Add macro to generate logging category declarations for Qt5.

This makes life a bit easier for developers who use the categorised
logging in Qt5 in the common case - rather than creating two new files,
and remembering to put in the #ifdef for the default verbosity settings
in Qt 5.4, they can just add a couple of lines to their CMakeLists.txt.

REVIEW: 124595

3 files changed, 140 insertions, 0 deletions

diff --git a/modules/ECMQtDeclareLoggingCategory.cmake b/modules/ECMQtDeclareLoggingCategory.cmake
new file mode 100644
index 00000000..b7f1ad39
--- /dev/null
+++ b/modules/ECMQtDeclareLoggingCategory.cmake
@@ -0,0 +1,118 @@
+#.rst:
+# ECMQtDeclareLoggingCategory
+# ---------------------------
+#
+# Generate declarations for logging categories in Qt5.
+#
+# ::
+#
+#   ecm_qt_declare_logging_category(<sources_var>
+#                                   HEADER <filename>
+#                                   IDENTIFIER <identifier>
+#                                   CATEGORY_NAME <category_name>
+#                                   [DEFAULT_SEVERITY
+#                                        <Debug|Info|Warning|
+#                                         Critical|Fatal>])
+#
+# A header file, ``<filename>``, will be generated along with a corresponding
+# source file, which will be added to ``<sources_var>``. These will provide a
+# QLoggingCategory category that can be referred to from C++ code using
+# ``<identifier>``, and from the logging configuration using
+# ``<category_name>``.
+#
+# If ``<filename>`` is not absolute, it will be taken relative to the current
+# binary directory.
+#
+# If the code is compiled against Qt 5.4 or later, by default it will only log
+# output that is at least the severity specified by ``DEFAULT_SEVERITY``, or
+# "Warning" level if ``DEFAULT_SEVERITY`` is not given. Note that, due to a
+# bug in Qt 5.5, "Info" may be treated as more severe than "Fatal".
+#
+# ``<identifier>`` may include namespaces (eg: ``foo::bar::IDENT``).
+#
+# Since 5.14.0.
+
+#=============================================================================
+# Copyright 2015 Alex Merry <alex.merry@kde.org>
+#
+# Distributed under the OSI-approved BSD License (the "License");
+# see accompanying file COPYING-CMAKE-SCRIPTS for details.
+#
+# This software is distributed WITHOUT ANY WARRANTY; without even the
+# implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+# See the License for more information.
+#=============================================================================
+# (To distribute this file outside of extra-cmake-modules, substitute the full
+#  License text for the above reference.)
+
+include(CMakeParseArguments)
+
+set(_ECM_QT_DECLARE_LOGGING_CATEGORY_TEMPLATE_CPP "${CMAKE_CURRENT_LIST_DIR}/ECMQtDeclareLoggingCategory.cpp.in")
+set(_ECM_QT_DECLARE_LOGGING_CATEGORY_TEMPLATE_H   "${CMAKE_CURRENT_LIST_DIR}/ECMQtDeclareLoggingCategory.h.in")
+
+function(ecm_qt_declare_logging_category sources_var)
+    set(options)
+    set(oneValueArgs HEADER IDENTIFIER CATEGORY_NAME DEFAULT_SEVERITY)
+    set(multiValueArgs)
+    cmake_parse_arguments(ARG "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})
+
+    if(ARG_UNPARSED_ARGUMENTS)
