#define NAMEOF(s) TEXT(#s)
#define COUNTOF(a) (sizeof(a)/sizeof(a[0]))
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
LRESULT CALLBACK CreateTabProc(HWND, UINT, WPARAM, LPARAM);
void ErrorExit(LPWSTR lpszFunction, int line, LPWSTR filename);
void InitComControls();
void ErrorExit(LPWSTR lpszFunction, int line, LPWSTR filename);
DWORD ShowLastError(LPWSTR lpszFunction, int line, LPWSTR filename);
void InitComControls();
void CreateTab(HWND hwnd);
void InsertTabItem(HWND tabHwnd, UINT id, LPWSTR text);
void CreateButtons(HWND hwnd);
RECT GetLocalCoordinates(HWND hWnd);
int scrollHeight(void);
int getHeight(HWND control);
void setUpScrollBar(HWND hwnd);
void pushControl(HWND);
inline int my_max(int a, int b);
inline int my_min(int a, int b);
void showText(HWND hwnd);
HINSTANCE ghInstance;
HWND hTab;
HWND hLabel1, hLabel2;
HWND hEdit1;
#define MAX_CONTROLS 8
static const wchar_t *title[] = { L"Button A1", L"Button B2", L"Button C3",
L"Button D4", L"Button E5", L"Button F6",
L"Button G" , L"Button 001", L"Button 002",
L"Button 003", L"Button 004",
L"Button 005", L"Button 006" };
HWND hButton[sizeof(title)/sizeof(title[0])] = {0};
HWND allControls[MAX_CONTROLS];
int allControls_indx = 0;
int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
PWSTR pCmdLine, int nCmdShow)
{
MSG msg = {0};
HWND hwnd;
WNDCLASSW wc = {0};
wc.lpszClassName = L"Window";
wc.hInstance = hInstance;
wc.hbrBackground = GetSysColorBrush(COLOR_3DFACE);
wc.lpfnWndProc = WndProc;
wc.hCursor = LoadCursor(0, IDC_ARROW);
InitComControls();
if(!RegisterClass(&wc)) {
ErrorExit(NAMEOF(RegisterClass), __LINE__, __FILENAME__);
}
int width = 500;
int height = 350/2; // half than the usual size, so that the scrollbar show up and we can test it
int screenWidth = GetSystemMetrics(SM_CXSCREEN);
int screenHeight = GetSystemMetrics(SM_CYSCREEN);
int cx = (screenWidth - width) / 2;
int cy = (screenHeight - height) / 2;
hwnd = CreateWindowW(wc.lpszClassName, L"Window",
WS_OVERLAPPEDWINDOW | WS_VISIBLE,
cx, cy, width, height, NULL, NULL,
hInstance, NULL);
pushControl(hwnd); // push main window too
ghInstance = hInstance;
while (GetMessage(&msg, NULL, 0, 0))
{
if (!IsDialogMessage(hwnd, &msg))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
return (int) msg.wParam;
}
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
static int g_scrollY;
switch(msg)
{
case WM_CREATE:
hLabel1 = CreateWindowW(L"Static", L"This is label 1...",
WS_VISIBLE | WS_CHILD | WS_TABSTOP,
50, 10, 130, 25, hwnd, (HMENU) 18, NULL, NULL);
pushControl(hLabel1);
hLabel2 = CreateWindowW(L"Static", L"This is label 2...",
WS_VISIBLE | WS_CHILD | WS_TABSTOP,
50, 40, 130, 25, hwnd, (HMENU) 19, NULL, NULL);
pushControl(hLabel2);
CreateTab(hwnd);
CreateButtons(hwnd);
setUpScrollBar(hwnd);
//ChangeToDefaultFont(hwnd);
break;
case WM_VSCROLL:
{
int action = LOWORD(wParam);
