Demos: Add OpenGL teapot demo :^)

Every GL library needs an implementation of this!
Currently drawn with "pixel vomit" colours as we don't
yet support lighting via the GL library.

This also ships with a super basic Wavefront OBJ loader.

9 files changed, 329 insertions, 0 deletions

diff --git a/Userland/Demos/CMakeLists.txt b/Userland/Demos/CMakeLists.txt
index 2239368dac..0d150f24bc 100644
--- a/Userland/Demos/CMakeLists.txt
+++ b/Userland/Demos/CMakeLists.txt
@@ -2,6 +2,7 @@ add_subdirectory(CatDog)
 add_subdirectory(Cube)
 add_subdirectory(Eyes)
 add_subdirectory(Fire)
+add_subdirectory(GLTeapot)
 add_subdirectory(LibGfxDemo)
 add_subdirectory(LibGfxScaleDemo)
 add_subdirectory(Mouse)
diff --git a/Userland/Demos/GLTeapot/CMakeLists.txt b/Userland/Demos/GLTeapot/CMakeLists.txt
new file mode 100644
index 0000000000..ff6420a889
--- /dev/null
+++ b/Userland/Demos/GLTeapot/CMakeLists.txt
@@ -0,0 +1,8 @@
+set(SOURCES
+    Mesh.cpp
+    WavefrontOBJLoader.cpp
+    main.cpp
+)
+
+serenity_app(GLTeapot ICON app-teapot)
+target_link_libraries(GLTeapot LibGUI LibGL)
diff --git a/Userland/Demos/GLTeapot/Common.h b/Userland/Demos/GLTeapot/Common.h
new file mode 100644
index 0000000000..feee346014
--- /dev/null
+++ b/Userland/Demos/GLTeapot/Common.h
@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2021, Jesse Buhagiar <jooster669@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibGL/GL/gl.h>
+
+// Point in 3D space
+struct Vertex {
+    GLfloat x;
+    GLfloat y;
+    GLfloat z;
+};
+
+// A triangle defines a single "face" of a mesh
+struct Triangle {
+    Vertex a;
+    Vertex b;
+    Vertex c;
+};
diff --git a/Userland/Demos/GLTeapot/Mesh.cpp b/Userland/Demos/GLTeapot/Mesh.cpp
new file mode 100644
index 0000000000..89329186a4
--- /dev/null
+++ b/Userland/Demos/GLTeapot/Mesh.cpp
@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2021, Jesse Buhagiar <jooster669@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibGL/GL/gl.h>
+#include <LibGfx/Color.h>
+#include <stdlib.h>
+
+#include "Mesh.h"
+
+const Color colors[] {
+    Color::Red,
+    Color::Green,
+    Color::Blue,
+    Color::Blue,
+    Color::Magenta,
+    Color::White,
+    Color::Yellow,
+};
+
+void Mesh::draw()
+{
+    u32 color_index = 0;
+    Color cur_color;
+
+    for (const auto& triangle : m_triangle_list) {
+        cur_color = colors[color_index];
+
+        glBegin(GL_TRIANGLES);
+        glColor4ub(cur_color.red(), cur_color.green(), cur_color.blue(), 255);
+
+        glVertex3f(triangle.a.x, triangle.a.y, triangle.a.z); // Vertex 1
+        glVertex3f(triangle.b.x, triangle.b.y, triangle.b.z); // Vertex 2
+        glVertex3f(triangle.c.x, triangle.c.y, triangle.c.z); // Vertex 3
+
+        glEnd();
+
+        color_index = ((color_index + 1) % 7);
+    }
+}
diff --git a/Userland/Demos/GLTeapot/Mesh.h b/Userland/Demos/GLTeapot/Mesh.h
new file mode 100644
index 0000000000..f0e2808f08
--- /dev/null
+++ b/Userland/Demos/GLTeapot/Mesh.h
@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2021, Jesse Buhagiar <jooster669@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/RefCounted.h>
+#include <AK/Vector.h>
+
+#include "Common.h"
+
+// NOTE: We don't support indexed
+class Mesh : public RefCounted<Mesh> {
+public:
+    Mesh() = delete;
+    Mesh(const Vector<Triangle>& triangles)
+        : m_triangle_list(triangles)
+    {
+    }
+
+    void draw();
+
+    size_t triangle_count() const { return m_triangle_list.size(); }
+
+private:
+    Vector<Triangle> m_triangle_list;
+};
