keymap

Documentation

Overview

Package keymap lays out an on-screen control-hint bar — the "key: action" row the family's apps show along the bottom of the window. It is display-free: it formats and positions the hints and returns them for the caller to draw with its own text face, wrapping to the window width using a caller-supplied width measurement so the layout is identical whatever font the app renders in.

Index

• func Rows(bindings []Binding, avail int, measure func(string) int) []string
• type Binding
  • func (b Binding) Label() string
• type Face
• type Line
  • func BottomBar(bindings []Binding, w, h, pad int, f Face) []Line
  • func CenterPrompt(b Binding, w, h int, f Face) Line

Examples

• BottomBar

Functions

func Rows

func Rows(bindings []Binding, avail int, measure func(string) int) []string

Rows formats bindings as "key: action", joins them with " | ", and wraps them into rows no wider than avail measured by measure. It is BottomBar's layout without its placement, for hints that live somewhere the bottom-left corner is not — inside a stats panel, beside a simulation, as a menu subtitle. The caller positions the rows itself. An empty bindings slice returns nil.

Types

type Binding

type Binding struct {
	// Key names the key or combination, e.g. "space", "+/-", "drag/arrows".
	Key string
	// Action describes what the key does, e.g. "pause", "new track".
	Action string
}

Binding is one control hint: a key or key combination and the action it triggers.

func (Binding) Label

func (b Binding) Label() string

Label renders the binding as "key: action".

type Face

type Face struct {
	// LineHeight is the vertical distance between wrapped rows, in pixels.
	LineHeight int
	// Measure returns the pixel width of s in the caller's font. Wrapping uses
	// it so a row never exceeds the available width.
	Measure func(s string) int
}

Face describes the caller's text metrics so the bar wraps and stacks correctly in whatever font the app draws with.

type Line

type Line struct {
	X, Y int
	Text string
}

Line is one laid-out row of the bar: the text to draw and where to draw it. X and Y are the row's top-left origin, matching the position most text calls expect; add your font's ascent if yours draws from the baseline instead.

func BottomBar

func BottomBar(bindings []Binding, w, h, pad int, f Face) []Line

BottomBar lays bindings out as a control bar anchored to the bottom-left of a w×h screen. It formats each binding as "key: action", joins them with " | ", wraps to the width f allows, and stacks the wrapped rows so the last sits pad above the bottom edge. Rows are returned top-to-bottom; an empty bindings slice returns nil.

Example

package main

import (
	"fmt"

	"github.com/danielriddell21/crucible/keymap"
)

func main() {
	bindings := []keymap.Binding{
		{Key: "space", Action: "pause"},
		{Key: "+/-", Action: "speed"},
		{Key: "r", Action: "restart"},
	}
	// A fixed 6-pixel-per-character face, like the built-in debug font.
	face := keymap.Face{LineHeight: 16, Measure: func(s string) int { return len(s) * 6 }}
	for _, line := range keymap.BottomBar(bindings, 640, 360, 8, face) {
		fmt.Printf("(%d,%d) %s\n", line.X, line.Y, line.Text)
	}
}

Output:
(8,336) space: pause | +/-: speed | r: restart

func CenterPrompt

func CenterPrompt(b Binding, w, h int, f Face) Line

CenterPrompt lays out a single binding as a contextual prompt, centred horizontally and sitting in the lower third of a w×h screen. Games use it for "look at a door → E: open" hints that appear only while an interactive object is in focus. The returned Line shares the top-left origin convention of BottomBar.