Magnifier: Add timeline for easy checking of animations

This patch adds a 512 frame timeline to Magnifier and the ability to
step through it with the arrow keys.

This makes it easier to check Serenity animations frame by frame for
correctness etc.

Userland/Applications/Magnifier/MagnifierWidget.cpp

@@ -27,6 +27,22 @@ void MagnifierWidget::set_scale_factor(int scale_factor)
     update();
 }
 
+void MagnifierWidget::display_previous_frame()
+{
+    --m_frame_offset_from_head;
+    auto index = m_grabbed_bitmaps.head_index() + m_frame_offset_from_head;
+    m_grabbed_bitmap = m_grabbed_bitmaps.at(index);
+    update();
+}
+
+void MagnifierWidget::display_next_frame()
+{
+    ++m_frame_offset_from_head;
+    auto index = m_grabbed_bitmaps.head_index() + m_frame_offset_from_head;
+    m_grabbed_bitmap = m_grabbed_bitmaps.at(index);
+    update();
+}
+
 void MagnifierWidget::sync()
 {
     if (m_pause_capture)
@@ -35,6 +51,7 @@ void MagnifierWidget::sync()
     auto size = frame_inner_rect().size();
     Gfx::IntSize grab_size { size.width() / m_scale_factor, size.height() / m_scale_factor };
     m_grabbed_bitmap = GUI::WindowServerConnection::the().get_screen_bitmap_around_cursor(grab_size).bitmap();
+    m_grabbed_bitmaps.enqueue(m_grabbed_bitmap);
     update();
 }
 

Userland/Applications/Magnifier/MagnifierWidget.h

@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include <AK/CircularQueue.h>
 #include <LibGUI/Frame.h>
 
 class MagnifierWidget final : public GUI::Frame {
@@ -14,7 +15,14 @@ class MagnifierWidget final : public GUI::Frame {
 public:
     virtual ~MagnifierWidget();
     void set_scale_factor(int scale_factor);
-    void pause_capture(bool pause) { m_pause_capture = pause; }
+    void pause_capture(bool pause)
+    {
+        m_pause_capture = pause;
+        if (!pause)
+            m_frame_offset_from_head = 0;
+    }
+    void display_previous_frame();
+    void display_next_frame();
 
 private:
     MagnifierWidget();
@@ -25,5 +33,7 @@ private:
 
     int m_scale_factor { 2 };
     RefPtr<Gfx::Bitmap> m_grabbed_bitmap;
+    CircularQueue<RefPtr<Gfx::Bitmap>, 512> m_grabbed_bitmaps {};
+    ssize_t m_frame_offset_from_head { 0 };
     bool m_pause_capture { false };
 };

Userland/Applications/Magnifier/main.cpp

@@ -75,6 +75,22 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     TRY(view_menu->try_add_separator());
     TRY(view_menu->try_add_action(pause_action));
 
+    auto timeline_menu = TRY(window->try_add_menu("&Timeline"));
+    auto previous_frame_action = GUI::Action::create(
+        "&Previous frame", { Key_Left }, [&](auto&) {
+            pause_action->set_checked(true);
+            magnifier->pause_capture(true);
+            magnifier->display_previous_frame();
+        });
+    auto next_frame_action = GUI::Action::create(
+        "&Next frame", { Key_Right }, [&](auto&) {
+            pause_action->set_checked(true);
+            magnifier->pause_capture(true);
+            magnifier->display_next_frame();
+        });
+    TRY(timeline_menu->try_add_action(previous_frame_action));
+    TRY(timeline_menu->try_add_action(next_frame_action));
+
     auto help_menu = TRY(window->try_add_menu("&Help"));
     help_menu->add_action(GUI::CommonActions::make_about_action("Magnifier", app_icon, window));