//HWND hScroll = (HWND)lParam;
int pos = -1;
if (action == SB_THUMBPOSITION || action == SB_THUMBTRACK) {
pos = HIWORD(wParam);
} else if (action == SB_LINEDOWN) {
pos = g_scrollY + 30;
} else if (action == SB_LINEUP) {
pos = g_scrollY - 30;
}
if (pos == -1)
break;
SCROLLINFO si = { 0 };
si.cbSize = sizeof(SCROLLINFO);
si.fMask = SIF_POS;
si.nPos = pos;
si.nTrackPos = 0;
SetScrollInfo(hwnd, SB_VERT, &si, TRUE);
GetScrollInfo(hwnd, SB_VERT, &si);
pos = si.nPos;
POINT pt;
pt.x = 0;
pt.y = pos - g_scrollY;
HDC hdc = GetDC(hwnd);
LPtoDP(hdc, &pt, 1);
ReleaseDC(hwnd, hdc);
ScrollWindow(hwnd, 0, -pt.y, NULL, NULL);
g_scrollY = pos;
return 0;
}
break;
case WM_DESTROY:
PostQuitMessage(0);
return 0;
}
return DefWindowProc(hwnd, msg, wParam, lParam);
}
void pushControl(HWND hwnd)
{
if(allControls_indx > MAX_CONTROLS) {
assert(!"no room for extra controls");
}
allControls[allControls_indx++] = hwnd;
}
void CreateTab(HWND hwnd)
{
hTab =
CreateWindow(WC_TABCONTROLW, NULL,
WS_CHILD | WS_VISIBLE | WS_CLIPSIBLINGS | WS_TABSTOP,
100, 80, 400, 250,
hwnd,
(HMENU) 1,
NULL,
NULL);
InsertTabItem(hTab, 2, L"Tab 1");
InsertTabItem(hTab, 3, L"Tab b");
pushControl(hTab);
}
void CreateButtons(HWND hwnd)
{
RECT rt = GetLocalCoordinates(hTab);
TabCtrl_AdjustRect(hTab, FALSE, &rt);
RECT rt2 = {0};
GetWindowRect(hTab, &rt2);
int tab_width = rt2.right - rt2.left;
int tab_height = rt2.bottom - rt2.top;
int id = 4;
const int cy_breakSize = 25;
int cx_initPos = rt.left;
int cy_initPos = rt.top;
int cx = cx_initPos;
int cy = cy_initPos;
const int button_width = 80;
const int button_height = 25;
const int cx_margin = 10;
int nMaxButtonPerRow = tab_width / (button_width + cx_margin);
for(int i = 0; i < sizeof(title)/sizeof(title[0]); ++i)
{
if(i != 0 && (i % nMaxButtonPerRow) == 0) {
cy += cy_breakSize;
cx = cx_initPos;
}
hButton[i] =
CreateWindow(L"button", title[i],
WS_VISIBLE | WS_CHILD | WS_TABSTOP | ES_AUTOHSCROLL,
cx,
cy,
button_width,
button_height,
hwnd, (HMENU) id++, NULL, NULL);
cx += button_width;
}
const int edit_width = 180;
const int edit_height = 25;
hEdit1 = CreateWindow(L"Edit", L"Hello, world!",
WS_VISIBLE | WS_CHILD | WS_BORDER,
cx,
// put below tab control's display area
getHeight(hTab) + cx,
edit_width,
edit_height,
hwnd,
(HMENU) id++,
NULL, NULL);
pushControl(hEdit1);
cx += edit_width;
}
void setUpScrollBar(HWND hwnd)
{
RECT rc = { 0 };
GetClientRect(hwnd, &rc);
SCROLLINFO si = { 0 };
si.cbSize = sizeof(SCROLLINFO);
si.fMask = SIF_ALL;
si.nMin = 0;
si.nMax = scrollHeight();
si.nPage = (rc.bottom - rc.top);
si.nPos = 0;
si.nTrackPos = 0;
SetScrollInfo(hwnd, SB_VERT, &si, TRUE);
}
int getHeight(HWND control)
{
RECT rt;
if(!GetWindowRect(control, &rt)) {
ErrorExit(NAMEOF(getHeight), __LINE__, __FILENAME__);
}
return rt.bottom - rt.top;
}
int scrollHeight(void)
{
int mTop = 0;
int mBottom = 0;
RECT rt = {0};
