fix(note-editor): allow toolbar button cursor at extremities

AnkiDroid/src/main/java/com/ichi2/anki/NoteEditorFragment.kt

@@ -2439,8 +2439,8 @@ class NoteEditorFragment :
             CustomToolbarButton(
                 index = currentButtonIndex,
                 buttonText = buttonText.ifEmpty { currentButton.buttonText },
-                prefix = prefix.ifEmpty { currentButton.prefix },
-                suffix = suffix.ifEmpty { currentButton.suffix },
+                prefix = prefix,
+                suffix = suffix,
             )
 
         saveToolbarButtons(toolbarButtons)
@@ -2565,6 +2565,14 @@ class NoteEditorFragment :
             )
         }
         editToolbarDialog.show()
+
+        fun updateSaveButton() {
+            editToolbarDialog.positiveButton.isEnabled = !et.text.isNullOrBlank() || !et2.text.isNullOrBlank()
+        }
+
+        et.doAfterTextChanged { updateSaveButton() }
+        et2.doAfterTextChanged { updateSaveButton() }
+        updateSaveButton()
     }
 
     private fun setNoteTypePosition() {

AnkiDroid/src/test/java/com/ichi2/anki/noteeditor/NoteEditorToolbarTest.kt

@@ -0,0 +1,111 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package com.ichi2.anki.noteeditor
+
+import android.view.View
+import android.view.ViewGroup
+import androidx.appcompat.app.AlertDialog
+import androidx.core.content.edit
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import com.ichi2.anki.NoteEditorActivity
+import com.ichi2.anki.RobolectricTest
+import com.ichi2.anki.common.destinations.NoteEditorDestination
+import com.ichi2.anki.common.destinations.toIntent
+import com.ichi2.anki.common.preferences.sharedPrefs
+import com.ichi2.anki.databinding.DialogNoteEditorToolbarEditCustomItemBinding
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.annotation.GraphicsMode
+import org.robolectric.shadows.ShadowDialog
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertNotNull
+import kotlin.test.assertTrue
+
+@RunWith(AndroidJUnit4::class)
+@GraphicsMode(GraphicsMode.Mode.NATIVE)
+class NoteEditorToolbarTest : RobolectricTest() {
+    @Test
+    fun `clearing the text before the cursor saves a button that inserts after the cursor`() {
+        checkEditedButton(prefix = "", suffix = "<br>", expectedCursor = 0)
+    }
+
+    @Test
+    fun `clearing the text after the cursor saves a button that inserts before the cursor`() {
+        checkEditedButton(prefix = "<br>", suffix = "", expectedCursor = 4)
+    }
+
+    @Test
+    fun `editing requires text on at least one side of the cursor`() {
+        val toolbar = createToolbar()
+        toolbar.findViewWithTag<View>("1").performLongClick()
+        val dialog = ShadowDialog.getLatestDialog() as AlertDialog
+        val binding = dialog.binding
+        val before = binding.noteEditorToolbarBefore
+        val after = binding.noteEditorToolbarAfter
+        val save = dialog.getButton(AlertDialog.BUTTON_POSITIVE)
+
+        assertTrue(save.isEnabled)
+        before.setText("")
+        assertTrue(save.isEnabled)
+        after.setText("")
+        assertFalse(save.isEnabled, "Both fields empty must disable Save")
+
+        after.setText("<br>")
+        assertTrue(save.isEnabled)
+        after.setText(" ")
+        assertFalse(save.isEnabled, "Whitespace alone must not enable Save")
+        before.setText("<br>")
+        assertTrue(save.isEnabled)
+        dialog.dismiss()
+    }
+
+    private fun checkEditedButton(
+        prefix: String,
+        suffix: String,
+        expectedCursor: Int,
+    ) {
+        val toolbar = createToolbar()
+        toolbar.findViewWithTag<View>("1").performLongClick()
+        val dialog = ShadowDialog.getLatestDialog() as AlertDialog
+        val binding = dialog.binding
+        binding.noteEditorToolbarBefore.setText(prefix)
+        binding.noteEditorToolbarAfter.setText(suffix)
+        clickAlertDialogButton { getButton(AlertDialog.BUTTON_POSITIVE) }
+
+        var formatted: Toolbar.StringFormat? = null
+        toolbar.formatListener = Toolbar.TextFormatListener { formatted = it.format("") }
+        toolbar.findViewWithTag<View>("1").performClick()
+        val result = assertNotNull(formatted)
+        assertEquals("<br>", result.result)
+        assertEquals(expectedCursor, result.selectionStart)
+        assertEquals(expectedCursor, result.selectionEnd)
+
+        // Reopening reads the saved button from preferences.
+        toolbar.findViewWithTag<View>("1").performLongClick()
+        val reopened = ShadowDialog.getLatestDialog() as AlertDialog
+        val reopenedBinding = reopened.binding
+        assertEquals(prefix, reopenedBinding.noteEditorToolbarBefore.text.toString())
+        assertEquals(suffix, reopenedBinding.noteEditorToolbarAfter.text.toString())
+        reopened.dismiss()
+    }
+
+    private fun createToolbar(): Toolbar {
+        // Start with both fields populated so saving must clear an existing value.
+        targetContext.sharedPrefs().edit {
+            putStringSet(
+                "note_editor_custom_buttons",
+                CustomToolbarButton.toStringSet(arrayListOf(CustomToolbarButton(0, "BR", "<b>", "</b>"))),
+            )
+        }
+        val editor =
+            startRegularActivity<NoteEditorActivity>(NoteEditorDestination.AddNote().toIntent()).getNoteEditorFragment()
+        return editor.binding.editorToolbar
+    }
+
+    private val AlertDialog.binding: DialogNoteEditorToolbarEditCustomItemBinding
+        get() {
+            val customPanel = assertNotNull(findViewById<ViewGroup>(androidx.appcompat.R.id.custom))
+            return DialogNoteEditorToolbarEditCustomItemBinding.bind(customPanel.getChildAt(0))
+        }
+}