Fix StoatSpriteEngine.SP_SetDrawMethod

The method parameter of this function has a different meaning from that
of SACT2.SP_SetDrawMethod.

I've only checked it in Widenyo, but it seems 0 and 1 are valid values
and 1 is additive blending.

include/gfx/gfx.h

@@ -27,10 +27,10 @@ struct cg;
 struct text_metrics;
 
 enum draw_method {
-	DRAW_METHOD_NORMAL = 0,
-	DRAW_METHOD_SCREEN = 1,
-	DRAW_METHOD_MULTIPLY = 2,
-	NR_DRAW_METHODS
+	DRAW_METHOD_NORMAL,
+	DRAW_METHOD_SCREEN,
+	DRAW_METHOD_MULTIPLY,
+	DRAW_METHOD_ADDITIVE,
 };
 
 typedef struct texture {

include/sprite.h

@@ -72,8 +72,8 @@ static inline void sprite_set_z2(struct sact_sprite *sp, int z, int z2) { scene_
 int sprite_get_blend_rate(struct sact_sprite *sp);
 void sprite_set_blend_rate(struct sact_sprite *sp, int rate);
 static inline void sprite_set_show(struct sact_sprite *sp, bool show) { scene_set_sprite_show(&sp->sp, show); }
-int sprite_set_draw_method(struct sact_sprite *sp, int method);
-int sprite_get_draw_method(struct sact_sprite *sp);
+int sprite_set_draw_method(struct sact_sprite *sp, enum draw_method method);
+enum draw_method sprite_get_draw_method(struct sact_sprite *sp);
 static inline int sprite_exists_alpha(struct sact_sprite *sp) { return sp->sp.has_alpha; }
 static inline int sprite_get_pos_x(struct sact_sprite *sp) { return sp->rect.x; }
 static inline int sprite_get_pos_y(struct sact_sprite *sp) { return sp->rect.y; }

src/hll/SACT2.c

@@ -337,15 +337,29 @@ int sact_SP_SetDrawMethod(int sp_no, int method)
 {
 	struct sact_sprite *sp = sact_get_sprite(sp_no);
 	if (!sp) return 0;
-	return sprite_set_draw_method(sp, method);
-	return 1;
+	switch (method) {
+	case 0: return sprite_set_draw_method(sp, DRAW_METHOD_NORMAL);
+	case 1: return sprite_set_draw_method(sp, DRAW_METHOD_SCREEN);
+	case 2: return sprite_set_draw_method(sp, DRAW_METHOD_MULTIPLY);
+	default:
+		WARNING("unknown draw method: %d", method);
+		return 0;
+	}
 }
 
 int sact_SP_GetDrawMethod(int sp_no)
 {
 	struct sact_sprite *sp = sact_try_get_sprite(sp_no);
 	if (!sp) return DRAW_METHOD_NORMAL;
-	return sprite_get_draw_method(sp);
+	int method = sprite_get_draw_method(sp);
+	switch (method) {
+	case DRAW_METHOD_NORMAL: return 0;
+	case DRAW_METHOD_SCREEN: return 1;
+	case DRAW_METHOD_MULTIPLY: return 2;
+	default:
+		WARNING("unknown draw method: %d", method);
+		return 0;
+	}
 }
 
 int sact_SP_IsUsing(int sp_no)

src/hll/StoatSpriteEngine.c

@@ -44,6 +44,33 @@ HLL_WARN_UNIMPLEMENTED( , void, StoatSpriteEngine, SetVolumeMixerSEGroupNum, int
 HLL_WARN_UNIMPLEMENTED( , void, StoatSpriteEngine, SetVolumeMixerBGMGroupNum, int n);
 HLL_WARN_UNIMPLEMENTED(0, int,  StoatSpriteEngine, Sound_GetGroupNumFromDataNum, int n);
 
