io/key: [API] implement key event propagation

Before this change, every Event would be passed to the focused InputOp
tag, making it impossible to implement, say, program-wide shortcuts.
This change implements key.Event routing similar to how pointer.Events
are routed: every InputOp describes the set of keys it can handle, and
the router use that information to deliver an Event to the matching
handler.

This is an API change, because every InputOp must now include a filter
matching the keys it wants to handle.

Fixes: https://todo.sr.ht/~eliasnaur/gio/395
Signed-off-by: Elias Naur <mail@eliasnaur.com>

widget/button.go

@@ -111,7 +111,7 @@ func (b *Clickable) Layout(gtx layout.Context, w layout.Widget) layout.Dimension
 	semantic.DisabledOp(disabled).Add(gtx.Ops)
 	b.click.Add(gtx.Ops)
 	if !disabled {
-		key.InputOp{Tag: &b.keyTag}.Add(gtx.Ops)
+		key.InputOp{Tag: &b.keyTag, Keys: "⏎|Space"}.Add(gtx.Ops)
 	} else {
 		b.focused = false
 	}

widget/editor.go

@@ -8,7 +8,6 @@ import (
 	"image"
 	"io"
 	"math"
-	"runtime"
 	"sort"
 	"strings"
 	"time"
@@ -364,10 +363,9 @@ func (e *Editor) processKey(gtx layout.Context) {
 					continue
 				}
 			}
-			if e.command(gtx, ke) {
-				e.caret.scroll = true
-				e.scroller.Stop()
-			}
+			e.command(gtx, ke)
+			e.caret.scroll = true
+			e.scroller.Stop()
 		case key.SnippetEvent:
 			e.updateSnippet(gtx, ke.Start, ke.End)
 		case key.EditEvent:
@@ -403,16 +401,12 @@ func (e *Editor) moveLines(distance int, selAct selectionAction) {
 	e.updateSelection(selAct)
 }
 
-func (e *Editor) command(gtx layout.Context, k key.Event) bool {
+func (e *Editor) command(gtx layout.Context, k key.Event) {
 	direction := 1
 	if e.locale.Direction.Progression() == system.TowardOrigin {
 		direction = -1
 	}
-	modSkip := key.ModCtrl
-	if runtime.GOOS == "darwin" {
-		modSkip = key.ModAlt
-	}
-	moveByWord := k.Modifiers.Contain(modSkip)
+	moveByWord := k.Modifiers.Contain(key.ModShortcutAlt)
 	selAct := selectionClear
 	if k.Modifiers.Contain(key.ModShift) {
 		selAct = selectionExtend
@@ -465,15 +459,9 @@ func (e *Editor) command(gtx layout.Context, k key.Event) bool {
 	// Initiate a paste operation, by requesting the clipboard contents; other
 	// half is in Editor.processKey() under clipboard.Event.
 	case "V":
-		if k.Modifiers != key.ModShortcut {
-			return false
-		}
 		clipboard.ReadOp{Tag: &e.eventKey}.Add(gtx.Ops)
 	// Copy or Cut selection -- ignored if nothing selected.
 	case "C", "X":
-		if k.Modifiers != key.ModShortcut {
-			return false
-		}
 		if text := e.SelectedText(); text != "" {
 			clipboard.WriteOp{Text: text}.Add(gtx.Ops)
 			if k.Name == "X" {
@@ -482,15 +470,9 @@ func (e *Editor) command(gtx layout.Context, k key.Event) bool {
 		}
 	// Select all
 	case "A":
-		if k.Modifiers != key.ModShortcut {
-			return false
-		}
 		e.caret.end = 0
 		e.caret.start = e.Len()
-	default:
-		return false
 	}
-	return true
 }
 
 // Focus requests the input focus for the Editor.
@@ -625,7 +607,8 @@ func (e *Editor) layout(gtx layout.Context, content layout.Widget) layout.Dimens
 
 	defer clip.Rect(image.Rectangle{Max: e.viewSize}).Push(gtx.Ops).Pop()
 	pointer.CursorText.Add(gtx.Ops)
-	key.InputOp{Tag: &e.eventKey, Hint: e.InputHint}.Add(gtx.Ops)
+	const keyFilter = "(Short)-(Shift)-[←,→,↑,↓]|(Shift)-[⏎,⌤]|(Short)-(Shift)-[⌫,⌦]|(Shift)-[⇞,⇟,⇱,⇲]|Short-[C,V,X,A]"
+	key.InputOp{Tag: &e.eventKey, Hint: e.InputHint, Keys: keyFilter}.Add(gtx.Ops)
 	if e.requestFocus {
 		key.FocusOp{Tag: &e.eventKey}.Add(gtx.Ops)
 		key.SoftKeyboardOp{Show: true}.Add(gtx.Ops)

widget/enum.go

@@ -120,7 +120,7 @@ func (e *Enum) Layout(gtx layout.Context, k string, content layout.Widget) layou
 	clk.Add(gtx.Ops)
 	disabled := gtx.Queue == nil
 	if !disabled {
-		key.InputOp{Tag: &state.tag}.Add(gtx.Ops)
+		key.InputOp{Tag: &state.tag, Keys: "⏎|Space"}.Add(gtx.Ops)
 	} else if e.focus == k {
 		e.focused = false
 	}