Add fmtlib for older compilers

CMakeLists.txt

@@ -75,10 +75,10 @@ include(GitRepo)
 
 ## Libraries ##
 ##############################
-# c++17 support
+# c++20 support
 ##############################
-#find_package(CXX17 REQUIRED COMPONENTS optional)
-#find_package(Filesystem REQUIRED COMPONENTS ghc Final Experimental)
+
+find_package(format)
 
 find_package(Backtrace)
 if (Backtrace_FOUND)
@@ -197,6 +197,7 @@ target_link_libraries(external_modules INTERFACE
         $<$<TARGET_EXISTS:X11::Xi>:X11::Xi>
         $<$<TARGET_EXISTS:X11::X11>:X11::X11>
         $<$<TARGET_EXISTS:Backtrace::backtrace>:Backtrace::backtrace>
+        $<$<TARGET_EXISTS:fmt::fmt>:fmt::fmt>
         ZLIB::ZLIB
         Threads::Threads
         )
@@ -372,7 +373,8 @@ Configuration:
     X11 support enabled:        ${X11_FOUND}
     GTEST enabled:              ${ENABLE_GTEST}
     GCOV enabled:               ${DEV_ENABLE_GCOV}
-    Filesystem library:         ${CXX_FILESYSTEM_NAMESPACE}
+    Filesystem library:         std::filesystem
+    Format library:             ${FORMAT_LIB}
     Profiling enabled:          ${ENABLE_PROFILING}
 ")
 

cmake/find/Find-format.cmake

@@ -0,0 +1,18 @@
+cmake_minimum_required(VERSION 3.14)
+
+enable_language(CXX)
+
+option(XOJ_USE_FMTLIB "Use fmtlib" OFF)
+include(xoj_check_cxx_definition)
+xoj_check_cxx_definition("__cpp_lib_format >= 202110L" "format" _XOJ_HAS_INCLUDE_FORMAT)
+
+if(_XOJ_HAS_INCLUDE_FORMAT AND NOT XOJ_USE_FMTLIB)
+    message(STATUS "Found <format>")
+    set(FORMAT_LIB "std::format")
+else()
+    message(STATUS "Could not find <format>, fetch {fmt}")
+    include(get_cpm)
+    CPMAddPackage("gh:fmtlib/fmt#7.1.3")
+    set(FORMAT_LIB "{fmt}")
+endif()
+set(format_FOUND TRUE)

cmake/include/get_cpm.cmake

@@ -0,0 +1,24 @@
+# SPDX-License-Identifier: MIT
+#
+# SPDX-FileCopyrightText: Copyright (c) 2019-2023 Lars Melchior and contributors
+
+set(CPM_DOWNLOAD_VERSION 0.39.0)
+set(CPM_HASH_SUM "66639bcac9dd2907b2918de466783554c1334446b9874e90d38e3778d404c2ef")
+
+if(CPM_SOURCE_CACHE)
+  set(CPM_DOWNLOAD_LOCATION "${CPM_SOURCE_CACHE}/cpm/CPM_${CPM_DOWNLOAD_VERSION}.cmake")
+elseif(DEFINED ENV{CPM_SOURCE_CACHE})
+  set(CPM_DOWNLOAD_LOCATION "$ENV{CPM_SOURCE_CACHE}/cpm/CPM_${CPM_DOWNLOAD_VERSION}.cmake")
+else()
+  set(CPM_DOWNLOAD_LOCATION "${CMAKE_BINARY_DIR}/cmake/CPM_${CPM_DOWNLOAD_VERSION}.cmake")
+endif()
+
+# Expand relative path. This is important if the provided path contains a tilde (~)
+get_filename_component(CPM_DOWNLOAD_LOCATION ${CPM_DOWNLOAD_LOCATION} ABSOLUTE)
+
+file(DOWNLOAD
+     https://github.com/cpm-cmake/CPM.cmake/releases/download/v${CPM_DOWNLOAD_VERSION}/CPM.cmake
+     ${CPM_DOWNLOAD_LOCATION} EXPECTED_HASH SHA256=${CPM_HASH_SUM}
+)
+
+include(${CPM_DOWNLOAD_LOCATION})

