From 26eee2c02dcb2621f2756eaf3a5116aa5e06fefa Mon Sep 17 00:00:00 2001
From: creator1creeper1 <creator1creeper1@airmail.cc>
Date: Fri, 7 Jan 2022 14:50:07 +0100
Subject: [PATCH] SystemMonitor: Propagate errors using try_set_main_widget
 build_process_window now uses try_set_main_widget and might return an error.
 process_properties_action handles a possible error by simply not updating the
 process window if an error occured while building it.

---
 Userland/Applications/SystemMonitor/main.cpp | 33 +++++++++++---------
 1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/Userland/Applications/SystemMonitor/main.cpp b/Userland/Applications/SystemMonitor/main.cpp
index cf1b61b604..7f13b5413c 100644
--- a/Userland/Applications/SystemMonitor/main.cpp
+++ b/Userland/Applications/SystemMonitor/main.cpp
@@ -51,7 +51,7 @@
 #include <stdio.h>
 #include <unistd.h>
 
-static NonnullRefPtr<GUI::Window> build_process_window(pid_t);
+static ErrorOr<NonnullRefPtr<GUI::Window>> build_process_window(pid_t);
 static NonnullRefPtr<GUI::Widget> build_storage_widget();
 static NonnullRefPtr<GUI::Widget> build_hardware_tab();
 static NonnullRefPtr<GUI::Widget> build_performance_tab();
@@ -139,20 +139,20 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     window->set_title("System Monitor");
     window->resize(560, 430);
 
-    auto& main_widget = window->set_main_widget<GUI::Widget>();
-    main_widget.set_layout<GUI::VerticalBoxLayout>();
-    main_widget.set_fill_with_background_color(true);
+    auto main_widget = TRY(window->try_set_main_widget<GUI::Widget>());
+    main_widget->set_layout<GUI::VerticalBoxLayout>();
+    main_widget->set_fill_with_background_color(true);
 
     // Add a tasteful separating line between the menu and the main UI.
-    auto& top_line = main_widget.add<GUI::SeparatorWidget>(Gfx::Orientation::Horizontal);
+    auto& top_line = main_widget->add<GUI::SeparatorWidget>(Gfx::Orientation::Horizontal);
     top_line.set_fixed_height(2);
 
-    auto& tabwidget_container = main_widget.add<GUI::Widget>();
+    auto& tabwidget_container = main_widget->add<GUI::Widget>();
     tabwidget_container.set_layout<GUI::VerticalBoxLayout>();
     tabwidget_container.layout()->set_margins({ 0, 4, 4 });
     auto& tabwidget = tabwidget_container.add<GUI::TabWidget>();
 
-    statusbar = main_widget.add<GUI::Statusbar>(3);
+    statusbar = main_widget->add<GUI::Statusbar>(3);
 
     auto process_model = ProcessModel::create();
     process_model->on_state_update = [&](int process_count, int thread_count) {
@@ -280,7 +280,10 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
             RefPtr<GUI::Window> process_window;
             auto it = process_windows.find(pid);
             if (it == process_windows.end()) {
-                process_window = build_process_window(pid);
+                auto process_window_or_error = build_process_window(pid);
+                if (process_window_or_error.is_error())
+                    return;
+                process_window = process_window_or_error.release_value();
                 process_window->on_close_request = [pid, &process_windows] {
                     process_windows.remove(pid);
                     return GUI::Window::CloseRequestDecision::Close;
@@ -396,17 +399,17 @@ public:
     }
 };
 
-NonnullRefPtr<GUI::Window> build_process_window(pid_t pid)
+ErrorOr<NonnullRefPtr<GUI::Window>> build_process_window(pid_t pid)
 {
     auto window = GUI::Window::construct();
     window->resize(480, 360);
     window->set_title(String::formatted("PID {} - System Monitor", pid));
 
-    auto& main_widget = window->set_main_widget<GUI::Widget>();
-    main_widget.set_fill_with_background_color(true);
-    main_widget.set_layout<GUI::VerticalBoxLayout>();
+    auto main_widget = TRY(window->try_set_main_widget<GUI::Widget>());
+    main_widget->set_fill_with_background_color(true);
+    main_widget->set_layout<GUI::VerticalBoxLayout>();
 
-    auto& hero_container = main_widget.add<GUI::Widget>();
+    auto& hero_container = main_widget->add<GUI::Widget>();
     hero_container.set_shrink_to_fit(true);
     hero_container.set_layout<GUI::HorizontalBoxLayout>();
     hero_container.layout()->set_margins(4);
@@ -436,10 +439,10 @@ NonnullRefPtr<GUI::Window> build_process_window(pid_t pid)
         process_index.sibling_at_column(ProcessModel::Column::Name).data().to_string(),
         pid));
 
-    auto& separator = main_widget.add<GUI::HorizontalSeparator>();
+    auto& separator = main_widget->add<GUI::HorizontalSeparator>();
     separator.set_fixed_height(2);
 
-    auto& widget_stack = main_widget.add<GUI::StackWidget>();
+    auto& widget_stack = main_widget->add<GUI::StackWidget>();
     auto& unavailable_process_widget = widget_stack.add<UnavailableProcessWidget>(String::formatted("Unable to access PID {}", pid));
 
     auto& process_tab_widget = widget_stack.add<GUI::TabWidget>();