Show a GUI alert when crashing on desktop platforms

This makes it possible to know that Godot has crashed without looking
at the console (which may not be visible to the user).

- Change the window title while dumping the backtrace, as this can
  take a while to finish.
- If file logging is enabled, print path to log file to standard error
  and the GUI alert. Clicking OK will open the log file in the default
  program associated with `.log` files. Notepad has native associations
  for `.log` on Windows, so this works on Windows too.

Co-authored-by: bruvzg <7645683+bruvzg@users.noreply.github.com>

platform/linuxbsd/crash_handler_linuxbsd.cpp

@@ -35,6 +35,7 @@
 #include "core/string/print_string.h"
 #include "core/version.h"
 #include "main/main.h"
+#include "servers/display_server.h"
 
 #ifdef DEBUG_ENABLED
 #define CRASH_HANDLER_ENABLED 1
@@ -62,19 +63,26 @@ static void handle_crash(int sig) {
 	String _execpath = OS::get_singleton()->get_executable_path();
 
 	String msg;
+	String log_path;
 	const ProjectSettings *proj_settings = ProjectSettings::get_singleton();
 	if (proj_settings) {
-		msg = proj_settings->get("debug/settings/crash_handler/message");
+		msg = proj_settings->get_setting_with_override("debug/settings/crash_handler/message");
+		if (proj_settings->get_setting_with_override("debug/file_logging/enable_file_logging")) {
+			log_path = proj_settings->globalize_path(proj_settings->get_setting_with_override("debug/file_logging/log_path"));
+		}
 	}
 
 	// Tell MainLoop about the crash. This can be handled by users too in Node.
 	if (OS::get_singleton()->get_main_loop()) {
 		OS::get_singleton()->get_main_loop()->notification(MainLoop::NOTIFICATION_CRASH);
 	}
 
+	// Set window title while dumping the backtrace, as this can take 10+ seconds to finish.
+	DisplayServer::get_singleton()->window_set_title("ERROR: Program crashed, dumping backtrace to log...");
+
 	// Dump the backtrace to stderr with a message to the user
 	print_error("\n================================================================");
-	print_error(vformat("%s: Program crashed with signal %d", __FUNCTION__, sig));
+	print_error(vformat("%s: Program crashed with signal %d.", __FUNCTION__, sig));
 
 	// Print the engine version just before, so that people are reminded to include the version in backtrace reports.
 	if (String(VERSION_HASH).is_empty()) {
@@ -141,6 +149,24 @@ static void handle_crash(int sig) {
 	print_error("-- END OF BACKTRACE --");
 	print_error("================================================================");
 
+	// Notify the user that backtrace dumping is finished.
+	DisplayServer::get_singleton()->window_set_title("ERROR: Program crashed, dumped backtrace to log");
+
+	// Show alert so the user is aware of the crash, even if the engine wasn't started with visible stdout/stderr.
+	// This must be done after printing the backtrace to prevent the process from being blocked too early (`OS::alert()` is blocking).
+	if (!log_path.is_empty()) {
+		// `fprintf()` is used instead of `print_error()`, as this printed line must not be present
+		// in the log file (it references the log file itself).
+		fprintf(stderr, "\nFind the log file for this session at:\n%s\n\n", log_path.utf8().get_data());
+
+		if (DisplayServer::get_singleton()->get_name() != "headless") {
+			OS::get_singleton()->alert(vformat("%s: Program crashed with signal %d.\n\nFind the log file for this session at:\n%s\n\nClicking OK will open this log file. Please include the this log file's contents in bug reports.", __FUNCTION__, sig, log_path));
+			OS::get_singleton()->shell_open(log_path.utf8().get_data());
+		}
+	} else if (DisplayServer::get_singleton()->get_name() != "headless") {
+		OS::get_singleton()->alert(vformat("%s: Program crashed with signal %d.", __FUNCTION__, sig));
+	}
+
 	// Abort to pass the error to the OS
 	abort();
 }

platform/macos/crash_handler_macos.mm

@@ -35,6 +35,7 @@
 #include "core/string/print_string.h"
 #include "core/version.h"
 #include "main/main.h"
+#include "servers/display_server.h"
 
 #include <string.h>
 #include <unistd.h>
@@ -85,19 +86,26 @@ static void handle_crash(int sig) {
 	String _execpath = OS::get_singleton()->get_executable_path();
 
 	String msg;
+	String log_path;
 	const ProjectSettings *proj_settings = ProjectSettings::get_singleton();
 	if (proj_settings) {
-		msg = proj_settings->get("debug/settings/crash_handler/message");
+		msg = proj_settings->get_setting_with_override("debug/settings/crash_handler/message");
+		if (proj_settings->get_setting_with_override("debug/file_logging/enable_file_logging")) {
+			log_path = proj_settings->globalize_path(proj_settings->get_setting_with_override("debug/file_logging/log_path"));
+		}
 	}
 
 	// Tell MainLoop about the crash. This can be handled by users too in Node.
 	if (OS::get_singleton()->get_main_loop()) {
 		OS::get_singleton()->get_main_loop()->notification(MainLoop::NOTIFICATION_CRASH);
 	}
 
+	// Set window title while dumping the backtrace, as this can take 10+ seconds to finish.
+	DisplayServer::get_singleton()->window_set_title("ERROR: Program crashed, dumping backtrace to log...");
+
 	// Dump the backtrace to stderr with a message to the user
 	print_error("\n================================================================");
-	print_error(vformat("%s: Program crashed with signal %d", __FUNCTION__, sig));
+	print_error(vformat("%s: Program crashed with signal %d.", __FUNCTION__, sig));
 
 	// Print the engine version just before, so that people are reminded to include the version in backtrace reports.
 	if (String(VERSION_HASH).is_empty()) {
@@ -171,6 +179,32 @@ static void handle_crash(int sig) {
 	print_error("-- END OF BACKTRACE --");
 	print_error("================================================================");
 
+	// Notify the user that backtrace dumping is finished.
+	DisplayServer::get_singleton()->window_set_title("ERROR: Program crashed, dumped backtrace to log");
+
+	// Show alert so the user is aware of the crash, even if the engine wasn't started with visible stdout/stderr.
+	// This must be done after printing the backtrace to prevent the process from being blocked too early (`OS::alert()` is blocking).
+	if (!log_path.is_empty()) {
+		// `fprintf()` is used instead of `print_error()`, as this printed line must not be present
+		// in the log file (it references the log file itself).
+		fprintf(stderr, "\nFind the log file for this session at:\n%s\n\n", log_path.utf8().get_data());
+
+		if (DisplayServer::get_singleton()->get_name() != "headless") {
+			List<String> args;
+			args.push_back("-e");
+			args.push_back(vformat("display alert \"Crash\" message \"%s: Program crashed with signal %d.\\n\\nFind the log file for this session at:\\n%s\\n\\nClicking OK will open this log file. Please include the this log file's contents in bug reports.\"", __FUNCTION__, sig, log_path.c_escape()));
+			OS::get_singleton()->execute("osascript", args);
+			args.clear();
+			args.push_back(log_path);
+			OS::get_singleton()->execute("open", args);
+		}
+	} else if (DisplayServer::get_singleton()->get_name() != "headless") {
+		List<String> args;
+		args.push_back("-e");
+		args.push_back(vformat("display alert \"Crash\" message \"%s: Program crashed with signal %d.\"", __FUNCTION__, sig));
+		OS::get_singleton()->execute("osascript", args);
+	}
+
 	// Abort to pass the error to the OS
 	abort();
 }