debugui: improve tests for control IDs

Closes #18

Author: hajimehoshi

control.go

@@ -152,9 +152,9 @@ func (c *Context) Label(text string) {
 	})
 }
 
-func (c *Context) button(label string, idStr string, opt option) bool {
+func (c *Context) button(label string, idStr string, opt option) (controlID, bool) {
 	id := c.idFromString(idStr)
-	return c.control(id, opt, func(bounds image.Rectangle) Response {
+	return id, c.control(id, opt, func(bounds image.Rectangle) Response {
 		var res Response
 		// handle click
 		if inpututil.IsMouseButtonJustPressed(ebiten.MouseButtonLeft) && c.focus == id {

export_test.go

@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: 2025 The Ebitengine Authors
+
+package debugui
+
+import "strings"
+
+type ControlID = controlID
+
+func (c *Context) ButtonID(label string) ControlID {
+	label, idStr, _ := strings.Cut(label, idSeparator)
+	id, _ := c.button(label, idStr, optionAlignCenter)
+	return id
+}

id_test.go

@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: 2025 The Ebitengine Authors
+
+package debugui_test
+
+import (
+	"image"
+	"testing"
+
+	"github.com/ebitengine/debugui"
+)
+
+func TestMultipleButtonsInForLoop(t *testing.T) {
+	d := debugui.New()
+	d.Update(func(ctx *debugui.Context) {
+		ctx.Window("Window", image.Rect(0, 0, 100, 100), func(layout debugui.ContainerLayout) {
+			var id debugui.ControlID
+			for range 10 {
+				id2 := ctx.ButtonID("a")
+				if id2 == 0 {
+					t.Errorf("Caller() returned 0")
+					continue
+				}
+				if id == 0 {
+					id = id2
+					continue
+				}
+				if id != id2 {
+					t.Errorf("Caller() returned different values: %d and %d", id, id2)
+				}
+			}
+			if id == 0 {
+				t.Errorf("Caller() returned 0")
+			}
+		})
+	})
+}
+
+func TestMultipleButtonsOnOneLine(t *testing.T) {
+	d := debugui.New()
+	d.Update(func(ctx *debugui.Context) {
+		ctx.Window("Window", image.Rect(0, 0, 100, 100), func(layout debugui.ContainerLayout) {
+			idA := ctx.ButtonID("a")
+			idB := ctx.ButtonID("b")
+			if idA == idB {
+				t.Errorf("Button() returned the same value twice: %d", idA)
+			}
+			idC, idD := ctx.ButtonID("c"), ctx.ButtonID("d")
+			if idC == idD {
+				t.Errorf("Button() returned the same value twice: %d", idC)
+			}
+		})
+	})
+}

internal/caller/caller.go

@@ -18,7 +18,7 @@ var (
 )
 
 // Caller returns a program counter of the caller outside of this module.
-func Caller() (pc uintptr) {
+func Caller() uintptr {
 	debugUIFileDirOnce.Do(func() {
 		pkg, err := build.Default.Import("github.com/ebitengine/debugui", "", build.FindOnly)
 		if err != nil {
@@ -40,7 +40,8 @@ func Caller() (pc uintptr) {
 		// The file should be with a slash, but just in case, convert it.
 		file = filepath.ToSlash(file)
 
-		if strings.HasSuffix(path.Base(file), "_test.go") {
+		// TODO: This is heuristic. Use a file set.
+		if strings.HasSuffix(path.Base(file), "_test.go") && path.Base(file) != "export_test.go" {
 			return pc
 		}
 

internal/caller/caller_test.go

@@ -12,7 +12,8 @@ const idSeparator = "\x00"
 
 func (c *Context) Button(label string) bool {
 	label, idStr, _ := strings.Cut(label, idSeparator)
-	return c.button(label, idStr, optionAlignCenter)
+	_, result := c.button(label, idStr, optionAlignCenter)
+	return result
 }
 
 func (c *Context) TextBox(buf *string) Response {