refactor(contacts): share case-insensitive compare, truncation helpers

The contacts list carried its own lowercase-and-compare sort, its own
lowercase substring search, and an inline linear middle-truncation loop
for fitting an address to a column width. These duplicated logic that
belongs in the shared text helpers.

- A new allocation-free case-insensitive compare replaces the per-sort
  lowercasing; it lowercases ASCII per byte and leaves bytes >= 0x80
  alone, so UTF-8 labels sort exactly as before.
- Search now uses the shared case-insensitive contains helper.
- Middle-truncation to a pixel width moves to a shared template that
  binary-searches the fit (about log2(n) width measurements instead of
  up to n) while producing the same result as the old linear shrink.

Tests: the compare matches lowercase-then-compare across ASCII, UTF-8
bytes and length ties, and the fit helper matches the old linear loop
across lengths and widths.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/util/text_format.cpp

@@ -5,6 +5,7 @@
 #include "text_format.h"
 #include "i18n.h"
 
+#include <algorithm>
 #include <cctype>
 #include <cstdio>
 #include <ctime>
@@ -90,6 +91,17 @@ std::string truncateMiddle(const std::string& s, int front, int back)
     return s.substr(0, front) + "..." + s.substr(s.length() - back);
 }
 
+int compareIgnoreCase(std::string_view a, std::string_view b)
+{
+    const std::size_t n = std::min(a.size(), b.size());
+    for (std::size_t i = 0; i < n; ++i) {
+        const unsigned char ca = static_cast<unsigned char>(std::tolower(static_cast<unsigned char>(a[i])));
+        const unsigned char cb = static_cast<unsigned char>(std::tolower(static_cast<unsigned char>(b[i])));
+        if (ca != cb) return ca < cb ? -1 : 1;
+    }
+    return a.size() == b.size() ? 0 : (a.size() < b.size() ? -1 : 1);
+}
+
 bool containsIgnoreCase(std::string_view haystack, std::string_view needle)
 {
     if (needle.empty()) return true;

src/util/text_format.h

@@ -8,6 +8,7 @@
 #pragma once
 
 #include <cstdint>
+#include <cstddef>
 #include <string>
 #include <string_view>
 
@@ -37,6 +38,11 @@ std::string formatTimeAgoShort(std::int64_t timestamp);
 // An empty needle matches everything. Safe for per-frame filtering of large lists.
 bool containsIgnoreCase(std::string_view haystack, std::string_view needle);
 
+// Case-insensitive ASCII three-way compare, allocation-free. Equivalent to
+// toLower(a).compare(toLower(b)) with C-locale tolower per byte (bytes >= 0x80 are left alone and
+// compared as unsigned), so UTF-8 labels sort exactly as before. Returns <0, 0, >0.
+int compareIgnoreCase(std::string_view a, std::string_view b);
+
 // Middle-ellipsis truncation, half/half form: "prefix...suffix" so the total (including "...")
 // is at most maxLen. Guards maxLen <= 3 (returns s unchanged) to avoid unsigned underflow on the
 // (maxLen - 3) split. Strings already at/under maxLen are returned unchanged.
@@ -46,5 +52,35 @@ std::string truncateMiddle(const std::string& s, int maxLen);
 // Returns s unchanged when it is no longer than front + back + 3 (the "..." would not save space).
 std::string truncateMiddle(const std::string& s, int front, int back);
 
+// Middle-ellipsis fit-to-width. Same result as a linear shrink (alternating head/tail removal from the
+// half/half split, ellipsis U+2026), but ~log2(n) measurements instead of up to n. `width(const std::string&)`
+// returns the rendered width. Assumes width is non-increasing as characters are removed (true for ImGui
+// text: positive advances, no kerning). Falls back to truncateMiddle(s, minFront, minBack) when nothing fits.
+template <class Measure>
+std::string truncateMiddleToFit(const std::string& s, int minFront, int minBack, float maxW, Measure&& width)
+{
+    if (width(s) <= maxW) return s;                                // fits in full
+    if (maxW <= 0.0f) return truncateMiddle(s, minFront, minBack); // nothing to measure against
+    const std::size_t n = s.size();
+    const std::size_t minKeep = static_cast<std::size_t>(minFront + minBack);
+    if (n <= minKeep) return truncateMiddle(s, minFront, minBack);
+    const std::size_t head0 = n / 2, tail0 = n - head0;
+    // Candidate after removing k chars (k = 0 is "s with an ellipsis in the middle"): removal strictly
+    // alternates, from the head first when head >= tail, else from the tail.
+    auto build = [&](std::size_t k) {
+        std::size_t h, t;
+        if (head0 >= tail0) { h = head0 - (k + 1) / 2; t = tail0 - k / 2; }   // even n: head first
+        else                { t = tail0 - (k + 1) / 2; h = head0 - k / 2; }   // odd n: tail first
+        return s.substr(0, h) + "\xE2\x80\xA6" + s.substr(n - t);
+    };
+    std::size_t lo = 0, hi = n - minKeep - 1;
+    if (width(build(hi)) > maxW) return truncateMiddle(s, minFront, minBack);
+    while (lo < hi) {
+        const std::size_t mid = lo + (hi - lo) / 2;
+        if (width(build(mid)) <= maxW) hi = mid; else lo = mid + 1;
+    }
+    return build(lo);
+}
+
 } // namespace util
 } // namespace dragonx