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guml_syntax.md

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GUML Syntax

Variable

GUML supports the following variables:

  • Alias variable
  • Global variable
  • Local variable

Alias variable

Alias for ui node. So that the corresponding ui node can be referenced in guml file or corresponding controller.

Global variable

Global variables bound externally via Guml.GlobalRefs . The scope is the entire guml file. Among them, $controller always points to the instance of the controller class corresponding to the current guml file.

Local variable

Used in each node to represent each parameter. Its scope is only within the corresponding each node.

Import Statements

A GUML document may have one or more imports at the top of the file.

Syntax:

import <guml path>
import_top <guml path>
  • guml path is a string, path to the guml file to load. Can be an absolute path or a relative path to the current file.

import will mount the loaded component under the current node, while import_top will mount it on the root node.

Redirect Statement

Used to redirect the controller corresponding to the current guml file.

Syntax:

redirect <redirect controller>
  • redirect controller is a string, the type name of the redirected controller.

Component Declarations

Syntax:

<alias name> <component type> {
    <property name>: <property value>,
    <signal name>: <method name>
}
  • alias name
  • component type must start with capital letter. Its value can be the component name of any UI component supported by Godot.
  • property name
  • property value
  • signal name is the signal name supported by the current component. It must start with # and be named using the underscore notation.
  • method name is a string whose value corresponds to the method name.

Value Type

  • string: Similar to C#'s string.
  • int: Similar to C#'s int.
  • float: Similar to C#'s float. Does not support scientific notation.
  • boolean: true or false.
  • object: { <property name>: <property value> }
  • ref: All variable ref
  • null
  • vector2: vec2(x: int, y: int) used to represent Godot's Vector2.
  • color: color(r: float, g: float, b: float, a: float) used to represent Godot's Color.
  • styleBox: style_box_empty() style_box_flat(properties: object) style_box_line(properties: object) style_box_texture(properties: object) used to represent Godot's StyleBox.
  • resource: resource(path: string) used to represent fonts, images, or audio.

Child Components

Any component declaration can define child components through nested component declarations. In this way, any component declaration implicitly declares an component tree that may contain any number of child components.

Example:

Panel {
    Label {
        text: "hello"
    }
    
    Panel {
        Button {}
        Button {}
    }
}

List Rendering

GUML use the each syntax to render a list of items based on an DataSource.

Syntax:

each <data source> { | <index variable define>, <value variable define> |
    <each body>
}
  • data source can be any variable.
  • index variable define && value variable define Declare local variables of index and value, whose scope is valid throughout each.
  • each body is multiple component declarations. Note that each cannot be nested directly.

❌Error:

each $controller.DataA { |index_a, value_a|
    each $controller.DataB { |index_b, value_b|
        // some components
    }
}

✔️Right:

each $controller.DataA { |index_a, value_a|
    Control {
        each $controller.DataB { |index_b, value_b|
            // some components
        }
    }
}

Comments

GUML only has single line comments. Single line comments start with // and finish at the end of the line.

Syntax:

// This is a single line comment

import "setting" // This is also allowed

Keywords

The component's property key cannot conflict with keywords.

import import_top redirect each resource vec2 color style_box_empty style_box_flat style_box_line style_box_texture