for(int i = 0; i < MAX_CONTROLS; i++)
{
HWND h = allControls[i];
if(h == NULL) break;
memset(&rt, 0, sizeof(RECT));
if(!GetWindowRect(h, &rt))
{
ErrorExit(NAMEOF(scrollHeight), __LINE__, __FILENAME__);
}
mBottom = my_max(mBottom, rt.bottom);
mTop = my_min(mTop, rt.top);
}
return mBottom - mTop;
}
inline int my_max(int a, int b)
{
return a > b ? a : b;
}
inline int my_min(int a, int b)
{
return a < b ? a : b;
}
RECT GetLocalCoordinates(HWND hWnd)
{
RECT Rect;
GetWindowRect(hWnd, &Rect);
MapWindowPoints(HWND_DESKTOP, GetParent(hWnd), (LPPOINT) &Rect, 2);
return Rect;
}
void InsertTabItem(HWND tabHwnd, UINT id, LPWSTR text)
{
TCITEMW tci = {0};
tci.mask = TCIF_TEXT;
tci.pszText = text;
tci.cchTextMax = lstrlenW(text);
SendMessage(tabHwnd, TCM_INSERTITEM, id, (LPARAM) &tci);
}
void InitComControls()
{
INITCOMMONCONTROLSEX icex;
/* initialize this component is required to use tab control,
it seems.
*/
icex.dwSize = sizeof(INITCOMMONCONTROLSEX);
icex.dwICC = ICC_TAB_CLASSES;
InitCommonControlsEx(&icex);
}
// display the error message from last error seen then
// exit the application, with that last error code seen.
// to test function, do something like:
// if(!GetProcessId(NULL))
// errorExit(TEXT("GetProcessId"));
// not quite a unittest but yeah.
void ErrorExit(LPWSTR lpszFunction, int line, LPWSTR filename)
{
DWORD dw = ShowLastError(lpszFunction, line, filename);
ExitProcess(dw);
}
DWORD ShowLastError(LPWSTR lpszFunction, int line, LPWSTR filename)
{
#define MAX_DIGITS 16
/*
* NOTE!!: calling GetLastError() must be done before calling
* any other function, that would reset the GetLastError(), making
* this function report error about the wrong function.
*/
DWORD dw = GetLastError();
LPVOID lpMsgBuf;
LPVOID lpDisplayBuf;
FormatMessage(
FORMAT_MESSAGE_ALLOCATE_BUFFER |
FORMAT_MESSAGE_FROM_SYSTEM |
FORMAT_MESSAGE_IGNORE_INSERTS,
NULL,
dw,
MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
(LPTSTR) &lpMsgBuf,
0,
NULL
);
lpDisplayBuf = (LPVOID) LocalAlloc(LMEM_ZEROINIT,
(lstrlen((LPCTSTR)lpMsgBuf) +
lstrlen((LPCTSTR)lpszFunction) + 40 +
(line > 0 ? MAX_DIGITS : 0) +
(filename != NULL ? lstrlen(filename) : 0)) *
sizeof(TCHAR)
);
StringCchPrintf((LPTSTR)lpDisplayBuf,
LocalSize(lpDisplayBuf) / sizeof(TCHAR),
TEXT("%s failed with %d: %s"),
lpszFunction, dw, lpMsgBuf
);
MessageBox(NULL, (LPCTSTR)lpDisplayBuf, TEXT("Error"), MB_OK);
LocalFree(lpMsgBuf);
LocalFree(lpDisplayBuf);
return dw;
}
This line in your scrollHeight() function is the problem:
mTop = my_min(mTop, rt.top);
mTop starts out as 0, so will always be the minimum. Instead of the distance between the top and bottom controls you end up with the distance from the top of the screen to the bottom of the bottom control (note that because you're using GetWindowRect you are dealing with screen coordinates, not client coordinates - so this magnifies the problem).
