XCEngine/editor/src/panels/SceneViewPanel.cpp

#include "Actions/ActionRouting.h"
#include "Core/IEditorContext.h"
#include "SceneViewPanel.h"
#include "ViewportPanelContent.h"
#include "UI/UI.h"

#include <XCEngine/Core/Math/Matrix4.h>
#include <XCEngine/Core/Math/Vector4.h>

#include <algorithm>
#include <cmath>

#include <imgui.h>

namespace XCEngine {
namespace Editor {

namespace {

float ComputeGridSpacing(float orbitDistance) {
    const float target = (std::max)(orbitDistance * 0.35f, 0.1f);
    const float exponent = std::floor(std::log10(target));
    const float base = std::pow(10.0f, exponent);
    const float normalized = target / base;
    if (normalized < 2.0f) {
        return base;
    }
    if (normalized < 5.0f) {
        return 2.0f * base;
    }
    return 5.0f * base;
}

Math::Matrix4x4 BuildOverlayViewMatrix(const SceneViewportOverlayData& overlay) {
    return Math::Matrix4x4::LookAt(
        overlay.cameraPosition,
        overlay.cameraPosition + overlay.cameraForward,
        overlay.cameraUp);
}

Math::Matrix4x4 BuildOverlayProjectionMatrix(
    const SceneViewportOverlayData& overlay,
    const ImVec2& viewportSize) {
    const float aspect = viewportSize.y > 0.0f
        ? viewportSize.x / viewportSize.y
        : 1.0f;
    return Math::Matrix4x4::Perspective(
        overlay.verticalFovDegrees * Math::DEG_TO_RAD,
        aspect,
        overlay.nearClipPlane,
        overlay.farClipPlane);
}

bool ProjectWorldPoint(
    const Math::Matrix4x4& viewProjection,
    const ImVec2& viewportMin,
    const ImVec2& viewportSize,
    const Math::Vector3& worldPoint,
    ImVec2& screenPoint,
    float& depth) {
    const Math::Vector4 clip = viewProjection * Math::Vector4(worldPoint, 1.0f);
    if (clip.w <= 0.001f) {
        return false;
    }

    const float invW = 1.0f / clip.w;
    const float ndcX = clip.x * invW;
    const float ndcY = clip.y * invW;
    const float ndcZ = clip.z * invW;
    if (ndcZ < -0.2f || ndcZ > 1.2f) {
        return false;
    }

    screenPoint.x = viewportMin.x + (ndcX * 0.5f + 0.5f) * viewportSize.x;
    screenPoint.y = viewportMin.y + (-ndcY * 0.5f + 0.5f) * viewportSize.y;
    depth = ndcZ;
    return true;
}

void DrawSceneAxisWidget(
    ImDrawList* drawList,
    const SceneViewportOverlayData& overlay,
    const ImVec2& viewportMin,
    const ImVec2& viewportMax) {
    if (drawList == nullptr || !overlay.valid) {
        return;
    }

    const Math::Matrix4x4 view = BuildOverlayViewMatrix(overlay);
    const ImVec2 center(viewportMin.x + 52.0f, viewportMax.y - 52.0f);
    const float radius = 26.0f;

    drawList->AddCircleFilled(center, radius + 10.0f, IM_COL32(18, 20, 24, 170), 24);
    drawList->AddCircle(center, radius + 10.0f, IM_COL32(255, 255, 255, 28), 24, 1.0f);

    struct AxisLine {
        Math::Vector3 axis;
        ImU32 color;
    };

    const AxisLine axes[] = {
        { Math::Vector3::Right(), IM_COL32(239, 83, 80, 255) },
        { Math::Vector3::Up(), IM_COL32(102, 187, 106, 255) },
        { Math::Vector3::Forward(), IM_COL32(66, 165, 245, 255) }
    };

