From 316b7ca9bb9b0f26d74a1e17f68bd86aeb1dc33c Mon Sep 17 00:00:00 2001
From: Matthias Braun <matze@braunis.de>
Date: Mon, 24 May 2004 23:02:34 +0000
Subject: [PATCH] added some comments to scrolling code

SVN-Revision: 1317
---
 src/camera.cpp | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/src/camera.cpp b/src/camera.cpp
index 2c145dafb..6ef816884 100644
--- a/src/camera.cpp
+++ b/src/camera.cpp
@@ -80,21 +80,28 @@ Camera::scroll_normal(float elapsed_time)
   if(elapsed_time < EPSILON)
     return;
 
+  /****** Vertical Scrolling part ******/
   bool do_y_scrolling = true;
 
   if(player->dying || level->height == 19)
     do_y_scrolling = false;
 
   if(do_y_scrolling) {
-    float target_y;
+    // target_y is the high we target our scrolling at. This is not always the
+    // high of the player, but if he is jumping upwards we should use the
+    // position where he last touched the ground.
+    float target_y; 
     if(player->fall_mode == Player::JUMPING)
       target_y = player->last_ground_y + player->base.height;
     else
       target_y = player->base.y + player->base.height;
 
+    // delta_y is the distance we'd have to travel to directly reach target_y
     float delta_y = translation.y - (target_y - screen->h/2);
+    // speed is the speed the camera would need to reach target_y in this frame
     float speed_y = delta_y / elapsed_time;
 
+    // limit the camera speed when jumping upwards
     if(player->fall_mode != Player::FALLING 
         && player->fall_mode != Player::TRAMPOLINE_JUMP) {
       if(speed_y > max_speed_y)
@@ -103,6 +110,7 @@ Camera::scroll_normal(float elapsed_time)
         speed_y = -max_speed_y;
     }
 
+    // finally scroll with calculated speed
     translation.y -= speed_y * elapsed_time;
 
     // don't scroll before the start or after the level's end
@@ -112,14 +120,24 @@ Camera::scroll_normal(float elapsed_time)
       translation.y = 0; 
   }
 
+  /****** Horizontal scrolling part *******/
+
+  // our camera is either in leftscrolling, rightscrolling or nonscrollingmode.
+  
+  // when suddenly changing directions while scrolling into the other direction.
+  // abort scrolling, since tux might be going left/right at a relatively small
+  // part of the map (like when jumping upwards)
   if((player->dir == ::LEFT && scrollchange == RIGHT)
       || (player->dir == ::RIGHT && scrollchange == LEFT))
     scrollchange = NONE;
+  // when in left 1/3rd of screen scroll left
   if(player->base.x < translation.x + screen->w/3 && level->back_scrolling)
     scrollchange = LEFT;
+  // scroll right when in right 1/3rd of screen
   else if(player->base.x > translation.x + screen->w/3*2)
     scrollchange = RIGHT;
 
+  // calculate our scroll target depending on scroll mode
   float target_x;
   if(scrollchange == LEFT)
     target_x = player->base.x - screen->w/3*2;
@@ -128,15 +146,19 @@ Camera::scroll_normal(float elapsed_time)
   else
     target_x = translation.x;
 
+  // that's the distance we would have to travel to reach target_x
   float delta_x = translation.x - target_x;
+  // the speed we'd need to travel to reach target_x in this frame
   float speed_x = delta_x / elapsed_time;
 
+  // limit our speed
   float maxv = 1 + fabsf(player->physic.get_velocity_x() * 1.3);
   if(speed_x > maxv)
     speed_x = maxv;
   else if(speed_x < -maxv)
     speed_x = -maxv;
-  
+ 
+  // apply scrolling
   translation.x -= speed_x * elapsed_time;
 
   // don't scroll before the start or after the level's end
-- 
2.11.0