The Interface API includes objects for UI components such as buttons, labels, and checkboxes and methods for access to the very primitive window manager and input events.

Classes

Component

Abstract class, no constructor

Component:visible

flag = Component:visible()
Component:visible(flag)

• flag: boolean true / false on whether the component or not

Component:size

width, height = Component:size()
Component:size(width, height)

• width: The width of the component
• height: The height of the component

Component:position

x, y = Component:position()
Component:position(x, y)

• x: The x coordinate of the component
• y: The y coordinate of the component

Button

Button Button:new(number x, number y, number width, number height, [string text = "", [string tooltip = ""]])

Extends Component, fires "action" when clicked

Button:action

Button:action(callback)

• callback: The callback, a function which receives one argument, sender
  • sender: The button itself

Sets the listener for button actions. The action is triggered whenever the button is left clicked (clicked means a full mousedown + mouseup happened inside the button).

Example:

local newButton = ui.button(10, 10, 100, 17, "Times clicked: 0")
local counter = 0
newButton:action(function(sender)
	counter = counter + 1
	sender:text("Times clicked: " .. counter)
end)
interface.addComponent(newButton)

Button:text

text = Button:text()
Button:text(text)

• text: The button text

Button:enabled

flag = Button:enabled()
Button:enabled(flag)

• flag: Whether or not the button is enabled

Controls the enabled flag of the button. Buttons that are disabled cannot be clicked, change to gray, and don't respond to mousemove events either.

ProgressBar

ProgressBar ProgressBar:new(number x, number y, number width, number height, number progress, string status)

Extends Component, used to indicate progress for long-running tasks

ProgressBar:progress

progress = ProgressBar:progress()
ProgressBar:progress(progress)

• progress: The current progress value

Gets or sets the current progress. Progress ranges from 0 to 100, but a special case of -1 will change the behavior of the progress bar to intermediate (constantly scrolling to indicate progress)

ProgressBar:status

text = ProgressBar:status()
ProgressBar:status(text)

• text: The progress bar status

Status is simply a text representation of the current action being performed, for example, "Working" or just a percentage

Slider

Slider Slider:new(number x, number y, number width, number height, [number steps = ""])

Extends Component, fires "onValueChanged" when the value is changed (i.e used by the user)

Slider:onValueChanged

Slider:onValueChanged(callback)

• callback: The callback, a function which receives two arguments, sender and value
  • sender: The slider itself
  • value: The value the slider was set to

Called whenever the slider value changes due to a change by the user. Changes made to the value from Lua don't trigger the callback.

Slider:value

value = Slider:value()
Slider:value(value)

• value: The value of the slider, which is a number in the range [0, steps]

Slider:steps

steps = Slider:steps()
Slider:steps(steps)

• steps: The number of steps the slider has. Must be a positive number. If the current slider position is greater than the new number of steps, the slider position will be set to the new max.

Checkbox

Checkbox Checkbox:new(number x, number y, number width, number height, [string text = ""])

Extends Component, fires "onValueChanged" when the checkbox is checked or unchecked

Checkbox:action

Checkbox:action(callback)

• callback: The callback, a function which receives two arguments, sender and checked
  • sender: The checkbox itself
  • checked: A true / false flag on whether the checkbox is currently checked

Called whenever the checkbox state is toggled due to a change by the user.

Checkbox:text

text = Checkbox:text()
Checkbox:text(text)

• text: The checkbox's text

Text is drawn to the right of the checkbox, see for example the options menu. The text that response to mouseover events is part of the checkbox itself. (The text underneath is a separate Label)

Checkbox:checked

flag = Checkbox:checked()
Checkbox:checked(flag)

• flag: The checked state of the checkbox, a boolean true / false flag

Label

Label Label:new(number x, number y, number width, number height, [string text = ""])

Extends Component, is a simple selectable, read-only text field

Label:text

text = Label:text()
Label:text(text)

• text: The label text

Textbox

Textbox Textbox:new(number x, number y, number width, number height [, string text = "" [, string placeholder = "" ]])

Extends Component, is a text input field, the placeholder text is shown if the component is not focused and contains no text

Textbox:onTextChanged

Textbox:onTextChanged(callback)

• callback: The callback, a function which receives one argument, sender
  • sender: The textbox itself

Called whenever the textbox is changed due to an action by the user. For example, typing or deleting a character, cutting or pasting text. Changes via Lua do not trigger this callback.

Textbox:text

text = Textbox:text()
Textbox:text(text)

• text: The textbox's text

When setting text, the old selection is cleared, the text is replaced, and the cursor is set to the end.

Textbox:readonly

flag Textbox:readonly()
Textbox:readonly(flag)

• flag: true / false flag for the textbox's readonly flag.

readonly textboxes can't have their text changed in any way. The only possible user interaction is moving the cursor and text selection operations.

Window

Window Window:new(number x, number y, number width, number height)

A modal form to display components, using -1 for either x or y values will center the Window on that axis.