diff --git a/Userland/Demos/GLTeapot/MeshLoader.h b/Userland/Demos/GLTeapot/MeshLoader.h
new file mode 100644
index 0000000000..fd62d49e64
--- /dev/null
+++ b/Userland/Demos/GLTeapot/MeshLoader.h
@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) 2021, Jesse Buhagiar <jooster669@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/String.h>
+
+#include "Common.h"
+#include "Mesh.h"
+
+class MeshLoader {
+public:
+    MeshLoader() { }
+    virtual ~MeshLoader() { }
+
+    virtual RefPtr<Mesh> load(const String& fname) = 0;
+};
diff --git a/Userland/Demos/GLTeapot/WavefrontOBJLoader.cpp b/Userland/Demos/GLTeapot/WavefrontOBJLoader.cpp
new file mode 100644
index 0000000000..677770ff03
--- /dev/null
+++ b/Userland/Demos/GLTeapot/WavefrontOBJLoader.cpp
@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2021, Jesse Buhagiar <jooster669@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "WavefrontOBJLoader.h"
+#include <LibCore/File.h>
+#include <stdlib.h>
+
+RefPtr<Mesh> WavefrontOBJLoader::load(const String& fname)
+{
+    auto obj_file_or_error = Core::File::open(fname, Core::IODevice::OpenMode::ReadOnly);
+    Vector<Vertex> vertices;
+    Vector<Triangle> triangles;
+
+    dbgln("Wavefront: Loading {}...", fname);
+
+    if (obj_file_or_error.is_error())
+        return nullptr;
+
+    // Start reading file line by line
+    for (auto line = obj_file_or_error.value()->line_begin(); !line.at_end(); ++line) {
+        auto object_line = *line;
+
+        // This line describes a vertex (a position in 3D space)
+        if (object_line.starts_with("v")) {
+            auto vertex_line = object_line.split_view(' ');
+            if (vertex_line.size() != 4) {
+                dbgln("Wavefront: Malformed vertex line. Aborting.");
+                return nullptr;
+            }
+
+            vertices.append(
+                { static_cast<GLfloat>(atof(String(vertex_line.at(1)).characters())),
+                    static_cast<GLfloat>(atof(String(vertex_line.at(2)).characters())),
+                    static_cast<GLfloat>(atof(String(vertex_line.at(3)).characters())) });
+        }
+        // This line describes a face (a collection of 3 vertices, aka a triangle)
+        else if (object_line.starts_with("f")) {
+            auto face_line = object_line.split_view(' ');
+            if (face_line.size() != 4) {
+                dbgln("Wavefront: Malformed face line. Aborting.");
+                return nullptr;
+            }
+
+            // Create a new triangle
+            triangles.append(
+                {
+                    vertices.at(face_line.at(1).to_uint().value() - 1),
+                    vertices.at(face_line.at(2).to_uint().value() - 1),
+                    vertices.at(face_line.at(3).to_uint().value() - 1),
+                });
+        }
+    }
+
+    dbgln("Wavefront: Done.");
+    return adopt_ref(*new Mesh(triangles));
+}
diff --git a/Userland/Demos/GLTeapot/WavefrontOBJLoader.h b/Userland/Demos/GLTeapot/WavefrontOBJLoader.h
new file mode 100644
index 0000000000..92ef601577
--- /dev/null
+++ b/Userland/Demos/GLTeapot/WavefrontOBJLoader.h
@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2021, Jesse Buhagiar <jooster669@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/RefCounted.h>
+#include <AK/RefPtr.h>
+
+#include "Mesh.h"
+#include "MeshLoader.h"
+
+class WavefrontOBJLoader : public MeshLoader {
+public:
+    WavefrontOBJLoader() { }
+    ~WavefrontOBJLoader() override { }
+
+    RefPtr<Mesh> load(const String& fname) override;
+};