If you change that line to the following it gives a much better result:
mTop = mTop ? my_min(mTop, rt.top) : rt.top;
On a regular combobox, you can jump to items that starts with the typed letter. e.g., if you have items like "baa", "arch", "foo", "art" and type "a" the item "arch" gets selected, you type "a" again then it jumps to "art". How can I implement this on owner-draw combobox? I thought I could handle WM_CHAR like below in the comobobox's subprocedure, however I couldn't even test it, since setting a procedure to the comobobox like that fails:
HWND hwndEdit = GetWindow(hwndCombo, GW_CHILD);
assert(hwndEdit != NULL); // fails here
lpfnEditWndProc = (WNDPROC) SetWindowLongPtr(hwndEdit, GWLP_WNDPROC, (LONG_PTR) SubClassProc);
the procecdure was going to be like this:
LRESULT CALLBACK SubClassProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
switch (msg)
{
case WM_CHAR:
{
static int prevIndex = 0;
static wchar_t buffer[2] = {0};
memset(&buffer, 0, sizeof(buffer));
buffer[0] = wParam;
prevIndex = SendMessage(hwndCombo, CB_FINDSTRING, (WPARAM) prevIndex, (LPARAM) buffer);
SendMessage(hwndCombo, CB_SETCURSEL, (WPARAM) prevIndex, 0);
return 0;
}
break;
}
return CallWindowProc(lpfnEditWndProc, hwnd, msg, wParam, lParam);
}
Here's the full code of owner-draw combobox:
#pragma comment(lib, "user32.lib")
#pragma comment(lib, "Comctl32.lib")
#pragma comment(lib, "Gdi32.lib")
#pragma comment(lib, "UxTheme.lib")
#pragma comment(lib, "Comdlg32.lib")
#define WIN32_LEAN_AND_MEAN
#define UNICODE
#define _UNICODE
#include <windows.h>
#include <Commctrl.h>
#include <assert.h>
#include <uxtheme.h>
#include <Commdlg.h>
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
void SetDefaultFont(HWND hwnd);
HFONT LoadSystemDefaultFont();
void DrawBorder(HDC hdc, RECT *rect);
void DrawLine(HDC hdc, LONG x1, LONG y1, LONG x2, LONG y2);
void freeBrushes();
HBRUSH getBrushAt(int index);
void drawColorRect(HDC dc, RECT *editRect, int colorIndex);
void EnableVisualStyles2(void);
LRESULT CALLBACK SubClassProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam);
HINSTANCE g_hinst;
HFONT hDefaultSystemFont;
HWND hwndCombo;
#define COUNTOF(a) (sizeof(a)/sizeof(a[0]))
#define LIST \
X(L"Black", RGB(0, 0, 0)) \
X(L"Red", RGB(255, 0, 0)) \
X(L"Blue", RGB(0, 0, 255)) \
X(L"Green", RGB(0, 128, 0)) \
X(L"Yellow", RGB(255, 255, 0))
#define X(a, b) a,
const wchar_t *items[] = { LIST };
#undef X
#define X(a, b) b,
const int colorCodes[] = { LIST };
#undef X
HBRUSH brushes[COUNTOF(items)];
WNDPROC lpfnEditWndProc;
enum
{
BTN_A = 20,
BTN_COMBO,
};
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);
}
DeleteObject(hDefaultSystemFont);
freeBrushes();
return (int) msg.wParam;
}
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg,
