LibGUI+WindowServer: Add a GResizeCorner widget.

This widget is automatically included in GStatusBar, but can be added in
any other place, too. When clicked (with the left button), it initiates a
window resize (using a WM request.)

In this patch I also fixed up some issues with override cursors being
cleared after the WindowServer finishes a drag or resize.

9 files changed, 97 insertions, 5 deletions

diff --git a/LibGUI/GEventLoop.cpp b/LibGUI/GEventLoop.cpp
index 5731d30387..ae41ad7da1 100644
--- a/LibGUI/GEventLoop.cpp
+++ b/LibGUI/GEventLoop.cpp
@@ -24,6 +24,7 @@
 //#define COALESCING_DEBUG
 
 int GEventLoop::s_event_fd = -1;
+int GEventLoop::s_my_client_id = -1;
 pid_t GEventLoop::s_server_pid = -1;
 
 void GEventLoop::connect_to_server()
@@ -59,8 +60,7 @@ void GEventLoop::connect_to_server()
     request.type = WSAPI_ClientMessage::Type::Greeting;
     request.greeting.client_pid = getpid();
     auto response = sync_request(request, WSAPI_ServerMessage::Type::Greeting);
-    s_server_pid = response.greeting.server_pid;
-    GDesktop::the().did_receive_screen_rect(Badge<GEventLoop>(), response.greeting.screen_rect);
+    handle_greeting(response);
 }
 
 GEventLoop::GEventLoop()
@@ -235,8 +235,7 @@ void GEventLoop::process_unprocessed_bundles()
     for (auto& bundle : unprocessed_bundles) {
         auto& event = bundle.message;
         if (event.type == WSAPI_ServerMessage::Type::Greeting) {
-            s_server_pid = event.greeting.server_pid;
-            GDesktop::the().did_receive_screen_rect(Badge<GEventLoop>(), event.greeting.screen_rect);
+            handle_greeting(event);
             continue;
         }
 
@@ -402,3 +401,10 @@ WSAPI_ServerMessage GEventLoop::sync_request(const WSAPI_ClientMessage& request,
     ASSERT(success);
     return response;
 }
+
+void GEventLoop::handle_greeting(WSAPI_ServerMessage& message)
+{
+    s_server_pid = message.greeting.server_pid;
+    s_my_client_id = message.greeting.your_client_id;
+    GDesktop::the().did_receive_screen_rect(Badge<GEventLoop>(), message.greeting.screen_rect);
+}
diff --git a/LibGUI/GEventLoop.h b/LibGUI/GEventLoop.h
index a88194a4ed..4e235aa21d 100644
--- a/LibGUI/GEventLoop.h
+++ b/LibGUI/GEventLoop.h
@@ -21,6 +21,7 @@ public:
     WSAPI_ServerMessage sync_request(const WSAPI_ClientMessage& request, WSAPI_ServerMessage::Type response_type);
 
     static pid_t server_pid() { return s_server_pid; }
+    static int my_client_id() { return s_my_client_id; }
 
     virtual void take_pending_events_from(CEventLoop& other) override
     {
@@ -59,6 +60,7 @@ private:
     void handle_menu_event(const WSAPI_ServerMessage&);
     void handle_window_entered_or_left_event(const WSAPI_ServerMessage&, GWindow&);
     void handle_wm_event(const WSAPI_ServerMessage&, GWindow&);
+    void handle_greeting(WSAPI_ServerMessage&);
     void connect_to_server();
 
     struct IncomingWSMessageBundle {
@@ -68,5 +70,6 @@ private:
 
