Handmade Hero

gamedev programming yt performance

• game programming series by Casey Muratori
• complete youtube playlist

main loop

static bool Running;
 
if (WindowHandle) {
	while (Running) {
		MSG Message;
		BOOL MessageResult = GetMessageA(&Message, 0 ,0, 0);
		if (MessageResult > 0) {
			TranslateMessage(&Message);
			DispatchMessage(&Message);
		}
	else {
		break;
	}
	}
}

backbuffer

Slightly slower method but good for learning, render everything yourself and send it to Windows to show, later on you should leverage the GPU.

internal void
Win32ResizeDIBSection(int Width, int Height) {
	if (BitmapHandle) {
		DeleteObject(BitmapHandle);
	}
 
	BITMAPINFO BitmapInfo;
	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;
	BitmapInfo.bmiHeader.biSizeImage = 0;
	...
	HDC DeviceContext = GetCompatibleDC(0);
	HBITMAP BitmapHandle = CreateDIBSection(
		DeviceContext, &BitmapInfo,
		DIB_RGB_COLORS, &BitmapMemory,
		0, 0);
 
	ReleaseContext(0, DeviceContext);
}
 
internal void
Win32UpdateWindow(HDC DeviceContext, int X, int Y, int Width, int Height) {
	StretchDIBits(  DeviceContext,
					X, Y, Width, Height,
					X, Y, Width, Height,
					const VOID *lpBits,
					const BITMAPINFO *lpBitsInfo,
					DIB_RGB_COLORS, SRCCOPY);
}

Memory

global_variable void *BitmapMemory;
...
if (BitmapMemory) {
	VirtualFree(BitmapMemory, 0, MEM_RELEASE);
}
 
int BytesPerPixel = 4;
int BitmapMemorySize = (Width*Height)*BytesPerPixel;
BitmapMemory = VirtualAlloc(0, BitmapMemorySize, MEM_COMMIT, PAGE_READWRITE);
...
int WidownWidth = WindowRect->right - WindowRect->left;
int WidownHeight = WindowRect->bottom - WindowRect->top;
StretchDIBits(DeviceContext,
				0,0,BitmapWidth,BitmapHeight,
				0,0,WindowWidth,WindowHeight,
				BitmapMemory, &BitmapInfo,
				DIB_RGB_COLORS, SRCCOPY);
...
int Pitch = Width*BytesPerPixel;
uint8 *Row = (uint8 *)BitmapMemory;
for(int Y = 0; Y<BitmapHeight; ++Y) {
	uint8 *Pixel = (uint8 *)Row;
	for(int X = 0; X<BetmapWidth;; ++X) {
		// this is a little endian architecture
		// so the CPU puts the first BYTE in the lowest position in memory
		// 0xBBGGRRxx
		*Pixel = 0;
		++Pixel;
		*Pixel = 0;
		++Pixel;
		*Pixel = 255;
		++Pixel;
		*Pixel = 0; // padding to have 4B alignment
		++Pixel;
	}
	Row += Pitch;
}

Animating the gradient

internal void
RenderWeirdGradient(int XOffset, intYOffset) {
	int Pitch = Width*BytesPerPixel;
	uint8 *Row = (uint8 *)BitmapMemory;
	for(int Y = 0; Y<BitmapHeight; ++Y) {
		uint8 *Pixel = (uint8 *)Row;
		for(int X = 0; X<BetmapWidth;; ++X) {
		// this is a little endian architecture
		// so the CPU puts the first BYTE in the lowest position in memory
		// 0xBBGGRRxx
			*Pixel = (uint8)(X + XOffset);
			++Pixel;
			*Pixel = (uint8)(Y + YOffset);
			++Pixel;
			*Pixel = 0;
			++Pixel;
			*Pixel = 0; // padding to have 4B alignment
			++Pixel;
		}
		Row += Pitch;
	}
}

Non Blocking msg queue

int XOffset = 0;
int YOffset = 0;
while(Running) {
	MSG Message;
	while(PeekMessage(&Message,0,0,0,PM_REMOVE)) {
		if(Message.message == WM_QUIT) {
			Running = false;
		}
		TranslateMessage(&Message);
		DispatchMessage(&Message);
	}
	RenderWeirdGradient(XOffset, YOffset);
	HDC DeviceContext = GetDC(WindowHandle);
	...
	Win32UpdateWindow(DeviceContext, WindowRect, 
						0, 0, WindowWidth, WindowHeight);
	ReleaseDC(WindowHandle, DeviceContext);
	++XOffset;
}