Merge ddnet#4989

4989: Add null backend r=def- a=ChillerDragon

Thanks to `@Jupeyy` for the idea.

Replacing graphics_threaded_null.h with a null backend
makes code maintenance and memory cleanup easier.

Fixes these memory leaks in headless client (ddnet#4970)

```
Direct leak of 1048576 byte(s) in 1 object(s) allocated from:
    #0 0x4b6f6d in malloc (/home/runner/work/ddnet/ddnet/san/DDNet+0x4b6f6d)
    #1 0xd92ffb in CTextRender::InitTextures(int, int, IGraphics::CTextureHandle (&) [2], unsigned char* (&) [2]) /home/runner/work/ddnet/ddnet/src/engine/client/text.cpp:325:24
    #2 0xd53795 in CTextRender::LoadFont(char const*, unsigned char const*, unsigned long) /home/runner/work/ddnet/ddnet/src/engine/client/text.cpp:729:3
    #3 0xade5cd in CClient::LoadFont() /home/runner/work/ddnet/ddnet/src/engine/client/client.cpp:4070:32
    #4 0x155b3de in CGameClient::OnInit() /home/runner/work/ddnet/ddnet/src/game/client/gameclient.cpp:246:12
    #5 0xa8ecfe in CClient::Run() /home/runner/work/ddnet/ddnet/src/engine/client/client.cpp:2933:16
    #6 0xaf6726 in main /home/runner/work/ddnet/ddnet/src/engine/client/client.cpp:4458:11
    #7 0x7fadd9e610b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x240b2)
```

## Checklist

- [x] Tested the change ingame
- [ ] Provided screenshots if it is a visual change
- [ ] Tested in combination with possibly related configuration options
- [ ] Written a unit test if it works standalone, system.c especially
- [ ] Considered possible null pointers and out of bounds array indexing
- [ ] Changed no physics that affect existing maps
- [x] Tested the change with [ASan+UBSan or valgrind's memcheck](https://github.com/ddnet/ddnet/#using-addresssanitizer--undefinedbehavioursanitizer-or-valgrinds-memcheck) (optional)


Co-authored-by: ChillerDrgon <ChillerDragon@gmail.com>

CMakeLists.txt

@@ -1824,6 +1824,8 @@ if(CLIENT)
     backend/backend_base.h
     backend/glsl_shader_compiler.cpp
     backend/glsl_shader_compiler.h
+    backend/null/backend_null.cpp
+    backend/null/backend_null.h
     backend/opengl/backend_opengl.cpp
     backend/opengl/backend_opengl.h
     backend/opengl/backend_opengl3.cpp
@@ -1858,7 +1860,6 @@ if(CLIENT)
     graphics_defines.h
     graphics_threaded.cpp
     graphics_threaded.h
-    graphics_threaded_null.h
     http.cpp
     http.h
     input.cpp

src/engine/client/backend/null/backend_null.cpp

@@ -0,0 +1,59 @@
+#include "backend_null.h"
+
+bool CCommandProcessorFragment_Null::RunCommand(const CCommandBuffer::SCommand *pBaseCommand)
+{
+	switch(pBaseCommand->m_Cmd)
+	{
+	case CCommandProcessorFragment_Null::CMD_INIT:
+		Cmd_Init(static_cast<const SCommand_Init *>(pBaseCommand));
+		break;
+	case CCommandBuffer::CMD_TEXTURE_CREATE:
+		Cmd_Texture_Create(static_cast<const CCommandBuffer::SCommand_Texture_Create *>(pBaseCommand));
+		break;
+	case CCommandBuffer::CMD_TEXT_TEXTURES_CREATE:
+		Cmd_TextTextures_Create(static_cast<const CCommandBuffer::SCommand_TextTextures_Create *>(pBaseCommand));
+		break;
+	case CCommandBuffer::CMD_TEXT_TEXTURE_UPDATE:
+		Cmd_TextTexture_Update(static_cast<const CCommandBuffer::SCommand_TextTexture_Update *>(pBaseCommand));
+		break;
+	}
+	return true;
+}
+
+bool CCommandProcessorFragment_Null::Cmd_Init(const SCommand_Init *pCommand)
+{
+	pCommand->m_pCapabilities->m_TileBuffering = false;
+	pCommand->m_pCapabilities->m_QuadBuffering = false;
+	pCommand->m_pCapabilities->m_TextBuffering = false;
+	pCommand->m_pCapabilities->m_QuadContainerBuffering = false;
+
+	pCommand->m_pCapabilities->m_MipMapping = false;
+	pCommand->m_pCapabilities->m_NPOTTextures = false;
+	pCommand->m_pCapabilities->m_3DTextures = false;
+	pCommand->m_pCapabilities->m_2DArrayTextures = false;
+	pCommand->m_pCapabilities->m_2DArrayTexturesAsExtension = false;
+	pCommand->m_pCapabilities->m_ShaderSupport = false;
+
+	pCommand->m_pCapabilities->m_TrianglesAsQuads = false;
+
+	pCommand->m_pCapabilities->m_ContextMajor = 0;
+	pCommand->m_pCapabilities->m_ContextMinor = 0;
+	pCommand->m_pCapabilities->m_ContextPatch = 0;
+	return false;
+}
+
+void CCommandProcessorFragment_Null::Cmd_Texture_Create(const CCommandBuffer::SCommand_Texture_Create *pCommand)
+{
+	free(pCommand->m_pData);
+}
+
+void CCommandProcessorFragment_Null::Cmd_TextTextures_Create(const CCommandBuffer::SCommand_TextTextures_Create *pCommand)
+{
+	free(pCommand->m_pTextData);
+	free(pCommand->m_pTextOutlineData);
+}
+
+void CCommandProcessorFragment_Null::Cmd_TextTexture_Update(const CCommandBuffer::SCommand_TextTexture_Update *pCommand)
+{
+	free(pCommand->m_pData);
+}

