Consolidate the host's UTF-8/wide conversions into util/utf8.hpp

Five files each carried their own copy of the WideCharToMultiByte /
MultiByteToWideChar UTF-8 conversion (injection_panel, audio_overrides,
imgui_layer's to_utf8, main's harness widen, and vk_layer_setup's inline
form). Replace them all with coop::narrow / coop::widen from one header.

audio_panel's image_basename dropped its lossy `c & 0x7F` ASCII mask for
the proper narrow(), so a non-ASCII game exe name is no longer mangled
in log lines.

host/src/audio/audio_overrides.cpp

@@ -9,6 +9,7 @@
 #include <mmreg.h> // WAVE_FORMAT_* (needs windows.h first)
 
 #include "coop/tool_paths.hpp"
+#include "util/utf8.hpp"
 
 namespace coop
 {
@@ -22,32 +23,8 @@ std::wstring to_lower(std::wstring s)
 	}
 	return s;
 }
-
+// A non-ASCII image name (e.g. a CJK game exe) round-trips through UTF-8 so it survives
-// UTF-8 round-trip so a non-ASCII image name (e.g. a CJK game exe) survives persist/reload and
+// persist/reload; ASCII names (the common case) are byte-identical. See util/utf8.hpp.
-// can't collide with another name; for ASCII names (the common case) UTF-8 is byte-identical.
-std::string narrow(const std::wstring& w)
-{
-	if (w.empty())
-	{
-		return {};
-	}
-	const int n = WideCharToMultiByte(CP_UTF8, 0, w.c_str(), static_cast<int>(w.size()), nullptr, 0, nullptr, nullptr);
-	std::string s(static_cast<std::size_t>(n), '\0');
-	WideCharToMultiByte(CP_UTF8, 0, w.c_str(), static_cast<int>(w.size()), s.data(), n, nullptr, nullptr);
-	return s;
-}
-
-std::wstring widen(const std::string& s)
-{
-	if (s.empty())
-	{
-		return {};
-	}
-	const int n = MultiByteToWideChar(CP_UTF8, 0, s.c_str(), static_cast<int>(s.size()), nullptr, 0);
-	std::wstring w(static_cast<std::size_t>(n), L'\0');
-	MultiByteToWideChar(CP_UTF8, 0, s.c_str(), static_cast<int>(s.size()), w.data(), n);
-	return w;
-}
 } // namespace
 
 AudioOverrideStore::AudioOverrideStore(std::wstring path) : path_(std::move(path))

host/src/audio_panel.cpp

@@ -8,6 +8,7 @@
 #include <mmreg.h>
 
 #include "ui/app_chrome.hpp"
+#include "util/utf8.hpp"
 
 namespace coop
 {
@@ -69,18 +70,11 @@ ImVec4 audio_format_state_color(std::uint32_t state)
 	}
 }
 
-// Basename of an image path, narrowed to ASCII for a log line.
+// Basename of an image path (UTF-8), for a log line.
 std::string image_basename(const std::wstring& image_path)
 {
 	const std::size_t slash = image_path.find_last_of(L"\\/");
-	const std::wstring w = slash == std::wstring::npos ? image_path : image_path.substr(slash + 1);
+	return narrow(slash == std::wstring::npos ? image_path : image_path.substr(slash + 1));
-	std::string out;
-	out.reserve(w.size());
-	for (wchar_t c : w)
-	{
-		out.push_back(static_cast<char>(c & 0x7F));
-	}
-	return out;
 }
 
 } // namespace

host/src/imgui_layer.cpp

@@ -9,27 +9,11 @@
 #include "coop/dpi.hpp"
 #include "coop/tool_paths.hpp"
 #include "ui/app_chrome.hpp"
+#include "util/utf8.hpp"
 
 namespace coop
 {
 
-namespace
-{
-// ImGui's file IO treats IniFilename as UTF-8 (it converts to wide for _wfopen), so
-// the path must be UTF-8 rather than the system ANSI code page.
-std::string to_utf8(const std::wstring& w)
-{
-	if (w.empty())
-	{
-		return {};
-	}
-	const int n = WideCharToMultiByte(CP_UTF8, 0, w.c_str(), static_cast<int>(w.size()), nullptr, 0, nullptr, nullptr);
-	std::string s(static_cast<std::size_t>(n), '\0');
-	WideCharToMultiByte(CP_UTF8, 0, w.c_str(), static_cast<int>(w.size()), s.data(), n, nullptr, nullptr);
-	return s;
-}
-} // namespace
-
 ImGuiLayer::~ImGuiLayer()
 {
 	if (initialized_)
@@ -52,7 +36,9 @@ bool ImGuiLayer::init(HWND hwnd, ID3D11Device* device, ID3D11DeviceContext* cont
 	// computed default on startup (which would clobber the restored positions).
 	const std::wstring ini_w = exe_directory() + L"coop_layout.ini";
 	const bool had_layout = GetFileAttributesW(ini_w.c_str()) != INVALID_FILE_ATTRIBUTES;
-	ini_path_ = to_utf8(ini_w);
+	// ImGui treats IniFilename as UTF-8 (it converts to wide for _wfopen), so narrow to UTF-8, not
+	// the system ANSI code page.
+	ini_path_ = narrow(ini_w);
 	io.IniFilename = ini_path_.c_str();
 	set_layout_persisted(had_layout);
 

host/src/injection_panel.cpp

@@ -10,6 +10,7 @@
 #include "inject/injector.hpp"
 #include "ui/app_chrome.hpp"
 #include "ui/text_match.hpp"
+#include "util/utf8.hpp"
 
 namespace coop
 {
@@ -21,18 +22,6 @@ const ImVec4 kGreen(0.4f, 1.0f, 0.4f, 1.0f);
 const ImVec4 kRed(1.0f, 0.45f, 0.4f, 1.0f);
 const ImVec4 kGrey(0.7f, 0.7f, 0.7f, 1.0f);
 