Window:addComponent

Window:addComponent(component)

• component: The component to add

Adds a component to the window. The component must not have already been added to another Window object.

Window:removeComponent

Window:removeComponent(component)

• component: The component to remove

Remove a component from the window. If this component isn't part of the window, does nothing.

Methods

interface.grabTextInput

nil interface.grabTextInput()

Signal to the interface engine that textinput events are expected and will be handled (for example, your textbox just gained focus and is ready for such events). Once called, it should not be called again until after calling interface.dropTextInput; see below.

From the API user's perspective, the grabTextInput-dropTextInput pair implements an on-off switch. The purpose of this switch is to help the interface engine determine when to enter and exit text input state. In this state, the engine asks for OS help with text input (which may or may not involve enabling an Input Method) and delivers textinput events received from the OS to the API user.

The engine should only enter the text input state when the API user expects textinput events (for example, when a textbox is in focus). To correctly communicate this, grabTextInput should be called when the processing of textinput events starts and dropTextInput when it ends. Note that textinput events may be delivered regardless of the state of this on-off switch, most likely as a result of another API user calling grabTextInput and dropTextInput.

interface.dropTextInput

nil interface.dropTextInput()

Signal to the interface engine that textinput events are not expected and will not be handled (for example, your textbox just lost focus and will not handle such events anymore). Once called, it should not be called again until after calling interface.grabTextInput; see above.

interface.addComponent

nil interface.addComponent(Component newComponent)

Adds a component to the master game window.

interface.removeComponent

nil interface.removeComponent(Component newComponent)

Removes a component from the master game window.

interface.showWindow

nil interface.showWindow(Window newWindow)

Push a Window into the top of the modal stack

interface.closeWindow

nil interface.closeWindow(Window newWindow)

Pop a Window off the top of the modal stack. If the given Window is not the top item in the stack, this will have no effect.

interface.textInputRect

nil interface.textInputRect(number x, number y, number w, number h)

Enables composition, for multi-byte Unicode characters.

interface.beginConfirm

Opens a confirm prompt, and runs a callback after the user's input.

interface.beginConfirm(title, message, buttonText, callback)

• title: Header message for the confirm prompt. Default "Title"
• message: Body message for the confirm prompt, can be multiple lines. Default "Message"
• buttonText: Text to display for the confirm button. Default "Confirm"
• callback: Callback function to run after the user gives input. Receives a single boolean as an argument.

Only the callback argument is required. The rest are optional. The final arg to the function will be used as the callback. If the user clicks "Confirm" or presses enter, true is passed in. If the user clicks "Cancel", presses escape, or closes the dialog any other way, false is passed.

interface.beginInput

Opens an input prompt, and runs a callback after the user's input.

interface.beginInput(title, prompt, text, shadow, callback)

• title: Header message for the input prompt. Default "Title"
• prompt: Body message for the input prompt, can be multiple lines. Default "Enter some text:"
• text: Default text for the textbox. Defaults to empty string.
• shadow: Default shadow text displayed when textbox is empty and defocused. Defaults to empty string.
• callback: Callback function to run after the user gives input. Receives either a string or nil as the only argument.

Only the callback argument is required. The rest are optional. The final arg to the function will be used as the callback. If the user clicks "Okay" or presses enter, the textbox's text is passed. If the user clicks "Cancel", presses escape, or closes the dialog any other way, nil is passed.

interface.beginMessageBox

Opens a message box, and runs a callback after the user closes it.

interface.beginMessageBox(title, message, large, callback)

• title: Header message for the message box. Default "Title"
• message: Body message for the message box, can be multiple lines. Default "Message"
• large: boolean that controls if the message box should be a fixed-size larger variant, that is both taller and wider. Default false.
• callback: Callback function to run after the user closes the message box. Runs no matter how it is closed, and takes no arguments.

All arguments are optional. The final arg to the function will be used as the callback.

interface.beginThrowError

Opens an error dialog box, and runs a callback after the user closes it.

interface.beginThrowError(errorMessage, callback)

• errorMessage: Body message for the error prompt, can be multiple lines. Default "Error Text"
• callback: Callback function to run after the user closes the error prompt. Runs no matter how it is closed, and takes no arguments.

All arguments are optional. The final arg to the function will be used as the callback.

interface.activeMenu

Gets or sets the active menu.

 interface.activeMenu(menuSection)
 menuSection = interface.activeMenu()

• menuSection: The menusection. See the reference of menusection constants in the elements api.

interface.menuEnabled

Controls whether menusections are enabled (shown) in the UI.

 interface.menuEnabled(menuSection, enabled)
 enabled = interface.menuEnabled(menuSection)

• menuSection: The menusection. See the reference of menusection constants in the elements api.
• enabled: boolean true/false describing if the menu section is enabled.

If using an invalid menusection, an Invalid Menu error is raised.

interface.numMenus

Returns the number of menus

 numMenus = interface.numMenus()

• numMenus: The number of enabled menus.

