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Day 003 - I don't have a black blank window

Eduard Tudor
#3528
When Casey run the the program it had a black blank window but mine does not have it.

Here is my win32_handmade.cpp

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#include <windows.h>

#define local_persist 	static
#define global_variable static
#define internal		static


global_variable bool 		Running;

global_variable BITMAPINFO 	BitmapInfo;
global_variable void 		*BitmapMemory;
global_variable HBITMAP 	BitmapHandle;
global_variable HDC			BitmapDeviceContext;

internal void
Win32ResizeDIBSection(int Width, int Height)
{
	// TODO: Bulletproff this.
	// Maybe don't free first, free after then free first if that fails

	// TODO: Free our DIBSection

	if (BitmapHandle)
	{
		DeleteObject(BitmapHandle);
	}

	if (!BitmapDeviceContext)
	{
		// TODO: Should we recreate these under certain special circumstances
		BitmapDeviceContext = CreateCompatibleDC(0);
	}

	BitmapInfo.bmiHeader.biSize = sizeof(BitmapInfo.bmiHeader);
	BitmapInfo.bmiHeader.biWidth = Width;
	BitmapInfo.bmiHeader.biHeight = Height;
	BitmapInfo.bmiHeader.biPlanes = 1;
	BitmapInfo.bmiHeader.biBitCount = 32;
	BitmapInfo.bmiHeader.biCompression = BI_RGB;

	BitmapDeviceContext = CreateCompatibleDC(0);

	BitmapHandle = CreateDIBSection(
		BitmapDeviceContext, &BitmapInfo,
		DIB_RGB_COLORS, &BitmapMemory,
		0, 0);
}

internal void
Win32UpdateWindow(HDC DeviceContext, int X, int Y, int Width, int Height)
{
	StretchDIBits(
		DeviceContext,
		X, Y, Width, Height,
		X, Y, Width, Height,
		BitmapMemory,
		&BitmapInfo,
		DIB_RGB_COLORS,
		SRCCOPY);
}

LRESULT CALLBACK 
Win32MainWindowCallback(HWND 	Window,
						UINT 	Message,
						WPARAM	wParam,
						LPARAM	lParam)
{
	LRESULT Result = 0;

	switch (Message)
	{
		case WM_SIZE:
		{
			RECT ClientRect;
			GetClientRect(Window, &ClientRect);
			int Width = ClientRect.right - ClientRect.left;
			int Height = ClientRect.bottom = ClientRect.top;
			Win32ResizeDIBSection(Width, Height);
		} break;

		case WM_CLOSE:
		{
			// TODO: Handle this with a message to the user?
			Running = false;
		} break;

		case WM_ACTIVATEAPP:
		{
			OutputDebugStringA("WM_ACTIVATEAPP\n");
		} break;

		case WM_DESTROY:
		{
			// TODO: Handle this as an error - recreate window?
			Running = false;
		} break;

		case WM_PAINT:
		{
			PAINTSTRUCT Paint;
			HDC DeviceContext = BeginPaint(Window, &Paint);
			int X = Paint.rcPaint.left;
			int Y = Paint.rcPaint.top;
			int Width = Paint.rcPaint.right - Paint.rcPaint.left;
			int Height = Paint.rcPaint.bottom - Paint.rcPaint.top;
			Win32UpdateWindow(DeviceContext, X, Y, Width, Height);
			EndPaint(Window, &Paint);
		} break;

		default:
		{
			Result = DefWindowProcA(Window, Message, wParam, lParam);
//			OutputDebugStringA("default\n");
		} break;
	}
	return (Result);
}


int CALLBACK
WinMain(HINSTANCE 	Instance,
		HINSTANCE 	PrevInstance,
		LPSTR		CommandLine,
		int			ShowCode)
{
	WNDCLASSA WindowClass = {};

	WindowClass.lpfnWndProc = Win32MainWindowCallback;
	WindowClass.hInstance = Instance;
//	WindowClass.hIcon = ;
	WindowClass.lpszClassName = "HandMadeHeroWindowClass";

	if (RegisterClassA(&WindowClass))
	{
		HWND WindowHandle = CreateWindowExA(
			0,
			WindowClass.lpszClassName,
			"Handmade Hero",
			WS_OVERLAPPEDWINDOW | WS_VISIBLE,
			CW_USEDEFAULT,
			CW_USEDEFAULT,
			CW_USEDEFAULT,
			CW_USEDEFAULT,
			0, 0, Instance, 0);

		if (WindowHandle)
		{
			Running = true;
			while (Running)
			{
				MSG Message;
				BOOL MessageResult = GetMessageA(&Message, 0, 0, 0);
				if (MessageResult > 0)
				{
					TranslateMessage(&Message);
					DispatchMessageA(&Message);
				}
				else
				{
					break;
				}
			}
		}
		else
		{
			// TODO: Logging
		}
	}
	else
	{
		// TODO: Logging
	}

	return (0);
}
Mārtiņš Možeiko
#3535
You should use debugger to step through code and examine variable values to see which ones have incorrect values.

For your code you would see that in "Win32ResizeDIBSection" function argument Height will always have value 0 and bitmap will be created with 0 height. So when drawing it to window, nothing will be actually drawn.

This error happens because of this line:
1
			int Height = ClientRect.bottom = ClientRect.top;

ClientRect.top is always 0, so that gets assigned to ClientRect.bottom and to Height.
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