     Vector<IncomingWSMessageBundle, 64> m_unprocessed_bundles;
     static pid_t s_server_pid;
-    static pid_t s_event_fd;
+    static int s_my_client_id;
+    static int s_event_fd;
 };
diff --git a/LibGUI/GResizeCorner.cpp b/LibGUI/GResizeCorner.cpp
new file mode 100644
index 0000000000..91407a509f
--- /dev/null
+++ b/LibGUI/GResizeCorner.cpp
@@ -0,0 +1,46 @@
+#include <LibGUI/GResizeCorner.h>
+#include <LibGUI/GPainter.h>
+#include <LibGUI/GWindow.h>
+#include <SharedGraphics/GraphicsBitmap.h>
+#include <WindowServer/WSAPITypes.h>
+
+GResizeCorner::GResizeCorner(GWidget* parent)
+    : GWidget(parent)
+{
+    set_size_policy(SizePolicy::Fixed, SizePolicy::Fixed);
+    set_preferred_size({ 16, 16 });
+    m_bitmap = GraphicsBitmap::load_from_file("/res/icons/resize-corner.png");
+    ASSERT(m_bitmap);
+}
+
+GResizeCorner::~GResizeCorner()
+{
+}
+
+void GResizeCorner::paint_event(GPaintEvent& event)
+{
+    GPainter painter(*this);
+    painter.add_clip_rect(event.rect());
+    painter.fill_rect(rect(), background_color());
+    painter.blit({ 0, 0 }, *m_bitmap, m_bitmap->rect());
+    GWidget::paint_event(event);
+}
+
+void GResizeCorner::mousedown_event(GMouseEvent& event)
+{
+    if (event.button() == GMouseButton::Left)
+        window()->start_wm_resize();
+    GWidget::mousedown_event(event);
+}
+
+void GResizeCorner::enter_event(CEvent& event)
+{
+    window()->set_override_cursor(GStandardCursor::ResizeDiagonalTLBR);
+    GWidget::enter_event(event);
+}
+
+void GResizeCorner::leave_event(CEvent& event)
+{
+    window()->set_override_cursor(GStandardCursor::None);
+    GWidget::leave_event(event);
+}
diff --git a/LibGUI/GResizeCorner.h b/LibGUI/GResizeCorner.h
new file mode 100644
index 0000000000..2d6ae0c670
--- /dev/null
+++ b/LibGUI/GResizeCorner.h
@@ -0,0 +1,18 @@
+#include <LibGUI/GWidget.h>
+
+class GResizeCorner : public GWidget {
+public:
+    explicit GResizeCorner(GWidget* parent);
+    virtual ~GResizeCorner() override;
+
+    virtual const char* class_name() const override { return "GResizeCorner"; }
+
+protected:
+    virtual void paint_event(GPaintEvent&) override;
+    virtual void mousedown_event(GMouseEvent&) override;
+    virtual void enter_event(CEvent&) override;
+    virtual void leave_event(CEvent&) override;
+
+private:
+    RetainPtr<GraphicsBitmap> m_bitmap;
+};
diff --git a/LibGUI/GStatusBar.cpp b/LibGUI/GStatusBar.cpp
index 65d0b2ade5..74c6816f22 100644
--- a/LibGUI/GStatusBar.cpp
+++ b/LibGUI/GStatusBar.cpp
@@ -3,6 +3,7 @@
 #include <LibGUI/GBoxLayout.h>
 #include <SharedGraphics/StylePainter.h>
 #include <LibGUI/GPainter.h>
+#include <LibGUI/GResizeCorner.h>
 
 GStatusBar::GStatusBar(GWidget* parent)
     : GWidget(parent)
@@ -17,6 +18,8 @@ GStatusBar::GStatusBar(GWidget* parent)
     m_label->set_frame_shape(FrameShape::Panel);
     m_label->set_frame_thickness(1);
     m_label->set_text_alignment(TextAlignment::CenterLeft);
+
+    m_corner = new GResizeCorner(this);
 }
 
 GStatusBar::~GStatusBar()
diff --git a/LibGUI/GStatusBar.h b/LibGUI/GStatusBar.h
index d01648ff52..9bac204c30 100644
--- a/LibGUI/GStatusBar.h
+++ b/LibGUI/GStatusBar.h
@@ -3,6 +3,7 @@
 #include <LibGUI/GWidget.h>
 
 class GLabel;
+class GResizeCorner;
 
 class GStatusBar : public GWidget {
 public:
@@ -18,4 +19,5 @@ private:
     virtual void paint_event(GPaintEvent&) override;
 
     GLabel* m_label { nullptr };
+    GResizeCorner* m_corner { nullptr };
 };
diff --git a/LibGUI/GWindow.cpp b/LibGUI/GWindow.cpp
index 36dbd2fe11..c1384ebe97 100644
--- a/LibGUI/GWindow.cpp
+++ b/LibGUI/GWindow.cpp
@@ -490,3 +490,12 @@ void GWindow::set_icon_path(const String& path)
     message.text_length = path.length();
     GEventLoop::post_message_to_server(message);
 }
+
+void GWindow::start_wm_resize()
+{
+    WSAPI_ClientMessage message;
+    message.type = WSAPI_ClientMessage::Type::WM_StartWindowResize;
+    message.wm.client_id = GEventLoop::my_client_id();
+    message.wm.window_id = m_window_id;
+    GEventLoop::post_message_to_server(message);
+}
diff --git a/LibGUI/GWindow.h b/LibGUI/GWindow.h
index cddebcef02..4adf2f7f9d 100644
--- a/LibGUI/GWindow.h
+++ b/LibGUI/GWindow.h
@@ -16,6 +16,8 @@ enum class GStandardCursor {
     IBeam,
     ResizeHorizontal,
     ResizeVertical,
+    ResizeDiagonalTLBR,
+    ResizeDiagonalBLTR,
 };
 
 class GWindow : public CObject {
@@ -71,6 +73,8 @@ public:
     void hide();
     void close();
 
+    void start_wm_resize();
+
     GWidget* main_widget() { return m_main_widget; }
     const GWidget* main_widget() const { return m_main_widget; }
     void set_main_widget(GWidget*);
diff --git a/LibGUI/Makefile b/LibGUI/Makefile
index 0255d05520..14b0427c43 100644
--- a/LibGUI/Makefile
+++ b/LibGUI/Makefile
@@ -53,6 +53,7 @@ LIBGUI_OBJS = \
     GSpinBox.o \
     GGroupBox.o \
     GSlider.o \
+    GResizeCorner.o \
     GWindow.o
 
 OBJS = $(SHAREDGRAPHICS_OBJS) $(LIBGUI_OBJS)