Add XCUI ImGui transition backend MVP

tests/editor/test_xcui_draw_data.cpp

@@ -0,0 +1,53 @@
+#include <gtest/gtest.h>
+
+#include <XCEngine/UI/DrawData.h>
+
+TEST(XCUIDrawDataTest, DrawListBuilderPreservesCommandOrderAndPayload) {
+    using XCEngine::UI::UIColor;
+    using XCEngine::UI::UIDrawCommandType;
+    using XCEngine::UI::UIDrawList;
+    using XCEngine::UI::UIPoint;
+    using XCEngine::UI::UIRect;
+    using XCEngine::UI::UITextureHandle;
+
+    UIDrawList drawList("PrimaryList");
+    drawList.PushClipRect(UIRect(0.0f, 0.0f, 200.0f, 120.0f));
+    drawList.AddFilledRect(UIRect(10.0f, 12.0f, 48.0f, 24.0f), UIColor(0.1f, 0.2f, 0.3f, 1.0f), 4.0f);
+    drawList.AddRectOutline(UIRect(10.0f, 12.0f, 48.0f, 24.0f), UIColor(0.4f, 0.5f, 0.6f, 1.0f), 2.0f, 4.0f);
+    drawList.AddText(UIPoint(18.0f, 22.0f), "XCUI", UIColor(1.0f, 1.0f, 1.0f, 1.0f), 16.0f);
+    drawList.AddImage(
+        UIRect(70.0f, 18.0f, 32.0f, 32.0f),
+        UITextureHandle{ 123u, 32u, 32u },
+        UIColor(0.8f, 0.9f, 1.0f, 1.0f));
+    drawList.PopClipRect();
+
+    ASSERT_EQ(drawList.GetCommandCount(), 6u);
+    const auto& commands = drawList.GetCommands();
+    EXPECT_EQ(commands[0].type, UIDrawCommandType::PushClipRect);
+    EXPECT_EQ(commands[1].type, UIDrawCommandType::FilledRect);
+    EXPECT_EQ(commands[2].type, UIDrawCommandType::RectOutline);
+    EXPECT_EQ(commands[3].type, UIDrawCommandType::Text);
+    EXPECT_EQ(commands[4].type, UIDrawCommandType::Image);
+    EXPECT_EQ(commands[5].type, UIDrawCommandType::PopClipRect);
+    EXPECT_FLOAT_EQ(commands[1].rounding, 4.0f);
+    EXPECT_FLOAT_EQ(commands[2].thickness, 2.0f);
+    EXPECT_EQ(commands[3].text, "XCUI");
+    EXPECT_EQ(commands[4].texture.nativeHandle, 123u);
+}
+
+TEST(XCUIDrawDataTest, DrawDataAggregatesMultipleLists) {
+    using XCEngine::UI::UIColor;
+    using XCEngine::UI::UIDrawData;
+    using XCEngine::UI::UIRect;
+
+    UIDrawData drawData = {};
+    auto& first = drawData.EmplaceDrawList("First");
+    first.AddFilledRect(UIRect(0.0f, 0.0f, 20.0f, 20.0f), UIColor(1.0f, 0.0f, 0.0f, 1.0f));
+
+    auto& second = drawData.EmplaceDrawList("Second");
+    second.AddFilledRect(UIRect(5.0f, 5.0f, 10.0f, 10.0f), UIColor(0.0f, 1.0f, 0.0f, 1.0f));
+    second.AddRectOutline(UIRect(5.0f, 5.0f, 10.0f, 10.0f), UIColor(1.0f, 1.0f, 1.0f, 1.0f));
+
+    EXPECT_EQ(drawData.GetDrawListCount(), 2u);
+    EXPECT_EQ(drawData.GetTotalCommandCount(), 3u);
+}