unused ={???}

unused: <unable to read memory>

#include <Windows.h>
#include <stdint.h> //for accss to unit8_t type

// these #defines reuse 'static' with more clarfied intent
#define internal static
#define local_persist static
#define global_variable static

// these typedefs redefine types from stdint.h
//for easier typing than 'unsigned char' etc
typedef uint8_t uint8;
typedef uint16_t uint16;
typedef uint32_t uint32;
typedef uint64_t uint64;

typedef int8_t int8;
typedef int16_t int16;
typedef int32_t int32;
typedef int64_t int64;

global_variable bool Running;

global_variable BITMAPINFO BitmapInfo;
global_variable void *BitmapMemory;
global_variable int BitmapWidth;
global_variable int BitmapHeight;

internal void Win32ResizeDIBSection(int Width, int Height)
{
	if (BitmapMemory)
	{
		VirtualFree(BitmapMemory, 0, MEM_RELEASE);
	}

	BitmapWidth = Width;
	BitmapHeight = Height;
	BITMAPINFO BitmapInfo;
	BitmapInfo.bmiHeader.biSize = sizeof(BitmapInfo.bmiHeader);
	BitmapInfo.bmiHeader.biWidth = BitmapWidth;
	BitmapInfo.bmiHeader.biHeight = -BitmapHeight; // negative top yield a 'top down'
	BitmapInfo.bmiHeader.biPlanes = 1;
	BitmapInfo.bmiHeader.biBitCount = 32;
	BitmapInfo.bmiHeader.biCompression = BI_RGB;

	int BytesPerPixel = 4;
	int BitmapMemorySize = (BitmapWidth * BitmapHeight) * BytesPerPixel;

	BitmapMemory = VirtualAlloc(
		0,				  //address 0 = we don't care yet
		BitmapMemorySize, //size in bytes
		MEM_COMMIT,		  // vs MEM_RESERVE
		PAGE_READWRITE	// access mode
	);

	// actually draw pixels!
	int Pitch = Width * BytesPerPixel;  // Pitch is the difference between rows of pixels in Bytes
	uint8 *Row = (uint8 *)BitmapMemory; // cast the void pointer BitmapMemory to unsigned 8 bit int
	for (int Y = 0; Y < BitmapHeight; ++Y)
	{
		//uint32 *Pixel = (uint32 *)Row; //pointer to first pixel of Row
		uint8 *Pixel = (uint8 *)Row; //pointer to first byte of first pixel of Row

		for (int X = 0; X < BitmapWidth; ++X)
		{
			/*
				32 Pixel in memory :
				RR GG BB AA (?) (as 1 byte Hex numbers)
		 	*/

			//https://www.youtube.com/watch?v=hNKU8Jiza2g&feature=youtu.be&t=1896
			// WHY NO WORK???
			*Pixel = 255;
			++Pixel;

			*Pixel = 0;
			++Pixel;

			*Pixel = 0;
			++Pixel;

			*Pixel = 0;
			++Pixel;
		}

		Row += Pitch;
	}
}

internal void Win32UpdateWindow(HDC DeviceContext, RECT *WindowRect, int x, int y, int Width, int Height)
{
	int WindowWidth = WindowRect->right - WindowRect->left;
	int WindowHeight = WindowRect->bottom - WindowRect->top;

	StretchDIBits(DeviceContext,
				  0, 0, BitmapWidth, BitmapHeight,
				  0, 0, WindowWidth, WindowHeight,
				  BitmapMemory,
				  &BitmapInfo,
				  DIB_RGB_COLORS, SRCCOPY);
}

LRESULT CALLBACK Win32MainWindowCallback(
	HWND Window,   // handle to a window
	UINT Message,  // window message we want to handle
	WPARAM WParam, // width
	LPARAM LParam) //Height
{
	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);
		OutputDebugStringA("WM_SIZE\n");
	}
	break;

	case WM_DESTROY:
	{
		//handle as error, recreate window
		Running = false;
		OutputDebugStringA("WM_DESTROY\n");
	}
	break;

	case WM_CLOSE:
	{
		//todo: handle with message to user
		Running = false;
		OutputDebugStringA("WM_CLOSE\n");
	}
	break;

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

			RECT ClientRect;
			GetClientRect(Window,&ClientRect);

			Win32UpdateWindow(DeviceContext,&ClientRect ,X,Y,Width,Height);
			PatBlt(DeviceContext, X, Y, Width, Height,BLACKNESS);
			EndPaint(Window,&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;
		RECT ClientRect;
		GetClientRect(Window, &ClientRect);
		Win32UpdateWindow(DeviceContext, &ClientRect, X, Y, Width, Height);
		EndPaint(Window, &Paint);
	}
	break;

	default:
	{

		//OutputDebugStringA("DEFAULT\n");
		Result = DefWindowProc(Window, Message, WParam, LParam);
	}
	break;
	}
	return (Result);
}

int CALLBACK WinMain(
	HINSTANCE Instance,
	HINSTANCE PrevInstance,
	LPSTR Command,
	int ShowCode)
{

	WNDCLASS WindowClass = {}; // declares a WNDCLASS instance 'windowClass', with members initialized to 0.

	WindowClass.style = CS_OWNDC | CS_HREDRAW | CS_VREDRAW; // bitfield flags to define windowstyle see MSDN
	WindowClass.lpfnWndProc = Win32MainWindowCallback;		// pointer to a function that defines window's response to events
	// WindowClass.cbClsExtra = ; // if we want to store extra bytes
	// WindowClass.cbWndExtra = ; // if we want to store extra bytes
	WindowClass.hInstance = Instance; // reference to the instance of this window, from WinMain function.(Could also use GetModuleHandle)
	// WindowClass.hIcon = ; // icon for window
	// WindowClass.hCursor = ; // cursor position
	// WindowClass.hbrBackground = ; // background brush
	// WindowClass.lpszMenuName = ; // menu name
	WindowClass.lpszClassName = "handmadeHeroWindowClass";

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

		if (WindowHandle)
		{
			MSG Message;
			Running = true;
			while (Running)
			{

				BOOL MessageResult = GetMessageA(&Message, 0, 0, 0);

				if (MessageResult > 0)
				{
					TranslateMessage(&Message);
					DispatchMessageA(&Message);
				}
				else
				{
					break;
				}
			}
		}
		else
		{
			//todo: logging
		}
	}
	else
	{
		//todo: logging
	}

	return (0);
}