From c64189ebe56e8132282335fcb9cf5e48e5c3961e Mon Sep 17 00:00:00 2001
From: "Jakob L. Kreuze" <jakob@memeware.net>
Date: Wed, 24 Oct 2018 15:44:36 -0400
Subject: Reimplementing features from two commits back + fixes for significant
 graphical bugs

---
 camera.fnl | 45 +++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 41 insertions(+), 4 deletions(-)

(limited to 'camera.fnl')

diff --git a/camera.fnl b/camera.fnl
index ba8a435..b46142d 100644
--- a/camera.fnl
+++ b/camera.fnl
@@ -15,9 +15,46 @@
 ;;;; You should have received a copy of the GNU General Public License along
 ;;;; with slime-the-world. If not, see <http://www.gnu.org/licenses/>.
 
-;; Returns a new camera object initially focused at the given world coordinates,
-;; (`x', `y').
-(fn new-camera [x y]
-  {:x-pos x :y-pos y})
+(local lume (require :lib.lume))
+
+(local tile-sheet (. (require :world) :tile-sheet))
+
+;; TODO: Document this
+(fn focus-on-object [camera object dt]
+  (let [last-x (. camera :x-pos)
+        last-y (. camera :y-pos)
+        max-x (. camera :max-x)
+        max-y (. camera :max-y)
+        object-x (. object :x-pos)
+        object-y (. object :y-pos)
+        width (. object :width)
+        height (. object :height)
+        screen-width (. camera :screen-width)
+        screen-height (. camera :screen-height)
+        x-offset (math.floor (- (/ screen-width 2) (/ width 2)))
+        y-offset (math.floor (- (/ screen-height 2) (/ height 2)))
+        x (lume.lerp last-x (- object-x x-offset) (* 4 dt))
+        x (lume.clamp x 0 max-x)
+        y (lume.lerp last-y (- object-y y-offset) (* 4 dt))
+        y (lume.clamp y 0 max-y)]
+    (values x y)))
+
+;; Returns a new camera object, aware of the bounds of `world' and the camera
+;; lock parameters entailed by the given screen dimensions.
+(fn new-camera [world screen-width screen-height]
+  (let [tile-width (. tile-sheet :width)
+        tile-height (. tile-sheet :height)
+        max-x (- (* tile-width (. world :width)) screen-width)
+        max-y (- (* tile-height (. world :height)) screen-height)]
+    {:x-pos 0
+     :y-pos 0
+
+     :screen-width screen-width
+     :screen-height screen-height
+
+     :max-x max-x
+     :max-y max-y
+
+     :focus-on-object focus-on-object}))
 
 {:new new-camera}
-- 
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