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@mmozeiko
Last active June 18, 2023 20:42
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What would you like to do?
drawing pixels in software & showing them to window by uploading via D3D11
#define COBJMACROS
#define NOMINMAX
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <d3d11.h>
#include <stdint.h>
#include <string.h>
#include <intrin.h>
#pragma comment(lib, "d3d11.lib")
#pragma comment(lib, "dxguid.lib")
#pragma comment(lib, "user32.lib")
#define Assert(cond) do { if (!(cond)) __debugbreak(); } while (0)
static LRESULT WINAPI WindowProc(HWND wnd, UINT msg, WPARAM wparam, LPARAM lparam)
{
switch (msg)
{
case WM_DESTROY:
PostQuitMessage(0);
return 0;
}
return DefWindowProcW(wnd, msg, wparam, lparam);
}
int WINAPI wWinMain(HINSTANCE instance, HINSTANCE prev, LPWSTR cmdline, int cmdshow)
{
WNDCLASSEXW wc =
{
.cbSize = sizeof(wc),
.lpfnWndProc = WindowProc,
.hInstance = instance,
.lpszClassName = L"pixels",
};
ATOM atom = RegisterClassExW(&wc);
Assert(atom);
HWND window = CreateWindowExW(
WS_EX_APPWINDOW,
wc.lpszClassName, L"pixels",
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT,
NULL, NULL, instance, NULL);
Assert(window);
ID3D11Device* device;
ID3D11DeviceContext* context;
IDXGISwapChain* swapChain;
ID3D11Texture2D* backBuffer = NULL;
ID3D11Texture2D* cpuBuffer = NULL;
RECT rect;
GetClientRect(window, &rect);
DWORD width = rect.right;
DWORD height = rect.bottom;
DXGI_SWAP_CHAIN_DESC desc =
{
.BufferDesc =
{
.Width = width,
.Height = height,
.RefreshRate = { 60, 1 },
.Format = DXGI_FORMAT_B8G8R8A8_UNORM,
},
.SampleDesc = { 1, 0 },
.BufferUsage = DXGI_USAGE_BACK_BUFFER,
.BufferCount = 1,
.OutputWindow = window,
.Windowed = TRUE,
.SwapEffect = DXGI_SWAP_EFFECT_DISCARD,
};
DWORD flags = 0;
#ifndef NDEBUG
flags |= D3D11_CREATE_DEVICE_DEBUG;
#endif
HRESULT hr = D3D11CreateDeviceAndSwapChain(
NULL, D3D_DRIVER_TYPE_HARDWARE, NULL, flags, NULL, 0, D3D11_SDK_VERSION,
&desc, &swapChain, &device, NULL, &context);
if (FAILED(hr))
{
// try WARP software driver in case hardware one failed (like in RDP session)
hr = D3D11CreateDeviceAndSwapChain(
NULL, D3D_DRIVER_TYPE_WARP, NULL, flags, NULL, 0, D3D11_SDK_VERSION,
&desc, &swapChain, &device, NULL, &context);
}
Assert(SUCCEEDED(hr));
uint32_t* pixels = NULL;
ShowWindow(window, SW_SHOWDEFAULT);
for (;;)
{
MSG msg;
while (PeekMessageW(&msg, NULL, 0, 0, PM_REMOVE))
{
if (msg.message == WM_QUIT)
{
ExitProcess(0);
}
TranslateMessage(&msg);
DispatchMessageW(&msg);
}
GetClientRect(window, &rect);
DWORD newWidth = rect.right;
DWORD newHeight = rect.bottom;
// handle resize
if ((width != newWidth || height != newHeight) || !pixels)
{
if (pixels)
{
VirtualFree(pixels, 0, MEM_RELEASE);
ID3D11Texture2D_Release(backBuffer);
ID3D11Texture2D_Release(cpuBuffer);
backBuffer = NULL;
cpuBuffer = NULL;
pixels = NULL;
}
width = newWidth;
height = newHeight;
// in case window is minimized, the size will be 0, no need to allocate resources
if (width && height)
{
pixels = VirtualAlloc(NULL, width * height * sizeof(*pixels), MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
Assert(pixels);
hr = IDXGISwapChain_ResizeBuffers(swapChain, 1, width, height, DXGI_FORMAT_B8G8R8A8_UNORM, 0);
Assert(SUCCEEDED(hr));
hr = IDXGISwapChain_GetBuffer(swapChain, 0, &IID_ID3D11Texture2D, (void**)&backBuffer);
Assert(SUCCEEDED(hr));
D3D11_TEXTURE2D_DESC texDesc =
{
.Width = width,
.Height = height,
.MipLevels = 1,
.ArraySize = 1,
.Format = DXGI_FORMAT_B8G8R8A8_UNORM,
.SampleDesc = { 1, 0 },
.Usage = D3D11_USAGE_DYNAMIC,
.BindFlags = D3D11_BIND_SHADER_RESOURCE,
.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE,
};
hr = ID3D11Device_CreateTexture2D(device, &texDesc, NULL, &cpuBuffer);
Assert(SUCCEEDED(hr));
}
}
// do your drawing to memory
if (pixels)
{
static DWORD counter;
for (int y = 0; y < height; y++)
{
for (int x = 0; x < width; x++)
{
DWORD r = (((x + counter) % width) * 255 / width);
DWORD g = (y * 255 / height);
DWORD b = 0;
pixels[y * width + x] = (r << 16) | (g << 8) | (b << 0);
}
}
counter++;
}
// copy pixel memory to GPU
if (width && height)
{
D3D11_MAPPED_SUBRESOURCE mapped;
hr = ID3D11DeviceContext_Map(context, (ID3D11Resource*)cpuBuffer, 0, D3D11_MAP_WRITE_DISCARD, 0, &mapped);
Assert(SUCCEEDED(hr));
// you can avoid doing this loop by writing your pixels directly to this memory
// then you won't need VirtualAlloc/VirtualFree for "pixels" pointer
for (DWORD y=0; y<height; y++)
{
memcpy((BYTE*)mapped.pData + y * mapped.RowPitch, pixels + y * width, width * sizeof(uint32_t));
}
ID3D11DeviceContext_Unmap(context, (ID3D11Resource*)cpuBuffer, 0);
ID3D11DeviceContext_CopyResource(context, (ID3D11Resource*)backBuffer, (ID3D11Resource*)cpuBuffer);
}
// swap buffers to display to window, 1 here means use vsync
hr = IDXGISwapChain_Present(swapChain, 1, 0);
if (hr == DXGI_STATUS_OCCLUDED)
{
// window is not visible, no vsync is possible, so sleep a bit instead
// no need for this if you don't use vsync
Sleep(5);
}
else
{
Assert(SUCCEEDED(hr));
}
}
}
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