02: add simple jumping demo

01-introduction/src/main.c

@@ -60,6 +60,14 @@ SDL_Texture *load_texture(const char *path) {
     return texture;
 }
 
+void switch_animation(struct object *object, SDL_Texture *animation) {
+    if (object->texture == animation)
+        return;
+
+    object->animation_slide = 0; 
+    object->texture = animation;
+}
+
 struct object *create_object(SDL_Texture *texture, int x, int y, int scale, int resolution) {
     struct object *object = (struct object *) calloc(1, sizeof(struct object));
 
@@ -70,7 +78,7 @@ struct object *create_object(SDL_Texture *texture, int x, int y, int scale, int
 
     object->texture = texture;
     object->resolution = resolution;
-    object->animation_speed = 15;
+    object->animation_speed = 13;
     object->scale = scale;
     object->x = x; 
     object->y = y;
@@ -149,15 +157,15 @@ int main(int argc, char *argv[]) {
         if (game.left) {
             player->x -= movement_speed; 
             player->flip = SDL_FLIP_HORIZONTAL;
-            player->texture = run_animation;
+            switch_animation(player, run_animation);
         }
         if (game.right) {
             player->x += movement_speed;
             player->flip = SDL_FLIP_NONE;
-            player->texture = run_animation;
+            switch_animation(player, run_animation);
         }
         if (!game.right && !game.left) {
-            player->texture = idle_animation;
+            switch_animation(player, idle_animation);
         }
 
         player->y += gravity;

02-jumping/Makefile

@@ -0,0 +1,28 @@
+CC=gcc 
+CFLAGS=`pkg-config --cflags sdl2 SDL2_image`
+LDFLAGS=`pkg-config --libs sdl2 SDL2_image`
+TARGET=jumping
+SDIR=src
+ADIR=assets
+ODIR=build
+
+SRC=$(shell find $(SDIR) -type f -name *.c) 
+OBJ=$(SRC:.c=.o)
+
+all: $(TARGET)
+
+.PHONY: default
+$(TARGET): $(OBJ) 
+	mkdir -p build 
+	cp -rf $(ADIR) $(ODIR)/$(ADIR)
+	$(CC) -o $(ODIR)/$@ $^ $(LDFLAGS)
+
+%.o: %.c 
+	$(CC) $(CFLAGS) -o $@ -c $< 
+
+run: 
+	$(ODIR)/$(TARGET)
+
+.PHONY: clean 
+clean: 
+	rm -f $(ODIR)/$(TARGET) $(OBJ)

02-jumping/README.md

@@ -0,0 +1,3 @@
+# Jumping
+
+Code added to 01-introduction for jumping around.

