Add "horplus" cvar to get Hor+ behavior with default FOV

If "horplus" is set, the "fov" cvar is interpreted as the horizontal FOV
in a 4:3 screen, and is adapted automatically to the current screen
aspect ratio accordingly. If not set, use the old Vert- approach.

In addition, "horplus" can also be set from the video menu by selecting
the "Auto" option for aspect ratio, which also resets the FOV value to the
standard 90 degrees.

Finally, add a 5:4 aspect ratio (1280x1024) and correct the 16:9 angle
slightly.

src/client/cl_entities.c

@@ -24,6 +24,7 @@
  * =======================================================================
  */
 
+#include <math.h>
 #include "header/client.h"
 
 extern struct model_s *cl_mod_powerscreen;
@@ -724,6 +725,28 @@ CL_AddViewWeapon(player_state_t *ps, player_state_t *ops)
 	V_AddEntity(&gun);
 }
 
+/*
+ * Adapts a 4:3 aspect FOV to the current aspect (Hor+)
+ */
+static inline float
+AdaptFov(float fov, float w, float h)
+{
+	static const float pi = M_PI; /* float instead of double */
+
+	if (w <= 0 || h <= 0)
+		return fov;
+
+	/*
+	 * Formula:
+	 *
+	 * fov = 2.0 * atan(width / height * 3.0 / 4.0 * tan(fov43 / 2.0))
+	 *
+	 * The code below is equivalent but precalculates a few values and
+	 * converts between degrees and radians when needed.
+	 */
+	return (atanf(tanf(fov / 360.0f * pi) * (w / h * 0.75f)) / pi * 360.0f);
+}
+
 /*
  * Sets cl.refdef view values
  */
@@ -731,7 +754,7 @@ void
 CL_CalcViewValues(void)
 {
 	int i;
-	float lerp, backlerp;
+	float lerp, backlerp, ifov;
 	frame_t *oldframe;
 	player_state_t *ps, *ops;
 
@@ -820,7 +843,15 @@ CL_CalcViewValues(void)
 	AngleVectors(cl.refdef.viewangles, cl.v_forward, cl.v_right, cl.v_up);
 
 	/* interpolate field of view */
-	cl.refdef.fov_x = ops->fov + lerp * (ps->fov - ops->fov);
+	ifov = ops->fov + lerp * (ps->fov - ops->fov);
+	if (horplus->value)
+	{
+		cl.refdef.fov_x = AdaptFov(ifov, cl.refdef.width, cl.refdef.height);
+	}
+	else
+	{
+		cl.refdef.fov_x = ifov;
+	}
 
 	/* don't interpolate blend color */
 	for (i = 0; i < 4; i++)

src/client/cl_main.c

@@ -87,6 +87,7 @@ cvar_t *name;
 cvar_t *skin;
 cvar_t *rate;
 cvar_t *fov;
+cvar_t *horplus;
 cvar_t *msg;
 cvar_t *hand;
 cvar_t *gender;
@@ -538,6 +539,7 @@ CL_InitLocal(void)
 	msg = Cvar_Get("msg", "1", CVAR_USERINFO | CVAR_ARCHIVE);
 	hand = Cvar_Get("hand", "0", CVAR_USERINFO | CVAR_ARCHIVE);
 	fov = Cvar_Get("fov", "90", CVAR_USERINFO | CVAR_ARCHIVE);
+	horplus = Cvar_Get("horplus", "1", CVAR_ARCHIVE);
 	gender = Cvar_Get("gender", "male", CVAR_USERINFO | CVAR_ARCHIVE);
 	gender_auto = Cvar_Get("gender_auto", "1", CVAR_ARCHIVE);
 	gender->modified = false;

src/client/header/client.h

@@ -287,6 +287,7 @@ extern	cvar_t	*cl_lightlevel;
 extern	cvar_t	*cl_paused;
 extern	cvar_t	*cl_timedemo;
 extern	cvar_t	*cl_vwep;
+extern	cvar_t  *horplus;
 
 typedef struct
 {

src/client/menu/videomenu.c

@@ -113,8 +113,24 @@ ApplyChanges(void *unused)
 		Cvar_SetValue("gl_mode", -1);
 	}
 
-	/* fov */
+	/* horplus */
 	if (s_aspect_list.curvalue == 0)
+	{
+		if (horplus->value != 1)
+		{
+			Cvar_SetValue("horplus", 1);
+		}
+	}
+	else
+	{
+		if (horplus->value != 0)
+		{
+			Cvar_SetValue("horplus", 0);
+		}
+	}
+
+	/* fov */
+	if (s_aspect_list.curvalue == 0 || s_aspect_list.curvalue == 1)
 	{
 		if (fov->value != 90)
 		{
@@ -122,7 +138,15 @@ ApplyChanges(void *unused)
 			Cvar_SetValue("fov", 90);
 		}
 	}
-	else if (s_aspect_list.curvalue == 1)
+	else if (s_aspect_list.curvalue == 2)
+	{
+		if (fov->value != 86)
+		{
+			/* Restarts automatically */
+			Cvar_SetValue("fov", 86);
+		}
+	}
+	else if (s_aspect_list.curvalue == 3)
 	{
 		if (fov->value != 100)
 		{
@@ -130,12 +154,12 @@ ApplyChanges(void *unused)
 			Cvar_SetValue("fov", 100);
 		}
 	}
-	else if (s_aspect_list.curvalue == 2)
+	else if (s_aspect_list.curvalue == 4)
 	{
-		if (fov->value != 105)
+		if (fov->value != 106)
 		{
 			/* Restarts automatically */
-			Cvar_SetValue("fov", 105);
+			Cvar_SetValue("fov", 106);
 		}
 	}
  
@@ -185,7 +209,9 @@ VID_MenuInit(void)
 	};
 
 	static const char *aspect_names[] = {
+		"Auto",
 		"4:3",
+		"5:4",
 		"16:10",
 		"16:9",
 		"Custom",
@@ -219,27 +245,40 @@ VID_MenuInit(void)
 				CVAR_USERINFO | CVAR_ARCHIVE);
 	}
 
+	if (!horplus)
+	{
+		horplus = Cvar_Get("horplus", "1", CVAR_ARCHIVE);
+	}
+
 	if (!fov)
 	{
 		fov = Cvar_Get("fov", "90",  CVAR_USERINFO | CVAR_ARCHIVE);
 	}
 
-	if (fov->value == 90)
+	if (horplus->value == 1)
 	{
 		s_aspect_list.curvalue = 0;
 	}
-	else if (fov->value == 100)
+	else if (fov->value == 90)
 	{
 		s_aspect_list.curvalue = 1;
 	}
-	else if (fov->value == 105)
+	else if (fov->value == 86)
 	{
 		s_aspect_list.curvalue = 2;
 	}
-	else
+	else if (fov->value == 100)
 	{
 		s_aspect_list.curvalue = 3;
 	}
+	else if (fov->value == 106)
+	{
+		s_aspect_list.curvalue = 4;
+	}
+	else
+	{
+		s_aspect_list.curvalue = 5;
+	}
 
 	/* custom mode */
 	if (gl_mode->value >= 0)