XCEngine/editor/src/panels/ViewportPanelContent.h

#pragma once

#include "Core/IEditorContext.h"
#include "Viewport/IViewportHostService.h"

#include <imgui.h>

#include <string>

namespace XCEngine {
namespace Editor {

struct ViewportPanelContentResult {
    EditorViewportFrame frame;
    ImVec2 availableSize = ImVec2(0.0f, 0.0f);
    ImVec2 itemMin = ImVec2(0.0f, 0.0f);
    ImVec2 itemMax = ImVec2(0.0f, 0.0f);
    bool hasViewportArea = false;
    bool hovered = false;
    bool focused = false;
};

inline void DrawViewportStatusMessage(const std::string& message) {
    if (message.empty()) {
        return;
    }

    ImDrawList* drawList = ImGui::GetWindowDrawList();
    if (drawList == nullptr) {
        return;
    }

    const ImVec2 min = ImGui::GetItemRectMin();
    const ImVec2 max = ImGui::GetItemRectMax();
    const ImVec2 textSize = ImGui::CalcTextSize(message.c_str());
    const ImVec2 textPos(
        min.x + ((max.x - min.x) - textSize.x) * 0.5f,
        min.y + ((max.y - min.y) - textSize.y) * 0.5f);

    drawList->AddText(textPos, ImGui::GetColorU32(ImGuiCol_TextDisabled), message.c_str());
}

inline ViewportPanelContentResult RenderViewportPanelContent(IEditorContext& context, EditorViewportKind kind) {
    ViewportPanelContentResult result = {};
    result.availableSize = ImGui::GetContentRegionAvail();
    result.focused = ImGui::IsWindowFocused(ImGuiFocusedFlags_RootAndChildWindows);

    IViewportHostService* viewportHostService = context.GetViewportHostService();
    if (result.availableSize.x <= 1.0f || result.availableSize.y <= 1.0f) {
        ImGui::Dummy(ImVec2(0.0f, 0.0f));
        return result;
    }

    result.hasViewportArea = true;

    if (viewportHostService == nullptr) {
        ImGui::Dummy(result.availableSize);
        result.itemMin = ImGui::GetItemRectMin();
        result.itemMax = ImGui::GetItemRectMax();
        result.hovered = ImGui::IsMouseHoveringRect(result.itemMin, result.itemMax, true);
        DrawViewportStatusMessage("Viewport host is unavailable");
        return result;
    }

    result.frame = viewportHostService->RequestViewport(kind, result.availableSize);
    if (result.frame.hasTexture) {
        ImGui::Image(result.frame.textureId, result.availableSize);
    } else {
        ImGui::Dummy(result.availableSize);
    }

    result.itemMin = ImGui::GetItemRectMin();
    result.itemMax = ImGui::GetItemRectMax();
    result.hovered = ImGui::IsMouseHoveringRect(result.itemMin, result.itemMax, true);

    DrawViewportStatusMessage(
        result.frame.statusText.empty() && !result.frame.hasTexture
            ? "Viewport is initializing"
            : result.frame.statusText);
    return result;
}

} // namespace Editor
} // namespace XCEngine