glmrefact.cpp

inline Rect full_transform(const Rect &r, const glm::mat4 &m)
{
    // Extract the translation, rotation, and scaling components from the transformation matrix
    glm::vec3 translation = glm::vec3(m[3][0], m[3][1], m[3][2]);
    glm::vec3 scaling = glm::vec3(m[0][0], m[1][1], m[2][2]);
    glm::quat rotation = glm::quat_cast(m);

    // Calculate the half-width and half-height of the original rectangle
    float half_width = 0.5f * (float)(r.Right - r.Left);
    float half_height = 0.5f * (float)(r.Bottom - r.Top);

    // Calculate the transformed corner points of the rectangle
    glm::vec3 p1 = translation + rotation * (scaling * glm::vec3(-half_width, -half_height, 0.0f));
    glm::vec3 p2 = translation + rotation * (scaling * glm::vec3( half_width, -half_height, 0.0f));
    glm::vec3 p3 = translation + rotation * (scaling * glm::vec3(-half_width,  half_height, 0.0f));
    glm::vec3 p4 = translation + rotation * (scaling * glm::vec3( half_width,  half_height, 0.0f));

    // Calculate the minimum and maximum x and y values of the transformed points
    float xmin = std::min(p1.x, std::min(p2.x, std::min(p3.x, p4.x)));
    float ymin = std::min(p1.y, std::min(p2.y, std::min(p3.y, p4.y)));
    float xmax = std::max(p1.x, std::max(p2.x, std::max(p3.x, p4.x)));
    float ymax = std::max(p1.y, std::max(p2.y, std::max(p3.y, p4.y)));

    // Round the transformed x and y values to integer values
    xmin = std::round(xmin);
    ymin = std::round(ymin);
    xmax = std::round(xmax);
    ymax = std::round(ymax);

    // Create and return the transformed rectangle
    return Rect((int)xmin, (int)ymin, (int)xmax, (int)ymax);
}