02-jumping/src/main.c

@@ -0,0 +1,207 @@
+#include <stdio.h>
+#include <SDL2/SDL.h>
+#include <SDL2/SDL_image.h>
+#include "structs.h"
+
+const int SCREEN_WIDTH = 1000; 
+const int SCREEN_HEIGHT = 480;
+const Uint32 WINDOW_FLAGS = SDL_WINDOW_SHOWN | SDL_WINDOW_OPENGL; 
+const Uint32 RENDERER_FLAGS = SDL_RENDERER_ACCELERATED;
+int GAME_RUNNING = 1;
+struct game game; 
+int movement_speed = 10;
+int gravity = 8;
+double delta_time; 
+double last_frame;
+
+void prepare_scene(void) {
+    SDL_SetRenderDrawColor(game.renderer, 96, 128, 255, 255);
+    SDL_RenderClear(game.renderer);
+}
+
+void key(SDL_KeyboardEvent *event) {
+    if (event->repeat != 0)
+        return;   
+
+    if (event->keysym.scancode == SDL_SCANCODE_A)
+        game.left = !game.left;
+    if (event->keysym.scancode == SDL_SCANCODE_D)
+        game.right = !game.right;
+    if (event->keysym.scancode == SDL_SCANCODE_SPACE)
+        game.jump = !game.jump;
+}
+
+void handle_input(void) {
+    SDL_Event event; 
+
+    while (SDL_PollEvent(&event)) {
+        switch (event.type) {
+            case SDL_QUIT: 
+                GAME_RUNNING = 0; 
+                break;
+            case SDL_KEYDOWN: 
+            case SDL_KEYUP: 
+                key(&event.key); 
+                break;
+            default:
+                break;
+        }
+        if (event.type == SDL_QUIT) {
+            GAME_RUNNING = 0;
+        }
+    }
+}
+
+SDL_Texture *load_texture(const char *path) {
+    SDL_Texture *texture; 
+    
+    SDL_LogMessage(SDL_LOG_CATEGORY_APPLICATION, SDL_LOG_PRIORITY_INFO, "Loading %s", path);
+    
+    texture = IMG_LoadTexture(game.renderer, path);
+
+    return texture;
+}
+
+void switch_animation(struct object *object, SDL_Texture *animation) {
+    if (object->texture == animation)
+        return;
+
+    object->animation_slide = 0; 
+    object->texture = animation;
+}
+
+struct object *create_object(SDL_Texture *texture, int x, int y, int scale, int resolution) {
+    struct object *object = (struct object *) calloc(1, sizeof(struct object));
+
+    if (object == NULL) {
+        fprintf(stderr, "Error: failed allocating memory for new object\n");
+        return NULL;
+    }
+
+    object->texture = texture;
+    object->resolution = resolution;
+    object->animation_speed = 13;
+    object->scale = scale;
+    object->x = x; 
+    object->y = y;
+
+    return object;
+}
+
+void draw_object(struct object *object) {
+    int texture_width; 
+    SDL_Rect src;
+    SDL_Rect dest;
+
+    src.x = object->animation_slide * object->resolution;
+    src.y = 0;
+
+    src.w = object->resolution;
+    src.h = object->resolution;
+
+    dest.x = object->x; 
+    dest.y = object->y; 
+    dest.w = object->resolution * object->scale;
+    dest.h = object->resolution * object->scale;
+
+    SDL_RenderCopyEx(game.renderer, object->texture, &src, &dest, 0, NULL, object->flip);
+
+    // update animation slide
+    SDL_QueryTexture(object->texture, NULL, NULL, &texture_width, NULL);
+
+    object->animation_clock += object->animation_speed*(delta_time/1000);
+
+    if (object->animation_clock >= 1) {
+        object->animation_clock = 0;    
+        object->animation_slide = (object->animation_slide+1) % (texture_width / object->resolution); // clock arithmetic: jump back to first animation slide 
+    }
+}
+
+void present_scene(void) {
+    SDL_RenderPresent(game.renderer);
+}
+
+int main(int argc, char *argv[]) {
+    if (SDL_Init(SDL_INIT_VIDEO) != 0) {
+        fprintf(stderr, "Error: could not initialize SDL\n%s\n", SDL_GetError());
+        return -1;
+    }
+
+    game.window = SDL_CreateWindow("02-jumping", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, WINDOW_FLAGS);
+
+    if (game.window == NULL) {
+        fprintf(stderr, "Error: could not create window\n%s\n", SDL_GetError());
+        return -1;
+    }
+
+    game.renderer = SDL_CreateRenderer(game.window, -1, RENDERER_FLAGS);    
+
+    if (game.renderer == NULL) {
+        fprintf(stderr, "Error: could not create renderer\n%s\n", SDL_GetError());
+        return -1;
+    }
+
+    // load player animations 
+    SDL_Texture *idle_animation = load_texture("assets/player/idle.png");
+    SDL_Texture *run_animation = load_texture("assets/player/run.png");
+    SDL_Texture *jump_animation = load_texture("assets/player/jump.png");
+
+    struct object *player = create_object(idle_animation, SCREEN_WIDTH/2, 0, 4, 48);
+
+    // game loop
+    while (GAME_RUNNING) {
+        double current_frame = SDL_GetTicks();
+        delta_time = current_frame - last_frame;
+        last_frame = current_frame;
+
+        prepare_scene();
+        handle_input(); 
+
+        // The reason why I don't do 
+        // that much game development 
+        // in my free time. Damn youuu ifs
+        if (player->colliding) {
+            if (game.left)
+                switch_animation(player, run_animation);
+            if (game.right) 
+                switch_animation(player, run_animation);
+            if (!game.left && !game.right) 
+                switch_animation(player, idle_animation);
+            if (game.jump) {
+                switch_animation(player, jump_animation);
+                player->force -= movement_speed * 3;
+                player->y += player->force;
+                player->colliding = 0;
+            }
+        }
+
+        if (game.left) {
+            player->x -= movement_speed; 
+            player->flip = SDL_FLIP_HORIZONTAL;
+        }
+        if (game.right) {
+            player->x += movement_speed;
+            player->flip = SDL_FLIP_NONE;
+        }
+
+        if (player->y < 200) {
+            player->force += 2;
+        } else {
+            player->colliding = 1;
+            player->force = 0;
+        }
+
+        player->y += player->force;
+
+        draw_object(player);
+
+        present_scene();
+
+        SDL_Delay(16);
+    }
+
+    SDL_DestroyWindow(game.window);
+    SDL_Quit();
+
+    return 0; 
+}

02-jumping/src/structs.h

@@ -0,0 +1,40 @@
+#ifndef STRUCTS_H
+#define STRUCTS_H
+
+#include <SDL2/SDL.h>
+
+struct game {
+    SDL_Window *window; 
+    SDL_Renderer *renderer;
+
+    int left; 
+    int right;
+    int jump;
+};
+
+struct animation {
+    SDL_Texture *tilemap;   
+    int resolution;
+
+    int skippable;
+};
+
+struct object {
+    SDL_Texture *texture;
+    int resolution;                 // of the texture/every tile
+
+    int x; 
+    int y;
+    int scale;
+    Uint32 flip;
+
+    // animation 
+    double animation_clock;         // everytime it reaches 1, the texture switches to the next slide
+    double animation_speed;         // how fast will the clock reach 1 with respect to delta_time
+    int animation_slide;            // the current slide of the animation
+
+    int colliding;
+    int force;
+};
+
+#endif