Make dummy compile again, if SDL is explicitly set to 0

(cherry picked from commit ba55947ee6ab36efc04598953a78a11173103bcf)

# Conflicts:
#	src/doomtype.h
#	src/dummy/i_system.c

src/Makefile

@@ -31,8 +31,8 @@
 # MINGW=1, MINGW64=1 - Windows (MinGW toolchain)
 # UNIX=1 - Generic Unix like system
 # FREEBSD=1
-# SDL=1 - Use SDL backend. SDL is the only backend though
+# SDL=1 - Use SDL backend. SDL is the only implemented backend though.
-#         and thus, always enabled.
+#         If disabled, a dummy backend will be used.
 #
 # A list of supported GCC versions can be found in
 # Makefile.d/detect.mk -- search 'gcc_versions'.

src/Makefile.d/detect.mk

@@ -16,7 +16,6 @@ all_systems:=\
 	UNIX\
 	LINUX\
 	FREEBSD\
-	SDL\
 
 # check for user specified system
 ifeq (,$(filter $(all_systems),$(.VARIABLES)))

src/Makefile.d/nix.mk

@@ -14,7 +14,7 @@ opts+=-I/usr/X11R6/include
 libs+=-L/usr/X11R6/lib
 endif
 
-SDL=1
+SDL?=1
 
 # In common usage.
 ifdef LINUX

src/Makefile.d/platform.mk

@@ -64,6 +64,8 @@ ifdef UNIX
 include Makefile.d/nix.mk
 endif
 
-ifdef SDL
+ifeq ($(SDL), 1)
 include Makefile.d/sdl.mk
+else
+include Makefile.d/dummy.mk
 endif

src/Makefile.d/win32.mk

@@ -15,7 +15,7 @@ libs+=-ladvapi32 -lkernel32 -lmsvcrt -luser32
 
 nasm_format:=win32
 
-SDL=1
+SDL?=1
 
 ifndef NOHW
 opts+=-DUSE_WGL_SWAP
@@ -83,6 +83,7 @@ else
 lib:=../libs/SDL2_mixer/$(mingw)
 endif
 
+ifdef SDL2
 mixer_opts:=-I$(lib)/include/SDL2
 mixer_libs:=-L$(lib)/lib
 
@@ -92,6 +93,7 @@ SDL_opts:=-I$(lib)/include/SDL2\
 SDL_libs:=-L$(lib)/lib $(mixer_libs)\
 	-lmingw32 -lSDL2main -lSDL2 -mwindows
 $(eval $(call _set,SDL))
+endif
 
 lib:=../libs/zlib
 ZLIB_opts:=-I$(lib)

src/dummy/Sourcefile

@@ -0,0 +1,5 @@
+i_net.c
+i_system.c
+i_main.c
+i_video.c
+i_sound.c

src/dummy/i_sound.c

@@ -139,29 +139,24 @@ boolean I_LoadSong(char *data, size_t len)
 
 void I_UnloadSong(void)
 {
-	(void)handle;
 }
 
 boolean I_PlaySong(boolean looping)
 {
-	(void)handle;
 	(void)looping;
 	return false;
 }
 
 void I_StopSong(void)
 {
-	(void)handle;
 }
 
 void I_PauseSong(void)
 {
-	(void)handle;
 }
 
 void I_ResumeSong(void)
 {
-	(void)handle;
 }
 
 void I_SetMusicVolume(UINT8 volume)
@@ -188,18 +183,20 @@ void I_StopFadingSong(void)
 {
 }
 
-boolean I_FadeSongFromVolume(UINT8 target_volume, UINT8 source_volume, UINT32 ms, void (*callback)(void));
+boolean I_FadeSongFromVolume(UINT8 target_volume, UINT8 source_volume, UINT32 ms, void (*callback)(void))
 {
 	(void)target_volume;
 	(void)source_volume;
 	(void)ms;
+	(void)callback;
 	return false;
 }
 
-boolean I_FadeSong(UINT8 target_volume, UINT32 ms, void (*callback)(void));
+boolean I_FadeSong(UINT8 target_volume, UINT32 ms, void (*callback)(void))
 {
 	(void)target_volume;
 	(void)ms;
+	(void)callback;
 	return false;
 }
 

src/dummy/i_system.c

@@ -1,6 +1,9 @@
 #include "../doomdef.h"
+#include "../doomtype.h"
 #include "../i_system.h"
 
+FILE *logstream = NULL;
+
 UINT8 graphics_started = 0;
 
 UINT8 keyboard_started = 0;
@@ -94,8 +97,6 @@ void I_StartupMouse(void){}
 
 void I_StartupMouse2(void){}
 
-void I_StartupKeyboard(void){}
-
 INT32 I_GetKey(void)
 {
 	return 0;
@@ -174,12 +175,18 @@ INT32 I_ClipboardCopy(const char *data, size_t size)
 	return -1;
 }
 
-char *I_ClipboardPaste(void)
+const char *I_ClipboardPaste(void)
 {
 	return NULL;
 }
 
 void I_RegisterSysCommands(void) {}
 
+void I_GetCursorPosition(INT32 *x, INT32 *y)
+{
+	(void)x;
+	(void)y;
+}
+
 #include "../sdl/dosstr.c"