WindowServer: Don't de-maximize windows immediately (SerenityOS#756)

At least 5 pixels of dragging in some direction needed until a window
gets de-maximized.

Libraries/LibDraw/Point.h

@@ -110,6 +110,16 @@ class Point {
  set_y(value);
  }
 
+ // Returns pixels moved from other in either direction
+ int pixels_moved(const Point &other) const
+ {
+ auto pixels_moved = max(
+ abs(other.x() - x()),
+ abs(other.y() - y())
+ );
+ return pixels_moved;
+ }
+
 private:
  int m_x { 0 };
  int m_y { 0 };

Servers/WindowServer/WSWindowManager.cpp

@@ -419,11 +419,6 @@ void WSWindowManager::start_window_drag(WSWindow& window, const WSMouseEvent& ev
  move_to_front_and_make_active(window);
  m_drag_window = window.make_weak_ptr();
  m_drag_origin = event.position();
- if (window.is_maximized()) {
- auto width_before_resize = window.width();
- window.set_maximized(false);
- window.move_to(m_drag_origin.x() - (window.width() * ((float)m_drag_origin.x() / width_before_resize)), m_drag_origin.y());
- }
  m_drag_window_origin = window.position();
  invalidate(window);
 }
@@ -489,14 +484,31 @@ bool WSWindowManager::process_ongoing_window_drag(WSMouseEvent& event, WSWindow*
  return true;
  }
  if (event.type() == WSEvent::MouseMove) {
+
 #ifdef DRAG_DEBUG
  dbg() << "[WM] Dragging, origin: " << m_drag_origin << ", now: " << event.position();
+ if (m_drag_window->is_maximized()) {
+ dbg() << " [!] The window is still maximized. Not dragging yet.";
+ }
 #endif
- Point pos = m_drag_window_origin.translated(event.position() - m_drag_origin);
- m_drag_window->set_position_without_repaint(pos);
- if (m_drag_window->rect().contains(event.position()))
- hovered_window = m_drag_window;
- return true;
+ if (m_drag_window->is_maximized()) {
+ auto pixels_moved_from_start = event.position().pixels_moved(m_drag_origin);
+ // dbg() << "[WM] " << pixels_moved_from_start << " moved since start of drag";
+ if (pixels_moved_from_start > 5) {
+ // dbg() << "[WM] de-maximizing window";
+ m_drag_origin = event.position();
+ auto width_before_resize = m_drag_window->width();
+ m_drag_window->set_maximized(false);
+ m_drag_window->move_to(m_drag_origin.x() - (m_drag_window->width() * ((float)m_drag_origin.x() / width_before_resize)), m_drag_origin.y());
+ m_drag_window_origin = m_drag_window->position();
+ }
+ } else {
+ Point pos = m_drag_window_origin.translated(event.position() - m_drag_origin);
+ m_drag_window->set_position_without_repaint(pos);
+ if (m_drag_window->rect().contains(event.position()))
+ hovered_window = m_drag_window;
+ return true;
+ }
  }
  return false;
 }