vm_tools: sommelier: Add Chromium-like logging macros and functions

This adds simple functions to print messages in various levels.
To print the messages, Sommelier needs to be built with
-Dlog_level=X with some number.

Example usage:

```
LOG(INFO) << window << " says hello world";
LOG(INFO) << "hello world";
```

BUG=b:328699937,b:331688838
TEST=N/A

Change-Id: Ie06fb1678b27320648cfd300beefdcaddb35441e
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/5464981
Reviewed-by: Chloe Pelling <[email protected]>
Tested-by: Max Lee <[email protected]>
Commit-Queue: Max Lee <[email protected]>

BUILD.gn

@@ -121,6 +121,7 @@ static_library("libsommelier") {
     "sommelier-gtk-shell.cc",
     "sommelier-idle-inhibit-manager.cc",
     "sommelier-inpututils.cc",
+    "sommelier-logging.cc",
     "sommelier-output.cc",
     "sommelier-pointer-constraints.cc",
     "sommelier-relative-pointer-manager.cc",

meson.build

@@ -165,6 +165,12 @@ if get_option('quirks')
   cpp_args += '-DQUIRKS_SUPPORT'
 endif
 
+#===========#
+# Log level #
+#===========#
+
+cpp_args += '-DLOG_LEVEL=' + get_option('log_level').to_string()
+
 #===========#
 # Sommelier #
 #===========#
@@ -205,6 +211,7 @@ libsommelier = static_library(
     'sommelier-global.cc',
     'sommelier-idle-inhibit-manager.cc',
     'sommelier-inpututils.cc',
+    'sommelier-logging.cc',
     'sommelier-output.cc',
     'sommelier-pointer-constraints.cc',
     'sommelier-relative-pointer-manager.cc',

meson_options.txt

@@ -57,3 +57,9 @@ option('with_tests',
   value: true,
   description: 'build the sommelier_test target'
 )
+
+option('log_level',
+  type: 'integer',
+  value: 0,
+  description: 'log level to print, -1 prints everything, default is 0 (up to INFO)'
+)

sommelier-logging.cc

@@ -0,0 +1,33 @@
+// Copyright 2024 The ChromiumOS Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "sommelier-logging.h"  // NOLINT(build/include_directory)
+
+namespace logging {
+
+std::string file_name(std::string file_path) {
+  // Extract file name from file path.
+  auto found = file_path.find_last_of('/');
+  if (found != std::string::npos) {
+    return file_path.substr(found + 1);
+  }
+  return file_path;
+}
+
+std::string log_level_to_string(int level) {
+  if (level == LOG_LEVEL_VERBOSE) {
+    return "VERBOSE";
+  } else if (level == LOG_LEVEL_INFO) {
+    return "INFO";
+  } else if (level == LOG_LEVEL_WARNING) {
+    return "WARNING";
+  } else if (level == LOG_LEVEL_ERROR) {
+    return "ERROR";
+  } else if (level == LOG_LEVEL_FATAL) {
+    return "FATAL";
+  }
+  return std::to_string(level);
+}
+
+}  // namespace logging

sommelier-logging.h

@@ -0,0 +1,95 @@
+// Copyright 2024 The ChromiumOS Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// Very simple logger that is similar to Chromium's logger. Example usage:
+//   LOG(INFO) << "hello world";
+//   LOG(INFO) << window << " says hello world";
+
+#ifndef VM_TOOLS_SOMMELIER_SOMMELIER_LOGGING_H_
+#define VM_TOOLS_SOMMELIER_SOMMELIER_LOGGING_H_
+
+#include <cstdarg>
+#include <cstring>
+#include <iosfwd>
+#include <iostream>
+#include <ostream>
+#include <sstream>
+#include <string>
+
+#include "sommelier-window.h"  // NOLINT(build/include_directory)
+
+// Build Sommelier with -Dlog_level=X to define LOG_LEVEL
+#ifndef LOG_LEVEL
+// Default log level is INFO
+#define LOG_LEVEL 0
+#endif  // LOG_LEVEL
+
+// Predefined log levels
+constexpr int LOG_LEVEL_VERBOSE = -1;
+constexpr int LOG_LEVEL_INFO = 0;
+constexpr int LOG_LEVEL_WARNING = 1;
+constexpr int LOG_LEVEL_ERROR = 2;
+constexpr int LOG_LEVEL_FATAL = 3;
+
+#define LOG(level)                                                            \
+  ::logging::Log(LOG_LEVEL_##level, __func__, ::logging::file_name(__FILE__), \
+                 __LINE__)
+
+namespace logging {
+
+std::string file_name(std::string file_path);
+std::string log_level_to_string(int level);
+
+class Log {
+ private:
+  std::stringstream log_content;
+
+ public:
+  std::string function;
+  std::string file;
+  int line;
+  int log_level;
+
+  explicit Log(int log_level,
+               std::string function,
+               std::string file,
+               int line) {
+    this->log_level = log_level;
+    this->function = function;
+    this->file = file;
+    this->line = line;
+  }
+
+  template <typename T>
+  Log& operator<<(T const& value) {
+    if (log_level >= LOG_LEVEL) {
+      this->log_content << value;
+    }
+    return *this;
+  }
+
+  Log& operator<<(sl_window* window) {
+    *this << "(" << window->name << "#" << std::hex << window->id << ")"
+          << std::dec;
+    return *this;
+  }
+
+  ~Log() {
+    // Example expected usage:
+    //   LOG(INFO) << "hello world ";
+    // Temporary objects are destroyed after the end of the expression, which
+    // means this destructor is called at 'semicolon', resulting in printing to
+    // cerr.
+    if (this->log_content.peek() == EOF) {
+      return;
+    }
+    std::cerr << log_level_to_string(this->log_level) << " <" << this->file
+              << ":" << this->line << "> " << this->function << ": "
+              << this->log_content.rdbuf() << std::endl;
+  }
+};
+
+}  // namespace logging
+
+#endif  // VM_TOOLS_SOMMELIER_SOMMELIER_LOGGING_H_