diff --git a/src/openrct2/OpenRCT2.cpp b/src/openrct2/OpenRCT2.cpp
index 8f2ffce22d..47827e97a5 100644
--- a/src/openrct2/OpenRCT2.cpp
+++ b/src/openrct2/OpenRCT2.cpp
@@ -37,9 +37,7 @@ extern "C"
     utf8 gCustomRCT2DataPath[MAX_PATH] = { 0 };
     utf8 gCustomPassword[MAX_PATH] = { 0 };
 
-    // This should probably be changed later and allow a custom selection of things to initialise like SDL_INIT
     bool gOpenRCT2Headless = false;
-
     bool gOpenRCT2ShowChangelog;
     bool gOpenRCT2SilentBreakpad;
 
diff --git a/src/openrct2/drawing/IDrawingEngine.h b/src/openrct2/drawing/IDrawingEngine.h
index f9e6ee65e2..ca5b15c9c6 100644
--- a/src/openrct2/drawing/IDrawingEngine.h
+++ b/src/openrct2/drawing/IDrawingEngine.h
@@ -41,7 +41,6 @@ enum DRAWING_ENGINE_FLAGS
 
 struct rct_drawpixelinfo;
 struct rct_palette_entry;
-struct SDL_Window;
 
 namespace OpenRCT2 { namespace Drawing
 {
diff --git a/src/openrct2/drawing/drawing.h b/src/openrct2/drawing/drawing.h
index 96523b4e93..981b6cd976 100644
--- a/src/openrct2/drawing/drawing.h
+++ b/src/openrct2/drawing/drawing.h
@@ -21,6 +21,8 @@
 #include "../interface/colour.h"
 #include "font.h"
 
+typedef struct SDL_Surface SDL_Surface;
+
 // For g1 only enable packing when still relying on vanilla
 #ifndef NO_RCT2
 #pragma pack(push, 1)
diff --git a/src/openrct2/drawing/font.c b/src/openrct2/drawing/font.c
index c6968378a6..34a7d89684 100644
--- a/src/openrct2/drawing/font.c
+++ b/src/openrct2/drawing/font.c
@@ -14,6 +14,10 @@
  *****************************************************************************/
 #pragma endregion
 
+#ifndef NO_TTF
+#include "../common.h"
+#include <SDL_ttf.h>
+#endif
 #include "../rct2/addresses.h"
 #include "../localisation/localisation.h"
 #include "../sprites.h"
diff --git a/src/openrct2/drawing/font.h b/src/openrct2/drawing/font.h
index 410ff75b83..a662431b45 100644
--- a/src/openrct2/drawing/font.h
+++ b/src/openrct2/drawing/font.h
@@ -18,7 +18,7 @@
 #define _DRAWING_FONT_H_
 
 #ifndef NO_TTF
-#include <SDL_ttf.h>
+typedef struct _TTF_Font TTF_Font;
 #endif // NO_TTF
 
 #include "../common.h"
diff --git a/src/openrct2/drawing/scrolling_text.c b/src/openrct2/drawing/scrolling_text.c
index a3b4d51451..3b13286098 100644
--- a/src/openrct2/drawing/scrolling_text.c
+++ b/src/openrct2/drawing/scrolling_text.c
@@ -14,6 +14,10 @@
  *****************************************************************************/
 #pragma endregion
 
+#ifndef NO_TTF
+#include "../common.h"
+#include <SDL_ttf.h>
+#endif
 #include "../rct2/addresses.h"
 #include "../config/Config.h"
 #include "../interface/colour.h"
diff --git a/src/openrct2/drawing/string.c b/src/openrct2/drawing/string.c
index 23e1197864..0304d13242 100644
--- a/src/openrct2/drawing/string.c
+++ b/src/openrct2/drawing/string.c
@@ -14,6 +14,10 @@
  *****************************************************************************/
 #pragma endregion
 
+#ifndef NO_TTF
+#include "../common.h"
+#include <SDL_ttf.h>
+#endif
 #include "../interface/colour.h"
 #include "../interface/viewport.h"
 #include "../localisation/localisation.h"
diff --git a/src/openrct2/platform/macos.m b/src/openrct2/platform/macos.m
index 84dd8340bc..5a6941bddd 100644
--- a/src/openrct2/platform/macos.m
+++ b/src/openrct2/platform/macos.m
@@ -33,11 +33,6 @@ void macos_disallow_automatic_window_tabbing()
     }
 }
 
-bool platform_check_steam_overlay_attached() {
-    STUB();
-    return false;
-}
-
 void platform_get_exe_path(utf8 *outPath, size_t outSize)
 {
     if (outSize == 0) return;
@@ -103,17 +98,6 @@ void platform_posix_sub_resolve_openrct_data_path(utf8 *out, size_t size) {
     }
 }
 
-void platform_show_messagebox(const char * message)
-{
-    @autoreleasepool
-    {
-        NSAlert *alert = [[[NSAlert alloc] init] autorelease];
-        [alert addButtonWithTitle:@"OK"];
-        alert.messageText = [NSString stringWithUTF8String:message];
-        [alert runModal];
-    }
-}
-
 utf8* macos_str_decomp_to_precomp(utf8 *input)
 {
     @autoreleasepool
@@ -225,9 +209,4 @@ uint8 platform_get_locale_measurement_format()
     }
 }
 
-sint32 platform_get_non_window_flags()
-{
-    return SDL_WINDOW_MINIMIZED | SDL_WINDOW_FULLSCREEN | SDL_WINDOW_FULLSCREEN_DESKTOP;
-}
-
 #endif
diff --git a/src/openrct2/platform/platform.h b/src/openrct2/platform/platform.h
index 88646e3058..e0f1960552 100644
--- a/src/openrct2/platform/platform.h
+++ b/src/openrct2/platform/platform.h
@@ -147,8 +147,6 @@ uint8 platform_get_locale_date_format();
 bool platform_get_font_path(TTFFontDescriptor *font, utf8 *buffer, size_t size);
 #endif // NO_TTF
 
-bool platform_check_steam_overlay_attached();
-
 datetime64 platform_get_datetime_now_utc();
 
 // Called very early in the program before parsing commandline arguments.
diff --git a/src/openrct2/platform/windows.c b/src/openrct2/platform/windows.c
index 79c916d29f..f38dd69162 100644
--- a/src/openrct2/platform/windows.c
+++ b/src/openrct2/platform/windows.c
@@ -786,11 +786,6 @@ uint8 platform_get_locale_date_format()
     return DATE_FORMAT_DAY_MONTH_YEAR;
 }
 
-bool platform_check_steam_overlay_attached()
-{
-    return GetModuleHandle("GameOverlayRenderer.dll") != NULL;
-}
-
 char *strndup(const char *src, size_t size)
 {
     size_t len = strnlen(src, size);
diff --git a/test/testpaint/generate.cpp b/test/testpaint/generate.cpp
index ad9b63734d..6794a50c7c 100644
--- a/test/testpaint/generate.cpp
+++ b/test/testpaint/generate.cpp
@@ -15,6 +15,7 @@
 #pragma endregion
 
 #include <algorithm>
+#include <cstdarg>
 #include <string>
 #include <vector>
 
diff --git a/test/testpaint/main.cpp b/test/testpaint/main.cpp
index 2b8dfa73d7..a565ef6626 100644
--- a/test/testpaint/main.cpp
+++ b/test/testpaint/main.cpp
@@ -15,6 +15,7 @@
 #pragma endregion
 
 #include <algorithm>
+#include <cstdarg>
 #include <string>
 #include <vector>