cmake/include/xoj_check_cxx_definition.cmake

@@ -0,0 +1,20 @@
+# Define the function
+function(xoj_check_cxx_definition definition header variable)
+    set(BINARY_DIR ${CMAKE_BINARY_DIR}/xoj_check_cxx_definition)
+    set(SOURCE_FILE ${CMAKE_BINARY_DIR}/xoj_check_cxx_definition/${variable}.cpp)
+    file(WRITE ${SOURCE_FILE} "#include <${header}> \n#if !(${definition}) \n#error \n#endif\nint main(){}")
+    try_compile(${variable} 
+                ${BINARY_DIR}
+                ${SOURCE_FILE}
+                CXX_STANDARD 20
+                CXX_STANDARD_REQUIRED TRUE
+                OUTPUT_VARIABLE _OUT_ERROR
+                )
+    if(${variable})
+        message(STATUS "${header} defines ${definition}")
+    else()
+        message(STATUS "${header} does not define ${definition}")
+        message(STATUS "${_OUT_ERROR}")
+    endif()
+    file(REMOVE ${SOURCE_FILE})
+endfunction()

src/core/control/Control.cpp

@@ -1,9 +1,8 @@
 #include "Control.h"
 
-#include <algorithm>  // for max
-#include <cstdlib>    // for size_t
-#include <exception>  // for exce...
-#include <format>
+#include <algorithm>   // for max
+#include <cstdlib>     // for size_t
+#include <exception>   // for exce...
 #include <functional>  // for bind
 #include <iterator>    // for end
 #include <memory>      // for make...
@@ -112,6 +111,7 @@
 #include "UndoRedoController.h"              // for Undo...
 #include "config-dev.h"                      // for SETT...
 #include "config.h"                          // for PROJ...
+#include "format.h"                          // for fmt::format
 
 using std::string;
 
@@ -1812,29 +1812,29 @@ void Control::updateWindowTitle() {
             title = _("Unsaved Document");
         } else {
             if (settings->isPageNumberInTitlebarShown()) {
-                title += std::format("[{}/{}]  ", getCurrentPageNo() + 1, doc->getPageCount());
+                title += fmt::format("[{}/{}]  ", getCurrentPageNo() + 1, doc->getPageCount());
             }
             if (undoRedo->isChanged()) {
                 title += "*";
             }
 
             if (settings->isFilepathInTitlebarShown()) {
-                title += std::format("[{}] - {}", char_cast(doc->getPdfFilepath().parent_path().u8string()),
+                title += fmt::format("[{}] - {}", char_cast(doc->getPdfFilepath().parent_path().u8string()),
                                      char_cast(doc->getPdfFilepath().filename().u8string()));
             } else {
                 title += char_cast(doc->getPdfFilepath().filename().u8string());
             }
         }
     } else {
         if (settings->isPageNumberInTitlebarShown()) {
-            title += ("[" + std::to_string(getCurrentPageNo() + 1) + "/" + std::to_string(doc->getPageCount()) + "]  ");
+            title += fmt::format("[{}/{}]  ", getCurrentPageNo() + 1 , doc->getPageCount());
         }
         if (undoRedo->isChanged()) {
             title += "*";
         }
 
         if (settings->isFilepathInTitlebarShown()) {
-            title += (std::format("[{}] - {}", char_cast(doc->getFilepath().parent_path().u8string()),
+            title += (fmt::format("[{}] - {}", char_cast(doc->getFilepath().parent_path().u8string()),
                                   char_cast(doc->getFilepath().filename().u8string())));
         } else {
             title += char_cast(doc->getFilepath().filename().u8string());

src/util/include/format.h

@@ -0,0 +1,41 @@
+#pragma once
+
+// define XOJ_USE_STD_FORMAT if std::format should be forced
+
+#if !defined(XOJ_USE_STD_FORMAT) && __has_include(<format>)
+#include <format>  // IWYU pragma: export
+#if defined(__cpp_lib_format) && __cpp_lib_format >= 202110L
+#define XOJ_USE_STD_FORMAT = 1
+#endif
+#endif
+
+#if !defined(XOJ_USE_STD_FORMAT)
+#include <fmt/format.h>  // IWYU pragma: export
+#else // Include all the symbols from std::format into the fmt namespace
+namespace fmt {
+using std::basic_format_arg;
+using std::basic_format_args;
+using std::basic_format_context;
+using std::basic_format_parse_context;
+using std::basic_format_string;
+using std::format;
+using std::format_args;
+using std::format_context;
+using std::format_error;
+using std::format_parse_context;
+using std::format_string;
+using std::format_to;
+using std::format_to_n;
+using std::formatted_size;
+using std::formatter;
+using std::make_format_args;
+using std::make_wformat_args;
+using std::vformat;
+using std::vformat_to;
+using std::visit_format_arg;
+using std::wformat_args;
+using std::wformat_context;
+using std::wformat_parse_context;
+using std::wformat_string;
+}  // namespace fmt
+#endif