Reorganized the code structure, fix a lot of issues.

src/history.h

@@ -75,7 +75,6 @@ static void hist_apply_prop(shape_t *s, hist_prop_t prop, const float val[4]) {
     }
 }
 
-// -- history API --
 
 /**
  * Zero-initialize the history stack. Call once during app init.
@@ -206,7 +205,37 @@ static void history_end_edit(history_t *h, vector_t *shapes) {
  * @param shapes  the shapes vector to modify
  * @param forward true to use new_val (redo), false to use old_val (undo)
  */
-static void history_apply_entry(hist_entry_t *entry, vector_t *shapes, bool forward) {
+// -- batch API for multi-shape operations (move, rotate, resize) --
+
+typedef struct {
+    hist_change_t *changes;
+    int count;
+    int capacity;
+} hist_batch_t;
+
+static void history_batch_init(hist_batch_t *batch, int count) {
+    batch->changes = (hist_change_t*) ALLOC((size_t)count * sizeof(hist_change_t));
+    batch->count = 0;
+    batch->capacity = count;
+}
+
+static void history_batch_add(hist_batch_t *batch, int shape_index, hist_prop_t prop,
+                               const float old_val[4], const float new_val[4]) {
+    hist_change_t *c = &batch->changes[batch->count++];
+    c->shape_index = shape_index;
+    c->prop = prop;
+    memcpy(c->old_val, old_val, sizeof(float[4]));
+    memcpy(c->new_val, new_val, sizeof(float[4]));
+}
+
+static void history_batch_commit(hist_batch_t *batch, history_t *h) {
+    hist_entry_t entry = { .changes = batch->changes, .count = batch->count };
+    history_push_entry(h, entry);
+}
+
+/**
+ * Apply every change in an entry to the shapes vector and regenerate buffers.
+ */static void history_apply_entry(hist_entry_t *entry, vector_t *shapes, bool forward) {
     for (int i = 0; i < entry->count; i++) {
         hist_change_t *c = &entry->changes[i];
         if (c->shape_index >= shapes->count) continue;
@@ -217,37 +246,19 @@ static void history_apply_entry(hist_entry_t *entry, vector_t *shapes, bool forw
     }
 }
 
-/**
- * Undo the most recent history entry.
- *
- * @param h              history stack
- * @param shapes         the shapes vector to revert
- * @param selected_count out-parameter for updated selection count (currently passed through)
- * @return               true if state was changed, false if nothing to undo
- */
-static bool history_undo(history_t *h, vector_t *shapes, int *selected_count) {
+static bool history_undo(history_t *h, vector_t *shapes) {
     if (h->current < 0) return false;
 
     history_apply_entry(&h->entries[h->current], shapes, false);
     h->current--;
-    (void)selected_count;
     return true;
 }
 
-/**
- * Redo the next history entry.
- *
- * @param h              history stack
- * @param shapes         the shapes vector to advance
- * @param selected_count out-parameter (currently passed through)
- * @return               true if state was changed, false if nothing to redo
- */
-static bool history_redo(history_t *h, vector_t *shapes, int *selected_count) {
+static bool history_redo(history_t *h, vector_t *shapes) {
     if (h->current + 1 >= h->count) return false;
 
     h->current++;
     history_apply_entry(&h->entries[h->current], shapes, true);
-    (void)selected_count;
     return true;
 }