devmode DEMO: replay buffer usage displayed in real-time on the HUD

- Buffer usage in megabytes, bytes and percentage
- Approximate usage per second
- Estimated time until buffer runs out and replay is stopped

src/doomdef.h

@@ -386,6 +386,7 @@ typedef enum
 	DBG_SETUP			= 0x00000400,
 	DBG_LUA				= 0x00000800,
 	DBG_RNG				= 0x00001000,
+	DBG_DEMO			= 0x00002000,
 } debugFlags_t;
 
 struct debugFlagNames_s

src/g_demo.c

@@ -2013,7 +2013,7 @@ void G_RecordDemo(const char *name)
 	demobuf.p = NULL;
 
 	demo.recording = true;
-	//demo.buffer = &demobuf;
+	demo.buffer = &demobuf;
 
 	/* FIXME: This whole file is in a wretched state. Take a
 	look at G_WriteAllGhostTics and G_WriteDemoTiccmd, they
@@ -2925,6 +2925,7 @@ void G_DoPlayDemo(char *defdemoname)
 	// read demo header
 	gameaction = ga_nothing;
 	demo.playback = true;
+	demo.buffer = &demobuf;
 	if (memcmp(demobuf.p, DEMOHEADER, 12))
 	{
 		snprintf(msg, 1024, M_GetText("%s is not a SRB2Kart replay file.\n"), pdemoname);

src/g_demo.h

@@ -58,6 +58,7 @@ struct demovars_s {
 
 	boolean freecam;
 
+	const savebuffer_t *buffer; // debug, valid only if recording or playback
 };
 
 extern struct demovars_s demo;

src/m_cheat.c

@@ -759,6 +759,8 @@ struct debugFlagNames_s const debug_flag_names[] =
 	{"Lua", DBG_LUA},
 	{"RNG", DBG_RNG},
 	{"Randomizer", DBG_RNG}, // alt name
+	{"Demo", DBG_DEMO},
+	{"Replay", DBG_DEMO}, // alt name
 	{NULL, 0}
 };
 

src/st_stuff.c

@@ -438,6 +438,31 @@ static void ST_drawRenderDebug(INT32 *height)
 	ST_pushDebugString(height, va("Skybox Portals: %4s", sizeu1(i->skybox_portals)));
 }
 
+static void ST_drawDemoDebug(INT32 *height)
+{
+	if (!demo.recording && !demo.playback)
+		return;
+
+	size_t needle = demo.buffer->p - demo.buffer->buffer;
+	size_t size = demo.buffer->size;
+	double percent = (double)needle / size * 100.0;
+	double avg = (double)needle / leveltime;
+
+	ST_pushDebugString(height, va("%s/%s bytes", sizeu1(needle), sizeu2(size)));
+	ST_pushDebugString(height, va(
+			"%.2f/%.2f MB %5.2f%%",
+			needle / (1024.0 * 1024.0),
+			size / (1024.0 * 1024.0),
+			percent
+	));
+	ST_pushDebugString(height, va(
+			"%.2f KB/s (ETA %.2f minutes)",
+			avg * TICRATE / 1024.0,
+			(size - needle) / (avg * TICRATE * 60.0)
+	));
+	ST_pushDebugString(height, va("Demo (%s)", demo.recording ? "recording" : "playback"));
+}
+
 static void ST_drawDebugInfo(void)
 {
 	INT32 height = 192;
@@ -508,6 +533,11 @@ static void ST_drawDebugInfo(void)
 		ST_drawRenderDebug(&height);
 	}
 
+	if (cht_debug & DBG_DEMO)
+	{
+		ST_drawDemoDebug(&height);
+	}
+
 	if (cht_debug & DBG_MEMORY)
 		V_DrawRightAlignedString(320, height,     V_MONOSPACE, va("Heap used: %7sKB", sizeu1(Z_TagsUsage(0, INT32_MAX)>>10)));
 }