Add SplashScene and transition effect

include/Constants.h

@@ -0,0 +1,8 @@
+#pragma once
+
+#include <bn_color.h>
+
+namespace sym::constants
+{
+constexpr const bn::color TRANSPARENT_BG_COLOR(4, 4, 6);
+}

include/Scene.h

@@ -0,0 +1,26 @@
+#pragma once
+
+#include <bn_optional.h>
+
+namespace sym
+{
+
+enum class SceneType
+{
+    SPLASH,
+    TITLE,
+    GAME,
+    LICENSE
+};
+
+class Scene
+{
+public:
+    virtual ~Scene() = default;
+    [[nodiscard]] virtual bn::optional<SceneType> Update() = 0;
+
+protected:
+    Scene() = default;
+};
+
+} // namespace sym

include/SplashScene.h

@@ -0,0 +1,41 @@
+#pragma once
+
+#include "Scene.h"
+
+#include <bn_array.h>
+#include <bn_blending_actions.h>
+#include <bn_regular_bg_ptr.h>
+
+namespace sym
+{
+
+class SplashScene : public Scene
+{
+public:
+    SplashScene();
+    ~SplashScene() = default;
+    [[nodiscard]] bn::optional<SceneType> Update() final;
+
+private:
+    void SwapBgWhenNeeded();
+    void SwapBg();
+    /**
+     * @brief Update the alpha transition action
+     *
+     * @return bn::optional<SceneType> Next scene type when transition is done, otherwise bn::nullopt
+     */
+    [[nodiscard]] bn::optional<SceneType> Transition();
+
+    static constexpr int BG_SWAP_UPDATE_COUNT = 30;
+    static constexpr int BG_SWAP_COUNT = 8;
+    static constexpr int FADE_UPDATE_COUNT = 60;
+
+    bn::array<bn::regular_bg_ptr, 2> bgs_;
+    int bgSwapCounter_ = BG_SWAP_COUNT;
+    int bgSwapUpdateCounter_ = BG_SWAP_UPDATE_COUNT;
+    bool isShowingFirstBg_ = false;
+    bool isFadeDone_ = false;
+    bn::optional<bn::blending_transparency_alpha_to_action> transparentAction_;
+};
+
+} // namespace sym

src/SplashScene.cpp

@@ -0,0 +1,72 @@
+#include "SplashScene.h"
+
+#include <bn_blending_actions.h>
+#include <bn_fixed.h>
+#include <bn_keypad.h>
+#include <bn_optional.h>
+
+#include "bn_regular_bg_items_bg_splash1.h"
+#include "bn_regular_bg_items_bg_splash2.h"
+
+namespace sym
+{
+
+SplashScene::SplashScene()
+    : bgs_{bn::regular_bg_items::bg_splash1.create_bg(0, 0), bn::regular_bg_items::bg_splash2.create_bg(0, 0)}
+{
+    bgs_[0].set_visible(isShowingFirstBg_);
+    for (auto& bg : bgs_)
+        bg.set_blending_enabled(true);
+}
+
+bn::optional<SceneType> SplashScene::Update()
+{
+    SwapBgWhenNeeded();
+
+    if (bn::keypad::a_pressed())
+    {
+        bgSwapCounter_ = 0;
+    }
+
+    if (0 >= bgSwapCounter_)
+    {
+        return Transition();
+    }
+
+    return bn::nullopt;
+}
+
+void SplashScene::SwapBgWhenNeeded()
+{
+    if (0 >= bgSwapUpdateCounter_--)
+    {
+        bgSwapUpdateCounter_ = BG_SWAP_UPDATE_COUNT;
+        --bgSwapCounter_;
+        SwapBg();
+    }
+}
+
+void SplashScene::SwapBg()
+{
+    isShowingFirstBg_ = !isShowingFirstBg_;
+    bgs_[0].set_visible(isShowingFirstBg_);
+    bgs_[1].set_visible(!isShowingFirstBg_);
+}
+
+bn::optional<SceneType> SplashScene::Transition()
+{
+    if (!transparentAction_)
+    {
+        transparentAction_ = bn::blending_transparency_alpha_to_action(FADE_UPDATE_COUNT, 0);
+    }
+
+    if (transparentAction_->done())
+    {
+        return SceneType::TITLE;
+    }
+
+    transparentAction_->update();
+    return bn::nullopt;
+}
+
+} // namespace sym

src/main.cpp

@@ -1,11 +1,46 @@
+#include <bn_bg_palettes.h>
+#include <bn_color.h>
 #include <bn_core.h>
+#include <bn_memory.h>
+
+#include "Constants.h"
+#include "SplashScene.h"
+#include "bn_assert.h"
 
 int main()
 {
     bn::core::init();
 
+    bn::bg_palettes::set_transparent_color(sym::constants::TRANSPARENT_BG_COLOR);
+    bn::unique_ptr<sym::Scene> scene(new sym::SplashScene);
+    bn::optional<sym::SceneType> nextScene;
+
     while (true)
     {
+        if (scene)
+        {
+            nextScene = scene->Update();
+        }
+
         bn::core::update();
+
+        if (nextScene)
+        {
+            switch (*nextScene)
+            {
+            case sym::SceneType::SPLASH:
+                scene.reset(new sym::SplashScene);
+                break;
+            case sym::SceneType::TITLE:
+                // TODO: scene.reset(new sym::TitleScene);
+                break;
+            // case sym::SceneType::GAME:
+            //     break;
+            // case sym::SceneType::LICENSE:
+            //     break;
+            default:
+                BN_ERROR("Unknown SceneType: ", (int)*nextScene);
+            }
+        }
     }
 }