WinAPI BitBlt flickering

[thawek]

Hello!

It seems this topic has been evaulated quite intensively here, but I can't get it to work anyways. This is a DLL injecting to the main APP via provided SDK. I tried to get memDC, but I still get massive flickering, and after some time (5-15 mins), I am getting completely messed up (resulting in total mess up and app crash: https://prnt.sc/zf1dh8 -> https://prnt.sc/zf0dfz )

#include "pch.h"
#include "ELW.h"
#include "ELWData.h"

int HWND_HEIGHT_CURRENT;

// Constructor
ELW::ELW()
{
	hInst = GetModuleHandle(NULL);
	 thread = CreateThread(0, NULL, ELW::ThreadProc, NULL, NULL, &threadId);
}


// WindowThread - Window Class Registry, Creation and Showing
DWORD WINAPI ELW::ThreadProc(LPVOID lpParam)
{
#pragma region WindowClassRegister
	
	// REGISTER THE WINDOW CLASS
	WNDCLASS wc = {};

	wc.lpfnWndProc = ELW::WindowProc;
	wc.hInstance = hInst;
	wc.lpszClassName = CLASS_NAME;
	wc.hCursor = LoadCursor(NULL, IDC_ARROW);


	RegisterClass(&wc);

#pragma endregion WindowClassRegister

	// CREATE THE WINDOW
#pragma region CreateWindow
	hWnd = CreateWindow(
		CLASS_NAME,					// WINDOW CLASS NAME
		WINDOW_NAME,				// WINDOW NAME
		WS_CAPTION,					// WINDOW STYLES
		CW_USEDEFAULT,				// int X
		CW_USEDEFAULT,				// int Y
		HWND_WIDTH,					// int WIDTH
		HWND_HEIGHTC,				// int HEIGHT
		NULL,						// hWnd PARENT WINDOW
		NULL,						// hMenu MENU
		hInst,						// handle Instance Handle
		NULL);						// Additional appllication data


	if (hWnd == NULL)
		return 0;

#pragma endregion CreateWindow

	// ELEMENTS


	// SHOW THE WINDOW
	ShowWindow(hWnd,SW_SHOWNORMAL);
	SetWindowPos(hWnd, HWND_TOPMOST, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE);
	// RUN THE MESSAGE LOOP
	MSG msg = {};
	while (GetMessage(&msg, NULL, 0, 0))
	{
		TranslateMessage(&msg);
		DispatchMessage(&msg);
	}

	

}

// WindowProc definition - Window Messages

LRESULT	CALLBACK ELW::WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
	switch (uMsg)
	{
		case WM_DESTROY:
			PostQuitMessage(0);
			break;

		case WM_PAINT:
			{
			ELW::DrawContent(hWnd, hInst, hdc);
			}
			break;

		case WM_CLOSE:
			{
			DestroyWindow(hWnd);
			UnregisterClass(CLASS_NAME, hInst);
			}
			break;

		case WM_SYSCOMMAND:
			{
			if (wParam == SC_CLOSE);
			break;
			}

		case WM_ERASEBKGND:
		{
			break;
		}
	}

	return DefWindowProc(hWnd, uMsg, wParam, lParam);
}

// ELW::DrawContent Content drawing - PaintStruct, hdc = BeginPaint, elements, EndPaint
void ELW::DrawContent(HWND hWnd, HINSTANCE hInst, HDC hdc)
{
	PAINTSTRUCT ps;
	hdc = BeginPaint(hWnd, &ps);
	// Bitmap double buffering
	if (GetDC(hWnd) == NULL)
		ELWmemdc = CreateCompatibleDC(hdc);
	else
		ELWmemdc = GetDC(hWnd);

