LibGUI: Add Widget shrink-to-fit layout flag

If this flag is enabled for a widget, it will be automatically sized
based on its children. This only works for widgets using a layout.

This allows you to put widgets inside each other without having to
manually calculate how large the container should be. It's not the
perfect API but it's a decent progression in ergonomics. :^)

Libraries/LibGUI/BoxLayout.cpp

@@ -44,6 +44,70 @@ BoxLayout::BoxLayout(Orientation orientation)
         "orientation", [this] { return m_orientation == Gfx::Orientation::Vertical ? "Vertical" : "Horizontal"; }, nullptr);
 }
 
+Gfx::IntSize BoxLayout::preferred_size() const
+{
+    Gfx::IntSize size;
+    size.set_primary_size_for_orientation(orientation(), preferred_primary_size());
+    size.set_secondary_size_for_orientation(orientation(), preferred_secondary_size());
+    return size;
+}
+
+int BoxLayout::preferred_primary_size() const
+{
+    int size = 0;
+
+    for (auto& entry : m_entries) {
+        if (!entry.widget)
+            continue;
+        int min_size = entry.widget->min_size().primary_size_for_orientation(orientation());
+        int max_size = entry.widget->max_size().primary_size_for_orientation(orientation());
+        int preferred_primary_size = -1;
+        if (entry.widget->is_shrink_to_fit() && entry.widget->layout()) {
+            preferred_primary_size = entry.widget->layout()->preferred_size().primary_size_for_orientation(orientation());
+        }
+        int item_size = max(0, preferred_primary_size);
+        item_size = max(min_size, item_size);
+        item_size = min(max_size, item_size);
+        size += item_size + spacing();
+    }
+    if (size > 0)
+        size -= spacing();
+
+    if (orientation() == Gfx::Orientation::Horizontal)
+        size += margins().left() + margins().right();
+    else
+        size += margins().top() + margins().bottom();
+
+    if (!size)
+        return -1;
+    return size;
+}
+
+int BoxLayout::preferred_secondary_size() const
+{
+    int size = 0;
+    for (auto& entry : m_entries) {
+        if (!entry.widget)
+            continue;
+        int min_size = entry.widget->min_size().secondary_size_for_orientation(orientation());
+        int preferred_secondary_size = -1;
+        if (entry.widget->is_shrink_to_fit() && entry.widget->layout()) {
+            preferred_secondary_size = entry.widget->layout()->preferred_size().secondary_size_for_orientation(orientation());
+            size = max(size, preferred_secondary_size);
+        }
+        size = max(min_size, size);
+    }
+
+    if (orientation() == Gfx::Orientation::Horizontal)
+        size += margins().top() + margins().bottom();
+    else
+        size += margins().left() + margins().right();
+
+    if (!size)
+        return -1;
+    return size;
+}
+
 void BoxLayout::run(Widget& widget)
 {
     if (m_entries.is_empty())
@@ -71,6 +135,12 @@ void BoxLayout::run(Widget& widget)
             continue;
         auto min_size = entry.widget->min_size();
         auto max_size = entry.widget->max_size();
+
+        if (entry.widget->is_shrink_to_fit() && entry.widget->layout()) {
+            auto preferred_size = entry.widget->layout()->preferred_size();
+            min_size = max_size = preferred_size;
+        }
+
         items.append(Item { entry.widget.ptr(), min_size.primary_size_for_orientation(orientation()), max_size.primary_size_for_orientation(orientation()) });
     }
 

Libraries/LibGUI/BoxLayout.h

@@ -41,11 +41,15 @@ public:
     Gfx::Orientation orientation() const { return m_orientation; }
 
     virtual void run(Widget&) override;
+    virtual Gfx::IntSize preferred_size() const override;
 
 protected:
     explicit BoxLayout(Gfx::Orientation);
 
 private:
+    int preferred_primary_size() const;
+    int preferred_secondary_size() const;
+
     Gfx::Orientation m_orientation;
 };
 

Libraries/LibGUI/Layout.h

@@ -32,6 +32,7 @@
 #include <LibCore/Object.h>
 #include <LibGUI/Forward.h>
 #include <LibGUI/Margins.h>
+#include <LibGfx/Forward.h>
 
 namespace GUI {
 
@@ -49,6 +50,7 @@ public:
     void remove_widget(Widget&);
 
     virtual void run(Widget&) = 0;
+    virtual Gfx::IntSize preferred_size() const = 0;
 
     void notify_adopted(Badge<Widget>, Widget&);
     void notify_disowned(Badge<Widget>, Widget&);

Libraries/LibGUI/Widget.cpp

@@ -105,6 +105,8 @@ Widget::Widget()
     REGISTER_INT_PROPERTY("fixed_height", dummy_fixed_height, set_fixed_height);
     REGISTER_SIZE_PROPERTY("fixed_size", dummy_fixed_size, set_fixed_size);
 
+    REGISTER_BOOL_PROPERTY("shrink_to_fit", is_shrink_to_fit, set_shrink_to_fit);
+
     REGISTER_INT_PROPERTY("x", x, set_x);
     REGISTER_INT_PROPERTY("y", y, set_y);
 
@@ -1010,4 +1012,12 @@ bool Widget::has_focus_within() const
     return window->focused_widget() == &effective_focus_widget || is_ancestor_of(*window->focused_widget());
 }
 
+void Widget::set_shrink_to_fit(bool b)
+{
+    if (m_shrink_to_fit == b)
+        return;
+    m_shrink_to_fit = b;
+    invalidate_layout();
+}
+
 }

Libraries/LibGUI/Widget.h

@@ -297,6 +297,9 @@ public:
 
     bool load_from_gml(const StringView&);
 
+    void set_shrink_to_fit(bool);
+    bool is_shrink_to_fit() const { return m_shrink_to_fit; }
+
 protected:
     Widget();
 
@@ -367,6 +370,7 @@ private:
     bool m_enabled { true };
     bool m_updates_enabled { true };
     bool m_accepts_emoji_input { false };
+    bool m_shrink_to_fit { false };
 
     NonnullRefPtr<Gfx::PaletteImpl> m_palette;