Handmade Hero

Intro

This is my personal code and study progress of the handmade hero project.

Progress

Day 001: Setting Up the Windows Build

• Setup the directory structure
• Make a command line with shell.bat startup script to set path and cl
• Use devenv to debug in visual studio
• WinMain: Entry of a Windows GUI program
• MessageBox: Show a message box

Day 002: Opening a Win32 Window

• Using WNDCLASS struct and RegisterClass
• Opening a window CreateWindow
• Get a window handle with GetModuleHandle
• WndProc and handling messages and DefWindowProc
• Making a loop and getting messages with GetMessage, TranslateMessage, DispatchMessage
• Drawing in WM_PAIN with BeginPaint, EndPaint, PatBlt

Day 003: Allocating a Backbuffer

• Closing window with PostQuitMessage and handling it with a running variable
• #define global_variable, local_persist and internal to static
• Resize Buffer on recieving WM_SIZE
• Using GetClientRect to get window dimensions
• Allocating the buffer using CreateDIBSection using BITMAPINFO struct
• Drawing the buffer using StretchDIBits
• Creating a Device Context using CreateCompatibleDC
• Using DeleteObject to release the buffer when reallocated

Tangent #1

at the end of day 3 I wanted to use the buffer to get something on the screen so I experimented a little on my own, the following is just some tinkering and will most likely be scrapped on Day 004

• Created a RenderPixel(int x, int y, int r, int g, int b) function
• It uses the windows COLORREF definition which is a uint32
• The color value is passed using the windows RGB() macro
• Used it to render a simple sine function across the screen
• Set biHeight to negative width to get a top-down coordinate where (0,0) is at top-left corner

// Definition
internal void
RenderPixel(int x, int y, int r = 255, int g = 255, int b = 255) {
    int width = paint.rcPaint.right - paint.rcPaint.left; // ignore this way of getting the width, will be changed later
    ((COLORREF*)bitmapData)[y * width + x] = RGB(r, g, b);
}

// Sine function draw, placed in Win32UpdateWindow
for (int i = 0; i < width; ++i)
{
    /*      amplitude*sin(angle in radians)    */
    int y = 100*sin(i*3.1415/180); // sin function from math.h
    y = (height/2) - y; // negative y is up in top-down coords -> (0,0) at upper-left corner

    RenderPixel(i, y);
}

Day 004: Animating the Backbuffer

• Using VirtualAlloc to allocate the bitmap memory ourselves instead of CreateDIBSection
• Using VirtualFree to free memory allocated
• Learn about VirtualProtect which helps in debugging use-after-free errors
• Setting biHeight to negative to get top-left origin (I found this already during #Tangent #1)
• Pass (0,0) for x and y in StretchDIBits and window dimensions in dest dimensions, bitmap dimensions in src dimensions
• Render a simple gradient. Pixel has the form 0x00RRGGBB where a padding byte is left for memory alignment
• Use PeekMessage instead of GetMessage so it doesn't block
• Draw the gradient and pass changing offsets to animate it in the main loop
• Call Win32UpdateWindow in the main loop to update and draw.
  • Handle deviceContext with GetDC(window) and ReleaseDC(window, deviceContext)
  • GetClientRect to get window RECT and dimensions

Day 005: Windows Graphics Review

• HREDRAW and VREDRAW are used to tell Windows to redraw the whole window
• Pulled the bitmap global variables into win32_offscreen_buffer struct
• Pull the GetClientRect calls and calculation into a function that returns win32_window_dimensions struct
• Create the back buffer just once with constant width and height, move it out of WM_SIZE
• The stack grows down starting from WinMain, we can change it's size by specifying the /F<num_of_bytes> argument in the build command
• OWNDC is used to have a single persistent Device Context HDC per Window HWND to use across the program

Tangent #2

As the new buffer had constant size and was being stretched it had some visual artifacts of black lines showing for the stretched color data, I looked into it and found about Stretch Modes which are set using SetStretchBltMode, COLORONCOLOR (or STRETCH_DELETESCANS) is used to preserve color in bitmaps so I've gone ahead and set it and it fixed the problem.