+static int StoatSpriteEngine_SP_SetDrawMethod(int sp_no, int method)
+{
+	struct sact_sprite *sp = sact_get_sprite(sp_no);
+	if (!sp) return 0;
+	switch (method) {
+	case 0: return sprite_set_draw_method(sp, DRAW_METHOD_NORMAL);
+	case 1: return sprite_set_draw_method(sp, DRAW_METHOD_ADDITIVE);
+	default:
+		WARNING("unknown draw method: %d", method);
+		return 0;
+	}
+}
+
+static int StoatSpriteEngine_SP_GetDrawMethod(int sp_no)
+{
+	struct sact_sprite *sp = sact_try_get_sprite(sp_no);
+	if (!sp) return DRAW_METHOD_NORMAL;
+	int method = sprite_get_draw_method(sp);
+	switch (method) {
+	case DRAW_METHOD_NORMAL: return 0;
+	case DRAW_METHOD_ADDITIVE: return 1;
+	default:
+		WARNING("unknown draw method: %d", method);
+		return 0;
+	}
+}
+
 struct text_metrics text_sprite_tm = {
 	.color = { .r = 255, .g = 255, .b = 255, .a = 255 },
 	.outline_color = { .r = 0, .g = 0, .b = 0, .a = 255 },
@@ -793,7 +820,7 @@ HLL_LIBRARY(StoatSpriteEngine,
 	    HLL_EXPORT(SP_SetZ, sact_SP_SetZ),
 	    HLL_EXPORT(SP_SetBlendRate, sact_SP_SetBlendRate),
 	    HLL_EXPORT(SP_SetShow, sact_SP_SetShow),
-	    HLL_EXPORT(SP_SetDrawMethod, sact_SP_SetDrawMethod),
+	    HLL_EXPORT(SP_SetDrawMethod, StoatSpriteEngine_SP_SetDrawMethod),
 	    HLL_EXPORT(SP_IsUsing, sact_SP_IsUsing),
 	    HLL_EXPORT(SP_ExistAlpha, sact_SP_ExistsAlpha),
 	    HLL_EXPORT(SP_GetPosX, sact_SP_GetPosX),
@@ -803,7 +830,7 @@ HLL_LIBRARY(StoatSpriteEngine,
 	    HLL_EXPORT(SP_GetZ, sact_SP_GetZ),
 	    HLL_EXPORT(SP_GetBlendRate, sact_SP_GetBlendRate),
 	    HLL_EXPORT(SP_GetShow, sact_SP_GetShow),
-	    HLL_EXPORT(SP_GetDrawMethod, sact_SP_GetDrawMethod),
+	    HLL_EXPORT(SP_GetDrawMethod, StoatSpriteEngine_SP_GetDrawMethod),
 	    HLL_EXPORT(SP_SetTextHome, sact_SP_SetTextHome),
 	    HLL_EXPORT(SP_SetTextLineSpace, sact_SP_SetTextLineSpace),
 	    HLL_EXPORT(SP_SetTextCharSpace, sact_SP_SetTextCharSpace),

src/sprite.c

@@ -179,18 +179,14 @@ void sprite_set_blend_rate(struct sact_sprite *sp, int rate)
 	sprite_dirty(sp);
 }
 
-int sprite_set_draw_method(struct sact_sprite *sp, int method)
+int sprite_set_draw_method(struct sact_sprite *sp, enum draw_method method)
 {
-	if (method < 0 || method >= NR_DRAW_METHODS) {
-		WARNING("unknown draw method: %d", method);
-		return 0;
-	}
 	sprite_get_texture(sp)->draw_method = method;
 	sprite_dirty(sp);
 	return 1;
 }
 
-int sprite_get_draw_method(struct sact_sprite *sp)
+enum draw_method sprite_get_draw_method(struct sact_sprite *sp)
 {
 	return sprite_get_texture(sp)->draw_method;
 }

src/video.c

@@ -419,6 +419,9 @@ void gfx_render_texture(struct texture *t, Rectangle *r)
 	case DRAW_METHOD_MULTIPLY:
 		glBlendFuncSeparate(GL_DST_COLOR, GL_ZERO, GL_ZERO, GL_ONE);
 		break;
+	case DRAW_METHOD_ADDITIVE:
+		glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE, GL_ZERO, GL_ONE);
+		break;
 	default:
 		// FIXME: why doesn't this work?
 		//if (t->alpha_mod != 255) {