src/engine/client/backend/null/backend_null.h

@@ -0,0 +1,16 @@
+#ifndef ENGINE_CLIENT_BACKEND_NULL_BACKEND_NULL_H
+#define ENGINE_CLIENT_BACKEND_NULL_BACKEND_NULL_H
+
+#include <engine/client/backend/backend_base.h>
+
+class CCommandProcessorFragment_Null : public CCommandProcessorFragment_GLBase
+{
+	virtual bool GetPresentedImageData(uint32_t &Width, uint32_t &Height, uint32_t &Format, std::vector<uint8_t> &DstData) { return false; };
+	virtual bool RunCommand(const CCommandBuffer::SCommand *pBaseCommand);
+	bool Cmd_Init(const SCommand_Init *pCommand);
+	virtual void Cmd_Texture_Create(const CCommandBuffer::SCommand_Texture_Create *pCommand);
+	virtual void Cmd_TextTextures_Create(const CCommandBuffer::SCommand_TextTextures_Create *pCommand);
+	virtual void Cmd_TextTexture_Update(const CCommandBuffer::SCommand_TextTexture_Update *pCommand);
+};
+
+#endif

src/engine/client/backend_sdl.cpp

@@ -34,6 +34,8 @@
 
 #include "backend_sdl.h"
 
+#include "backend/null/backend_null.h"
+
 #if !defined(CONF_BACKEND_OPENGL_ES)
 #include "backend/opengl/backend_opengl3.h"
 #endif
@@ -266,6 +268,9 @@ CCommandProcessor_SDL_GL::CCommandProcessor_SDL_GL(EBackendType BackendType, int
 {
 	m_BackendType = BackendType;
 
+#if defined(CONF_HEADLESS_CLIENT)
+	m_pGLBackend = new CCommandProcessorFragment_Null();
+#else
 	if(BackendType == BACKEND_TYPE_OPENGL_ES)
 	{
 #if defined(CONF_BACKEND_OPENGL_ES) || defined(CONF_BACKEND_OPENGL_ES3)
@@ -306,6 +311,7 @@ CCommandProcessor_SDL_GL::CCommandProcessor_SDL_GL(EBackendType BackendType, int
 		m_pGLBackend = CreateVulkanCommandProcessorFragment();
 #endif
 	}
+#endif
 }
 
 CCommandProcessor_SDL_GL::~CCommandProcessor_SDL_GL()
@@ -858,6 +864,15 @@ CGraphicsBackend_SDL_GL::CGraphicsBackend_SDL_GL()
 
 int CGraphicsBackend_SDL_GL::Init(const char *pName, int *pScreen, int *pWidth, int *pHeight, int *pRefreshRate, int FsaaSamples, int Flags, int *pDesktopWidth, int *pDesktopHeight, int *pCurrentWidth, int *pCurrentHeight, IStorage *pStorage)
 {
+#if defined(CONF_HEADLESS_CLIENT)
+	int InitError = 0;
+	const char *pErrorStr = NULL;
+	int GlewMajor = 0;
+	int GlewMinor = 0;
+	int GlewPatch = 0;
+	IsVersionSupportedGlew(m_BackendType, g_Config.m_GfxGLMajor, g_Config.m_GfxGLMinor, g_Config.m_GfxGLPatch, GlewMajor, GlewMinor, GlewPatch);
+	BackendInitGlew(m_BackendType, GlewMajor, GlewMinor, GlewPatch);
+#else
 	// print sdl version
 	{
 		SDL_version Compiled;
@@ -1102,6 +1117,7 @@ int CGraphicsBackend_SDL_GL::Init(const char *pName, int *pScreen, int *pWidth,
 
 		return EGraphicsBackendErrorCodes::GRAPHICS_BACKEND_ERROR_CODE_GL_VERSION_FAILED;
 	}
+#endif // CONF_HEADLESS_CLIENT
 
 	// start the command processor
 	dbg_assert(m_pProcessor == nullptr, "Processor was not cleaned up properly.");

src/engine/client/graphics_threaded.cpp

@@ -31,7 +31,6 @@
 #endif
 
 #include "graphics_threaded.h"
-#include "graphics_threaded_null.h"
 
 static CVideoMode g_aFakeModes[] = {
 	{8192, 4320, 8192, 4320, 0, 8, 8, 8, 0}, {7680, 4320, 7680, 4320, 0, 8, 8, 8, 0}, {5120, 2880, 5120, 2880, 0, 8, 8, 8, 0},
@@ -2842,9 +2841,5 @@ int CGraphics_Threaded::GetVideoModes(CVideoMode *pModes, int MaxModes, int Scre
 
 extern IEngineGraphics *CreateEngineGraphicsThreaded()
 {
-#ifdef CONF_HEADLESS_CLIENT
-	return new CGraphics_ThreadedNull();
-#else
 	return new CGraphics_Threaded();
-#endif
 }