LibGUI: Add a GStackWidget for many widgets sharing a single location.

Call set_active_widget(GWidget*) to put a new widget on top.

LibGUI/GBoxLayout.cpp

@@ -1,7 +1,7 @@
 #include <LibGUI/GBoxLayout.h>
 #include <LibGUI/GWidget.h>
 
-//#define GBOXLAYOUT_DEBUG
+#define GBOXLAYOUT_DEBUG
 
 #ifdef GBOXLAYOUT_DEBUG
 #include <stdio.h>
@@ -41,14 +41,19 @@ void GBoxLayout::run(GWidget& widget)
     Size available_size = widget.size();
     int number_of_entries_with_fixed_size = 0;
 
+    int number_of_visible_entries = 0;
+
     for (auto& entry : m_entries) {
+        if (!entry.widget->is_visible())
+            continue;
+        ++number_of_visible_entries;
         if (entry.widget && entry.widget->size_policy(orientation()) == SizePolicy::Fixed) {
             available_size -= entry.widget->preferred_size();
             ++number_of_entries_with_fixed_size;
         }
     }
 
-    int number_of_entries_with_automatic_size = m_entries.size() - number_of_entries_with_fixed_size;
+    int number_of_entries_with_automatic_size = number_of_visible_entries - number_of_entries_with_fixed_size;
 
 #ifdef GBOXLAYOUT_DEBUG
     printf("GBoxLayout: available_size=%s, fixed=%d, fill=%d\n", available_size.to_string().characters(), number_of_entries_with_fixed_size, number_of_entries_with_automatic_size);
@@ -74,6 +79,8 @@ void GBoxLayout::run(GWidget& widget)
     int current_y = margins().top();
 
     for (auto& entry : m_entries) {
+        if (!entry.widget->is_visible())
+            continue;
         Rect rect(current_x, current_y, 0, 0);
         if (entry.layout) {
             // FIXME: Implement recursive layout.

LibGUI/GEvent.cpp

@@ -0,0 +1,12 @@
+#include <LibGUI/GEvent.h>
+#include <LibGUI/GObject.h>
+
+GChildEvent::GChildEvent(Type type, GObject& child)
+    : GEvent(type)
+    , m_child(child.make_weak_ptr())
+{
+}
+
+GChildEvent::~GChildEvent()
+{
+}

LibGUI/GEvent.h

@@ -4,8 +4,11 @@
 #include <SharedGraphics/Rect.h>
 #include <AK/AKString.h>
 #include <AK/Types.h>
+#include <AK/WeakPtr.h>
 #include <Kernel/KeyCode.h>
 
+class GObject;
+
 class GEvent {
 public:
     enum Type {
@@ -31,6 +34,8 @@ public:
         FocusIn,
         FocusOut,
         WindowCloseRequest,
+        ChildAdded,
+        ChildRemoved,
     };
 
     GEvent() { }
@@ -170,3 +175,15 @@ public:
 private:
     int m_timer_id;
 };
+
+class GChildEvent final : public GEvent {
+public:
+    GChildEvent(Type, GObject& child);
+    ~GChildEvent();
+
+    GObject* child() { return m_child.ptr(); }
+    const GObject* child() const { return m_child.ptr(); }
+
+private:
+    WeakPtr<GObject> m_child;
+};

LibGUI/GObject.cpp

@@ -28,6 +28,9 @@ void GObject::event(GEvent& event)
     case GEvent::DeferredDestroy:
         delete this;
         break;
+    case GEvent::ChildAdded:
+    case GEvent::ChildRemoved:
+        return child_event(static_cast<GChildEvent&>(event));
     case GEvent::Invalid:
         ASSERT_NOT_REACHED();
         break;
@@ -39,6 +42,7 @@ void GObject::event(GEvent& event)
 void GObject::add_child(GObject& object)
 {
     m_children.append(&object);
+    GEventLoop::main().post_event(*this, make<GChildEvent>(GEvent::ChildAdded, object));
 }
 
 void GObject::remove_child(GObject& object)
@@ -46,6 +50,7 @@ void GObject::remove_child(GObject& object)
     for (ssize_t i = 0; i < m_children.size(); ++i) {
         if (m_children[i] == &object) {
             m_children.remove(i);
+            GEventLoop::main().post_event(*this, make<GChildEvent>(GEvent::ChildRemoved, object));
             return;
         }
     }
@@ -55,6 +60,10 @@ void GObject::timer_event(GTimerEvent&)
 {
 }
 
+void GObject::child_event(GChildEvent&)
+{
+}
+
 void GObject::start_timer(int ms)
 {
     if (m_timer_id) {

LibGUI/GObject.h

@@ -4,6 +4,7 @@
 #include <AK/Weakable.h>
 
 class GEvent;
+class GChildEvent;
 class GTimerEvent;
 
 class GObject : public Weakable<GObject> {
@@ -29,12 +30,14 @@ public:
 
     void delete_later();
 