WPARAM wParam, LPARAM lParam)
{
switch(msg)
{
case WM_CREATE:
{
hwndCombo = CreateWindow(L"Combobox", NULL,
WS_CHILD | WS_VISIBLE | CBS_DROPDOWNLIST |
CBS_OWNERDRAWFIXED | CBS_AUTOHSCROLL | WS_VSCROLL | WS_HSCROLL,
10, 10, 100, 110, hwnd, (HMENU) BTN_COMBO, g_hinst, NULL);
SendMessage(hwndCombo, CB_SETMINVISIBLE, 5, 0);
SetDefaultFont(hwndCombo);
COMBOBOXINFO ci = {0};
ci.cbSize = sizeof(COMBOBOXINFO);
GetComboBoxInfo(hwndCombo, &ci);
lpfnEditWndProc = (WNDPROC)SetWindowLongPtr(ci.hwndList, GWLP_WNDPROC, (LONG_PTR)SubClassProc);
for (int i = 0; i < COUNTOF(items); ++i)
{
SendMessage(hwndCombo, CB_ADDSTRING, 0, (LPARAM) items[i]);
}
}
break;
case WM_DRAWITEM:
{
LPDRAWITEMSTRUCT b = (LPDRAWITEMSTRUCT) lParam;
SetBkMode(b->hDC, TRANSPARENT);
if(b->itemState & ODS_SELECTED)
{
FillRect(b->hDC, &b->rcItem, (HBRUSH) (COLOR_HIGHLIGHT+1));
SetTextColor(b->hDC, GetSysColor(COLOR_HIGHLIGHTTEXT+1));
}
else
{
FillRect(b->hDC, &b->rcItem, (HBRUSH) (COLOR_WINDOW+1));
SetTextColor(b->hDC, GetSysColor(COLOR_WINDOWTEXT+1));
}
if(b->itemID != -1)
{
drawColorRect(b->hDC, &b->rcItem, b->itemID);
DrawText(b->hDC, items[b->itemID], -1, &b->rcItem, DT_CENTER | DT_VCENTER | DT_SINGLELINE);
}
if(b->itemAction & ODA_FOCUS)
{
DrawFocusRect(b->hDC, &b->rcItem);
}
return (INT_PTR) TRUE;
}
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
}
return DefWindowProc(hwnd, msg, wParam, lParam);
}
HFONT LoadSystemDefaultFont()
{
if(hDefaultSystemFont == NULL) {
NONCLIENTMETRICS ncm;
ncm.cbSize = sizeof(NONCLIENTMETRICS);
SystemParametersInfo(SPI_GETNONCLIENTMETRICS, sizeof(NONCLIENTMETRICS), &ncm, 0);
hDefaultSystemFont = CreateFontIndirect(&ncm.lfMessageFont);
}
return hDefaultSystemFont;
}
void SetDefaultFont(HWND hwnd)
{
SendMessage(hwnd, WM_SETFONT, (LPARAM) LoadSystemDefaultFont(), TRUE);
}
void drawColorRect(HDC dc, RECT *editRect, int colorIndex)
{
assert(colorIndex >= 0 && colorIndex < COUNTOF(brushes));
assert(editRect != NULL);
RECT rt = {0};
rt.left = editRect->left + 2;
rt.top = editRect->top - 2;
rt.right = editRect->right / 5;
rt.bottom = editRect->bottom - 2;
InflateRect(&rt, -1, -1);
DrawBorder(dc, &rt);
//FrameRect(dc, &rt, getBrushAt(0));
FillRect(dc, &rt, getBrushAt(colorIndex));
}
void DrawLine(HDC hdc, LONG x1, LONG y1, LONG x2, LONG y2)
{
MoveToEx(hdc, x1, y1, NULL);
LineTo(hdc, x2, y2);
}
void DrawBorder(HDC hdc, RECT *rect)
{
DrawLine(hdc, rect->left, rect->top, rect->left, rect->bottom);
DrawLine(hdc, rect->left, rect->top, rect->right, rect->top);
DrawLine(hdc, rect->right, rect->top, rect->right, rect->bottom);
DrawLine(hdc, rect->left, rect->bottom, rect->right, rect->bottom);
}
HBRUSH getBrushAt(int index)
{
assert(index >= 0 && index < COUNTOF(brushes));
HBRUSH b = brushes[index];
if(b == NULL) {