+        message(FATAL_ERROR "Unexpected arguments to ecm_qt_declare_logging_category: ${ARG_UNPARSED_ARGUMENTS}")
+    endif()
+    if(NOT ARG_HEADER)
+        message(FATAL_ERROR "Missing HEADER argument for ecm_qt_declare_logging_category")
+    endif()
+    if(NOT ARG_IDENTIFIER)
+        message(FATAL_ERROR "Missing IDENTIFIER argument for ecm_qt_declare_logging_category")
+    endif()
+    if(NOT ARG_CATEGORY_NAME)
+        message(FATAL_ERROR "Missing CATEGORY_NAME argument for ecm_qt_declare_logging_category")
+    endif()
+    if(NOT ARG_DEFAULT_SEVERITY)
+        set(ARG_DEFAULT_SEVERITY Warning)
+    else()
+        set(acceptible_severities Debug Info Warning Critical Fatal)
+        list(FIND acceptible_severities "${ARG_DEFAULT_SEVERITY}" pos)
+        if (pos EQUAL -1)
+            message(FATAL_ERROR "Unknown DEFAULT_SEVERITY ${pos}")
+        endif()
+    endif()
+
+    if (NOT IS_ABSOLUTE "${ARG_HEADER}")
+        set(ARG_HEADER "${CMAKE_CURRENT_BINARY_DIR}/${ARG_HEADER}")
+    endif()
+
+    string(REPLACE "::" ";" namespaces "${ARG_IDENTIFIER}")
+    list(LENGTH namespaces len)
+    math(EXPR last_pos "${len} - 1")
+    list(GET namespaces ${last_pos} IDENTIFIER)
+    list(REMOVE_AT namespaces ${last_pos})
+
+    set(OPEN_NAMESPACES)
+    set(CLOSE_NAMESPACES)
+    foreach(ns ${namespaces})
+        set(OPEN_NAMESPACES "${OPEN_NAMESPACES} namespace ${ns} {")
+        set(CLOSE_NAMESPACES "} ${CLOSE_NAMESPACES}")
+    endforeach()
+
+    string(FIND "${ARG_HEADER}" "." pos REVERSE)
+    if (pos EQUAL -1)
+        set(cpp_filename "${ARG_HEADER}.cpp")
+    else()
+        string(SUBSTRING "${ARG_HEADER}" 0 ${pos} cpp_filename)
+        set(cpp_filename "${cpp_filename}.cpp")
+    endif()
+
+    get_filename_component(HEADER_NAME "${ARG_HEADER}" NAME)
+
+    string(REPLACE "::" "_" GUARD_NAME "${ARG_IDENTIFIER}_H")
+    string(TOUPPER "${GUARD_NAME}" GUARD_NAME)
+
+    configure_file("${_ECM_QT_DECLARE_LOGGING_CATEGORY_TEMPLATE_CPP}" "${cpp_filename}")
+    configure_file("${_ECM_QT_DECLARE_LOGGING_CATEGORY_TEMPLATE_H}" "${ARG_HEADER}")
+
+    set(sources "${${sources_var}}")
+    list(APPEND sources "${cpp_filename}")
+    set(${sources_var} "${sources}" PARENT_SCOPE)
+endfunction()
+
diff --git a/modules/ECMQtDeclareLoggingCategory.cpp.in b/modules/ECMQtDeclareLoggingCategory.cpp.in
new file mode 100644
index 00000000..20c14af5
--- /dev/null
+++ b/modules/ECMQtDeclareLoggingCategory.cpp.in
@@ -0,0 +1,11 @@
+// This file is autogenerated by CMake: DO NOT EDIT
+
+#include "@HEADER_NAME@"
+
+@OPEN_NAMESPACES@
+#if QT_VERSION >= QT_VERSION_CHECK(5, 4, 0)
+Q_LOGGING_CATEGORY(@IDENTIFIER@, "@ARG_CATEGORY_NAME@", Qt@ARG_DEFAULT_SEVERITY@Msg)
+#else
+Q_LOGGING_CATEGORY(@IDENTIFIER@, "@ARG_CATEGORY_NAME@")
+#endif
+@CLOSE_NAMESPACES@
diff --git a/modules/ECMQtDeclareLoggingCategory.h.in b/modules/ECMQtDeclareLoggingCategory.h.in
new file mode 100644
index 00000000..fedecd2f
--- /dev/null
+++ b/modules/ECMQtDeclareLoggingCategory.h.in
@@ -0,0 +1,11 @@
+// This file is autogenerated by CMake: DO NOT EDIT
+
+#ifndef @GUARD_NAME@
+#define @GUARD_NAME@
+
+#include <QLoggingCategory>
+@OPEN_NAMESPACES@
+Q_DECLARE_LOGGING_CATEGORY(@IDENTIFIER@)
+@CLOSE_NAMESPACES@
+
+#endif