Fix various issues with SACT2

Ensure that sact_get_sprite always returns a sprite object if sprite
number is not negative. SACT2 functions in general should work before
pixel data is attached to a sprite.

This also fixes the default for the 'show' property (true) and changes
the logic for adding/removing sprites from the scene to be less
error-prone (checked whenever a sprite is dirtied).

include/sprite.h

@@ -28,9 +28,14 @@ union vm_value;
 
 struct sact_sprite {
 	TAILQ_ENTRY(sact_sprite) entry;
+	// The sprite's texture (CG or solid color). Initialized lazily.
 	struct texture texture;
+	// If no CG is attached to the sprite, the solid color to fill with.
 	SDL_Color color;
+	// The position and dimensions of the sprite.
 	Rectangle rect;
+	// Arbitrary text can be attached to the sprite. This is rendered on a
+	// separate texture and overlayed.
 	struct {
 		struct string *str;
 		struct texture texture;
@@ -39,18 +44,39 @@ struct sact_sprite {
 		int char_space;
 		int line_space;
 	} text;
+	// The Z-layer of the sprite within the scene.
 	int z;
-	bool show;
+	// This flag indicates that pixel data has been attached to a sprite; it
+	// does NOT guarantee that the texture is initialized.
+	bool has_pixel;
+	// This flag indicates whether or not the sprite is included in the
+	// the current scene. A sprite should be in the scene if there is pixel
+	// or text data attached to it and it is not hidden.
+	bool in_scene;
+	// When a sprite is hidden, it is removed from the scene. Attaching new
+	// pixel data does not alter the state of this flag.
+	bool hidden;
+	// The sprite handle.
 	int no;
+	// The CG number attached to the sprite.
 	int cg_no;
 };
 
 extern bool sact_dirty;
 
+void sprite_register(struct sact_sprite *sp);
+void sprite_unregister(struct sact_sprite *sp);
+
 static inline void sprite_dirty(struct sact_sprite *sp)
 {
-	if (sp && sp->show)
-		sact_dirty = true;
+	if (!sp)
+		return;
+	sact_dirty = true;
+	if (sp->hidden) {
+		sprite_unregister(sp);
+	} else if (sp->has_pixel || sp->text.texture.handle) {
+		sprite_register(sp);
+	}
 }
 
 static inline void scene_dirty(void)
@@ -58,9 +84,6 @@ static inline void scene_dirty(void)
 	sact_dirty = true;
 }
 
-
-void sprite_register(struct sact_sprite *sp);
-void sprite_unregister(struct sact_sprite *sp);
 void sprite_free(struct sact_sprite *sp);
 void sprite_render_scene(void);
 void sprite_flip(void);
@@ -85,7 +108,7 @@ static inline int sprite_get_pos_y(struct sact_sprite *sp) { return sp->rect.y;
 static inline int sprite_get_width(struct sact_sprite *sp) { return sp->rect.w; }
 static inline int sprite_get_height(struct sact_sprite *sp) { return sp->rect.h; }
 static inline int sprite_get_z(struct sact_sprite *sp) { return sp->z; }
-static inline int sprite_get_show(struct sact_sprite *sp) { return sp->show; }
+static inline int sprite_get_show(struct sact_sprite *sp) { return !sp->hidden; }
 void sprite_set_text_home(struct sact_sprite *sp, int x, int y);
 void sprite_set_text_line_space(struct sact_sprite *sp, int px);
 void sprite_set_text_char_space(struct sact_sprite *sp, int px);

src/hll/SACT2.c

@@ -35,14 +35,6 @@
 static struct sact_sprite **sprites = NULL;
 static int nr_sprites = 0;
 
