add animations (lerp only for now)

src/engine/render/anim.c

@@ -1,38 +1,89 @@
 #include <dangerzone/render/anim.h>
 
+#include <string.h>
+
 void
-anim_rect_pos(
-    framebuffer_e framebuffer,
-    uint32_t x0,
-    uint32_t y0,
-    uint32_t x1,
-    uint32_t y1,
-    uint32_t w,
-    uint32_t h,
-    uint32_t color
-) {
-    // there's nowhere to move
-    if (x0 == x1 && y0 == y1) {
-        return;
+anim_init(anim_t *anim)
+{
+    if (anim != NULL)
+        memset(anim, 0, sizeof *anim);
+}
+
+bool
+anim_start(anim_t *anim, const anim_track_t *tracks,
+           size_t count, float duration)
+{
+    if (anim == NULL || (count != 0 && tracks == NULL) ||
+        count > ANIM_MAX_TRACKS || duration < 0.0f) {
+        return false;
     }
+
+    anim->count = count;
+    anim->elapsed = 0.0f;
+    anim->duration = duration;
+    anim->active = duration > 0.0f && count > 0;
 
-    uint32_t dirx = (x1 - x0 > 0) ? 1 : -1;
-    uint32_t diry = (y1 - y0 > 0) ? 1 : -1;
+    for (size_t i = 0; i < count; ++i) {
+        anim->tracks[i] = tracks[i];
+        anim->items[i].payload = tracks[i].payload;
+        anim->items[i].rect = tracks[i].from;
+    }
 
-    if (x0 == x1) {
-        dirx = 0;
+    if (!anim->active) {
+        for (size_t i = 0; i < count; ++i)
+            anim->items[i].rect = tracks[i].to;
     }
-    
-    if (y0 == y1) {
-        diry = 0;
+
+    return true;
+}
+
+bool
+anim_update(anim_t *anim, float dt)
+{
+    if (anim == NULL || !anim->active)
+        return true;
+
+    if (dt < 0.0f)
+        dt = 0.0f;
+
+    anim->elapsed += dt;
+
+    float t = anim->elapsed / anim->duration;
+    if (t >= 1.0f) {
+        t = 1.0f;
+        anim->active = false;
     }
 
-    /**
-     * 1. shift the rectangle by one pixel in the direction of movement
-     * 2. remove the trailing row / column left  
-     */
+    /* Ease-out. Replace with t for linear motion. */
+    float eased = 1.0f - (1.0f - t) * (1.0f - t);
 
-    if (true) {
+    for (size_t i = 0; i < anim->count; ++i) {
+        const anim_track_t *track = &anim->tracks[i];
+        anim_rect_t *rect = &anim->items[i].rect;
 
+        rect->x = track->from.x + (track->to.x - track->from.x) * eased;
+        rect->y = track->from.y + (track->to.y - track->from.y) * eased;
+        rect->w = track->from.w + (track->to.w - track->from.w) * eased;
+        rect->h = track->from.h + (track->to.h - track->from.h) * eased;
     }
+
+    return !anim->active;
+}
+
+bool
+anim_is_active(const anim_t *anim)
+{
+    return anim != NULL && anim->active;
+}
+
+size_t
+anim_count(const anim_t *anim)
+{
+    return anim != NULL ? anim->count : 0;
+}
+
+const anim_item_t *
+anim_items(const anim_t *anim)
+{
+    return anim != NULL ? anim->items : NULL;
 }