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

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

kernel/include/kernel/BootInfo.h

@@ -55,5 +55,6 @@ namespace Kernel
 	BAN::StringView get_early_boot_command_line(uint32_t magic, uint32_t info);
 
 	extern BootInfo g_boot_info;
+	extern bool g_disable_disk_write;
 
 }

kernel/kernel/BootInfo.cpp

@@ -6,6 +6,7 @@ namespace Kernel
 {
 
 	BootInfo g_boot_info;
+	bool g_disable_disk_write { false };
 
 	static MemoryMapEntry::Type bios_number_to_memory_type(uint32_t number)
 	{

kernel/kernel/Storage/DiskCache.cpp

@@ -1,3 +1,4 @@
+#include <kernel/BootInfo.h>
 #include <kernel/Lock/LockGuard.h>
 #include <kernel/Memory/Heap.h>
 #include <kernel/Memory/PageTable.h>
@@ -105,6 +106,9 @@ namespace Kernel
 
 	BAN::ErrorOr<void> DiskCache::sync()
 	{
+		if (g_disable_disk_write)
+			return {};
+
 		for (auto& cache : m_cache)
 		{
 			if (cache.dirty_mask == 0)

kernel/kernel/Storage/StorageDevice.cpp

@@ -2,6 +2,7 @@
 #include <BAN/ScopeGuard.h>
 #include <BAN/StringView.h>
 #include <BAN/UTF8.h>
+#include <kernel/BootInfo.h>
 #include <kernel/FS/DevFS/FileSystem.h>
 #include <kernel/FS/VirtualFileSystem.h>
 #include <kernel/Lock/LockGuard.h>
@@ -265,6 +266,13 @@ namespace Kernel
 
 		LockGuard _(m_mutex);
 
+		if (g_disable_disk_write)
+		{
+			if (!m_disk_cache.has_value())
+				return BAN::Error::from_errno(EIO);
+			return m_disk_cache->write_to_cache(lba, buffer, true);
+		}
+
 		if (!m_disk_cache.has_value())
 			return write_sectors_impl(lba, sector_count, buffer);
 

kernel/kernel/kernel.cpp

@@ -85,6 +85,8 @@ static void parse_command_line()
 			cmdline.disable_usb = true;
 		else if (argument == "noacpi")
 			cmdline.disable_acpi = true;
+		else if (argument == "readonly")
+			Kernel::g_disable_disk_write = true;
 		else if (argument == "nodebug")
 			g_disable_debug = true;
 		else if (argument.starts_with("ps2="))

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
+

userspace/libraries/LibGUI/include/LibGUI/Window.h

@@ -43,6 +43,8 @@ namespace LibGUI
 			return m_framebuffer[y * m_width + x];
 		}
 
+		BAN::Span<uint32_t> pixels() { return m_framebuffer.span(); }
+
 		void fill_rect(int32_t x, int32_t y, uint32_t width, uint32_t height, uint32_t color);
 		void fill(uint32_t color) { return fill_rect(0, 0, width(), height(), color); }