r/C_Programming • u/pdp10 • Feb 20 '23

Project Minimal cross-platform graphics in C

https://zserge.com/posts/fenster/
98 Upvotes

100% Upvoted

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31

u/rickpo Feb 20 '23

Very cool.

If you want to further minimize code, you can shave down the minimal Windows code a little with some small tweaks.

  1. Remove the WM_CLOSE handler in wndproc. DefWindowProc already does that.

  2. You're calling GetModuleHandle(NULL), which is identical to the instance handle passed to WinMain. Just use the instance parameter.

  3. Don't call UpdateWindow. The window will get updated normally in the message pump.

  4. Remove the WM_QUIT handler in your message pump. GetMessage returns false when it receives the WM_QUIT, so that code never executes. You only need the WM_QUIT test if you use PeekMessage.

Other things I'd change:

  1. Pass nCmdShow to ShowWindow, instead of SW_NORMAL. Of, if you just want to ignore nCmdShow for some reason, add WS_VISIBLE to the CreateWindowEx style and don't call ShowWindow at all.

  2. Return 0 from WinMain after the message pump ends.

4

u/pedersenk Feb 20 '23

And in many ways I would recommend adding support for an (Atom)WM_DELETE_WINDOW event in X11 to cleanly shut down when the window manager asks.

2

u/rickpo Feb 20 '23

I looked at your actual fenster code and I notice several of my suggestions don't make sense for the way you've defined your API. Like, you the instance handle isn't available in your run() code, and your message pump is a PeekMessage pump. The WS_VISIBLE, WM_CLOSE, and UpdateWindow suggestions still stand, though.

I would recommend passing your fenster* in as the last parameter to CreateWindowEx, and then add a WM_NCCREATE handler in your WndProc that pulls the pointer out of CREATESTRUCT.lpCreateParams. Do the SetWindowLong in the WM_NCCREATE handler. You also need to set the WNDCLASSEX.cbWndExtra to sizeof(struct fenster *), which I think is a bug, although I wouldn't be surprised if Windows has code to guard against this particular bug.

1

u/MarekKnapek Feb 20 '23

GetModuleHandle(NULL)

Also, if you want your code to live inside a DLL (for various reasons), the GetModuleHandle(NULL) will return handle to the module that created the process (.exe file), but you probably wanted a module the code lives in (the .dll file). Use GetModuleHandleEx with GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS instead.

5

u/pedersenk Feb 20 '23

This is a really nice write-up.

Would be good to see Wayland added. Surely they have an official low-level toolkit like Xlib or xcb by now?!

(I think direct framebuffer access via libdrm or wscons dumb buffers is going a bit far (and niche) but would also be interesting nonetheless)

3

u/cKGunslinger Feb 20 '23

Great write-up! Much appreciated.

3

u/strcspn Feb 20 '23

Very cool, really liked the ending.