refactor(new_editor): snapshot hosted editor restructuring

new_editor/include/XCEditor/Widgets/UIEditorTextLayout.h

@@ -1,9 +1,12 @@
 #pragma once
 
+#include <XCEngine/UI/Text/UITextEditing.h>
 #include <XCEngine/UI/DrawData.h>
 
 #include <algorithm>
+#include <chrono>
 #include <cmath>
+#include <string>
 
 namespace XCEngine::UI::Editor::Widgets {
 
@@ -32,4 +35,79 @@ inline ::XCEngine::UI::UIRect ResolveUIEditorTextClipRect(
         rect.height + extraPadding + 1.0f);
 }
 
+inline float MeasureUIEditorTextWidth(
+    const std::string& text,
+    float fontSize) {
+    return fontSize * 0.56f *
+        static_cast<float>(::XCEngine::UI::Text::CountUtf8Codepoints(text));
+}
+
+inline float MeasureUIEditorTextWidthToCaret(
+    const std::string& text,
+    std::size_t caretOffset,
+    float fontSize) {
+    return fontSize * 0.56f *
+        static_cast<float>(::XCEngine::UI::Text::CountUtf8CodepointsInRange(
+            text,
+            0u,
+            (std::min)(caretOffset, text.size())));
+}
+
+inline std::uint64_t GetUIEditorTextCaretClockNanoseconds() {
+    using Clock = std::chrono::steady_clock;
+    const auto now = Clock::now().time_since_epoch();
+    return static_cast<std::uint64_t>(
+        std::chrono::duration_cast<std::chrono::nanoseconds>(now).count());
+}
+
+inline bool ShouldBlinkUIEditorTextCaret(std::uint64_t blinkStartNanoseconds) {
+    constexpr std::uint64_t kInitialVisibleDurationNanoseconds = 500000000ull;
+    constexpr std::uint64_t kBlinkPhaseDurationNanoseconds = 500000000ull;
+
+    if (blinkStartNanoseconds == 0u) {
+        return true;
+    }
+
+    const std::uint64_t nowNanoseconds = GetUIEditorTextCaretClockNanoseconds();
+    if (nowNanoseconds <= blinkStartNanoseconds) {
+        return true;
+    }
+
+    const std::uint64_t elapsedNanoseconds = nowNanoseconds - blinkStartNanoseconds;
+    if (elapsedNanoseconds < kInitialVisibleDurationNanoseconds) {
+        return true;
+    }
+
+    const std::uint64_t blinkElapsedNanoseconds =
+        elapsedNanoseconds - kInitialVisibleDurationNanoseconds;
+    return ((blinkElapsedNanoseconds / kBlinkPhaseDurationNanoseconds) % 2u) == 0u;
+}
+
+inline void AppendUIEditorTextCaret(
+    ::XCEngine::UI::UIDrawList& drawList,
+    const ::XCEngine::UI::UIRect& rect,
+    const std::string& text,
+    std::size_t caretOffset,
+    std::uint64_t blinkStartNanoseconds,
+    const ::XCEngine::UI::UIColor& color,
+    float fontSize,
+    float insetX,
+    float insetY = 0.0f,
+    float thickness = 1.0f) {
+    if (color.a <= 0.0f || !ShouldBlinkUIEditorTextCaret(blinkStartNanoseconds)) {
+        return;
+    }
+
+    const float caretX = (std::min)(
+        rect.x + rect.width - 1.0f,
+        rect.x + insetX + MeasureUIEditorTextWidthToCaret(text, caretOffset, fontSize));
+    const float top = ResolveUIEditorTextTop(rect, fontSize, insetY);
+    const float bottom = top + MeasureUIEditorTextLayoutHeight(fontSize);
+    drawList.AddLine(
+        ::XCEngine::UI::UIPoint(caretX, top),
+        ::XCEngine::UI::UIPoint(caretX, bottom),
+        color,
+        thickness);
+}
+
 } // namespace XCEngine::UI::Editor::Widgets