Add version number and documentation

docs.go

@@ -0,0 +1,10 @@
+/*
+Package ui provides a user interface toolkit for Go.
+
+The UI toolkit targets SDL2 applications on desktop (Linux, Mac and Windows)
+or an HTML Canvas render engine for web browsers.
+
+It provides various widgets such as Frame, Label, Button, Checkbox, Radiobox
+and Tooltip and an event supervisor to monitor the state of the widgets.
+*/
+package ui

go.mod

@@ -2,8 +2,4 @@ module git.kirsle.net/go/ui
 
 go 1.13
 
-require (
-	git.kirsle.net/go/render v0.0.0-20200102014411-4d008b5c468d
-	github.com/veandco/go-sdl2 v0.4.1 // indirect
-	golang.org/x/image v0.0.0-20200119044424-58c23975cae1 // indirect
-)
+require git.kirsle.net/go/render v0.0.0-20200102014411-4d008b5c468d

tooltip_test.go

@@ -0,0 +1,30 @@
+package ui_test
+
+import "git.kirsle.net/go/ui"
+
+// Tooltip usage example.
+func ExampleTooltip() {
+	mw, err := ui.NewMainWindow("Tooltip Example", 800, 600)
+	if err != nil {
+		panic(err)
+	}
+
+	// Add a widget that will have a tooltip attached, i.e. a button.
+	btn := ui.NewButton("My Button", ui.NewLabel(ui.Label{
+		Text: "Hello world!",
+	}))
+	mw.Place(btn, ui.Place{
+		Center: true,
+		Middle: true,
+	})
+
+	// Add a tooltip to it. The tooltip attaches itself to the button's
+	// MouseOver, MouseOut, Compute and Present handlers -- you don't need to
+	// place the tooltip inside the window or parent frame.
+	ui.NewTooltip(btn, ui.Tooltip{
+		Text: "This is a tooltip that pops up\non mouse hover!",
+		Edge: ui.Right,
+	})
+
+	mw.MainLoop()
+}

version.go

@@ -0,0 +1,4 @@
+package ui
+
+// Version of the UI toolkit.
+const Version = "0.1.0"