Add cv_debugrender_spriteclip, toggle sprite clipping

This cvar can be used to reveal which sprites are
technically drawn but clipped completely by level
geometry.

src/r_debug.cpp

@@ -31,6 +31,8 @@ CV_PossibleValue_t contrast_cons_t[] = {{-FRACUNIT, "MIN"}, {FRACUNIT, "MAX"}, {
 consvar_t cv_debugrender_contrast =
 	CVAR_INIT("debugrender_contrast", "0.0", CV_CHEAT | CV_FLOAT, contrast_cons_t, nullptr);
 
+consvar_t cv_debugrender_spriteclip = CVAR_INIT("debugrender_spriteclip", "Off", CV_CHEAT, CV_OnOff, nullptr);
+
 UINT32 debugrender_highlight;
 
 void R_CheckDebugHighlight(debugrender_highlight_t k)

src/r_main.c

@@ -1660,6 +1660,7 @@ void R_RegisterEngineStuff(void)
 	// debugging
 
 	CV_RegisterVar(&cv_debugrender_contrast);
+	CV_RegisterVar(&cv_debugrender_spriteclip);
 
 	COM_AddCommand("debugrender_highlight", Command_Debugrender_highlight);
 }

src/r_main.h

@@ -145,7 +145,8 @@ INT32 R_AdjustLightLevel(INT32 light);
 void Command_Debugrender_highlight(void);
 
 extern consvar_t
-	cv_debugrender_contrast;
+	cv_debugrender_contrast,
+	cv_debugrender_spriteclip;
 
 // Called by startup code.
 void R_Init(void);

src/r_things.c

@@ -2982,6 +2982,16 @@ static void R_CreateDrawNodes(maskcount_t* mask, drawnode_t* head, boolean temps
 
 		for (r2 = head->next; r2 != head; r2 = r2->next)
 		{
+			if (cv_debugrender_spriteclip.value)
+			{
+				// Only sort behind other sprites; sorts in
+				// front of everything else.
+				if (!r2->sprite)
+				{
+					continue;
+				}
+			}
+
 			if (r2->plane)
 			{
 				fixed_t planeobjectz, planecameraz;
@@ -3244,6 +3254,16 @@ void R_ClipVisSprite(vissprite_t *spr, INT32 x1, INT32 x2, portal_t* portal)
 	fixed_t		lowscale;
 	INT32		silhouette;
 
+	if (cv_debugrender_spriteclip.value)
+	{
+		for (x = x1; x <= x2; x++)
+		{
+			spr->clipbot[x] = (INT16)viewheight;
+			spr->cliptop[x] = (INT16)con_clipviewtop;
+		}
+		return;
+	}
+
 	for (x = x1; x <= x2; x++)
 	{
 		spr->clipbot[x] = spr->cliptop[x] = CLIP_UNDEF;