From a6d1ded1a41d0f461bf340a33e21fa896ce9da66 Mon Sep 17 00:00:00 2001
From: Kelly Rauchenberger <fefferburbia@gmail.com>
Date: Thu, 11 Mar 2021 17:29:02 -0500
Subject: Added sliding around solid tiles

#3
---
 src/transform_system.cpp | 70 +++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 69 insertions(+), 1 deletion(-)

(limited to 'src/transform_system.cpp')

diff --git a/src/transform_system.cpp b/src/transform_system.cpp
index a643255..825514f 100644
--- a/src/transform_system.cpp
+++ b/src/transform_system.cpp
@@ -2,6 +2,10 @@
 #include "game.h"
 #include "map.h"
 
+bool checkCollisionOptionsContains(CheckCollisionOptions options, CheckCollisionOptions value) {
+  return (static_cast<int>(options) & static_cast<int>(value)) != 0;
+}
+
 void TransformSystem::initSprite(int spriteId, vec2i loc, SpriteLayer layer) {
   Sprite& sprite = game_.getSprite(spriteId);
   sprite.loc = loc;
@@ -47,7 +51,7 @@ void TransformSystem::moveSprite(int spriteId, vec2i newLoc) {
   }
 }
 
-CollisionResult TransformSystem::checkCollision(int spriteId, vec2i curLoc, vec2i newLoc, Direction dir) {
+CollisionResult TransformSystem::checkCollision(int spriteId, vec2i curLoc, vec2i newLoc, Direction dir, CheckCollisionOptions options) {
   CollisionResult result;
 
   Sprite& sprite = game_.getSprite(spriteId);
@@ -87,6 +91,22 @@ CollisionResult TransformSystem::checkCollision(int spriteId, vec2i curLoc, vec2
           break;
         }
       }
+
+      if (checkCollisionOptionsContains(options, CheckCollisionOptions::AllowSliding) &&
+          sprite.sliding &&
+          dir == Direction::right &&
+          horizBlocked &&
+          oldTileUL.y() != oldTileDR.y()) {
+        // If sliding is enabled for this sprite, check if we can slide
+        // either perpendicular direction. Because sliding can only happen
+        // if we were moving in a cardinal direction, we can use tail
+        // recursion and exit early.
+        if (!map.isBlocked(oldTileDR.x()+1, oldTileUL.y())) {
+          return checkCollision(spriteId, curLoc, curLoc - vec2i{0,1} * sprite.movementSpeed, Direction::up);
+        } else if (!map.isBlocked(oldTileDR.x()+1, oldTileDR.y())) {
+          return checkCollision(spriteId, curLoc, curLoc + vec2i{0,1} * sprite.movementSpeed, Direction::down);
+        }
+      }
     }
 
     if (!horizBlocked && enclosureZone) {
@@ -128,6 +148,22 @@ CollisionResult TransformSystem::checkCollision(int spriteId, vec2i curLoc, vec2
           break;
         }
       }
+
+      if (checkCollisionOptionsContains(options, CheckCollisionOptions::AllowSliding) &&
+          sprite.sliding &&
+          dir == Direction::left &&
+          horizBlocked &&
+          oldTileUL.y() != oldTileDR.y()) {
+        // If sliding is enabled for this sprite, check if we can slide
+        // either perpendicular direction. Because sliding can only happen
+        // if we were moving in a cardinal direction, we can use tail
+        // recursion and exit early.
+        if (!map.isBlocked(oldTileUL.x()-1, oldTileUL.y())) {
+          return checkCollision(spriteId, curLoc, curLoc - vec2i{0,1} * sprite.movementSpeed, Direction::up);
+        } else if (!map.isBlocked(oldTileUL.x()-1, oldTileDR.y())) {
+          return checkCollision(spriteId, curLoc, curLoc + vec2i{0,1} * sprite.movementSpeed, Direction::down);
+        }
+      }
     }
 
     if (!horizBlocked && enclosureZone) {
@@ -191,6 +227,22 @@ CollisionResult TransformSystem::checkCollision(int spriteId, vec2i curLoc, vec2
           break;
         }
       }
+
+      if (checkCollisionOptionsContains(options, CheckCollisionOptions::AllowSliding) &&
+          sprite.sliding &&
+          dir == Direction::down &&
+          vertBlocked &&
+          oldTileUL.x() != oldTileDR.x()) {
+        // If sliding is enabled for this sprite, check if we can slide
+        // either perpendicular direction. Because sliding can only happen
+        // if we were moving in a cardinal direction, we can use tail
+        // recursion and exit early.
+        if (!map.isBlocked(oldTileUL.x(), oldTileDR.y()+1)) {
+          return checkCollision(spriteId, curLoc, curLoc - vec2i{1,0} * sprite.movementSpeed, Direction::left);
+        } else if (!map.isBlocked(oldTileDR.x(), oldTileDR.y()+1)) {
+          return checkCollision(spriteId, curLoc, curLoc + vec2i{1,0} * sprite.movementSpeed, Direction::right);
+        }
+      }
     }
 
     if (!vertBlocked && enclosureZone) {
@@ -232,6 +284,22 @@ CollisionResult TransformSystem::checkCollision(int spriteId, vec2i curLoc, vec2
           break;
         }
       }
+
+      if (checkCollisionOptionsContains(options, CheckCollisionOptions::AllowSliding) &&
+          sprite.sliding &&
+          dir == Direction::up &&
+          vertBlocked &&
+          oldTileUL.x() != oldTileDR.x()) {
+        // If sliding is enabled for this sprite, check if we can slide
+        // either perpendicular direction. Because sliding can only happen
+        // if we were moving in a cardinal direction, we can use tail
+        // recursion and exit early.
+        if (!map.isBlocked(oldTileUL.x(), oldTileUL.y()-1)) {
+          return checkCollision(spriteId, curLoc, curLoc - vec2i{1,0} * sprite.movementSpeed, Direction::left);
+        } else if (!map.isBlocked(oldTileDR.x(), oldTileUL.y()-1)) {
+          return checkCollision(spriteId, curLoc, curLoc + vec2i{1,0} * sprite.movementSpeed, Direction::right);
+        }
+      }
     }
 
     if (!vertBlocked && enclosureZone) {
-- 
cgit 1.4.1