add file picking for osx and ios and implement equirectangular import

engine/canvas.cpp

@@ -800,6 +800,45 @@ void ui::Canvas::clear_context()
     }
 };
 
+void ui::Canvas::import_equirectangular(std::string file_path)
+{
+    std::thread t(&ui::Canvas::import_equirectangular_thread, this, file_path);
+    t.detach();
+}
+
+void ui::Canvas::import_equirectangular_thread(std::string file_path)
+{
+    Texture2D tex;
+    gl_state gl;
+    App::I.async_start();
+    gl.save();
+    snap_history({0,1,2,3,4,5});
+    tex.load_file(file_path);
+    ui::Sphere sphere;
+    glDisable(GL_DEPTH_TEST);
+    sphere.create<64, 64>(2.f);
+    draw_objects([&](const glm::mat4& camera, const glm::mat4& proj){
+        m_sampler.bind(0);
+        glActiveTexture(GL_TEXTURE0);
+        tex.bind();
+        ShaderManager::use(ui::kShader::Texture);
+        ShaderManager::u_int(kShaderUniform::Tex, 0);
+        ShaderManager::u_mat4(kShaderUniform::MVP, proj * camera *
+            glm::eulerAngleY(glm::radians(-90.f)) * glm::scale(glm::vec3(1,-1,1)));
+        sphere.draw_fill();
+        tex.unbind();
+        m_sampler.unbind();
+    });
+    for (int i = 0; i < 6; i++)
+    {
+        m_dirty_box[i] = glm::vec4(0, 0, m_width, m_height);
+        m_dirty_face[i] = true;
+    }
+    App::I.async_update();
+    gl.restore();
+    App::I.async_end();
+}
+
 void ui::Canvas::export_equirectangular(std::string file_path)
 {
     std::thread t(&ui::Canvas::export_equirectangular_thread, this, file_path);