Destrum/destrum/src/Util/TransformGizmo.cpp

#include <destrum/Util/TransformGizmo.h>

#include <destrum/Graphics/Camera.h>
#include <destrum/ObjectModel/GameObject.h>

#include <glm/gtc/type_ptr.hpp>
#include <glm/gtx/matrix_decompose.hpp>

#include <imgui.h>
#include <ImGuizmo.h>

namespace {
    ImGuizmo::OPERATION toImGuizmo(GizmoOperation operation)
    {
        switch (operation) {
        case GizmoOperation::Rotate:
            return ImGuizmo::ROTATE;
        case GizmoOperation::Scale:
            return ImGuizmo::SCALE;
        case GizmoOperation::Translate:
            break;
        }
        return ImGuizmo::TRANSLATE;
    }
}

void TransformGizmo::HandleShortcuts()
{
    if (ImGui::GetIO().WantTextInput || ImGuizmo::IsUsing()) {
        return;
    }

    if (ImGui::IsKeyPressed(ImGuiKey_T, false)) {
        operation = GizmoOperation::Translate;
    }
    if (ImGui::IsKeyPressed(ImGuiKey_R, false)) {
        operation = GizmoOperation::Rotate;
    }
    if (ImGui::IsKeyPressed(ImGuiKey_Y, false)) {
        operation = GizmoOperation::Scale;
    }
    if (ImGui::IsKeyPressed(ImGuiKey_L, false)) {
        space = space == GizmoSpace::World ? GizmoSpace::Local : GizmoSpace::World;
    }
}

void TransformGizmo::DrawToolbar()
{
    if (!ImGui::Begin("Gizmo", nullptr, ImGuiWindowFlags_AlwaysAutoResize)) {
        ImGui::End();
        return;
    }

    const auto operationButton = [this](const char* label, GizmoOperation buttonOperation) {
        if (ImGui::RadioButton(label, operation == buttonOperation)) {
            operation = buttonOperation;
        }
    };
    operationButton("Move (T)", GizmoOperation::Translate);
    ImGui::SameLine();
    operationButton("Rotate (R)", GizmoOperation::Rotate);
    ImGui::SameLine();
    operationButton("Scale (Y)", GizmoOperation::Scale);

    if (operation != GizmoOperation::Scale) {
        bool local = space == GizmoSpace::Local;
        if (ImGui::Checkbox("Local (L)", &local)) {
            space = local ? GizmoSpace::Local : GizmoSpace::World;
        }
        ImGui::SameLine();
    }

    ImGui::Checkbox("Snap", &snap);
    if (snap) {
        ImGui::SetNextItemWidth(80.0f);
        switch (operation) {
        case GizmoOperation::Translate:
            ImGui::DragFloat("Step", &translationSnap, 0.05f, 0.01f, 10.0f, "%.2f m");
            break;
        case GizmoOperation::Rotate:
            ImGui::DragFloat("Step", &rotationSnapDegrees, 1.0f, 1.0f, 90.0f, "%.0f deg");
            break;
        case GizmoOperation::Scale:
            ImGui::DragFloat("Step", &scaleSnap, 0.01f, 0.01f, 1.0f, "%.2f");
            break;
        }
    }

    ImGui::End();
}

bool TransformGizmo::Manipulate(GameObject& object, const Camera& camera)
{
    ImGuizmo::BeginFrame();

    const ImGuiViewport* viewport = ImGui::GetMainViewport();
    ImGuizmo::SetOrthographic(false);
    ImGuizmo::SetRect(viewport->Pos.x, viewport->Pos.y, viewport->Size.x, viewport->Size.y);

    const glm::mat4 view = camera.GetViewMatrix();
    glm::mat4 projection = camera.GetProjectionMatrix();
    // ImGuizmo expects OpenGL's y up clip space, the engine flips y for Vulkan
    projection[1][1] *= -1.0f;

    Transform& transform = object.GetTransform();
    glm::mat4 worldMatrix = transform.GetWorldMatrix();

    const float snapStep = operation == GizmoOperation::Translate ? translationSnap
                         : operation == GizmoOperation::Rotate    ? rotationSnapDegrees
                                                                  : scaleSnap;
    const float snapValues[3] = {snapStep, snapStep, snapStep};
    const ImGuizmo::MODE mode =
        operation == GizmoOperation::Scale || space == GizmoSpace::Local ? ImGuizmo::LOCAL : ImGuizmo::WORLD;

    const bool changed = ImGuizmo::Manipulate(
        glm::value_ptr(view),
        glm::value_ptr(projection),
        toImGuizmo(operation),
        mode,
        glm::value_ptr(worldMatrix),
        nullptr,
        snap ? snapValues : nullptr);

    // Stops the click on a handle from reaching the game, e.g. grabbing the mouse for first person
    if (ImGuizmo::IsOver() || ImGuizmo::IsUsing()) {
        ImGui::SetNextFrameWantCaptureMouse(true);
    }

    if (!changed) {
        return false;
    }

    glm::vec3 position;
    glm::quat rotation;
    glm::vec3 scale;
    glm::vec3 skew;
    glm::vec4 perspective;
    if (!glm::decompose(worldMatrix, scale, rotation, position, skew, perspective)) {
        return false;
    }

    switch (operation) {
    case GizmoOperation::Translate:
        transform.SetWorldPosition(position);
        break;
    case GizmoOperation::Rotate:
        transform.SetWorldRotation(rotation);
        break;
    case GizmoOperation::Scale:
        transform.SetWorldScale(scale);
        break;
    }

    object.RefreshPhysicsInHierarchy();
    return true;
}

bool TransformGizmo::IsUsing() const
{
    return ImGuizmo::IsUsing();
}

bool TransformGizmo::IsOver() const
{
    return ImGuizmo::IsOver();
}