-private:
+    virtual bool is_widget() const { return false; }
+
+protected:
     virtual void timer_event(GTimerEvent&);
+    virtual void child_event(GChildEvent&);
 
+private:
     GObject* m_parent { nullptr };
-
     int m_timer_id { 0 };
-
     Vector<GObject*> m_children;
 };

LibGUI/GStackWidget.cpp

@@ -0,0 +1,62 @@
+#include <LibGUI/GStackWidget.h>
+#include <LibGUI/GBoxLayout.h>
+
+GStackWidget::GStackWidget(GWidget* parent)
+    : GWidget(parent)
+{
+    set_fill_with_background_color(true);
+    set_background_color(Color::Red);
+}
+
+GStackWidget::~GStackWidget()
+{
+}
+
+void GStackWidget::set_active_widget(GWidget* widget)
+{
+    dbgprintf("XXX: GStackWidget: set_active_widget %p\n", widget);
+    if (widget == m_active_widget)
+        return;
+
+    if (m_active_widget)
+        m_active_widget->set_visible(false);
+    m_active_widget = widget;
+    if (m_active_widget) {
+        m_active_widget->set_relative_rect(rect());
+        m_active_widget->set_visible(true);
+    }
+}
+
+void GStackWidget::resize_event(GResizeEvent& event)
+{
+    if (!m_active_widget)
+        return;
+    m_active_widget->set_relative_rect({ { }, event.size() });
+}
+
+void GStackWidget::child_event(GChildEvent& event)
+{
+    if (!event.child() || !event.child()->is_widget())
+        return;
+    auto& child = static_cast<GWidget&>(*event.child());
+    if (event.type() == GEvent::ChildAdded) {
+        dbgprintf("XXX: GStackWidget: did_add_child %p\n", &child);
+        if (!m_active_widget) {
+            set_active_widget(&child);
+        } else {
+            child.set_visible(false);
+        }
+    } else if (event.type() == GEvent::ChildRemoved) {
+        dbgprintf("XXX: GStackWidget: did_remove_child %p\n", &child);
+        if (m_active_widget == &child) {
+            GWidget* new_active_widget = nullptr;
+            for (auto* new_child : children()) {
+                if (new_child->is_widget()) {
+                    new_active_widget = static_cast<GWidget*>(new_child);
+                    break;
+                }
+            }
+            set_active_widget(new_active_widget);
+        }
+    }
+}

LibGUI/GStackWidget.h

@@ -0,0 +1,21 @@
+#pragma once
+
+#include <LibGUI/GWidget.h>
+
+class GStackWidget : public GWidget {
+public:
+    explicit GStackWidget(GWidget* parent);
+    virtual ~GStackWidget() override;
+
+    GWidget* active_widget() const { return m_active_widget; }
+    void set_active_widget(GWidget*);
+
+protected:
+    virtual void child_event(GChildEvent&) override;
+    virtual void resize_event(GResizeEvent&) override;
+
+private:
+    virtual const char* class_name() const override { return "GStackWidget"; }
+
+    GWidget* m_active_widget { nullptr };
+};

LibGUI/GWidget.cpp

@@ -91,6 +91,8 @@ void GWidget::handle_paint_event(GPaintEvent& event)
     paint_event(event);
     for (auto* ch : children()) {
         auto* child = (GWidget*)ch;
+        if (!child->is_visible())
+            continue;
         if (child->relative_rect().intersects(event.rect())) {
             auto local_rect = event.rect();
             local_rect.intersect(child->relative_rect());
@@ -303,3 +305,14 @@ void GWidget::invalidate_layout()
         return;
     w->main_widget()->do_layout();
 }
+
+void GWidget::set_visible(bool visible)
+{
+    if (visible == m_visible)
+        return;
+    m_visible = visible;
+    if (auto* parent = parent_widget())
+        parent->invalidate_layout();
+    if (m_visible)
+        update();
+}

LibGUI/GWidget.h

@@ -122,7 +122,12 @@ public:
 
     void notify_layout_changed(Badge<GLayout>);
 
+    bool is_visible() const { return m_visible; }
+    void set_visible(bool);
+
 private:
+    virtual bool is_widget() const final { return true; }
+
     void handle_paint_event(GPaintEvent&);
     void handle_resize_event(GResizeEvent&);
     void do_layout();
@@ -141,4 +146,5 @@ private:
     Size m_preferred_size;
 
     bool m_fill_with_background_color { false };
+    bool m_visible { true };
 };

LibGUI/Makefile

@@ -35,6 +35,8 @@ LIBGUI_OBJS = \
     GTextEditor.o \
     GClipboard.o \
     GSortingProxyTableModel.o \
+    GStackWidget.o \
+    GEvent.o \
     GWindow.o
 
 OBJS = $(SHAREDGRAPHICS_OBJS) $(LIBGUI_OBJS)