Merge pull request 'perf(ui): memoize the input-field caret prefix width (#128)' (#146) from claude/issue-128 into master

interfaces/Crafter.Graphics-InputField.cppm

@@ -58,6 +58,20 @@ export namespace Crafter {
         InputFieldType type      = InputFieldType::Text;
         bool           focused   = false;
         std::size_t    cursorPos = 0;     // byte offset into `value`
+
+        // Caret-x memo (issue #128). For a focused field DrawInputField measures
+        // the cursor prefix via Font::GetLineWidth every frame, but only the
+        // blink (caretVisible) changes frame-to-frame — value/cursorPos/fontSize
+        // are stable across the vast majority of frames. Cache the measured
+        // prefix WIDTH (the GetLineWidth result, in px) keyed on the inputs that
+        // determine it: the prefix bytes and fontSize. The final caretX adds the
+        // layout-dependent textX each frame, so it is intentionally NOT cached —
+        // a field that moves on screen with an unchanged value would otherwise
+        // get a stale caret. `mutable` so the `const InputField&` draw fn can
+        // refresh it; these fields are internal and need no user initialisation.
+        mutable std::string caretCachePrefix_;
+        mutable float       caretCacheFontSize_ = -1.0f;   // <0 = unset
+        mutable float       caretCacheWidth_    = 0.0f;
     };
 
     // Returns true if `s` is a valid candidate for the given type, including