int code = colorCodes[index];
brushes[index] = CreateSolidBrush(code);
b = brushes[index];
}
return b;
}
void freeBrushes()
{
for(int i = 0; i < COUNTOF(brushes); ++i){
DeleteObject(brushes[i]);
brushes[i] = NULL;
}
}
void EnableVisualStyles2(void)
{
TCHAR dir[MAX_PATH] = {0};
GetSystemDirectory(dir, sizeof(dir) / sizeof(*dir));
ACTCTX actCtx = {0};
actCtx.cbSize = sizeof(ACTCTX);
actCtx.dwFlags = ACTCTX_FLAG_RESOURCE_NAME_VALID |
ACTCTX_FLAG_SET_PROCESS_DEFAULT |
ACTCTX_FLAG_ASSEMBLY_DIRECTORY_VALID;
actCtx.lpSource = L"shell32.dll";
actCtx.lpAssemblyDirectory = dir;
actCtx.lpResourceName = (LPCTSTR) 124;
ULONG_PTR cookie = FALSE;
HANDLE h = CreateActCtx(&actCtx);
assert(h != INVALID_HANDLE_VALUE);
ActivateActCtx(h, &cookie);
}
LRESULT CALLBACK SubClassProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
switch (msg)
{
case WM_CHAR:
{
static int prevIndex = 0;
static wchar_t buffer[2] = {0};
buffer[0] = wParam;
MessageBox(NULL, buffer, L"", MB_OK);
prevIndex = SendMessage(hwndCombo, CB_FINDSTRING, (WPARAM) prevIndex, (LPARAM) buffer);
SendMessage(hwndCombo, CB_SETCURSEL, (WPARAM) prevIndex, 0);
return 0;
}
break;
}
return CallWindowProc(lpfnEditWndProc, hwnd, msg, wParam, lParam);
}
UPDDATE sorry, I past the code sample from other file than the owner-draw combobox. As pointed out by #Song Zhu - MSFT, set the procedure to properly but that still doesn't process WM_CHAR.
The drop-down COMBOBOX does not have an EDIT control. Instead, it has a drop-down list.
I recommend you to use GetComboBoxInfo to get the child window of the COMBOBOX control.
Try to modify the code as:
COMBOBOXINFO ci{};
ci.cbSize = sizeof(COMBOBOXINFO);
GetComboBoxInfo(hwndCombo, &ci);
lpfnEditWndProc = (WNDPROC)SetWindowLongPtr(ci.hwndList, GWLP_WNDPROC, (LONG_PTR)SubClassProc);
Of course, you can use this code to see that hwndItem of COMBOBOXINFO returns NULL. You can adjust which handle you need to control according to your combobox type.
Edit:
Your message loop code and setting style are wrong(need CBS_HASSTRINGS), please refer to:
while (GetMessage(&msg, NULL, 0, 0)) {
TranslateMessage(&msg);
DispatchMessage(&msg);
}
......
hwndCombo = CreateWindow(L"Combobox", NULL,
WS_CHILD | WS_VISIBLE | CBS_DROPDOWNLIST |
CBS_OWNERDRAWFIXED | CBS_AUTOHSCROLL | WS_VSCROLL | WS_HSCROLL | CBS_HASSTRINGS,
10, 10, 100, 110, hwnd, (HMENU) BTN_COMBO, g_hinst, NULL);
I'm using GetTextExtentPoint32() to measure the text size and calculate the width and height of my combobox. However, it seems to be adding margin proportional to the amount of text, that I'd to get rid of. It seems the larger the string is, the larger margin I get on right. How do I it doesn't add this margin? a small one is acceptable but look at the second image, the big empty space on right.