	// DrawContent 
	const char* defaultFont = "Euroscope";
	int defaultFontSize = 16;
	FillRect(ELWmemdc, &ps.rcPaint, (HBRUSH)(COLOR_GRAYTEXT + 1));
	ELW::AddTextControl(ELWData::Callsign(), 5, 5, 100, 20, CUSTOM_COLOR_GREEN, defaultFontSize, defaultFont, ELWmemdc, 'l');
	ELW::AddTextControl("W", 90, 5, 25, 20, CUSTOM_COLOR_GREEN, defaultFontSize, defaultFont, ELWmemdc, NULL);
	ELW::AddTextControl("Y", 100, 5, 25, 20, CUSTOM_COLOR_LIGHTGRAY, defaultFontSize, defaultFont, ELWmemdc, NULL);
	ELW::AddTextControl(ELWData::RadioCallsign(), 130, 5, 55, 20, CUSTOM_COLOR_GREEN, defaultFontSize, defaultFont, ELWmemdc, 'l');
	ELW::AddTextControl(ELWData::SSR().c_str(), (HWND_WIDTH - 115), 5, 90, 20, CUSTOM_COLOR_WHITE, defaultFontSize, defaultFont, ELWmemdc, 'r');
	ELW::AddTextControl(ELWData::ACTypeWtc().c_str(), 35, NEWLINE, 50, 20, CUSTOM_COLOR_WHITE, defaultFontSize, defaultFont, ELWmemdc, 'l');
	ELW::AddTextControl(ELWData::ASSR().c_str(), (HWND_WIDTH - 75), NEWLINE, 50, 20, CUSTOM_COLOR_YELLOW, defaultFontSize, defaultFont, ELWmemdc, 'r');
	ELW::AddTextControl(ELWData::ADEP().c_str(), 5, 3 * NEWLINE, 40, 20, CUSTOM_COLOR_WHITE, defaultFontSize, defaultFont, ELWmemdc,'l');
	ELW::AddTextControl(ELWData::DEST().c_str(), 47, 3 * NEWLINE, 40, 20, CUSTOM_COLOR_WHITE, defaultFontSize, defaultFont, ELWmemdc, 'l');
	if (ELWData::CheckDestinationIsEP())
	{
		ELW::AddTextControl("(", 92, 3 * NEWLINE, 5, 20, CUSTOM_COLOR_WHITE, defaultFontSize, defaultFont, ELWmemdc, 'l');
		ELW::AddTextControl(ELWData::ALT().c_str(), 101, 3 * NEWLINE, 40, 20, CUSTOM_COLOR_WHITE, defaultFontSize, defaultFont, ELWmemdc, 'l');
		ELW::AddTextControl(")", 138, 3 * NEWLINE, 3, 20, CUSTOM_COLOR_WHITE, defaultFontSize, defaultFont, ELWmemdc, 'l');
		ELW::AddTextControl(ELWData::STAR().c_str(), 160, 3 * NEWLINE, 60, 20, CUSTOM_COLOR_WHITE, defaultFontSize, defaultFont, ELWmemdc, 'l');
		ELW::AddTextControl(ELWData::RWY().c_str(), 235, 3 * NEWLINE, 60, 20, CUSTOM_COLOR_WHITE, defaultFontSize, defaultFont, ELWmemdc, 'l');
	}
	ELW::AddTextControl(ELWData::NextFreq().c_str(), (HWND_WIDTH - 125), 3 * NEWLINE, 100, 20, CUSTOM_COLOR_GREEN, defaultFontSize, defaultFont, ELWmemdc, 'r');
	ELW::AddTextControl(ELWData::FPType().c_str(), 5, 4 * NEWLINE, 5, 20, CUSTOM_COLOR_YELLOW, defaultFontSize, defaultFont, ELWmemdc, 'l');
	ELW::AddTextControl(ELWData::RouteToBePassed().c_str(), 20, 4 * NEWLINE, 400, 20, CUSTOM_COLOR_WHITE, defaultFontSize, defaultFont, ELWmemdc, 'l');
	
	BitBlt(hdc, 0, 0, HWND_WIDTH, HWND_HEIGHT_CURRENT, ELWmemdc, 0, 0, SRCCOPY);
	ReleaseDC(hWnd, ELWmemdc);
	ReleaseDC(hWnd, hdc);
	EndPaint(hWnd, &ps);

};

