LibGUI: Switch to a resizing cursor when hovering or using a GSplitter.

Also expose the various standard cursors on WSWindowManager so they can
be reused by the override mechanism.

AK/RetainPtr.h

@@ -14,6 +14,7 @@ public:
     RetainPtr(const T* ptr) : m_ptr(const_cast<T*>(ptr)) { retain_if_not_null(m_ptr); }
     RetainPtr(T* ptr) : m_ptr(ptr) { retain_if_not_null(m_ptr); }
     RetainPtr(T& object) : m_ptr(&object) { m_ptr->retain(); }
+    RetainPtr(const T& object) : m_ptr(const_cast<T*>(&object)) { m_ptr->retain(); }
     RetainPtr(AdoptTag, T& object) : m_ptr(&object) { }
     RetainPtr(RetainPtr& other) : m_ptr(other.copy_ref().leak_ref()) { }
     RetainPtr(RetainPtr&& other) : m_ptr(other.leak_ref()) { }

AK/Retained.h

@@ -35,6 +35,7 @@ class CONSUMABLE(unconsumed) Retained {
 public:
     enum AdoptTag { Adopt };
 
+    RETURN_TYPESTATE(unconsumed) Retained(const T& object) : m_ptr(&object) { m_ptr->retain(); }
     RETURN_TYPESTATE(unconsumed) Retained(T& object) : m_ptr(&object) { m_ptr->retain(); }
     template<typename U> RETURN_TYPESTATE(unconsumed) Retained(U& object) : m_ptr(&static_cast<T&>(object)) { m_ptr->retain(); }
     RETURN_TYPESTATE(unconsumed) Retained(AdoptTag, T& object) : m_ptr(&object) { }

LibGUI/GSplitter.cpp

@@ -1,5 +1,6 @@
 #include <LibGUI/GSplitter.h>
 #include <LibGUI/GBoxLayout.h>
+#include <LibGUI/GWindow.h>
 
 GSplitter::GSplitter(Orientation orientation, GWidget* parent)
     : GFrame(parent)
@@ -18,12 +19,15 @@ GSplitter::~GSplitter()
 void GSplitter::enter_event(GEvent&)
 {
     set_background_color(Color::from_rgb(0xd6d2ce));
+    window()->set_override_cursor(m_orientation == Orientation::Horizontal ? GStandardCursor::ResizeHorizontal : GStandardCursor::ResizeVertical);
     update();
 }
 
 void GSplitter::leave_event(GEvent&)
 {
     set_background_color(Color::LightGray);
+    if (!m_resizing)
+        window()->set_override_cursor(GStandardCursor::None);
     update();
 }
 
@@ -108,4 +112,7 @@ void GSplitter::mouseup_event(GMouseEvent& event)
     if (event.button() != GMouseButton::Left)
         return;
     m_resizing = false;
+    if (!rect().contains(event.position()))
+        window()->set_override_cursor(GStandardCursor::None);
+
 }

LibGUI/GWindow.h

@@ -12,6 +12,8 @@ enum class GStandardCursor {
     None = 0,
     Arrow,
     IBeam,
+    ResizeHorizontal,
+    ResizeVertical,
 };
 
 class GWindow : public GObject {

Servers/WindowServer/WSAPITypes.h

@@ -51,6 +51,8 @@ enum class WSAPI_StandardCursor : unsigned char {
     None = 0,
     Arrow,
     IBeam,
+    ResizeHorizontal,
+    ResizeVertical,
 };
 
 struct WSAPI_ServerMessage {

Servers/WindowServer/WSCursor.cpp

@@ -1,4 +1,5 @@
 #include <WindowServer/WSCursor.h>
+#include <WindowServer/WSWindowManager.h>
 
 WSCursor::WSCursor(Retained<GraphicsBitmap>&& bitmap, const Point& hotspot)
     : m_bitmap(move(bitmap))
@@ -26,9 +27,13 @@ RetainPtr<WSCursor> WSCursor::create(WSStandardCursor standard_cursor)
     case WSStandardCursor::None:
         return nullptr;
     case WSStandardCursor::Arrow:
-        return create(*GraphicsBitmap::load_from_file("/res/cursors/arrow.png"));
+        return WSWindowManager::the().arrow_cursor();
     case WSStandardCursor::IBeam:
-        return create(*GraphicsBitmap::load_from_file("/res/cursors/i-beam.png"));
+        return WSWindowManager::the().i_beam_cursor();
+    case WSStandardCursor::ResizeHorizontal:
+        return WSWindowManager::the().resize_horizontally_cursor();
+    case WSStandardCursor::ResizeVertical:
+        return WSWindowManager::the().resize_vertically_cursor();
     }
     ASSERT_NOT_REACHED();
 }

Servers/WindowServer/WSCursor.h

@@ -6,6 +6,8 @@ enum class WSStandardCursor {
     None = 0,
     Arrow,
     IBeam,
+    ResizeHorizontal,
+    ResizeVertical,
 };
 
 class WSCursor : public Retainable<WSCursor> {

Servers/WindowServer/WSWindowManager.h

@@ -87,6 +87,15 @@ public:
     const WSCursor& active_cursor() const;
     Rect current_cursor_rect() const;
 
+    const WSCursor& arrow_cursor() const { return *m_arrow_cursor; }
+    const WSCursor& resize_horizontally_cursor() const { return *m_resize_horizontally_cursor; }
+    const WSCursor& resize_vertically_cursor() const { return *m_resize_vertically_cursor; }
+    const WSCursor& resize_diagonally_tlbr_cursor() const { return *m_resize_diagonally_tlbr_cursor; }
+    const WSCursor& resize_diagonally_bltr_cursor() const { return *m_resize_diagonally_bltr_cursor; }
+    const WSCursor& i_beam_cursor() const { return *m_i_beam_cursor; }
+    const WSCursor& disallowed_cursor() const { return *m_disallowed_cursor; }
+    const WSCursor& move_cursor() const { return *m_move_cursor; }
+
 private:
     void process_mouse_event(const WSMouseEvent&, WSWindow*& event_window);
     bool process_ongoing_window_resize(const WSMouseEvent&, WSWindow*& event_window);