fix: update tests and fix SetCursorFromPoint panic

- Rewrite cursor_test.go to use the current GlyphLayout-based API
  instead of the deleted byteOffsetToLineCol function
- Add guard for empty/missing layout slices in SetCursorFromPoint
  to prevent index-out-of-range panic on empty documents
- Add missing Advance field to e2e test GlyphLayout initialization
- Add cmd/pad/pad binary to .gitignore

.gitignore

@@ -8,6 +8,7 @@
 # build files
 *.apk
 *.idsig
+cmd/pad/pad
 
 # IDE
 .idea/

internal/editor/cursor_test.go

@@ -2,22 +2,90 @@ package editor
 
 import (
 	"testing"
+
+	"pad/internal/ui"
 )
 
-// TestByteOffsetToLineCol_Logical verifies that the current logic
-// only handles logical lines (newline-delimited).
-func TestByteOffsetToLineCol_Logical(t *testing.T) {
-	buf := "hello\nworld"
-	// 012345 67890
+// TestCursorPositioning_Basic verifies cursor positioning via GlyphLayout.
+func TestCursorPositioning_Basic(t *testing.T) {
+TheState = NewState()
+TheState.Editor.Buffer = "hello\nworld"
 
-	// Logical line 0: "hello" (0-4), pos 5 is '\n', line 1 starts at 6
-	line, col := byteOffsetToLineCol(buf, 5)
-	if line != 0 || col != 5 {
-		t.Errorf("expected (0, 5) for pos 5, got (%d, %d)", line, col)
+	// Two lines: "hello\n" (bytes 0-5) and "world" (bytes 6-10)
+	// Line 0 glyphs at Y=70, Line 1 glyphs at Y=140
+	TheState.Editor.GlyphLayout = ui.GlyphLayout{
+		ByteOffsets: []int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10},
+		X:           []ui.Dp{10, 20, 30, 40, 50, 10, 20, 30, 40, 50, 60},
+		Y:           []ui.Dp{70, 70, 70, 70, 70, 70, 140, 140, 140, 140, 140},
+		Advance:     []ui.Dp{10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10},
 	}
 
-	line, col = byteOffsetToLineCol(buf, 6)
-	if line != 1 || col != 0 {
-		t.Errorf("expected (1, 0) for pos 6, got (%d, %d)", line, col)
+	// Test tapping on first line near X=30 (glyph index 2, byteOffset 2)
+	SetCursorFromPoint(25, 70)
+	if TheState.Editor.CursorPosition < 0 || TheState.Editor.CursorPosition > len(TheState.Editor.Buffer) {
+		t.Errorf("cursor position %d out of bounds after first tap", TheState.Editor.CursorPosition)
+	}
+
+	// Test tapping on second line
+	SetCursorFromPoint(35, 140)
+	if TheState.Editor.CursorPosition < 0 || TheState.Editor.CursorPosition > len(TheState.Editor.Buffer) {
+		t.Errorf("cursor position %d out of bounds after second tap", TheState.Editor.CursorPosition)
+	}
+}
+
+// TestCursorPositioning_EmptyDocument verifies cursor positioning handles empty documents.
+func TestCursorPositioning_EmptyDocument(t *testing.T) {
+TheState = NewState()
+TheState.Editor.Buffer = ""
+TheState.Editor.GlyphLayout = ui.GlyphLayout{}
+
+	// Should not panic on empty layout
+	SetCursorFromPoint(50, 50)
+
+	if TheState.Editor.CursorPosition != 0 {
+		t.Errorf("expected cursor at 0 for empty document, got %d", TheState.Editor.CursorPosition)
+	}
+}
+
+// TestCursorPositioning_IncompleteLayout verifies cursor positioning handles missing layout slices.
+func TestCursorPositioning_IncompleteLayout(t *testing.T) {
+TheState = NewState()
+TheState.Editor.Buffer = "test"
+	// GlyphLayout with ByteOffsets and X but no Advance (partial data)
+	TheState.Editor.GlyphLayout = ui.GlyphLayout{
+		ByteOffsets: []int{0, 1, 2, 3},
+		X:           []ui.Dp{10, 20, 30, 40},
+		Y:           []ui.Dp{70, 70, 70, 70},
+		// Advance intentionally omitted
+	}
+
+	// Should not panic when Advance is missing
+	SetCursorFromPoint(25, 70)
+}
+
+// TestHandleCursorMove_Bounds verifies cursor movement stays within buffer bounds.
+func TestHandleCursorMove_Bounds(t *testing.T) {
+TheState = NewState()
+TheState.Editor.Buffer = "hello"
+TheState.Editor.CursorPosition = 0
+
+	// Move right 3 times
+	HandleCursorMove(1)
+	HandleCursorMove(1)
+	HandleCursorMove(1)
+	if TheState.Editor.CursorPosition != 3 {
+		t.Errorf("expected cursor at 3, got %d", TheState.Editor.CursorPosition)
+	}
+
+	// Move right past end — should clamp to buffer length
+	HandleCursorMove(10)
+	if TheState.Editor.CursorPosition != len(TheState.Editor.Buffer) {
+		t.Errorf("expected cursor at %d (end of buffer), got %d", len(TheState.Editor.Buffer), TheState.Editor.CursorPosition)
+	}
+
+	// Move left past start — should clamp to 0
+	HandleCursorMove(-100)
+	if TheState.Editor.CursorPosition != 0 {
+		t.Errorf("expected cursor at 0, got %d", TheState.Editor.CursorPosition)
 	}
 }

internal/editor/state.go

@@ -453,7 +453,7 @@ func EditorLayout(screenWidth, screenHeight ui.Dp, wordWrap bool) []ui.Element {
 // SetCursorFromPoint updates the cursor position based on screen coordinates (Dp).
 func SetCursorFromPoint(x, y float64) {
 	layout := TheState.Editor.GlyphLayout
-	if len(layout.ByteOffsets) == 0 {
+	if len(layout.ByteOffsets) == 0 || len(layout.X) == 0 || len(layout.Advance) == 0 {
 		return
 	}
 

internal/test/e2e/cursor_interaction_test.go

@@ -29,6 +29,7 @@ func TestEditorClickToMoveCursor(t *testing.T) {
 		ByteOffsets: []int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11},
 		X:           []ui.Dp{10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120},
 		Y:           []ui.Dp{70, 70, 70, 70, 70, 70, 70, 70, 70, 70, 70, 70},
+		Advance:     []ui.Dp{10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10},
 	}
 
 	// Initial cursor position should be 0 (or end of text, depending on implementation)