feat: add event stringers

doc.go

@@ -52,4 +52,9 @@
 // Reference: https://github.com/gogpu/gpucontext
 package gpucontext
 
-const stringNone = "None"
+const (
+	stringNone   = "None"
+	stringLeft   = "Left"
+	stringRight  = "Right"
+	stringMiddle = "Middle"
+)

event_stringers.go

@@ -0,0 +1,60 @@
+// Copyright 2026 The gogpu Authors
+// SPDX-License-Identifier: MIT
+
+package gpucontext
+
+import "strings"
+
+// String returns the mouse button name for debugging.
+//
+// The names for the extra buttons match [Button.String]: X1 and X2. Values
+// outside the defined buttons are reported as Unknown.
+func (b MouseButton) String() string {
+	switch b {
+	case MouseButtonLeft:
+		return stringLeft
+	case MouseButtonRight:
+		return stringRight
+	case MouseButtonMiddle:
+		return stringMiddle
+	case MouseButton4:
+		return "X1"
+	case MouseButton5:
+		return "X2"
+	default:
+		return "Unknown"
+	}
+}
+
+// String returns a human-readable representation of the modifier keys.
+//
+// Combined modifiers are ordered as Ctrl, Alt, Shift, Super, CapsLock, and
+// NumLock, matching the gogpu/ui event convention. Unknown bits are ignored,
+// also matching the gogpu/ui event convention; a value containing only unknown
+// bits therefore produces an empty string.
+func (m Modifiers) String() string {
+	if m == 0 {
+		return stringNone
+	}
+
+	parts := make([]string, 0, 6)
+	if m&ModControl != 0 {
+		parts = append(parts, "Ctrl")
+	}
+	if m&ModAlt != 0 {
+		parts = append(parts, "Alt")
+	}
+	if m&ModShift != 0 {
+		parts = append(parts, "Shift")
+	}
+	if m&ModSuper != 0 {
+		parts = append(parts, "Super")
+	}
+	if m&ModCapsLock != 0 {
+		parts = append(parts, "CapsLock")
+	}
+	if m&ModNumLock != 0 {
+		parts = append(parts, "NumLock")
+	}
+	return strings.Join(parts, "+")
+}

event_stringers_test.go

@@ -0,0 +1,63 @@
+// Copyright 2026 The gogpu Authors
+// SPDX-License-Identifier: MIT
+
+package gpucontext
+
+import "testing"
+
+func TestMouseButtonString(t *testing.T) {
+	tests := []struct {
+		name   string
+		button MouseButton
+		want   string
+	}{
+		{name: "left", button: MouseButtonLeft, want: "Left"},
+		{name: "right", button: MouseButtonRight, want: "Right"},
+		{name: "middle", button: MouseButtonMiddle, want: "Middle"},
+		{name: "button four", button: MouseButton4, want: "X1"},
+		{name: "button five", button: MouseButton5, want: "X2"},
+		{name: "invalid", button: MouseButton(255), want: "Unknown"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := tt.button.String(); got != tt.want {
+				t.Errorf("MouseButton(%d).String() = %q, want %q", tt.button, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestModifiersString(t *testing.T) {
+	const unknown Modifiers = 1 << 6
+
+	tests := []struct {
+		name string
+		mods Modifiers
+		want string
+	}{
+		{name: "zero", mods: 0, want: "None"},
+		{name: "control", mods: ModControl, want: "Ctrl"},
+		{name: "alt", mods: ModAlt, want: "Alt"},
+		{name: "shift", mods: ModShift, want: "Shift"},
+		{name: "super", mods: ModSuper, want: "Super"},
+		{name: "caps lock", mods: ModCapsLock, want: "CapsLock"},
+		{name: "num lock", mods: ModNumLock, want: "NumLock"},
+		{name: "control and shift", mods: ModControl | ModShift, want: "Ctrl+Shift"},
+		{name: "control alt shift", mods: ModControl | ModAlt | ModShift, want: "Ctrl+Alt+Shift"},
+		{name: "all known", mods: ModControl | ModAlt | ModShift | ModSuper | ModCapsLock | ModNumLock, want: "Ctrl+Alt+Shift+Super+CapsLock+NumLock"},
+		// Unknown bits are ignored to stay compatible with gogpu/ui's
+		// event.Modifiers.String implementation.
+		{name: "unknown only", mods: unknown, want: ""},
+		{name: "unknown mixed", mods: ModControl | unknown, want: "Ctrl"},
+		{name: "unknown and all known", mods: ModControl | ModAlt | ModShift | ModSuper | ModCapsLock | ModNumLock | unknown, want: "Ctrl+Alt+Shift+Super+CapsLock+NumLock"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := tt.mods.String(); got != tt.want {
+				t.Errorf("Modifiers(%d).String() = %q, want %q", tt.mods, got, tt.want)
+			}
+		})
+	}
+}

events.go

@@ -491,9 +491,9 @@ func (k Key) String() string {
 	case KeyPageDown:
 		return "PageDown"
 	case KeyLeft:
-		return "Left"
+		return stringLeft
 	case KeyRight:
-		return "Right"
+		return stringRight
 	case KeyUp:
 		return "Up"
 	case KeyDown:

pointer.go

@@ -248,11 +248,11 @@ func (b Button) String() string {
 	case ButtonNone:
 		return stringNone
 	case ButtonLeft:
-		return "Left"
+		return stringLeft
 	case ButtonMiddle:
-		return "Middle"
+		return stringMiddle
 	case ButtonRight:
-		return "Right"
+		return stringRight
 	case ButtonX1:
 		return "X1"
 	case ButtonX2: