From d470f7e6478c12d3dd212af7f2d20e20a2798085 Mon Sep 17 00:00:00 2001
From: Noah Petherbridge <root@kirsle.net>
Date: Wed, 2 Jun 2021 21:49:29 -0700
Subject: [PATCH] Collision: Fix walking up leftward slopes

* Actors can now walk up gentle inclines to the left as well as they can
  to the right. The bug was introduced as a hack to prevent clipping
  thru the left wall of a 90 degree corner, but that problem seems
  resolved now.
---
 pkg/collision/collide_level.go | 15 ++++++++++-----
 pkg/doodads/dummy/dummy.go     |  5 +++++
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/pkg/collision/collide_level.go b/pkg/collision/collide_level.go
index f455fae..1e240b7 100644
--- a/pkg/collision/collide_level.go
+++ b/pkg/collision/collide_level.go
@@ -73,9 +73,13 @@ func CollidesWithGrid(d Actor, grid *level.Chunker, target render.Point) (*Colli
 	)
 
 	// Adjust the actor's bounding rect by its stated Hitbox from its script.
-	S = SizePlusHitbox(S, hitbox)
+	// e.g.: Boy's Canvas size is 56x56 but he is a narrower character with a
+	// hitbox width smaller than its Canvas size.
+	S = SizePlusHitbox(GetBoundingRect(d), hitbox)
 
-	// Test all of the bounding boxes for a collision with level geometry.
+	// Test if we are ALREADY colliding with level geometry and try and wiggle
+	// free. ScanBoundingBox scans level pixels along the four edges of the
+	// actor's hitbox in world space.
 	if ok := result.ScanBoundingBox(GetBoundingRectHitbox(d, hitbox), grid); ok {
 		// We've already collided! Try to wiggle free.
 		if result.Bottom {
@@ -108,7 +112,8 @@ func CollidesWithGrid(d Actor, grid *level.Chunker, target render.Point) (*Colli
 			// We're moving upward.
 			d.SetGrounded(false)
 		} else {
-			// Cap our downward motion to our current position.
+			// Cap our downward motion to our current position,
+			// fighting the force of gravity.
 			target.Y = P.Y
 		}
 	}
@@ -117,7 +122,7 @@ func CollidesWithGrid(d Actor, grid *level.Chunker, target render.Point) (*Colli
 	if (result.Left && target.X < P.X) || (result.Right && target.X > P.X) {
 		// If the step is short enough, try and jump up.
 		height := P.Y + S.H
-		if result.Left && target.X < P.X {
+		if result.Left { // && target.X < P.X {
 			height -= result.LeftPoint.Y
 		} else {
 			height -= result.RightPoint.Y
@@ -182,7 +187,7 @@ func CollidesWithGrid(d Actor, grid *level.Chunker, target render.Point) (*Colli
 
 			if result.Left && !hitLeft {
 				hitLeft = true
-				capLeft = result.LeftPoint.X + 1
+				capLeft = result.LeftPoint.X // + 1
 
 				// TODO: there was a clipping bug where the player could clip
 				// thru a left wall if they jumped slightly while pressing into
diff --git a/pkg/doodads/dummy/dummy.go b/pkg/doodads/dummy/dummy.go
index 00ba051..d619906 100644
--- a/pkg/doodads/dummy/dummy.go
+++ b/pkg/doodads/dummy/dummy.go
@@ -22,3 +22,8 @@ func NewDrawing(id string, doodad *doodads.Doodad) *Drawing {
 func (d *Drawing) Size() render.Rect {
 	return d.Drawing.Size()
 }
+
+// MoveTo changes the drawing's position.
+func (d *Drawing) MoveTo(to render.Point) {
+	d.Drawing.MoveTo(to)
+}