/*ELW:AddTextControl text - Text to be labeled
xPos - initial horizontal position, yPos - initial vertical position
xSize, ySize - RECT size
rgb - Colour of the text
fontSize, fontName - font styles to be applied,
hdc - current dc, 
align - 'l' for left, 'r' for right, else for center */
void ELW::AddTextControl(const char* text, int xPos, int yPos, int xSize, int ySize, COLORREF rgb, int fontSize, const char* fontName, HDC hdc, char align)
{

	RECT TextRectangle = { xPos, yPos, ( xPos + xSize ) , ( yPos + ySize ) }; // Left, Top, Right, Bottom
	
	
	if (rgb == NULL)
		rgb = RGB(0, 0, 0);
	if (fontSize == NULL)
		fontSize = 10;
	if (fontName == NULL)
		fontName = "Euroscope";


	HFONT hFont = CreateFontA(fontSize, 8, 0, 0, 800, FALSE, FALSE, FALSE, DEFAULT_CHARSET, OUT_OUTLINE_PRECIS, CLIP_DEFAULT_PRECIS, CLEARTYPE_QUALITY, VARIABLE_PITCH, TEXT(fontName));
	SelectObject(hdc, hFont);
	SetBkMode(hdc, TRANSPARENT);
	SetTextColor(hdc, rgb);

	if (align == 'l')
		DrawTextA(hdc, text, strlen((text)), &TextRectangle, DT_LEFT | DT_NOCLIP);
	else if (align == 'r')
		DrawTextA(hdc, text, strlen((text)), &TextRectangle, DT_RIGHT | DT_NOCLIP);
	else
		DrawTextA(hdc, text, strlen((text)), &TextRectangle, DT_CENTER | DT_NOCLIP);
}

/*Force redrawing the window*/
void ELW::UpdateContent()
{
	if (ELWData::CheckIsModeS())
	{
		SetWindowPos(hWnd, NULL, 0, 0, HWND_WIDTH, HWND_HEIGHTS, SWP_NOMOVE | SWP_NOACTIVATE);
		HWND_HEIGHT_CURRENT = HWND_HEIGHTS;
	}
	else
	{
		SetWindowPos(hWnd, NULL, 0, 0, HWND_WIDTH, HWND_HEIGHTC, SWP_NOMOVE | SWP_NOACTIVATE);
		HWND_HEIGHT_CURRENT = HWND_HEIGHTC;
	}
	InvalidateRect(hWnd, NULL, TRUE);
	//RedrawWindow(hWnd, NULL, NULL, RDW_INVALIDATE);
}

// Destructor 
ELW::~ELW()
{
	SendMessage(hWnd, WM_CLOSE, 0, 0);
	WaitForSingleObject(thread, INFINITE);
	CloseHandle(thread);
};

@EDIT: Regarding the messup (as per screenshots), after debugging it crashed with CResourceException. Seems like some leak? This code is heap-allocated.

[salem c]

> thread = CreateThread(0, NULL, ELW::ThreadProc, NULL, NULL, &threadId);
The Win32 GUI API is not thread safe.

[thawek]

How can I create a window if I don't have winmain/dllmain then? Let's say I have a place where constructor (and destructor, if closed) is called from.

I tried to change DWORD WINAPI ELW::ThreadProc(LPVOID lpParam) to int WINAPI ELW::ThreadProcWinApi(HINSTANCE hInst) and call it from the constructor of the class

ELW::ELW()
{
	hInst = GetModuleHandle(NULL);
	// thread = CreateThread(0, NULL, ELW::ThreadProc, NULL, NULL, &threadId);
	ELW::ThreadProcWinApi(hInst);
}

Window opens, but it crashes (does not redraw, hangs, as well as crash once close command is sent called in the destructor:

// Destructor 
ELW::~ELW()
{
	SendMessage(hWnd, WM_CLOSE, 0, 0);
	//WaitForSingleObject(thread, INFINITE);
	//CloseHandle(thread);
	WaitForSingleObject(hInst, INFINITE);
	CloseHandle(hInst);
};

The ELW::UpdateContent() did not change, previously worked properly.

[thawek]

Rearranged some code, found HFONT and HDC leak as well the fact, that I did my double buffer incorrectly.