LibGUI: Rewrite layout system in terms of min and max sizes

This patch removes size policies and preferred sizes, and replaces them
with min-size and max-size for each widget.

Box layout now works in 3 passes:

    1) Set all items (widgets/spacers) to their min-size
    2) Distribute remaining space evenly, respecting max-size
    3) Place widgets one after the other, adding spacing in between

I've also added convenience helpers for setting a fixed size (which is
the same as setting min-size and max-size to the same value.)

This significantly reduces the verbosity of widget layout and makes GML
a bit more pleasant to write, too. :^)

1 files changed, 2 insertions, 4 deletions

diff --git a/Applications/ThemeEditor/main.cpp b/Applications/ThemeEditor/main.cpp
index f4675c19d7..d4a5936770 100644
--- a/Applications/ThemeEditor/main.cpp
+++ b/Applications/ThemeEditor/main.cpp
@@ -99,13 +99,11 @@ int main(int argc, char** argv)
     main_widget.set_layout<GUI::VerticalBoxLayout>();
 
     auto& preview_widget = main_widget.add<ThemeEditor::PreviewWidget>(app->palette());
-    preview_widget.set_preferred_size(480, 360);
-    preview_widget.set_size_policy(GUI::SizePolicy::Fixed, GUI::SizePolicy::Fixed);
+    preview_widget.set_fixed_size(480, 360);
 
     auto& horizontal_container = main_widget.add<GUI::Widget>();
     horizontal_container.set_layout<GUI::HorizontalBoxLayout>();
-    horizontal_container.set_preferred_size(480, 20);
-    horizontal_container.set_size_policy(GUI::SizePolicy::Fixed, GUI::SizePolicy::Fixed);
+    horizontal_container.set_fixed_size(480, 20);
 
     auto& combo_box = horizontal_container.add<GUI::ComboBox>();
     auto& color_input = horizontal_container.add<GUI::ColorInput>();