From 1ef17e89181619c830f75e75f7b2e43ab3d1ed43 Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Sat, 13 May 2023 00:04:18 +0300
Subject: [PATCH] Add platformer example

---
 examples/platformer.cpp | 132 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 132 insertions(+)
 create mode 100644 examples/platformer.cpp

diff --git a/examples/platformer.cpp b/examples/platformer.cpp
new file mode 100644
index 00000000..a50166de
--- /dev/null
+++ b/examples/platformer.cpp
@@ -0,0 +1,132 @@
+#include <psemek/app/app.hpp>
+#include <psemek/app/main.hpp>
+#include <psemek/gfx/painter.hpp>
+#include <psemek/gfx/gl.hpp>
+#include <psemek/geom/scale.hpp>
+#include <psemek/geom/camera.hpp>
+#include <psemek/geom/constants.hpp>
+#include <psemek/geom/intersection.hpp>
+#include <psemek/util/clock.hpp>
+#include <psemek/util/to_string.hpp>
+
+using namespace psemek;
+
+struct map
+{
+	std::vector<geom::box<float, 2>> platforms;
+};
+
+struct player
+{
+	geom::vector<float, 2> size;
+	geom::point<float, 2> position;
+	geom::vector<float, 2> velocity;
+
+	geom::box<float, 2> bbox() const
+	{
+		return geom::expand(geom::box<float, 2>::singleton(position), size);
+	}
+};
+
+struct platformer_app : app::app
+{
+	platformer_app()
+		: app("Platformer", 4)
+	{
+		map_.platforms.push_back({{{-10.f, 10.f}, {-5.f, -4.f}}});
+
+		map_.platforms.push_back({{{-5.f, -3.f}, {-2.5f, -2.f}}});
+		map_.platforms.push_back({{{-1.f,  1.f}, {-2.f, -1.5f}}});
+		map_.platforms.push_back({{{ 3.f,  5.f}, {-1.5f, -1.f}}});
+
+		map_.platforms.push_back({{{-7.f, -6.f}, {-3.5f, -3.f}}});
+
+		player_.size = {0.25f, 0.5f};
+		player_.position = {0.f, 5.f};
+		player_.velocity = {0.f, 0.f};
+	}
+
+	void update() override
+	{
+		float const dt = frame_clock_.restart().count();
+
+		float const gravity = -50.f;
+		float const acceleration = 50.f;
+		float const friction = 10.f;
+		float const jump_speed = 15.f;
+
+		if (is_key_down(SDLK_a))
+			player_.velocity[0] -= acceleration * dt;
+		if (is_key_down(SDLK_d))
+			player_.velocity[0] += acceleration * dt;
+
+		player_.velocity[0] *= std::exp(- friction * dt);
+
+		player_.velocity[1] += dt * gravity;
+
+		player_.position += player_.velocity * dt;
+
+		bool grounded = false;
+
+		for (auto const & platform : map_.platforms)
+		{
+			auto const player_box = player_.bbox();
+			auto const intersection = platform & player_box;
+			if (intersection.empty()) continue;
+
+			if (intersection[0].length() < intersection[1].length())
+			{
+				if (intersection[0].center() < player_.position[0])
+					player_.position[0] += intersection[0].length();
+				else
+					player_.position[0] -= intersection[0].length();
+
+				player_.velocity[0] = 0.f;
+			}
+			else
+			{
+				if (intersection[1].center() < player_.position[1])
+				{
+					player_.position[1] += intersection[1].length();
+					grounded = true;
+				}
+				else
+					player_.position[1] -= intersection[1].length();
+
+				player_.velocity[1] = 0.f;
+			}
+		}
+
+		if (grounded && is_key_down(SDLK_w))
+			player_.velocity[1] += jump_speed;
+	}
+
+	void present() override
+	{
+		gl::ClearColor(1.f, 1.f, 1.f, 0.f);
+		gl::Clear(gl::COLOR_BUFFER_BIT);
+
+		for (auto const & box : map_.platforms)
+			painter_.rect(box, {0, 0, 0, 255});
+
+		painter_.rect(player_.bbox(), {255, 0, 0, 255});
+
+		float const aspect_ratio = width() * 1.f / height();
+		float const view_size = 5.f;
+		geom::box<float, 2> view_box{{{-view_size * aspect_ratio, view_size * aspect_ratio}, {-view_size, view_size}}};
+
+		painter_.render(geom::orthographic_camera{view_box}.transform());
+	}
+
+private:
+	map map_;
+	player player_;
+
+	util::clock<> frame_clock_;
+	gfx::painter painter_;
+};
+
+int main()
+{
+	return app::main<platformer_app>();
+}