src/engine/camera.cpp


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#include "engine/camera.hpp"

void Camera::set_viewport(int width, int height) {
    vp_width_  = width;
    vp_height_ = height;
}

void Camera::set_position(glm::vec2 pos) {
    pos_ = pos;
}

void Camera::set_zoom(float zoom) {
    if (zoom < min_zoom) zoom = min_zoom;
    if (zoom > max_zoom) zoom = max_zoom;
    zoom_ = zoom;
}

void Camera::pan(glm::vec2 delta) {
    pos_ += delta;
}

void Camera::zoom_at(float delta, glm::vec2 world_cursor) {
    float new_zoom = zoom_ * (1.0f + delta * zoom_speed);
    if (new_zoom < min_zoom) new_zoom = min_zoom;
    if (new_zoom > max_zoom) new_zoom = max_zoom;

    // Adjust position so world_cursor stays under the same screen point
    float ratio = zoom_ / new_zoom;
    pos_ = world_cursor + (pos_ - world_cursor) * ratio;
    zoom_ = new_zoom;
}

void Camera::compute_view_proj() {
    float half_w = (vp_width_  / zoom_) * 0.5f;
    float half_h = (vp_height_ / zoom_) * 0.5f;

    proj_ = glm::ortho(-half_w, half_w, -half_h, half_h, -1.0f, 1.0f);
    view_ = glm::translate(glm::mat4(1.0f), glm::vec3(-pos_.x, -pos_.y, 0.0f));

    glm::mat4 vp = proj_ * view_;

    // Copy to column-major float array for bgfx
    const float* src = &vp[0][0];
    float* dst = &vp_[0][0];
    for (int i = 0; i < 16; i++) {
        dst[i] = src[i];
    }
}

glm::vec2 Camera::screen_to_world(glm::vec2 screen) const {
    // Convert from screen (y-down) to world (y-up)
    float world_x = pos_.x + (screen.x - vp_width_  * 0.5f) / zoom_;
    float world_y = pos_.y - (screen.y - vp_height_ * 0.5f) / zoom_;
    return glm::vec2(world_x, world_y);
}