Add XCUI ImGui transition backend MVP

editor/src/XCUIBackend/ImGuiTransitionBackend.h

@@ -0,0 +1,188 @@
+#pragma once
+
+#include <XCEngine/UI/DrawData.h>
+
+#include <imgui.h>
+
+#include <algorithm>
+#include <cstddef>
+#include <utility>
+#include <vector>
+
+namespace XCEngine {
+namespace Editor {
+namespace XCUIBackend {
+
+class ImGuiTransitionBackend {
+public:
+    void BeginFrame() {
+        m_lastFlushedDrawListCount = 0;
+        m_lastFlushedCommandCount = 0;
+        m_pendingCommandCount = 0;
+        m_pendingDrawLists.clear();
+    }
+
+    void Submit(const ::XCEngine::UI::UIDrawList& drawList) {
+        m_pendingCommandCount += drawList.GetCommandCount();
+        m_pendingDrawLists.push_back(drawList);
+    }
+
+    void Submit(::XCEngine::UI::UIDrawList&& drawList) {
+        m_pendingCommandCount += drawList.GetCommandCount();
+        m_pendingDrawLists.push_back(std::move(drawList));
+    }
+
+    void Submit(const ::XCEngine::UI::UIDrawData& drawData) {
+        for (const ::XCEngine::UI::UIDrawList& drawList : drawData.GetDrawLists()) {
+            Submit(drawList);
+        }
+    }
+
+    bool HasPendingDrawData() const {
+        return !m_pendingDrawLists.empty();
+    }
+
+    std::size_t GetPendingDrawListCount() const {
+        return m_pendingDrawLists.size();
+    }
+
+    std::size_t GetPendingCommandCount() const {
+        return m_pendingCommandCount;
+    }
+
+    std::size_t GetLastFlushedDrawListCount() const {
+        return m_lastFlushedDrawListCount;
+    }
+
+    std::size_t GetLastFlushedCommandCount() const {
+        return m_lastFlushedCommandCount;
+    }
+
+    bool EndFrame(ImDrawList* targetDrawList = nullptr) {
+        ImDrawList* drawList = targetDrawList != nullptr ? targetDrawList : ImGui::GetWindowDrawList();
+        if (drawList == nullptr) {
+            ClearPendingState();
+            return false;
+        }
+
+        std::size_t clipDepth = 0;
+        for (const ::XCEngine::UI::UIDrawList& pendingDrawList : m_pendingDrawLists) {
+            for (const ::XCEngine::UI::UIDrawCommand& command : pendingDrawList.GetCommands()) {
+                RenderCommand(*drawList, command, clipDepth);
+            }
+        }
+
+        while (clipDepth > 0) {
+            drawList->PopClipRect();
+            --clipDepth;
+        }
+
+        m_lastFlushedDrawListCount = m_pendingDrawLists.size();
+        m_lastFlushedCommandCount = m_pendingCommandCount;
+        ClearPendingState();
+        return true;
+    }
+
+private:
+    static ImVec2 ToImVec2(const ::XCEngine::UI::UIPoint& point) {
+        return ImVec2(point.x, point.y);
+    }
+
+    static ImVec2 ToImVec2Min(const ::XCEngine::UI::UIRect& rect) {
+        return ImVec2(rect.x, rect.y);
+    }
+
+    static ImVec2 ToImVec2Max(const ::XCEngine::UI::UIRect& rect) {
+        return ImVec2(rect.x + rect.width, rect.y + rect.height);
+    }
+
+    static ImTextureID ToImTextureId(const ::XCEngine::UI::UITextureHandle& texture) {
+        return static_cast<ImTextureID>(texture.nativeHandle);
+    }
+
+    static ImU32 ToImU32(const ::XCEngine::UI::UIColor& color) {
+        const float r = (std::max)(0.0f, (std::min)(1.0f, color.r));
+        const float g = (std::max)(0.0f, (std::min)(1.0f, color.g));
+        const float b = (std::max)(0.0f, (std::min)(1.0f, color.b));
+        const float a = (std::max)(0.0f, (std::min)(1.0f, color.a));
+        return IM_COL32(
+            static_cast<int>(r * 255.0f),
+            static_cast<int>(g * 255.0f),
+            static_cast<int>(b * 255.0f),
+            static_cast<int>(a * 255.0f));
+    }
+
+    static void RenderCommand(
+        ImDrawList& drawList,
+        const ::XCEngine::UI::UIDrawCommand& command,
+        std::size_t& clipDepth) {
+        switch (command.type) {
+        case ::XCEngine::UI::UIDrawCommandType::FilledRect:
+            drawList.AddRectFilled(
+                ToImVec2Min(command.rect),
+                ToImVec2Max(command.rect),
+                ToImU32(command.color),
+                command.rounding);
+            break;
+        case ::XCEngine::UI::UIDrawCommandType::RectOutline:
+            drawList.AddRect(
+                ToImVec2Min(command.rect),
+                ToImVec2Max(command.rect),
+                ToImU32(command.color),
+                command.rounding,
+                0,
+                command.thickness > 0.0f ? command.thickness : 1.0f);
+            break;
+        case ::XCEngine::UI::UIDrawCommandType::Text:
+            if (!command.text.empty()) {
+                drawList.AddText(
+                    nullptr,
+                    command.fontSize > 0.0f ? command.fontSize : ImGui::GetFontSize(),
+                    ToImVec2(command.position),
+                    ToImU32(command.color),
+                    command.text.c_str());
+            }
+            break;
+        case ::XCEngine::UI::UIDrawCommandType::Image:
+            if (command.texture.IsValid()) {
+                drawList.AddImage(
+                    ToImTextureId(command.texture),
+                    ToImVec2Min(command.rect),
+                    ToImVec2Max(command.rect),
+                    ImVec2(0.0f, 0.0f),
+                    ImVec2(1.0f, 1.0f),
+                    ToImU32(command.color));
+            }
+            break;
+        case ::XCEngine::UI::UIDrawCommandType::PushClipRect:
+            drawList.PushClipRect(
+                ToImVec2Min(command.rect),
+                ToImVec2Max(command.rect),
+                command.intersectWithCurrentClip);
+            ++clipDepth;
+            break;
+        case ::XCEngine::UI::UIDrawCommandType::PopClipRect:
+            if (clipDepth > 0) {
+                drawList.PopClipRect();
+                --clipDepth;
+            }
+            break;
+        default:
+            break;
+        }
+    }
+
+    void ClearPendingState() {
+        m_pendingCommandCount = 0;
+        m_pendingDrawLists.clear();
+    }
+
+    std::vector<::XCEngine::UI::UIDrawList> m_pendingDrawLists;
+    std::size_t m_pendingCommandCount = 0;
+    std::size_t m_lastFlushedDrawListCount = 0;
+    std::size_t m_lastFlushedCommandCount = 0;
+};
+
+} // namespace XCUIBackend
+} // namespace Editor
+} // namespace XCEngine