[sound] Add a function to set ambient sounds

This gets ambient sounds (in particular, water and sky) working again
for quakeworld after the recent sound changes, and again for nq after I
don't know how long.

include/QF/plugin/snd_render.h

@@ -38,6 +38,7 @@ typedef struct snd_render_funcs_s {
 	void      (*init) (void);
 	void      (*ambient_off) (void);
 	void      (*ambient_on) (void);
+	void      (*set_ambient) (int amb_channel, struct sfx_s *sfx);
 	void      (*static_sound) (struct sfx_s *sfx, vec4f_t origin, float vol, float attenuation);
 	void      (*start_sound) (int entnum, int entchannel, struct sfx_s *sfx, const vec4f_t, float vol, float attenuation);
 	void      (*local_sound) (const char *s);

include/QF/sound.h

@@ -181,6 +181,8 @@ void S_AmbientOff (void);
 */
 void S_AmbientOn (void);
 
+void S_SetAmbient (int amb_channel, sfx_t *sfx);
+
 /** Link sound engine builtins into the specified progs vm
 	\param pr	the vm to link the builtins into.
 */

include/snd_internal.h

@@ -386,6 +386,8 @@ void SND_AmbientOff (snd_t *snd);
 */
 void SND_AmbientOn (snd_t *snd);
 
+void SND_SetAmbient (snd_t *snd, int amb_channel, sfx_t *sfx);
+
 /** Update the sound engine with the client's position and orientation and
 	render some sound.
 	\param snd		sound system state

libs/audio/renderer/snd_channels.c

@@ -419,6 +419,15 @@ SND_AmbientOn (snd_t *snd)
 	snd_ambient = true;
 }
 
+void
+SND_SetAmbient (snd_t *snd, int amb_channel, sfx_t *sfx)
+{
+	if (amb_channel < 0 || amb_channel > NUM_AMBIENTS) {
+		return;
+	}
+	ambient_sfx[amb_channel] = sfx;
+}
+
 static void
 s_updateAmbientSounds (snd_t *snd, const byte *ambient_sound_level)
 {

libs/audio/renderer/snd_dma.c

@@ -418,6 +418,14 @@ s_ambient_on (void)
 	SND_AmbientOn (&snd);
 }
 
+static void
+s_set_ambient (int amb_channel, sfx_t *sfx)
+{
+	if (!sound_started)
+		return;
+	SND_SetAmbient (&snd, amb_channel, sfx);
+}
+
 static void
 s_static_sound (sfx_t *sfx, vec4f_t origin, float vol,
 				float attenuation)
@@ -551,6 +559,7 @@ static snd_render_funcs_t plugin_info_render_funcs = {
 	.init = s_init,
 	.ambient_off     = s_ambient_off,
 	.ambient_on      = s_ambient_on,
+	.set_ambient     = s_set_ambient,
 	.static_sound    = s_static_sound,
 	.start_sound     = s_start_sound,
 	.local_sound     = s_local_sound,

libs/audio/snd.c

@@ -148,6 +148,13 @@ S_AmbientOn (void)
 		snd_render_funcs->ambient_on ();
 }
 
+VISIBLE void
+S_SetAmbient (int amb_channel, sfx_t *sfx)
+{
+	if (snd_render_funcs)
+		snd_render_funcs->set_ambient (amb_channel, sfx);
+}
+
 VISIBLE void
 S_StaticSound (sfx_t *sfx, vec4f_t origin, float vol, float attenuation)
 {

libs/client/cl_temp_entities.c

@@ -129,6 +129,8 @@ CL_TEnts_Precache (void)
 	if (!cl_mod_beam) {
 		cl_mod_beam = cl_mod_bolt;
 	}
+	S_SetAmbient (AMBIENT_WATER, S_PrecacheSound ("ambience/water1.wav"));
+	S_SetAmbient (AMBIENT_SKY, S_PrecacheSound ("ambience/wind2.wav"));
 }
 
 static void