Add config package

Closes #6

attribute.go

@@ -13,6 +13,8 @@ type Attr interface {
 	attr   ()
 }
 
+// AttrKind enumerates all attribute kinds. There is one of these for each
+// attribute type.
 type AttrKind int; const (
 	AttrKindColor AttrKind = iota
 	AttrKindTexture
@@ -28,6 +30,7 @@ type AttrKind int; const (
 	AttrKindAlign
 	AttrKindOverflow
 	AttrKindLayout
+	AttrKindCursor
 )
 
 // AttrColor sets the background color of a box.
@@ -58,6 +61,8 @@ type AttrAlign struct { X, Y Align }
 type AttrOverflow struct { X, Y bool }
 // AttrLayout sets the layout, if the box is a ContentBox.
 type AttrLayout struct { Layout }
+// AttrCursor sets the mouse cursor shape.
+type AttrCursor Cursor
 
 // AColor is a convenience constructor for the color attribute.
 func AColor (col color.Color) AttrColor {
@@ -115,6 +120,10 @@ func AOverflow (x, y bool) AttrOverflow {
 func ALayout (layout Layout) AttrLayout {
 	return AttrLayout { Layout: layout }
 }
+// ACursor is a convenience constructor for the cursor attribute.
+func ACursor (cursor Cursor) AttrCursor {
+	return AttrCursor(cursor)
+}
 
 // Equals returns true if both attributes can reasonably be declared equal.
 func (this AttrColor) Equals (other Attr) bool {
@@ -233,6 +242,14 @@ func (this AttrLayout) Equals (other Attr) bool {
 	// two layouts cannot "reasonably" be declared equal
 	return false
 }
+// Equals returns true if both attributes can reasonably be declared equal.
+func (this AttrCursor) Equals (other Attr) bool {
+	if other, ok := other.(AttrCursor); ok {
+		return this == other
+	} else {
+		return false
+	}
+}
 
 func (AttrColor)       Kind () AttrKind { return AttrKindColor }
 func (AttrTexture)     Kind () AttrKind { return AttrKindTexture }
@@ -248,6 +265,7 @@ func (AttrWrap)        Kind () AttrKind { return AttrKindWrap }
 func (AttrAlign)       Kind () AttrKind { return AttrKindAlign }
 func (AttrOverflow)    Kind () AttrKind { return AttrKindOverflow }
 func (AttrLayout)      Kind () AttrKind { return AttrKindLayout }
+func (AttrCursor)      Kind () AttrKind { return AttrKindCursor }
 
 func (AttrColor)       attr () { }
 func (AttrTexture)     attr () { }
@@ -263,3 +281,4 @@ func (AttrWrap)        attr () { }
 func (AttrAlign)       attr () { }
 func (AttrOverflow)    attr () { }
 func (AttrLayout)      attr () { }
+func (AttrCursor)      attr () { }

backend.go

@@ -18,12 +18,7 @@ type Backend interface {
 	NewContainerBox () ContainerBox
 
 	// NewWindow creates a normal Window and returns it.
-	NewWindow (image.Rectangle) (Window, error)
-
-	// NewPlainWindow creates an undecorated window that does not appear in
-	// window lists and returns it. This is intended for making things like
-	// panels, docks, etc.
-	NewPlainWindow (image.Rectangle) (Window, error)
+	NewWindow (WindowKind, image.Rectangle) (Window, error)
 
 	// NewTexture creates a new texture from an image. The backend must
 	// reject any texture that was not made by it.

config/config.go

@@ -0,0 +1,15 @@
+// Package config stores common configuration parameters. These are unmanaged,
+// and must be queried each time they are used. These are intended to be set by
+// things like application frameworks. Values set by objects or applications are
+// subject to being overridden.
+package config
+
+import "time"
+
+// DoubleClickDelay is the maximum amount of time that can pass between two
+// consecutive clicks for them to be considered a double-click.
+var DoubleClickDelay time.Duration = time.Second
+
+// ScrollSpeed is how many units (pixels at a scale of 1.0) the content of a
+// ContentBox should be moved in response to a scroll delta of 1.0.
+var ScrollSpeed int = 16

