From cba8a468e166156dd8cab3358da369b1df76eb8b Mon Sep 17 00:00:00 2001
From: hgn <hgodden00@gmail.com>
Date: Mon, 10 Jul 2023 20:34:29 +0100
Subject: [PATCH] smooth replay resume

---
 player_replay.c | 85 +++++++++++++++++++++++++++++++------------------
 skaterift.h     |  4 +++
 2 files changed, 58 insertions(+), 31 deletions(-)

diff --git a/player_replay.c b/player_replay.c
index 79db8da..47da357 100644
--- a/player_replay.c
+++ b/player_replay.c
@@ -356,49 +356,72 @@ void skaterift_restore_frame( replay_frame *frame ){
 
    memcpy( &localplayer.cam_control, &gs->cam_control, 
             sizeof(struct player_cam_controller) );
+
+   /* chop end off replay */
+   frame->r = NULL;
+   skaterift.replay.statehead = frame;
+   skaterift.replay.head = frame;
+   skaterift.replay.cursor_frame = frame;
+   skaterift.replay.cursor = frame->time;
+   skaterift.replay_control = k_replay_control_scrub;
+   skaterift.activity = k_skaterift_default;
+   vg.time = frame->time;
 }
 
 VG_STATIC void skaterift_replay_pre_update(void){
    if( skaterift.activity != k_skaterift_replay ) return;
 
-   f64 speed = 1.0;
+   f64 speed = vg.time_frame_delta * 1.0;
    f64 target = skaterift.replay.cursor;
 
-   if( vg_getkey( SDLK_9 ) ){
-      target -= vg.time_frame_delta * speed;
-      skaterift.replay_control = k_replay_control_scrub;
-      replay_seek( &skaterift.replay, target );
-   }
-   if( vg_getkey( SDLK_0 ) ){
-      target += vg.time_frame_delta * speed;
-      skaterift.replay_control = k_replay_control_scrub;
-      replay_seek( &skaterift.replay, target );
+   if( skaterift.replay_control == k_replay_control_resume ){
+      if( skaterift.replay.cursor_frame == skaterift.resume_target ||
+          skaterift.replay.cursor_frame == NULL ){
+         skaterift_restore_frame( skaterift.resume_target );
+      }
+      else {
+         vg_slewf( &skaterift.resume_transition, 1.0f, 
+                   vg.time_frame_delta * (1.0f/1.0f) );
+
+         if( skaterift.resume_transition >= 1.0f )
+            skaterift_restore_frame( skaterift.resume_target );
+         else {
+            target = vg_lerp( skaterift.resume_begin, 
+                              skaterift.resume_target->time, 
+                              vg_smoothstepf( skaterift.resume_transition ) );
+            replay_seek( &skaterift.replay, target );
+         }
+      }
    }
+   else {
+      if( vg_getkey( SDLK_9 ) ){
+         target -= speed;
+         skaterift.replay_control = k_replay_control_scrub;
+         replay_seek( &skaterift.replay, target );
+      }
+      if( vg_getkey( SDLK_0 ) ){
+         target += speed;
+         skaterift.replay_control = k_replay_control_scrub;
+         replay_seek( &skaterift.replay, target );
+      }
 
-   if( vg_getkey( SDLK_7 ) )
-      skaterift.replay_control = k_replay_control_play;
-
-   if( skaterift.replay_control == k_replay_control_play ){
-      target += vg.time_frame_delta;
-      replay_seek( &skaterift.replay, target );
-   }
+      if( vg_getkey( SDLK_7 ) )
+         skaterift.replay_control = k_replay_control_play;
 
-   if( vg_getkey( SDLK_8 ) ){
-      replay_frame *prev = replay_find_recent_stateframe( &skaterift.replay );
+      if( skaterift.replay_control == k_replay_control_play ){
+         target += vg.time_frame_delta;
+         replay_seek( &skaterift.replay, target );
+      }
 
-      if( prev ){
-         skaterift_restore_frame( prev );
+      if( vg_getkey( SDLK_8 ) ){
+         replay_frame *prev = replay_find_recent_stateframe(&skaterift.replay);
 
-         /* chop end off replay */
-         prev->r = NULL;
-         skaterift.replay.statehead = prev;
-         skaterift.replay.head = prev;
-         skaterift.replay.cursor_frame = prev;
-         skaterift.replay.cursor = prev->time;
-         skaterift.replay_control = k_replay_control_scrub;
-         skaterift.activity = k_skaterift_default;
-         vg.time = prev->time;
-         return;
+         if( prev ){
+            skaterift.replay_control = k_replay_control_resume;
+            skaterift.resume_target = prev;
+            skaterift.resume_begin = skaterift.replay.cursor;
+            skaterift.resume_transition = 0.0f;
+         }
       }
    }
 }
diff --git a/skaterift.h b/skaterift.h
index 1e2fba3..1aa3c51 100644
--- a/skaterift.h
+++ b/skaterift.h
@@ -29,6 +29,10 @@ struct{
    camera cam, replay_cam;
    
    replay_buffer replay;
+   replay_frame *resume_target;
+   f64 resume_begin;
+   f32 resume_transition;
+
    enum replay_control {
       k_replay_control_scrub,
       k_replay_control_play,
-- 
2.25.1