-// NOTE: Used externally by DrawGraph and SengokuRanceFont
-struct sact_sprite *sact_get_sprite(int sp)
-{
-	if (sp < -1 || sp >= nr_sprites)
-		return NULL;
-	return sprites[sp];
-}
-
 static struct sact_sprite *sact_alloc_sprite(int sp)
 {
 	sprites[sp] = xcalloc(1, sizeof(struct sact_sprite));
@@ -71,6 +63,19 @@ static void realloc_sprite_table(int n)
 	memset(sprites + old_nr_sprites, 0, sizeof(struct sact_sprite*) * (nr_sprites - old_nr_sprites));
 }
 
+// NOTE: Used externally by DrawGraph and SengokuRanceFont
+struct sact_sprite *sact_get_sprite(int sp)
+{
+	if (sp < -1)
+		return NULL;
+	if (sp >= nr_sprites)
+		realloc_sprite_table(sp+256);
+	if (!sprites[sp]) {
+		return sact_alloc_sprite(sp);
+	}
+	return sprites[sp];
+}
+
 int sact_Init(possibly_unused void *_, possibly_unused int cg_cache_size)
 {
 	// already initialized

src/sprite.c

@@ -39,29 +39,34 @@ TAILQ_HEAD(listhead, sact_sprite) sprite_list =
 
 void sprite_register(struct sact_sprite *sp)
 {
+	if (sp->in_scene)
+		return;
+
 	struct sact_sprite *p;
 	TAILQ_FOREACH(p, &sprite_list, entry) {
 		if (p->z > sp->z) {
 			TAILQ_INSERT_BEFORE(p, sp, entry);
+			sp->in_scene = true;
 			return;
 		}
 	}
 	TAILQ_INSERT_TAIL(&sprite_list, sp, entry);
-	if (sp->show)
-		scene_dirty();
+	sp->in_scene = true;
+	scene_dirty();
 }
 
 void sprite_unregister(struct sact_sprite *sp)
 {
+	if (!sp->in_scene)
+		return;
 	TAILQ_REMOVE(&sprite_list, sp, entry);
-	if (sp->show)
-		scene_dirty();
+	sp->in_scene = false;
+	scene_dirty();
 }
 
 void sprite_free(struct sact_sprite *sp)
 {
-	if (sp->show)
-		sprite_unregister(sp);
+	sprite_unregister(sp);
 	gfx_delete_texture(&sp->texture);
 	gfx_delete_texture(&sp->text.texture);
 }
@@ -135,20 +140,23 @@ int sprite_set_cg(struct sact_sprite *sp, int cg_no)
 	sp->rect.h = cg->metrics.h;
 	sp->cg_no = cg_no;
 	cg_free(cg);
+
+	sp->has_pixel = true;
 	sprite_dirty(sp);
 	return 1;
 }
 
+/*
+ * Attach pixel data to a sprite. The texture is initialized lazily.
+ */
 void sprite_init(struct sact_sprite *sp, int w, int h, int r, int g, int b, int a)
 {
 	sp->color = (SDL_Color) { .r = r, .g = g, .b = b, .a = (a >= 0 ? a : 255) };
 	sp->rect.w = w;
 	sp->rect.h = h;
-	if (!sp->show) {
-		sp->show = true;
-		sprite_register(sp);
-	}
 	gfx_delete_texture(&sp->texture);
+
+	sp->has_pixel = true;
 	sprite_dirty(sp);
 }
 
@@ -181,7 +189,7 @@ void sprite_set_y(struct sact_sprite *sp, int y)
 void sprite_set_z(struct sact_sprite *sp, int z)
 {
 	sp->z = z;
-	if (sp->show) {
+	if (sp->in_scene) {
 		sprite_unregister(sp);
 		sprite_register(sp);
 	}
@@ -200,14 +208,8 @@ void sprite_set_blend_rate(struct sact_sprite *sp, int rate)
 
 void sprite_set_show(struct sact_sprite *sp, bool show)
 {
-	if (show == sp->show)
-		return;
-	sp->show = show;
+	sp->hidden = !show;
 	sprite_dirty(sp);
-	if (show)
-		sprite_register(sp);
-	else
-		sprite_unregister(sp);
 }
 
 int sprite_set_draw_method(struct sact_sprite *sp, int method)