diff --git a/Userland/Demos/GLTeapot/main.cpp b/Userland/Demos/GLTeapot/main.cpp
new file mode 100644
index 0000000000..0107db298f
--- /dev/null
+++ b/Userland/Demos/GLTeapot/main.cpp
@@ -0,0 +1,126 @@
+/*
+ * Copyright (c) 2021, Jesse Buhagiar <jooster669@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibCore/ElapsedTimer.h>
+#include <LibGL/GL/gl.h>
+#include <LibGL/GLContext.h>
+#include <LibGUI/Application.h>
+#include <LibGUI/Icon.h>
+#include <LibGUI/Painter.h>
+#include <LibGUI/Widget.h>
+#include <LibGUI/Window.h>
+#include <LibGfx/Bitmap.h>
+#include <unistd.h>
+
+#include "Mesh.h"
+#include "MeshLoader.h"
+#include "WavefrontOBJLoader.h"
+
+static constexpr u16 RENDER_WIDTH = 640;
+static constexpr u16 RENDER_HEIGHT = 480;
+
+class GLContextWidget final : public GUI::Widget {
+    C_OBJECT(GLContextWidget)
+public:
+private:
+    GLContextWidget()
+    {
+        m_bitmap = Gfx::Bitmap::create(Gfx::BitmapFormat::BGRx8888, { RENDER_WIDTH, RENDER_HEIGHT });
+        m_context = GL::create_context(*m_bitmap);
+
+        start_timer(20);
+
+        GL::make_context_current(m_context);
+        glFrontFace(GL_CW);
+        glEnable(GL_CULL_FACE);
+
+        // Set projection matrix
+        glMatrixMode(GL_PROJECTION);
+        glLoadIdentity();
+        glFrustum(-0.5, 0.5, -0.5, 0.5, 1, 1500);
+
+        // Load the teapot
+        auto mesh_loader = adopt_own(*new WavefrontOBJLoader());
+        m_teapot = mesh_loader->load("/res/gl/teapot.obj");
+
+        dbgln("GLTeapot: teapot mesh has {} triangles.", m_teapot->triangle_count());
+    }
+
+    virtual void paint_event(GUI::PaintEvent&) override;
+    virtual void timer_event(Core::TimerEvent&) override;
+
+private:
+    RefPtr<Mesh> m_teapot;
+    RefPtr<Gfx::Bitmap> m_bitmap;
+    OwnPtr<GL::GLContext> m_context;
+};
+
+void GLContextWidget::paint_event(GUI::PaintEvent& event)
+{
+    GUI::Painter painter(*this);
+    painter.add_clip_rect(event.rect());
+
+    /* Blit it! */
+    painter.draw_scaled_bitmap(event.rect(), *m_bitmap, m_bitmap->rect());
+}
+
+void GLContextWidget::timer_event(Core::TimerEvent&)
+{
+    static float angle = 0.0f;
+
+    angle -= 0.01f;
+
+    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
+    glClear(GL_COLOR_BUFFER_BIT);
+
+    auto matrix = FloatMatrix4x4::translate(FloatVector3(0, 0, -8.5))
+        * FloatMatrix4x4::rotate(FloatVector3(1, 0, 0), angle)
+        * FloatMatrix4x4::rotate(FloatVector3(0, 1, 0), 0.0f)
+        * FloatMatrix4x4::rotate(FloatVector3(0, 0, 1), angle);
+
+    glMatrixMode(GL_MODELVIEW);
+    glLoadMatrixf((float*)matrix.elements());
+
+    m_teapot->draw();
+
+    m_context->present();
+    update();
+}
+
+int main(int argc, char** argv)
+{
+    auto app = GUI::Application::construct(argc, argv);
+
+    if (pledge("stdio recvfd sendfd rpath", nullptr) < 0) {
+        perror("pledge");
+        return 1;
+    }
+
+    if (unveil("/res", "r") < 0) {
+        perror("unveil");
+        return 1;
+    }
+
+    if (unveil(nullptr, nullptr) < 0) {
+        perror("unveil");
+        return 1;
+    }
+
+    // Construct the main window
+    auto window = GUI::Window::construct();
+    auto app_icon = GUI::Icon::default_icon("app-teapot");
+
+    window->set_icon(app_icon.bitmap_for_size(16));
+    window->set_title("GLTeapot");
+    window->resize(640, 480);
+    window->set_resizable(false);
+    window->set_double_buffering_enabled(true);
+    window->set_main_widget<GLContextWidget>();
+
+    window->show();
+
+    return app->exec();
+}