ports/doom: Allow doomgeneric to write directly to window framebuffer

This prevents an unnecessary `malloc` of the framebuffer and a copy
every frame.

ports/doom/patches/0003-Remove-unnecessary-copy-from-framebuffer.patch

@@ -0,0 +1,47 @@
+From 70c235938f0b64c4f08a478d3107e5254ad904c6 Mon Sep 17 00:00:00 2001
+From: Bananymous <bananymousosq@gmail.com>
+Date: Wed, 27 Nov 2024 13:28:42 +0200
+Subject: [PATCH] Remove unnecessary copy from framebuffer
+
+---
+ doomgeneric/doomgeneric.c            | 2 --
+ doomgeneric/doomgeneric_banan_os.cpp | 6 +++---
+ 2 files changed, 3 insertions(+), 5 deletions(-)
+
+diff --git a/doomgeneric/doomgeneric.c b/doomgeneric/doomgeneric.c
+index 782a7e7..f4eb63e 100644
+--- a/doomgeneric/doomgeneric.c
++++ b/doomgeneric/doomgeneric.c
+@@ -18,8 +18,6 @@ void doomgeneric_Create(int argc, char **argv)
+ 
+ 	M_FindResponseFile();
+ 
+-	DG_ScreenBuffer = malloc(DOOMGENERIC_RESX * DOOMGENERIC_RESY * 4);
+-
+ 	DG_Init();
+ 
+ 	D_DoomMain ();
+diff --git a/doomgeneric/doomgeneric_banan_os.cpp b/doomgeneric/doomgeneric_banan_os.cpp
+index d00c30d..9d13b43 100644
+--- a/doomgeneric/doomgeneric_banan_os.cpp
++++ b/doomgeneric/doomgeneric_banan_os.cpp
+@@ -80,13 +80,13 @@ void DG_Init()
+ 			s_key_write_index = (s_key_write_index + 1) % s_key_queue_size;
+ 		}
+ 	);
++
++	ASSERT(DG_ScreenBuffer == nullptr);
++	DG_ScreenBuffer = s_window->pixels().data();
+ }
+ 
+ void DG_DrawFrame()
+ {
+-	for (size_t y = 0; y < DOOMGENERIC_RESY; y++)
+-		for (size_t x = 0; x < DOOMGENERIC_RESX; x++)
+-			s_window->set_pixel(x, y, 0xFF000000 | DG_ScreenBuffer[y * DOOMGENERIC_RESX + x]);
+ 	s_window->invalidate();
+ 	s_window->poll_events();
+ }
+-- 
+2.47.1
+