Gum Forms Controls

Gum Forms Controls

Forms controls are interactive UI classes whose names mirror WPF (Button, CheckBox, TextBox, …), but they are laid out and rendered by Gum, not WPF. Reach for a Forms control for anything the player clicks, types in, or scrolls. For non-interactive HUD/decoration, use raw visuals instead (see below). Docs: https://docs.flatredball.com/gum/code/controls.

Common controls

Button, ToggleButton, RadioButton, CheckBox, Label, TextBox, PasswordBox, ComboBox, ListBox, Slider, ScrollBar, ScrollViewer, StackPanel, Panel, Menu, Window, Splitter.

Using a control in code

using Gum.Forms.Controls;

var button = new Button();
button.Text = "Play";
button.AddToRoot();               // adds it to the screen
button.Click += (_, _) => StartGame();

Text-bearing controls share this shape — new Label(), new TextBox(), etc. all expose .Text. Set position/size with Gum's unit system (see gum-layout), not WPF layout.

Composing controls (parenting in code)

AddToRoot() attaches a control to the screen. To nest one control inside another — buttons inside a panel, anything inside a container — call AddChild on the parent. There is no .Children.Add(...) on a Forms control.

var menu = new StackPanel();   // stacks its children; vertical by default
menu.Spacing = 8;              // gap between children (StackPanel.Spacing)
menu.AddToRoot();

var play = new Button { Text = "Play" };
var quit = new Button { Text = "Quit" };
menu.AddChild(play);           // parents the control under the panel
menu.AddChild(quit);

AddChild(child) sets the child's visual parent; the parent's layout then positions it — a StackPanel stacks them, and any container with ChildrenLayout set arranges them. RemoveChild undoes it. StackPanel defaults to Orientation.Vertical; set Orientation = Orientation.Horizontal for a row.

Forms vs raw visuals

Raw visuals: https://docs.flatredball.com/gum/code/standard-visuals.

Landmine: WPF conventions do not carry over

The names match WPF; the property model does not. On a Forms control:

• No Margin, Padding, or WPF-style HorizontalAlignment/VerticalAlignment. Position and size come from Gum units (X, XUnits, Width, WidthUnits, …).
• No Background, Foreground, or BorderBrush. Color and appearance come from states (below), not brush properties.
• No Visibility enum. Use the IsVisible bool.
• No WPF Auto sizing. A Button with Width = 128 is 128 px wide regardless of its text unless WidthUnits = RelativeToChildren. See gum-layout.

For a fuller WPF-to-Gum translation: https://docs.flatredball.com/gum/code/about/for-wpf-users.

The state / category system (how styling works)

Appearance is driven by named states grouped into a category on the control's visual, not by per-property setters. A Button's visual, for example, carries a category with Enabled, Highlighted, Pushed, Focused, and Disabled states; the control switches between them automatically as the player interacts. Each state sets a batch of variables (colors, sizes) at once.

To recognize this in code: applying a state name changes the look; the control does this for you on hover/press/focus. To customize appearance you edit the states (in the tool, or via the styling APIs) or swap in a different visual — you do not look for a Color property on the control. Don't panic when you see categories and states; they are Gum's equivalent of a style sheet. Styling guide: https://docs.flatredball.com/gum/code/styling.

Default visuals

A newly-constructed control (new Button()) gets a built-in default visual so it renders without any project. Replacing or restyling that visual is the styling story above. If a control looks unstyled or blank, its visual — not the control class — is what to inspect.