misc: Add fallback for no XTerm alternate screen

This cannot be determined at runtime without terminfo.

3 files changed, 14 insertions, 0 deletions

diff --git a/README.txt b/README.txt
index bdb0e43..50a13ae 100644
--- a/README.txt
+++ b/README.txt
@@ -93,6 +93,9 @@ Bonus example:
     -DDFM_NO_COLOR \
     -DDFM_COL_NAV="VT_SGR(34,7)"
 
+NOTE: If you are building for an environment without support for the XTerm
+alternate screen, add -DDFM_CLEAR_EDIT to your configure flags.
+
 
 CONFIGURATION
 ________________________________________________________________________________
diff --git a/config.h.in b/config.h.in
index ece0ddc..d4f1218 100644
--- a/config.h.in
+++ b/config.h.in
@@ -63,6 +63,12 @@
 #define DFM_SHOW_HIDDEN 0
 
 //
+// Clear screen on exit.
+// Useful when XTerm alt screen is unavailable.
+//
+// #define DFM_CLEAR_EXIT
+
+//
 // Disable colors.
 // Uncomment to disable all colors.
 //
diff --git a/lib/vt.h b/lib/vt.h
index 9248a6c..cb29e0b 100644
--- a/lib/vt.h
+++ b/lib/vt.h
@@ -63,8 +63,13 @@
 // XTerm Alternate Screen.
 // https://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h2-The-Alternate-Screen-Buffer
 //
+#ifdef DFM_CLEAR_EXIT
+#define VT_ALT_SCREEN_Y  VT_ED0
+#define VT_ALT_SCREEN_N  VT_ED0
+#else
 #define VT_ALT_SCREEN_Y  VT_ESC "[?1049h"
 #define VT_ALT_SCREEN_N  VT_ESC "[?1049l"
+#endif
 
 //
 // Synchronized Updates.