    for (const AxisLine& axis : axes) {
        const Math::Vector3 viewAxis = view.MultiplyVector(axis.axis);
        const ImVec2 end(
            center.x + viewAxis.x * radius,
            center.y - viewAxis.y * radius);
        drawList->AddLine(center, end, axis.color, 2.2f);
        drawList->AddCircleFilled(end, 4.0f, axis.color, 12);
    }
}

void DrawSceneGridOverlay(
    ImDrawList* drawList,
    const SceneViewportOverlayData& overlay,
    const ImVec2& viewportMin,
    const ImVec2& viewportMax,
    const ImVec2& viewportSize) {
    if (drawList == nullptr || !overlay.valid || viewportSize.x <= 1.0f || viewportSize.y <= 1.0f) {
        return;
    }

    const Math::Matrix4x4 viewProjection =
        BuildOverlayProjectionMatrix(overlay, viewportSize) * BuildOverlayViewMatrix(overlay);
    const float spacing = ComputeGridSpacing(overlay.orbitDistance);
    const int halfLineCount = 14;
    const float extent = spacing * static_cast<float>(halfLineCount);

    drawList->PushClipRect(viewportMin, viewportMax, true);

    for (int lineIndex = -halfLineCount; lineIndex <= halfLineCount; ++lineIndex) {
        const float offset = static_cast<float>(lineIndex) * spacing;
        const bool majorLine = (lineIndex % 5) == 0;
        const ImU32 lineColor = majorLine
            ? IM_COL32(255, 255, 255, 58)
            : IM_COL32(255, 255, 255, 24);

        ImVec2 a = {};
        ImVec2 b = {};
        ImVec2 c = {};
        ImVec2 d = {};
        float depthA = 0.0f;
        float depthB = 0.0f;
        float depthC = 0.0f;
        float depthD = 0.0f;

        if (ProjectWorldPoint(
                viewProjection,
                viewportMin,
                viewportSize,
                Math::Vector3(offset, 0.0f, -extent),
                a,
                depthA) &&
            ProjectWorldPoint(
                viewProjection,
                viewportMin,
                viewportSize,
                Math::Vector3(offset, 0.0f, extent),
                b,
                depthB)) {
            drawList->AddLine(a, b, lineColor, majorLine ? 1.35f : 1.0f);
        }

        if (ProjectWorldPoint(
                viewProjection,
                viewportMin,
                viewportSize,
                Math::Vector3(-extent, 0.0f, offset),
                c,
                depthC) &&
            ProjectWorldPoint(
                viewProjection,
                viewportMin,
                viewportSize,
                Math::Vector3(extent, 0.0f, offset),
                d,
                depthD)) {
            drawList->AddLine(c, d, lineColor, majorLine ? 1.35f : 1.0f);
        }
    }

    ImVec2 origin = {};
    ImVec2 xAxisEnd = {};
    ImVec2 yAxisEnd = {};
    ImVec2 zAxisEnd = {};
    float originDepth = 0.0f;
    float xDepth = 0.0f;
    float yDepth = 0.0f;
    float zDepth = 0.0f;
    const float axisLength = spacing * 3.0f;
    if (ProjectWorldPoint(viewProjection, viewportMin, viewportSize, Math::Vector3::Zero(), origin, originDepth)) {
        if (ProjectWorldPoint(
                viewProjection,
                viewportMin,
                viewportSize,
                Math::Vector3(axisLength, 0.0f, 0.0f),
                xAxisEnd,
                xDepth)) {
            drawList->AddLine(origin, xAxisEnd, IM_COL32(239, 83, 80, 220), 1.8f);
        }
        if (ProjectWorldPoint(
                viewProjection,
                viewportMin,
                viewportSize,
                Math::Vector3(0.0f, axisLength, 0.0f),
                yAxisEnd,
                yDepth)) {
            drawList->AddLine(origin, yAxisEnd, IM_COL32(102, 187, 106, 220), 1.8f);
        }
        if (ProjectWorldPoint(
                viewProjection,
                viewportMin,
                viewportSize,
                Math::Vector3(0.0f, 0.0f, axisLength),
                zAxisEnd,
                zDepth)) {
            drawList->AddLine(origin, zAxisEnd, IM_COL32(66, 165, 245, 220), 1.8f);
        }
    }

