Magnifier: Add option to display grid over the image

Userland/Applications/Magnifier/MagnifierWidget.cpp

@@ -32,6 +32,14 @@ void MagnifierWidget::lock_location(bool lock)
         m_locked_location = {};
 }
 
+void MagnifierWidget::show_grid(bool new_value)
+{
+    if (m_show_grid == new_value)
+        return;
+    m_show_grid = new_value;
+    update();
+}
+
 void MagnifierWidget::set_color_filter(OwnPtr<Gfx::ColorBlindnessFilter> color_filter)
 {
     m_color_filter = move(color_filter);
@@ -75,10 +83,37 @@ void MagnifierWidget::paint_event(GUI::PaintEvent& event)
 {
     GUI::Frame::paint_event(event);
 
+    if (!m_grabbed_bitmap)
+        return;
+
     GUI::Painter painter(*this);
 
     if (m_grabbed_bitmap)
-        painter.draw_scaled_bitmap(frame_inner_rect(), *m_grabbed_bitmap, m_grabbed_bitmap->rect());
+        painter.draw_scaled_bitmap(frame_inner_rect(), *m_grabbed_bitmap, m_grabbed_bitmap->rect(), 1.0, Gfx::Painter::ScalingMode::NearestFractional);
+
+    if (m_show_grid) {
+        auto line_color = Color(Color::NamedColor::Magenta);
+        line_color.set_alpha(100);
+
+        auto grid_rect = frame_inner_rect();
+        if (m_grabbed_bitmap)
+            grid_rect = frame_inner_rect().intersected({ 0,
+                0,
+                m_grabbed_bitmap->rect().width() * m_scale_factor,
+                m_grabbed_bitmap->rect().height() * m_scale_factor });
+
+        int start_y = grid_rect.top(),
+            start_x = grid_rect.left();
+
+        int end_y = grid_rect.bottom(),
+            end_x = grid_rect.right();
+
+        for (int current_y = start_y; current_y <= end_y; current_y += m_scale_factor)
+            painter.draw_line({ start_x, current_y }, { end_x, current_y }, line_color);
+
+        for (int current_x = start_y; current_x <= end_x; current_x += m_scale_factor)
+            painter.draw_line({ current_x, start_y }, { current_x, end_y }, line_color);
+    }
 }
 
 void MagnifierWidget::second_paint_event(GUI::PaintEvent&)

Userland/Applications/Magnifier/MagnifierWidget.h

@@ -21,6 +21,8 @@ public:
     virtual ~MagnifierWidget() override = default;
     void set_scale_factor(int scale_factor);
     virtual void set_color_filter(OwnPtr<Gfx::ColorBlindnessFilter>) override;
+    void show_grid(bool);
+
     void pause_capture(bool pause)
     {
         m_pause_capture = pause;
@@ -47,4 +49,5 @@ private:
     ssize_t m_frame_offset_from_head { 0 };
     bool m_pause_capture { false };
     Optional<Gfx::IntPoint> m_locked_location {};
+    bool m_show_grid { false };
 };

Userland/Applications/Magnifier/main.cpp

@@ -116,6 +116,11 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
             magnifier->lock_location(action.is_checked());
         });
 
+    auto show_grid_action = GUI::Action::create_checkable(
+        "Show &Grid", { Key_G }, [&](auto& action) {
+            magnifier->show_grid(action.is_checked());
+        });
+
     size_action_group->add_action(two_x_action);
     size_action_group->add_action(four_x_action);
     size_action_group->add_action(eight_x_action);
@@ -130,6 +135,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     TRY(view_menu->try_add_separator());
     TRY(view_menu->try_add_action(pause_action));
     TRY(view_menu->try_add_action(lock_location_action));
+    TRY(view_menu->try_add_action(show_grid_action));
 
     auto timeline_menu = TRY(window->try_add_menu("&Timeline"));
     auto previous_frame_action = GUI::Action::create(