cursor.go

@@ -0,0 +1,35 @@
+package tomo
+
+// Cursor represents a mouse cursor shape.
+type Cursor string
+
+// A list of standard cursor shapes. This is based off of the XDG Cursor
+// Conventions Specification
+// (https://www.freedesktop.org/wiki/Specifications/cursor-spec/)
+const (
+	CursorUnknown      Cursor = ""
+	CursorDefault      Cursor = "Default"
+	CursorText         Cursor = "Text"
+	CursorPointer      Cursor = "Pointer"
+	CursorHelp         Cursor = "Help"
+	CursorProgress     Cursor = "Progress"
+	CursorWait         Cursor = "Wait"
+	CursorCopy         Cursor = "Copy"
+	CursorAlias        Cursor = "Alias"
+	CursorNoDrop       Cursor = "NoDrop"
+	CursorNotAllowed   Cursor = "NotAllowed"
+	CursorAllScroll    Cursor = "AllScroll"
+	CursorRowResize    Cursor = "RowResize"
+	CursorColResize    Cursor = "ColResize"
+	CursorEResize      Cursor = "EResize"
+	CursorNEResize     Cursor = "NEResize"
+	CursorNWResize     Cursor = "NWResize"
+	CursorNResize      Cursor = "NResize"
+	CursorSEResize     Cursor = "SEResize"
+	CursorSWResize     Cursor = "SWResize"
+	CursorSResize      Cursor = "SResize"
+	CursorWResize      Cursor = "WResize"
+	CursorVerticalText Cursor = "VerticalText"
+	CursorCrosshair    Cursor = "Crosshair"
+	CursorCell         Cursor = "Cell"
+)

event/event.go

@@ -2,11 +2,36 @@
 // handlers.
 package event
 
+import "io"
+import "errors"
+
 // A cookie is returned when you add an event handler so you can remove it
-// later if you so choose.
-type Cookie interface {
-	// Close removes the event handler this cookie is for.
-	Close ()
+// later if you so choose. When the Close behavior is called, the handler must
+// be removed, even if an error is returned.
+type Cookie io.Closer
+
+// FuncCookie is a cookie that calls a function (itself) when closed.
+type FuncCookie func () error
+func (cookie FuncCookie) Close () error { return cookie () }
+
+// NoCookie is a cookie that does nothing when closed.
+type NoCookie struct { }
+func (NoCookie) Close () error { return nil }
+
+type multiCookie []Cookie
+
+// MultiCookie creates a single cookie that, when closed, closes a list of other
+// cookies.
+func MultiCookie (cookies ...Cookie) Cookie {
+	return multiCookie(cookies)
+}
+
+func (cookies multiCookie) Close () error {
+	errs := make([]error, len(cookies))
+	for index, cookie := range cookies {
+		errs[index] = cookie.Close()
+	}
+	return errors.Join(errs...)
 }
 
 // Broadcaster manages event listeners.
@@ -31,9 +56,9 @@ func (broadcaster *Broadcaster[L]) Listeners () map[int] L {
 	return broadcaster.listeners
 }
 
-func (broadcaster *Broadcaster[L]) newCookie () cookie[L] {
+func (broadcaster *Broadcaster[L]) newCookie () broadcasterCookie[L] {
 	broadcaster.lastID ++
-	return cookie[L] {
+	return broadcasterCookie[L] {
 		id:          broadcaster.lastID,
 		broadcaster: broadcaster,
 	}
@@ -45,17 +70,14 @@ func (broadcaster *Broadcaster[L]) ensure () {
 	}
 }
 
-// NoCookie is a cookie that does nothing when closed.
-type NoCookie struct { }
-func (NoCookie) Close () { }
-
-type cookie[L any] struct {
+type broadcasterCookie[L any] struct {
 	id int
 	broadcaster *Broadcaster[L]
 }
 
-func (cookie cookie[L]) Close () {
+func (cookie broadcasterCookie[L]) Close () error {
 	delete(cookie.broadcaster.listeners, cookie.id)
+	return nil
 }
 
