Move all engine stuff to GoRetro. Still many interactions between game and engine code that there should not be.

component_animator.go

@@ -0,0 +1,147 @@
+package GoRetro
+
+/*
+ * --------------------
+ * Animator
+ * --------------------
+ * Handles sprites and their associated animation sequences
+ */
+
+import (
+	"fmt"
+	"io/ioutil"
+	"path"
+	"time"
+
+	"github.com/veandco/go-sdl2/sdl"
+)
+
+type animator struct {
+	container       *Element
+	sequences       map[string]*Sequence // All of the available sequences
+	current         string               // The current sequence
+	lastFrameChange time.Time            // When we last ticked between frames
+	finished        bool                 // We're on the last frame
+}
+
+func NewAnimator(
+	container *Element,
+	sequences map[string]*Sequence,
+	defaultSequence string) *animator {
+	var an animator
+
+	an.container = container
+	an.sequences = sequences
+	an.current = defaultSequence
+	an.lastFrameChange = time.Now()
+
+	return &an
+}
+
+func (an *animator) onUpdate() error {
+	sequence := an.sequences[an.current]
+
+	// Calculate time per frame
+	frameInterval := float64(time.Second) / sequence.sampleRate
+
+	// If we've exceeded that time since the last frame, bump it along one
+	if time.Since(an.lastFrameChange) >= time.Duration(frameInterval) {
+		an.finished = sequence.nextFrame()
+		an.lastFrameChange = time.Now()
+	}
+
+	return nil
+}
+
+func (an *animator) onDraw() error {
+	tex := an.sequences[an.current].texture()
+
+	return drawTexture(
+		tex,
+		an.container.Position,
+		an.container.Rotation,
+		an.container.Renderer)
+}
+
+func (an *animator) onCollision(other *Element) error {
+	return nil
+}
+
+func (an *animator) setSequence(name string) bool {
+	_, ok := an.sequences[name]
+	if ok {
+		// If we *are* changing sequence, change the name and reset the frame
+		if an.current != name {
+			// Reset the old sequence to frame 0
+			sequence := an.sequences[an.current]
+			sequence.resetFrame()
+
+			// Use the new sequence
+			an.current = name
+			an.lastFrameChange = time.Now()
+		}
+	}
+	return ok
+}
+
+type Sequence struct {
+	textures   []*sdl.Texture // The frames
+	frame      int            // Current frame
+	sampleRate float64        // Frames per second
+	loop       bool           // Does this sequence play continuously?
+}
+
+func NewSequence(
+	filepath string, // Path to the folder for this sequence
+	sampleRate float64,
+	loop bool,
+	renderer *sdl.Renderer) (*Sequence, error) {
+
+	var seq Sequence
+
+	// Get a list of frames
+	files, err := ioutil.ReadDir(filepath)
+	if err != nil {
+		return nil, fmt.Errorf("reading directory %v: %v", filepath, err)
+	}
+
+	for _, file := range files {
+		filename := path.Join(filepath, file.Name())
+
+		// Load this frame and turn it into a texture
+		tex, err := loadTextureFromBMP(filename, renderer)
+		if err != nil {
+			return nil, fmt.Errorf("loading sequence frame: %v", err)
+		}
+		seq.textures = append(seq.textures, tex)
+	}
+
+	seq.sampleRate = sampleRate
+	seq.loop = loop
+
+	return &seq, nil
+}
+
+func (seq *Sequence) texture() *sdl.Texture {
+	return seq.textures[seq.frame]
+}
+
+func (seq *Sequence) resetFrame() {
+	seq.frame = 0
+}
+
+func (seq *Sequence) nextFrame() bool {
+	// If we're at the end
+	if seq.frame == len(seq.textures)-1 {
+		if seq.loop {
+			// Reset for a looping sequence
+			seq.resetFrame()
+		} else {
+			return true
+		}
+	} else {
+		seq.frame++
+	}
+
+	return false
+}