From 803bb1a8a4cd5d8bfebdfc7a4d2bd10c2671c476 Mon Sep 17 00:00:00 2001
From: kichikuou <KichikuouChrome@gmail.com>
Date: Sun, 11 Sep 2022 20:58:57 +0900
Subject: [PATCH] ReignEngine: Fix BackCG issues

- Enable both alpha map and alpha mod, using the new drawing function
  gfx_copy_stretch_blend_amap_alpha().
- Do not draw if `bcg->show` flag is false.
- Do not WARNING() for SetBackCGNum(0) as it's used to unload the CG.
---
 include/gfx/gfx.h |  1 +
 src/3d/reign.c    |  3 +++
 src/3d/renderer.c |  4 ++--
 src/draw.c        | 14 ++++++++++++++
 4 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/include/gfx/gfx.h b/include/gfx/gfx.h
index e98d78c..188c334 100644
--- a/include/gfx/gfx.h
+++ b/include/gfx/gfx.h
@@ -144,6 +144,7 @@ void gfx_copy_stretch(struct texture *dst, int dx, int dy, int dw, int dh, struc
 void gfx_copy_stretch_amap(struct texture *dst, int dx, int dy, int dw, int dh, struct texture *src, int sx, int sy, int sw, int sh);
 void gfx_copy_stretch_blend(struct texture *dst, int dx, int dy, int dw, int dh, struct texture *src, int sx, int sy, int sw, int sh, int a);
 void gfx_copy_stretch_blend_amap(struct texture *dst, int dx, int dy, int dw, int dh, struct texture *src, int sx, int sy, int sw, int sh);
+void gfx_copy_stretch_blend_amap_alpha(struct texture *dst, int dx, int dy, int dw, int dh, struct texture *src, int sx, int sy, int sw, int sh, int a);
 void gfx_copy_rot_zoom(Texture *dst, Texture *src, int sx, int sy, int w, int h, float rotate, float mag);
 void gfx_copy_rot_zoom_amap(Texture *dst, Texture *src, int sx, int sy, int w, int h, float rotate, float mag);
 void gfx_copy_rot_zoom_use_amap(Texture *dst, Texture *src, int sx, int sy, int w, int h, float rotate, float mag);
diff --git a/src/3d/reign.c b/src/3d/reign.c
index 51e2017..30eae28 100644
--- a/src/3d/reign.c
+++ b/src/3d/reign.c
@@ -888,6 +888,9 @@ bool RE_back_cg_set(struct RE_back_cg *bcg, int no)
 	bcg->no = no;
 	gfx_delete_texture(&bcg->texture);
 
+	if (!no)  // unload only.
+		return true;
+
 	struct cg *cg = asset_cg_load(no);
 	if (!cg) {
 		WARNING("cannot load back CG: %d", no);
diff --git a/src/3d/renderer.c b/src/3d/renderer.c
index d595e18..2d668a0 100644
--- a/src/3d/renderer.c
+++ b/src/3d/renderer.c
@@ -505,11 +505,11 @@ static void render_shadow_map(struct RE_plugin *plugin, mat4 light_space_transfo
 
 static void render_back_cg(struct texture *dst, struct RE_back_cg *bcg, struct RE_renderer *r)
 {
-	if (!bcg->texture.handle)
+	if (!bcg->show || !bcg->texture.handle)
 		return;
 	int sw = bcg->texture.w;
 	int sh = bcg->texture.h;
-	gfx_copy_stretch_blend(dst, bcg->x, bcg->y, sw * bcg->mag, sh * bcg->mag, &bcg->texture, 0, 0, sw, sh, bcg->blend_rate * 255);
+	gfx_copy_stretch_blend_amap_alpha(dst, bcg->x, bcg->y, sw * bcg->mag, sh * bcg->mag, &bcg->texture, 0, 0, sw, sh, bcg->blend_rate * 255);
 }
 
 static void setup_lights(struct RE_plugin *plugin)
diff --git a/src/draw.c b/src/draw.c
index 0afbb18..98ba36a 100644
--- a/src/draw.c
+++ b/src/draw.c
@@ -712,6 +712,20 @@ void gfx_copy_stretch_blend_amap(struct texture *dst, int dx, int dy, int dw, in
 	restore_blend_mode();
 }
 
+void gfx_copy_stretch_blend_amap_alpha(struct texture *dst, int dx, int dy, int dw, int dh, struct texture *src, int sx, int sy, int sw, int sh, int a)
+{
+	glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_DST_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+
+	struct copy_data data = STRETCH_DATA(dx, dy, dw, dh, sx, sy, sw, sh);
+	data.r = 1.0;
+	data.g = 1.0;
+	data.b = 1.0;
+	data.a = a / 255.0;
+	run_copy_shader(&blend_amap_alpha_bright_shader.s, dst, src, &data);
+
+	restore_blend_mode();
+}
+
 // FIXME: this doesn't work correctly when the src rectangle crosses the edge of the CG.
 static void copy_rot_zoom(Texture *dst, Texture *src, int sx, int sy, int w, int h, float rotate, float mag, Shader *shader)
 {