ClockSettings: Display a map to show the current time zone's location

Author: https://github.com/trflynn89
Commit: https://github.com/SerenityOS/serenity/commit/4d2ea773dbc
Pull-request: https://github.com/SerenityOS/serenity/pull/12263
Reviewed-by: https://github.com/davidot ✅

Userland/Applications/ClockSettings/ClockSettingsWidget.cpp

@@ -7,14 +7,30 @@
 #include "ClockSettingsWidget.h"
 #include <Applications/ClockSettings/ClockSettingsWidgetGML.h>
 #include <LibGUI/ComboBox.h>
+#include <LibGUI/Event.h>
+#include <LibGUI/ImageWidget.h>
 #include <LibGUI/ItemListModel.h>
 #include <LibGUI/Label.h>
+#include <LibGUI/Layout.h>
+#include <LibGUI/Margins.h>
+#include <LibGUI/Painter.h>
+#include <LibGfx/Palette.h>
 #include <LibTimeZone/TimeZone.h>
+#include <math.h>
 #include <spawn.h>
 #include <unistd.h>
 
 using StringViewListModel = GUI::ItemListModel<StringView, Span<StringView const>>;
 
+static constexpr auto PI_OVER_180 = M_PIf32 / 180.0f;
+static constexpr auto PI_OVER_4 = M_PIf32 / 4.0f;
+static constexpr auto TAU = M_PIf32 * 2.0f;
+
+// The map as stored on disk is a valid Mercadian projected map. But it has quite a bit of dead space that
+// we can remove. This makes the map non-Mercadian, so we need to adjust our math based on what we removed.
+static constexpr auto TIME_ZONE_MAP_NORTHERN_TRIM = 78;
+static constexpr auto TIME_ZONE_MAP_SOUTHERN_TRIM = 50;
+
 ClockSettingsWidget::ClockSettingsWidget()
 {
     load_from_gml(clock_settings_widget_gml);
@@ -26,19 +42,84 @@ ClockSettingsWidget::ClockSettingsWidget()
     m_time_zone_combo_box->set_only_allow_values_from_model(true);
     m_time_zone_combo_box->set_model(*StringViewListModel::create(time_zones));
     m_time_zone_combo_box->set_text(m_time_zone);
+
+    auto time_zone_map_bitmap = Gfx::Bitmap::try_load_from_file("/res/graphics/map.png"sv).release_value_but_fixme_should_propagate_errors();
+    auto time_zone_rect = time_zone_map_bitmap->rect().shrunken(TIME_ZONE_MAP_NORTHERN_TRIM, 0, TIME_ZONE_MAP_SOUTHERN_TRIM, 0);
+    time_zone_map_bitmap = time_zone_map_bitmap->cropped(time_zone_rect).release_value_but_fixme_should_propagate_errors();
+
+    m_time_zone_map = *find_descendant_of_type_named<GUI::ImageWidget>("time_zone_map");
+    m_time_zone_map->set_bitmap(time_zone_map_bitmap);
+
+    auto time_zone_marker = Gfx::Bitmap::try_load_from_file("/res/icons/32x32/ladyball.png").release_value_but_fixme_should_propagate_errors();
+    m_time_zone_marker = time_zone_marker->scaled(0.75f, 0.75f).release_value_but_fixme_should_propagate_errors();
+
+    set_time_zone_location();
+}
+
+void ClockSettingsWidget::second_paint_event(GUI::PaintEvent& event)
+{
+    GUI::Widget::second_paint_event(event);
+
+    if (!m_time_zone_location.has_value())
+        return;
+
+    GUI::Painter painter(*this);
+    painter.add_clip_rect(event.rect());
+    painter.add_clip_rect(m_time_zone_map->relative_rect());
+
+    auto x = m_time_zone_map->x() + m_time_zone_map->parent_widget()->layout()->margins().left();
+    auto y = m_time_zone_map->y() + m_time_zone_map->parent_widget()->layout()->margins().top();
+
+    auto point = m_time_zone_location->to_type<int>().translated(x, y);
+    point.translate_by(-m_time_zone_marker->width() / 2, -m_time_zone_marker->height() / 2);
+    painter.blit(point, *m_time_zone_marker, rect());
 }
 
