Animating Button Clicks in SDL
How would I implement a button that triggers an animation when clicked?
Implementing a button that triggers an animation when clicked is a great way to provide visual feedback to the user. We can achieve this by extending our existing Button class and incorporating a simple animation system. Let's walk through the process step by step.
First, let's create an AnimatedButton class that inherits from our Button class:
#include <SDL.h>
#include <chrono>
#include <vector>
class AnimatedButton : public Button {
public:
AnimatedButton(int x, int y, int w, int h)
: Button{x, y, w, h} {}
void HandleLeftClick() override {
Button::HandleLeftClick();
StartAnimation();
}
void Render(SDL_Surface* Surface) override {
Button::Render(Surface);
if (isAnimating) {
RenderAnimation(Surface);
}
}
void Update() {
if (isAnimating) { UpdateAnimation(); }
}
private:
void StartAnimation() {
isAnimating = true;
animationStart =
std::chrono::steady_clock::now();
currentFrame = 0;
}
void UpdateAnimation() {
auto now = std::chrono::steady_clock::now();
auto elapsed =
std::chrono::duration_cast<
std::chrono::milliseconds>(
now - animationStart)
.count();
if (elapsed > animationDuration) {
isAnimating = false;
} else {
currentFrame = (elapsed / frameDuration) %
frames.size();
}
}
void RenderAnimation(SDL_Surface* Surface) {
// Render current animation frame
SDL_BlitSurface(frames[currentFrame],
nullptr, Surface, &Rect);
}
bool isAnimating{false};
std::chrono::steady_clock::time_point
animationStart;
std::vector<SDL_Surface*> frames;
int currentFrame{0};
int animationDuration{1000}; // milliseconds
int frameDuration{
100}; // milliseconds per frame
};In this AnimatedButton class, we've added:
- An
isAnimatingflag to track the animation state. - A vector of
SDL_Surfacepointers to store animation frames. StartAnimation(),UpdateAnimation(), andRenderAnimation()methods to manage the animation.- An overridden
HandleLeftClick()method that starts the animation when the button is clicked. - An
Update()method that should be called in your game loop to update the animation state.
Now, let's see how we can use this AnimatedButton in our main game loop:
#include <SDL.h>
#include <SDL_image.h>
int main(int argc, char* argv[]) {
SDL_Init(SDL_INIT_VIDEO);
IMG_Init(IMG_INIT_PNG);
Window GameWindow;
AnimatedButton MyButton{50, 50, 100, 50};
// Load animation frames
std::vector<std::string> framePaths = {
"frame1.png", "frame2.png", "frame3.png",
"frame4.png"};
for (const auto& path : framePaths) {
MyButton.AddFrame(IMG_Load(path.c_str()));
}
SDL_Event Event;
bool shouldQuit{false};
while (!shouldQuit) {
while (SDL_PollEvent(&Event)) {
MyButton.HandleEvent(Event);
if (Event.type == SDL_QUIT) {
shouldQuit = true;
}
}
MyButton.Update(); // Update animation state
GameWindow.Render();
MyButton.Render(GameWindow.GetSurface());
GameWindow.Update();
SDL_Delay(16); // Cap at ~60 FPS
}
IMG_Quit();
SDL_Quit();
return 0;
}In this main loop, we create an AnimatedButton, load its animation frames, and ensure we call its Update() method each frame to progress the animation.
To make this example more concrete, let's consider a "power-up" button that plays a glowing animation when clicked:
class PowerUpButton : public AnimatedButton {
public:
PowerUpButton(int x, int y, int w, int h)
: AnimatedButton{x, y, w, h} {
LoadAnimationFrames();
}
void HandleLeftClick() override {
AnimatedButton::HandleLeftClick();
std::cout << "Power-up activated!\n";
// Add game logic for power-up here
}
private:
void LoadAnimationFrames() {
std::vector<std::string> framePaths = {
"powerup_glow1.png",
"powerup_glow2.png",
"powerup_glow3.png",
"powerup_glow4.png"};
for (const auto& path : framePaths) {
AddFrame(IMG_Load(path.c_str()));
}
}
};This PowerUpButton loads specific "glow" animation frames and includes some game logic when clicked. By using this approach, you can create visually appealing, interactive buttons that provide immediate feedback to the user through animations!
Creating SDL2 Buttons
Learn to create interactive buttons in SDL2 and manage communication between different UI components.