Initial patterm project

internal/app/viewport_renderer_test.go

@@ -0,0 +1,63 @@
+package app
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestViewportRendererShiftsCursor(t *testing.T) {
+	vr := newViewportRenderer(newTerminalLayout(120, 40))
+	got := string(vr.Render([]byte("\x1b[H")))
+	if got != "\x1b[2;1H" {
+		t.Fatalf("CUP home: got %q", got)
+	}
+}
+
+func TestViewportRendererSwallowsAltScreenToggles(t *testing.T) {
+	vr := newViewportRenderer(newTerminalLayout(120, 40))
+	got := string(vr.Render([]byte("a\x1b[?1049hb\x1b[?1049lc")))
+	if got != "abc" {
+		t.Fatalf("alt-screen toggles: got %q", got)
+	}
+}
+
+func TestViewportRendererClearScreenIsViewportOnly(t *testing.T) {
+	vr := newViewportRenderer(newTerminalLayout(20, 5))
+	got := string(vr.Render([]byte("\x1b[2J")))
+	if strings.Contains(got, "\x1b[2J") {
+		t.Fatalf("host clear-screen leaked through: %q", got)
+	}
+	if strings.Count(got, "                    ") != 3 {
+		t.Fatalf("clear rows: got %q", got)
+	}
+	if !strings.Contains(got, "\x1b[2;1H") || !strings.Contains(got, "\x1b[4;1H") {
+		t.Fatalf("clear did not target viewport rows: %q", got)
+	}
+}
+
+func TestViewportRendererClearLineUsesEraseChars(t *testing.T) {
+	vr := newViewportRenderer(newTerminalLayout(20, 5))
+	got := string(vr.Render([]byte("\x1b[K")))
+	if strings.Contains(got, "\x1b[K") {
+		t.Fatalf("host clear-line leaked through: %q", got)
+	}
+	if got != "\x1b[20X" {
+		t.Fatalf("clear-line: got %q want ECH", got)
+	}
+}
+
+func TestViewportRendererClearLineStopsAtViewportRight(t *testing.T) {
+	vr := newViewportRenderer(newTerminalLayout(20, 5))
+	got := string(vr.Render([]byte("\x1b[10G\x1b[K")))
+	if !strings.HasSuffix(got, "\x1b[11X") {
+		t.Fatalf("clear-line from col 10 should erase 11 cells: %q", got)
+	}
+}
+
+func TestViewportRendererTracksPrintableCursor(t *testing.T) {
+	vr := newViewportRenderer(newTerminalLayout(20, 5))
+	got := string(vr.Render([]byte("hello\x1b[K")))
+	if !strings.HasSuffix(got, "\x1b[15X") {
+		t.Fatalf("clear-line after five chars should erase 15 cells: %q", got)
+	}
+}