-std::string narrow(const std::wstring& w)
-{
-	if (w.empty())
-	{
-		return {};
-	}
-	const int len = WideCharToMultiByte(CP_UTF8, 0, w.c_str(), static_cast<int>(w.size()), nullptr, 0, nullptr, nullptr);
-	std::string out(static_cast<std::size_t>(len), '\0');
-	WideCharToMultiByte(CP_UTF8, 0, w.c_str(), static_cast<int>(w.size()), out.data(), len, nullptr, nullptr);
-	return out;
-}
-
 // Case-insensitive equality of two image names (e.g. "game.exe").
 bool iequals_name(const std::wstring& a, const std::wstring& b)
 {

host/src/main.cpp

@@ -35,6 +35,7 @@
 #include "log_panel.hpp"
 #include "test_harness.hpp"
 #include "ui/app_chrome.hpp"
+#include "util/utf8.hpp"
 #include "vk_layer_setup.hpp"
 
 namespace
@@ -91,17 +92,7 @@ void draw_screenshot_toast(double seconds_since, const std::string& name)
 }
 
 #ifdef COOP_TEST_HARNESS
-std::wstring widen(const std::string& s)
+using coop::widen;
-{
-	if (s.empty())
-	{
-		return {};
-	}
-	const int n = MultiByteToWideChar(CP_UTF8, 0, s.c_str(), static_cast<int>(s.size()), nullptr, 0);
-	std::wstring w(static_cast<std::size_t>(n), L'\0');
-	MultiByteToWideChar(CP_UTF8, 0, s.c_str(), static_cast<int>(s.size()), w.data(), n);
-	return w;
-}
 
 // Run a test-harness command on the main thread, hitting the same code the UI buttons do.
 // Returns a one-line response the driver reads back.

host/src/util/utf8.hpp

@@ -0,0 +1,39 @@
+// UTF-8 <-> wide-string conversion, shared by the host code that bridges Win32's UTF-16
+// (image names, window titles, paths) and the UTF-8 the ImGui overlay / .ini files use.
+#pragma once
+
+#include <string>
+
+#include <windows.h>
+
+namespace coop
+{
+
+// UTF-16 -> UTF-8.
+inline std::string narrow(const std::wstring& w)
+{
+	if (w.empty())
+	{
+		return {};
+	}
+	const int n =
+	    WideCharToMultiByte(CP_UTF8, 0, w.c_str(), static_cast<int>(w.size()), nullptr, 0, nullptr, nullptr);
+	std::string s(static_cast<std::size_t>(n), '\0');
+	WideCharToMultiByte(CP_UTF8, 0, w.c_str(), static_cast<int>(w.size()), s.data(), n, nullptr, nullptr);
+	return s;
+}
+
+// UTF-8 -> UTF-16.
+inline std::wstring widen(const std::string& s)
+{
+	if (s.empty())
+	{
+		return {};
+	}
+	const int n = MultiByteToWideChar(CP_UTF8, 0, s.c_str(), static_cast<int>(s.size()), nullptr, 0);
+	std::wstring w(static_cast<std::size_t>(n), L'\0');
+	MultiByteToWideChar(CP_UTF8, 0, s.c_str(), static_cast<int>(s.size()), w.data(), n);
+	return w;
+}
+
+} // namespace coop

host/src/vk_layer_setup.cpp

@@ -3,6 +3,7 @@
 #include <windows.h>
 
 #include "coop/tool_paths.hpp"
+#include "util/utf8.hpp"
 
 namespace coop
 {
@@ -33,11 +34,7 @@ bool register_vk_layer(const std::wstring& target_image)
 	{
 		const std::size_t slash = target_image.find_last_of(L"\\/");
 		const std::wstring base = slash == std::wstring::npos ? target_image : target_image.substr(slash + 1);
-		const int n = WideCharToMultiByte(CP_UTF8, 0, base.c_str(), static_cast<int>(base.size()), nullptr, 0,
+		const std::string utf8 = narrow(base);
-		                                  nullptr, nullptr);
-		std::string utf8(static_cast<std::size_t>(n), '\0');
-		WideCharToMultiByte(CP_UTF8, 0, base.c_str(), static_cast<int>(base.size()), utf8.data(), n, nullptr,
-		                    nullptr);
 		HANDLE f = CreateFileW(sf.c_str(), GENERIC_WRITE, 0, nullptr, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, nullptr);
 		if (f != INVALID_HANDLE_VALUE)
 		{