Menus that aren't enabled don't count towards this limit.

interface.activeTool

Gets or sets an active element selection.

 interface.activeTool(toolIndex, identifier)
 identifier = interface.activeTool(toolIndex)

• toolIndex: The tool index. Should be between 0 and interface.NUM_TOOLINDICES. The indices correspond to:
  • 0: Left click
  • 1: Right click
  • 2: Middle click
  • 3: "Replace Mode" element
• identifier. The tool identifier. This is a string that uniquely identifies a tool, for example "DEFAULT_PT_BGLA" or "DEFAULT_TOOL_HEAT".

interface.brushID

Gets or set the brush index.

 interface.brushID(brushIndex)
 brushIndex = interface.brushID()

• brushIndex: The index of the brush to set. Should be between 0 and sim.NUM_BRUSHES. For default brushes, the following constants can be used:
  • sim.BRUSH_CIRCLE: Circle brush
  • sim.BRUSH_SQUARE: Square brush
  • sim.BRUSH_TRIANGLE: Triangle brush
  • sim.NUM_DEFAULTBRUSHES: Number of default brushes, excluding custom brushes

interface.brushRadius

Gets or sets the radius of the brush

 interface.brushRadius(w, h)
 w, h = interface.brushRadius()

• w: Brush width
• h: Brush height

interface.perfectCircleBrush

Gets / Sets the "Perfect Circle" option

 interface.perfectCircleBrush(flag)
 flag = interface.perfectCircleBrush()

• flag: boolean true / false on whether the setting is enabled or not

interface.mousePosition

Returns the current mouse position

 mouseX, mouseY = interface.mousePosition()

• mouseX: mouse x position
• mouseY: mouse y position

This is the position of the mouse in the full interface, so it ignores zoom window and can be outside of sim bounds. To convert into sim coords and adjust for zoom window, see sim.adjustCoords.

interface.console

Control or check whether the console is open

 interface.console(shown)
 shown = interface.console()

• shown: boolean true/false on whether or not the console is shown.

If you set it to false while in the console, it will close. Scripts can also use it to open the console. This action is non-blocking, so script execution will continue. But as soon as control is returned to the engine, further Lua callbacks will stop (because no event handlers run while the console is open).

Constants

All SDL scancodes, keycodes, and button codes are exposed as constants. For a full list, check out LuaSDLKeys.h

Example

This code has examples of some of the features of the interface API, it shows a window with various components with some testing behavior.

-- Test Window
local testWindow = Window:new(-1, -1, 300, 200)

local currentY = 10

--Example label
local testLabel = Label:new(10, currentY, (select(1, testWindow:size())/2)-20, 16, "This is a test label")

--Example button
local buttonPresses = 1
currentY = currentY + 20
local testButton = Button:new(10, currentY, (select(1, testWindow:size())/2)-20, 16, "This is a test button")
testButton:enabled(false)
testButton:action(
	function(sender)
		sender:text("Pressed " .. buttonPresses .. " times")
		buttonPresses = buttonPresses + 1
	end
)

--Example Textbox
currentY = currentY + 20
local textboxInfo = Label:new(10+((select(1, testWindow:size())/2)-20), currentY, (select(1, testWindow:size())/2)-20, 16, "0 characters")
local testTextbox = Textbox:new(10, currentY, (select(1, testWindow:size())/2)-20, 16, "", "[place text here]")
testTextbox:onTextChanged(
	function(sender)
		textboxInfo:text(sender:text():len().." characters");
	end
)

--Example Checkbox
currentY = currentY + 20
local testCheckbox = Checkbox:new(10, currentY, (select(1, testWindow:size())/2)-20, 16, "Unchecked");
testCheckbox:action(
	function(sender, checked)
		if(checked) then
			sender:text("Checked")
		else
			sender:text("Unchecked")
		end
		testButton:enabled(checked);
	end
)

--Example progress bar
currentY = currentY + 20
local testProgressBar = ProgressBar:new(10, currentY, (select(1, testWindow:size())/2)-20, 16, 0, "Slider: 0");

--Example slider
currentY = currentY + 20
local testSlider = Slider:new(10, currentY, (select(1, testWindow:size())/2)-20, 16, 10);
testSlider:onValueChanged(
	function(sender, value)
		testProgressBar:progress(value * 10)
		testProgressBar:status("Slider: " .. value)
	end
)

-- Close button
local closeButton = Button:new(10, select(2, testWindow:size())-26, 100, 16, "Close")

closeButton:action(function() interface.closeWindow(testWindow) end)

testWindow:onTryExit(function() interface.closeWindow(testWindow) end) -- Allow the default exit events
testWindow:onMouseMove(
	function(x, y, dx, dy)
		testLabel:text("Mouse: "..x..", "..y)
	end
)

testWindow:addComponent(testLabel)
testWindow:addComponent(testButton)
testWindow:addComponent(testTextbox)
testWindow:addComponent(testCheckbox)
testWindow:addComponent(testProgressBar)
testWindow:addComponent(testSlider)
testWindow:addComponent(textboxInfo)
testWindow:addComponent(closeButton)

interface.showWindow(testWindow)