With small strings, I find this margin acceptable:
However, with big ones, I get this big white space on right side, that I'd to get rid of:
I'm measuring the text size like this:
int len = wcslen(s);
HDC dc = GetDC(hwndCombo);
SIZE sz;
assert(GetTextExtentPoint32(dc, s, len, &sz));
ReleaseDC(hwndCombo, dc);
int weight = sz.cx + 10;
int height = sz.cy;
assert(SetWindowPos(hwndCombo, HWND_TOP, 0, 0, weight, height, SWP_NOMOVE));
full code:
#pragma comment(lib, "user32.lib")
#pragma comment(lib, "Comctl32.lib")
#pragma comment(lib, "Gdi32.lib")
#pragma comment(lib, "Comdlg32.lib")
#define WIN32_LEAN_AND_MEAN
#define UNICODE
#define _UNICODE
#include <windows.h>
#include <winuser.h>
#include <assert.h>
#define COUNTOF(a) (sizeof(a)/sizeof(a[0]))
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
int largestIndex();
HFONT getDefaultFont();
void SetDefaultFont(HWND hwnd);
HFONT hDefaultSystemFont;
HINSTANCE g_hinst;
const wchar_t *items[] =
{
L"Windows", L"Mac",
L"FreeBSD", L"Arch",
L"aaaaaa!!!!!!!aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa#",
L"foo",
L"baaaa"
};
HWND hwndCombo;
enum
{
ID_COMBO = 10,
ID_BTN1,
};
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"",
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) {
switch(msg)
{
case WM_CREATE:
{
hwndCombo = CreateWindowW(L"Combobox", NULL,
WS_CHILD | WS_VISIBLE | CBS_DROPDOWN,
10, 10, 60, 110, hwnd, (HMENU) ID_COMBO, g_hinst, NULL);
for (int i = 0; i < COUNTOF(items); i++ )
{
SendMessageW(hwndCombo, CB_ADDSTRING, 0, (LPARAM) items[i]);
}
SetDefaultFont(hwndCombo);
HWND btn1 =
CreateWindowW(L"Button", L"Click me",
WS_CHILD | WS_VISIBLE,
5, 40, 90, 25, hwnd, (HMENU) ID_BTN1, g_hinst, NULL);
SetDefaultFont(btn1);
}
break;
case WM_COMMAND:
{
switch(LOWORD(wParam))
{
case ID_BTN1:
{
int i = largestIndex();
wchar_t *s = (wchar_t*) items[i];
int len = wcslen(s);
HDC dc = GetDC(hwndCombo);
SIZE sz;
assert(GetTextExtentPoint32(dc, s, len, &sz));
ReleaseDC(hwndCombo, dc);
int weight = sz.cx + 10;
int height = sz.cy;
assert(SetWindowPos(hwndCombo, HWND_TOP, 0, 0, weight, height, SWP_NOMOVE));
}
break;
default:
break;
}
}
break;
case WM_DESTROY:
DeleteObject(hDefaultSystemFont);
hDefaultSystemFont = NULL;
PostQuitMessage(0);
break;
}
return DefWindowProcW(hwnd, msg, wParam, lParam);
}
int largestIndex()
{
int m = 0;
int idx = -1;
for(int i = 0; i < COUNTOF(items); i++) {
int l = wcslen(items[i]);
if(l > m) {
m = l;
idx = i;
}
}
return idx;
}
HFONT getDefaultFont()
{
if(hDefaultSystemFont == NULL) {
NONCLIENTMETRICS ncm;
ncm.cbSize = sizeof(NONCLIENTMETRICS);
SystemParametersInfo(SPI_GETNONCLIENTMETRICS, sizeof(NONCLIENTMETRICS), &ncm, 0);
hDefaultSystemFont = CreateFontIndirect(&ncm.lfMessageFont);
}
return hDefaultSystemFont;
}
void SetDefaultFont(HWND hwnd)
{
SendMessage(hwnd, WM_SETFONT, (LPARAM) getDefaultFont(), TRUE);
}
You are using different font for measurements.
Try
int len = wcslen(s);
HDC dc = GetDC(hwndCombo);
SIZE sz;
// Set correct font
HFONT old = SelectObject(dc,hDefaultSystemFont);
// or
// HFONT control_font = (HFONT)SendMessage(hwndCombo, WM_GETFONT, 0, 0);
// HFONT old = SelectObject(dc,control_font);
assert(GetTextExtentPoint32(dc, s, len, &sz));
// Restore font for cleanup
SelectObject(dc,old);
ReleaseDC(hwndCombo, dc);
int weight = sz.cx + 10;
int height = sz.cy;