    DrawSceneAxisWidget(drawList, overlay, viewportMin, viewportMax);
    drawList->PopClipRect();
}

} // namespace

SceneViewPanel::SceneViewPanel() : Panel("Scene") {}

void SceneViewPanel::Render() {
    UI::PanelWindowScope panel(m_name.c_str());
    if (!panel.IsOpen()) {
        return;
    }

    const ViewportPanelContentResult content = RenderViewportPanelContent(*m_context, EditorViewportKind::Scene);
    if (IViewportHostService* viewportHostService = m_context->GetViewportHostService()) {
        const ImGuiIO& io = ImGui::GetIO();
        const bool altDown = io.KeyAlt;

        if (!m_lookDragging && content.hovered && !altDown && ImGui::IsMouseClicked(ImGuiMouseButton_Right)) {
            m_lookDragging = true;
        }
        if (!m_orbitDragging && content.hovered && altDown && ImGui::IsMouseClicked(ImGuiMouseButton_Left)) {
            m_orbitDragging = true;
        }
        if (!m_panDragging && content.hovered && ImGui::IsMouseClicked(ImGuiMouseButton_Middle)) {
            m_panDragging = true;
        }

        if (m_lookDragging && (!ImGui::IsMouseDown(ImGuiMouseButton_Right) || altDown)) {
            m_lookDragging = false;
        }
        if (m_orbitDragging && (!ImGui::IsMouseDown(ImGuiMouseButton_Left) || !altDown)) {
            m_orbitDragging = false;
        }
        if (m_panDragging && !ImGui::IsMouseDown(ImGuiMouseButton_Middle)) {
            m_panDragging = false;
        }

        SceneViewportInput input = {};
        input.viewportSize = content.availableSize;
        input.deltaTime = io.DeltaTime;
        input.hovered = content.hovered;
        input.focused = content.focused;
        input.mouseWheel = content.hovered ? -io.MouseWheel : 0.0f;
        input.looking = m_lookDragging;
        input.orbiting = m_orbitDragging;
        input.panning = m_panDragging;
        input.fastMove = io.KeyShift;
        input.focusSelectionRequested =
            content.focused && !io.WantTextInput && ImGui::IsKeyPressed(ImGuiKey_F, false);

        if (m_lookDragging && content.focused && !io.WantTextInput) {
            input.moveForward =
                (ImGui::IsKeyDown(ImGuiKey_W) ? 1.0f : 0.0f) -
                (ImGui::IsKeyDown(ImGuiKey_S) ? 1.0f : 0.0f);
            input.moveRight =
                (ImGui::IsKeyDown(ImGuiKey_D) ? 1.0f : 0.0f) -
                (ImGui::IsKeyDown(ImGuiKey_A) ? 1.0f : 0.0f);
            input.moveUp =
                (ImGui::IsKeyDown(ImGuiKey_E) ? 1.0f : 0.0f) -
                (ImGui::IsKeyDown(ImGuiKey_Q) ? 1.0f : 0.0f);
        }

        if (m_lookDragging || m_orbitDragging || m_panDragging) {
            input.mouseDelta = io.MouseDelta;
        }

        viewportHostService->UpdateSceneViewInput(*m_context, input);

        if (content.hasViewportArea && content.frame.hasTexture) {
            const SceneViewportOverlayData overlay = viewportHostService->GetSceneViewOverlayData();
            DrawSceneGridOverlay(
                ImGui::GetWindowDrawList(),
                overlay,
                content.itemMin,
                content.itemMax,
                content.availableSize);
        }
    }

    Actions::ObserveInactiveActionRoute(*m_context);
}

}
}