Centralise engine access, add Portal FOV changer

- A bunch of stuff is now defined in one header, engineapi.h
- engineapi.c is responsible for setting up any interfaces/stuff that's
  used in more than one place
- mkgamedata is pretty much rewritten and now supports nested
  conditionals
- gamedata variables no longer have the gamedata_ prefix because it was
  just annoyingly long all the time
- vcall macros are somewhat revamped and support dynamic (gamedata)
  indices
- Portal 1 FOV can be set anywhere from 75-120 using fov_desired -
  tested in both the main versions currently used by runners
- A few typos were also fixed ("intput," "writeable," "indexes")

1 files changed, 136 insertions, 0 deletions

diff --git a/src/fov.c b/src/fov.c
new file mode 100644
index 0000000..f60f067
--- /dev/null
+++ b/src/fov.c
@@ -0,0 +1,136 @@
+/*
+ * Copyright © 2022 Michael Smith <mikesmiffy128@gmail.com>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED “AS IS” AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+ * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+ * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+ * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+// TODO(linux): theoretically, probably ifdef out the cvar-replacement stuff; we
+// expect any game that's been ported to linux to already have fov_desired
+
+#include <stdbool.h>
+
+#include "con_.h"
+#include "engineapi.h"
+#include "ent.h"
+#include "gametype.h"
+#include "hook.h"
+#include "intdefs.h"
+#include "mem.h"
+#include "vcall.h"
+#include "x86.h"
+
+bool changedmax = false;
+DEF_CVAR_MINMAX_UNREG(fov_desired,
+		"Set the base field of view (SST reimplementation)", 75, 75, 120,
+		CON_HIDDEN | CON_ARCHIVE)
+static struct con_var *real_fov_desired; // engine's if it has it, or ours
+
+typedef void (*VCALLCONV SetDefaultFOV_func)(void *, int);
+static SetDefaultFOV_func orig_SetDefaultFOV;
+static void VCALLCONV hook_SetDefaultFOV(void *this, int fov) {
+	// the game normally clamps fov_desired on the server side, disregard
+	// whatever it tries to set and force our own value instead
+	orig_SetDefaultFOV(this, con_getvari(real_fov_desired));
+}
+
+static bool find_SetDefaultFOV(struct con_cmd *fov) {
+	uchar *fovcb = (uchar *)fov->cb;
+	int callcnt = 0;
+	for (uchar *p = fovcb; p - fovcb < 96;) {
+		// fov command source, and consequent asm, calls 4 functions, one of
+		// them virtual (i.e. via register). of the 3 direct calls,
+		// SetDefaultFOV is the third.
+		if (p[0] == X86_CALL && ++callcnt == 3) {
+			orig_SetDefaultFOV = (SetDefaultFOV_func)(p + 5 +
+					mem_loadoffset(p + 1)); 
+			return true;
+		}
+		int len = x86_len(p);
+		if (len == -1) {
+			con_warn("fov: find_SetDefaultFOV: unknown or invalid instruction\n");
+			return false;
+		}
+		p += len;
+	}
+	return true;
+}
+
+// replacement cvar needs to actively set player fov if in a map
+static void fovcb(struct con_var *v) {
+	void *player = ent_get(1); // NOTE: singleplayer only!
+	if (player) orig_SetDefaultFOV(player, con_getvari(v));
+}
+
+// called by sst.c in ClientActive to ensure fov is applied on load
+void fov_onload(void) {
+	if (real_fov_desired == fov_desired) {
+		void *player = ent_get(1); // "
+		if (player) orig_SetDefaultFOV(player, con_getvari(fov_desired));
+	}
+}
+
+static struct con_cmd *cmd_fov;
+
+bool fov_init(bool has_ent) {
+	// could work for other games, but generally only portal 1 people want this
+	// (the rest of us consider this cheating and a problem for runs...)
+	if (!GAMETYPE_MATCHES(Portal1)) { return false; }
+
+	cmd_fov = con_findcmd("fov");
+	if (!cmd_fov) return false; // shouldn't really happen but just in case!
+
+	if (real_fov_desired = con_findvar("fov_desired")) {
+		// latest steampipe already goes up to 120 fov
+		if (real_fov_desired->parent->maxval == 120) return false;
+		real_fov_desired->parent->maxval = 120;
+	}
+	else {
+		if (!has_ent) return false;
+		con_reg(fov_desired);
+		real_fov_desired = fov_desired;
+	}
+	if (!find_SetDefaultFOV(cmd_fov)) {
+		con_warn("fov: couldn't find SetDefaultFOV function\n");
+		return false;
+	}
+	orig_SetDefaultFOV = (SetDefaultFOV_func)hook_inline(
+			(void *)orig_SetDefaultFOV, (void *)&hook_SetDefaultFOV);
+	if (!orig_SetDefaultFOV) {
+		con_warn("fov: couldn't hook SetDefaultFOV function\n");
+		return false;
+	}
+
+	// we might not be using our cvar but simpler to do this unconditionally
+	fov_desired->cb = &fovcb;
+	fov_desired->parent->base.flags &= ~CON_HIDDEN;
+	// hide the original fov command since we've effectively broken it anyway :)
+	cmd_fov->base.flags |= CON_DEVONLY;
+	return true;
+}
+
+void fov_end(void) {
+	if (real_fov_desired && real_fov_desired != fov_desired) {
+		real_fov_desired->parent->maxval = 90;
+		if (con_getvarf(real_fov_desired) > 90) {
+			con_setvarf(real_fov_desired, 90); // blegh.
+		}
+	}
+	else {
+		void *player = ent_get(1); // also singleplayer only
+		if (player) orig_SetDefaultFOV(player, 75);
+	}
+	unhook_inline((void *)orig_SetDefaultFOV);
+	cmd_fov->base.flags &= ~CON_DEVONLY;
+}
+
+// vi: sw=4 ts=4 noet tw=80 cc=80