From 4f433796b497df98d195a97042f42e02b6f3a450 Mon Sep 17 00:00:00 2001
From: Gregory Eremin <g@erem.in>
Date: Sun, 4 Oct 2015 16:53:19 +0300
Subject: [PATCH] Implement ball and basic collisions

---
 src/breakout.hpp |  3 ++
 src/brick.cpp    | 19 +++++++++++++
 src/brick.hpp    |  3 ++
 src/scene.cpp    | 74 ++++++++++++++++++++++++++++++++++++++++++++++--
 src/scene.hpp    |  7 +++++
 5 files changed, 104 insertions(+), 2 deletions(-)

diff --git a/src/breakout.hpp b/src/breakout.hpp
index 32667d1..f845c9a 100644
--- a/src/breakout.hpp
+++ b/src/breakout.hpp
@@ -5,12 +5,15 @@
 #define SCREEN_WIDTH 407
 #define SCREEN_HEIGHT 600
 
+#define BALL_RADIUS 8
+
 #define PAD_WIDTH 100
 #define PAD_HEIGHT 10
 #define KEY_MOVE_STEP 5
 
 #define BRICK_ROWS 7
 #define BRICK_COLS 8
+#define NUM_BRICKS BRICK_ROWS*BRICK_COLS
 #define BRICK_WIDTH 50
 #define BRICK_HEIGHT 15
 
diff --git a/src/brick.cpp b/src/brick.cpp
index c461ac0..8814dcb 100644
--- a/src/brick.cpp
+++ b/src/brick.cpp
@@ -7,11 +7,30 @@ Brick::Brick(SDL_Renderer *r, int x, int y, Color c) {
     brick.w = BRICK_WIDTH;
     brick.h = BRICK_HEIGHT;
     color = c;
+    visible = true;
 }
 
 Brick::~Brick() {}
 
+bool Brick::collides_with(int x1, int y1, int x2, int y2) {
+    return (
+        visible &&
+        brick.x < x2 &&
+        brick.x + BRICK_WIDTH > x1 &&
+        brick.y < y2 &&
+        brick.y + BRICK_HEIGHT > y1
+    );
+}
+
+void Brick::destroy() {
+    visible = false;
+}
+
 void Brick::render() {
+    if (!visible) {
+        return;
+    }
+
     switch (color) {
     case RED:
         SDL_SetRenderDrawColor(renderer, 255, 51, 51, 255);
diff --git a/src/brick.hpp b/src/brick.hpp
index b3bd389..2cacff8 100644
--- a/src/brick.hpp
+++ b/src/brick.hpp
@@ -16,10 +16,13 @@ public:
     Brick(SDL_Renderer *r, int x, int y, Color c);
     ~Brick();
 
+    bool collides_with(int x1, int y1, int x2, int y2);
+    void destroy();
     void render();
 private:
     SDL_Renderer *renderer;
 
     SDL_Rect brick;
     Color color;
+    bool visible;
 };
diff --git a/src/scene.cpp b/src/scene.cpp
index e7c5579..e9f8cc3 100644
--- a/src/scene.cpp
+++ b/src/scene.cpp
@@ -5,10 +5,19 @@ Scene::Scene(SDL_Renderer *r) {
     renderer = r;
 
     pad.x = (SCREEN_WIDTH - PAD_WIDTH) / 2;
-    pad.y = (SCREEN_HEIGHT - PAD_HEIGHT);
+    pad.y = SCREEN_HEIGHT - PAD_HEIGHT;
     pad.w = PAD_WIDTH;
     pad.h = PAD_HEIGHT;
 
+    ball.x = SCREEN_WIDTH/2 - BALL_RADIUS;
+    ball.y = SCREEN_HEIGHT/2 - BALL_RADIUS;
+    ball.w = BALL_RADIUS * 2;
+    ball.h = BALL_RADIUS * 2;
+    ball_moving = true;
+    ball_velx = 0;
+    ball_vely = 0;
+    launch_ball();
+
     for (int i = 0; i < BRICK_ROWS; i++) {
         for (int j = 0; j < BRICK_COLS; j++) {
             bricks.push_back(Brick(renderer, j * BRICK_WIDTH + j, i * BRICK_HEIGHT + i, (Color)i));
@@ -21,13 +30,24 @@ Scene::Scene(SDL_Renderer *r) {
 Scene::~Scene() {}
 
 void Scene::render() {
+    // Draw background
     SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
     SDL_RenderClear(renderer);
+
+    // Draw pad
     SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
     SDL_RenderFillRect(renderer, &pad);
-    for (int i = 0; i < BRICK_ROWS * BRICK_COLS; i++) {
+
+    // Draw bricks
+    for (int i = 0; i < NUM_BRICKS; i++) {
         bricks[i].render();
     }
+
+    // Draw ball
+    move_ball();
+    SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
+    SDL_RenderFillRect(renderer, &ball);
+
     SDL_RenderPresent(renderer);
 }
 
@@ -44,3 +64,53 @@ void Scene::move_pad(int x) {
 void Scene::move_pad_relative(int delta) {
     move_pad(pad.x + delta);
 }
+
+void Scene::launch_ball() {
+    ball_moving = true;
+    ball_velx = 3;
+    ball_vely = -2;
+}
+
+void Scene::move_ball() {
+    if (!ball_moving) {
+        return;
+    }
+
+    ball.x += ball_velx;
+    ball.y += ball_vely;
+
+    // Collisions
+
+    // Left
+    if (ball.x <= 0) {
+        ball_velx = -ball_velx;
+    }
+    // Right
+    if (ball.x >= SCREEN_WIDTH - 2*BALL_RADIUS) {
+        ball_velx = -ball_velx;
+    }
+    // Top
+    if (ball.y <= 0) {
+        ball_vely = -ball_vely;
+    }
+    // Bottom
+    if (ball.y >= SCREEN_HEIGHT) {
+        // Game over
+    }
+    // Pad
+    if (ball.x >= pad.x && ball.x <= pad.x + PAD_WIDTH && ball.y + 2*BALL_RADIUS >= pad.y) {
+        ball_vely = -ball_vely;
+    }
+    // Bricks
+    for (int i = NUM_BRICKS; i > 0; --i) {
+        int x1 = ball.x;
+        int y1 = ball.y;
+        int x2 = ball.x + 2*BALL_RADIUS;
+        int y2 = ball.y + 2*BALL_RADIUS;
+
+        if (bricks[i].collides_with(x1, y1, x2, y2)) {
+            ball_vely = -ball_vely;
+            bricks[i].destroy();
+        }
+    }
+}
diff --git a/src/scene.hpp b/src/scene.hpp
index ead0e33..428c6bc 100644
--- a/src/scene.hpp
+++ b/src/scene.hpp
@@ -11,9 +11,16 @@ public:
     void render();
     void move_pad(int x);
     void move_pad_relative(int delta);
+    void launch_ball();
 private:
+    void move_ball();
+
     SDL_Renderer *renderer;
 
+    bool ball_moving;
+    int ball_velx;
+    int ball_vely;
+    SDL_Rect ball;
     SDL_Rect pad;
     std::vector<Brick> bricks;
 };