 void ClockSettingsWidget::reset_default_values()
 {
     m_time_zone = "UTC"sv;
     m_time_zone_combo_box->set_text(m_time_zone);
+    m_time_zone_location.clear();
+
     set_time_zone();
+    update();
 }
 
 void ClockSettingsWidget::apply_settings()
 {
     m_time_zone = m_time_zone_combo_box->text();
+
+    set_time_zone_location();
     set_time_zone();
+    update();
+}
+
+void ClockSettingsWidget::set_time_zone_location()
+{
+    m_time_zone_location = compute_time_zone_location();
+}
+
+// https://en.wikipedia.org/wiki/Mercator_projection#Derivation
+Optional<Gfx::FloatPoint> ClockSettingsWidget::compute_time_zone_location() const
+{
+    auto location = TimeZone::get_time_zone_location(m_time_zone);
+    if (!location.has_value())
+        return {};
+
+    auto latitude = location->latitude.decimal_coordinate();
+    auto longitude = location->longitude.decimal_coordinate();
+
+    auto rect = m_time_zone_map->bitmap()->rect().to_type<float>();
+
+    latitude = logf(tanf(PI_OVER_4 + (latitude * PI_OVER_180 / 2.0f)));
+
+    auto mercadian_x = (longitude + 180.0f) * (rect.width() / 360.0f);
+    auto mercadian_y = (rect.height() / 2.0f) - (rect.width() * latitude / TAU);
+
+    mercadian_y -= TIME_ZONE_MAP_NORTHERN_TRIM / 2;
+    mercadian_y += TIME_ZONE_MAP_SOUTHERN_TRIM / 2;
+
+    return Gfx::FloatPoint { mercadian_x, mercadian_y };
 }
 
 void ClockSettingsWidget::set_time_zone() const

Userland/Applications/ClockSettings/ClockSettingsWidget.gml

@@ -8,7 +8,6 @@
 
     @GUI::GroupBox {
         title: "Time Zone Settings"
-        fixed_height: 120
 
         layout: @GUI::VerticalBoxLayout {
             margins: [16, 8, 8]
@@ -36,5 +35,10 @@
                 name: "time_zone_input"
             }
         }
+
+        @GUI::ImageWidget {
+            name: "time_zone_map"
+            auto_resize: true
+        }
     }
 }

Userland/Applications/ClockSettings/ClockSettingsWidget.h

@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include <AK/Optional.h>
 #include <AK/RefPtr.h>
 #include <AK/String.h>
 #include <LibGUI/SettingsWindow.h>
@@ -18,10 +19,19 @@ class ClockSettingsWidget final : public GUI::SettingsWindow::Tab {
 private:
     ClockSettingsWidget();
 
+    virtual void second_paint_event(GUI::PaintEvent&) override;
+
     virtual void apply_settings() override;
     virtual void reset_default_values() override;
+
+    void set_time_zone_location();
+    Optional<Gfx::FloatPoint> compute_time_zone_location() const;
     void set_time_zone() const;
 
     String m_time_zone;
     RefPtr<GUI::ComboBox> m_time_zone_combo_box;
+    RefPtr<GUI::ImageWidget> m_time_zone_map;
+    RefPtr<Gfx::Bitmap> m_time_zone_marker;
+
+    Optional<Gfx::FloatPoint> m_time_zone_location;
 };

Userland/Applications/ClockSettings/main.cpp

@@ -28,6 +28,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     auto window = TRY(GUI::SettingsWindow::create("Clock Settings", GUI::SettingsWindow::ShowDefaultsButton::Yes));
     (void)TRY(window->add_tab<ClockSettingsWidget>("Clock"));
     window->set_icon(app_icon.bitmap_for_size(16));
+    window->resize(540, 570);
 
     window->show();
     return app->exec();