 // FuncBroadcaster is a broadcaster that manages functions with no arguments.
@@ -69,17 +91,3 @@ func (broadcaster *FuncBroadcaster) Broadcast () {
 		listener()
 	}
 }
-
-type multiCookie []Cookie
-
-// MultiCookie creates a single cookie that, when closed, closes a list of other
-// cookies.
-func MultiCookie (cookies ...Cookie) Cookie {
-	return multiCookie(cookies)
-}
-
-func (cookies multiCookie) Close () {
-	for _, cookie := range cookies {
-		cookie.Close()
-	}
-}

icon.go

@@ -93,7 +93,7 @@ const (
 	IconListRemove                   Icon = "ListRemove"
 	IconListChoose                   Icon = "ListChoose"
 	IconListExpand                   Icon = "ListExpand"
-	IconListContract                 Icon = "ListExpand"
+	IconListContract                 Icon = "ListContract"
 	// actions: mail
 	IconMailForward                  Icon = "MailForward"
 	IconMailMarkImportant            Icon = "MailMarkImportant"

object.go

@@ -283,6 +283,32 @@ type BoxArranger interface {
 	SetBounds (index int, bounds image.Rectangle)
 }
 
+// WindowKind specifies a window's kind, which determines how it is displayed
+// and managed by the operating system.
+type WindowKind string; const (
+	// Normal is a normal window.
+	WindowKindNormal WindowKind = "Normal"
+	// Plain is an undecorated window that does not appear in window lists.
+	// It is intended for things like docks, panels, etc.
+	WindowKindPlain WindowKind = "Plain"
+	// Utility is a small window for toolboxes, command palletes, etc. It is
+	// usually given special styling and management by the OS.
+	WindowKindUtility WindowKind = "Utility"
+	// Toolbar is a small window for menus and window panes which have been
+	// "torn off" from their main window or position. It is usually given
+	// special styling and management by the OS.
+	WindowKindToolbar WindowKind = "Toolbar"
+	// Menu is an undecorated window for drop down menus, context menus,
+	// etc. It closes once the user interacts outside of it.
+	WindowKindMenu WindowKind = "Menu"
+	// Modal, while open, blocks all user input from reaching its parent
+	// window, forcing the user's attention. It is usually given special
+	// styling and management by the OS. Note that in some environments it
+	// will not be given window controls, so it should contain some "Close"
+	// or "Cancel" button.
+	WindowKindModal WindowKind = "Modal"
+)
+
 // Window is an operating system window. It can contain one object. Windows
 // themselves are completely transparent, and become opaque once an opaque
 // object is added as their root.
@@ -310,15 +336,8 @@ type Window interface {
 	SetBounds (image.Rectangle)
 	// NewChild creates a new window that is semantically a child of this
 	// window. It does not actually reside within this window, but it may be
-	// linked to it via some other means. This is intended for things like
-	// toolboxes and tear-off menus.
-	NewChild (image.Rectangle) (Window, error)
-	// NewMenu creates a new menu window. This window is undecorated and
-	// will close once the user clicks outside of it.
-	NewMenu (image.Rectangle) (Window, error)
-	// NewModal creates a new modal window that blocks all input to this
-	// window until it is closed.
-	NewModal (image.Rectangle) (Window, error)
+	// linked to it via some other means.
+	NewChild (WindowKind, image.Rectangle) (Window, error)
 	// Modifiers returns which modifier keys on the keyboard are currently
 	// being held down.
 	Modifiers () input.Modifiers
@@ -335,8 +354,13 @@ type Window interface {
 	SetVisible (bool)
 	// Visible returns whether or not this window is visible.
 	Visible () bool
-	// Close closes the window.
-	Close ()
+	// Close closes the window. This does not trigger the TryClose event.
+	Close () error
+	// OnTryClose specifies a function to be called when the user attempts
+	// to close the window. If any registered handlers returns false, the
+	// window will not be closed. This can be used to display some sort of
+	// "Unsaved changes" warning to the user.
+	OnTryClose (func () bool) event.Cookie
 	// OnClose specifies a function to be called when the window is closed.
 	OnClose (func ()) event.Cookie
 }

tomo.go

@@ -42,17 +42,9 @@ func Do (callback func ()) {
 }
 
 // NewWindow creates and returns a window within the specified bounds on screen.
-func NewWindow (bounds image.Rectangle) (Window, error) {
+func NewWindow (kind WindowKind, bounds image.Rectangle) (Window, error) {
 	assertBackend()
-	return backend.NewWindow(bounds)
-}
-
-// NewPlainWindow is like NewWindow, but it creates an undecorated window that
-// does not appear in window lists. It is intended for creating things like
-// docks, panels, etc.
-func NewPlainWindow (bounds image.Rectangle) (Window, error) {
-	assertBackend()
-	return backend.NewPlainWindow(bounds)
+	return backend.NewWindow(kind, bounds)
 }
 
 // NewBox creates and returns a basic Box.