From d5922b3f25287cb826fe166485c446de94400ce2 Mon Sep 17 00:00:00 2001
From: Jesse Luehrs <doy@tozt.net>
Date: Mon, 14 Apr 2014 18:50:43 -0400
Subject: implement the alternate screen buffer

---
 display.c | 33 +++++++++++++++++++++++++++++++++
 display.h |  2 ++
 parser.c  |  6 ++++++
 parser.l  |  6 ++++++
 term.h    |  2 ++
 5 files changed, 49 insertions(+)

diff --git a/display.c b/display.c
index bdf0c77..ce3cec8 100644
--- a/display.c
+++ b/display.c
@@ -12,6 +12,7 @@ void runes_display_init(RunesTerm *t)
     runes_window_backend_get_size(t, &x, &y);
 
     t->cr = NULL;
+    t->alternate_cr = NULL;
 
     t->colors[0] = cairo_pattern_create_rgb(0.0, 0.0, 0.0);
     t->colors[1] = cairo_pattern_create_rgb(1.0, 0.0, 0.0);
@@ -331,6 +332,38 @@ void runes_display_restore_cursor(RunesTerm *t)
     t->col = t->saved_col;
 }
 
+void runes_display_use_alternate_buffer(RunesTerm *t)
+{
+    int x, y;
+
+    if (t->alternate) {
+        return;
+    }
+
+    runes_display_save_cursor(t);
+    t->alternate = 1;
+    t->alternate_cr = t->cr;
+    t->cr = NULL;
+    x = t->xpixel;
+    y = t->ypixel;
+    t->xpixel = -1;
+    t->ypixel = -1;
+    runes_display_set_window_size(t, x, y);
+}
+
+void runes_display_use_normal_buffer(RunesTerm *t)
+{
+    if (!t->alternate) {
+        return;
+    }
+
+    runes_display_restore_cursor(t);
+    t->alternate = 0;
+    cairo_destroy(t->cr);
+    t->cr = t->alternate_cr;
+    t->alternate_cr = NULL;
+}
+
 static cairo_scaled_font_t *runes_display_make_font(RunesTerm *t)
 {
     cairo_font_face_t *font_face;
diff --git a/display.h b/display.h
index 4efddef..fa989c5 100644
--- a/display.h
+++ b/display.h
@@ -29,5 +29,7 @@ void runes_display_hide_cursor(RunesTerm *t);
 void runes_display_visual_bell(RunesTerm *t);
 void runes_display_save_cursor(RunesTerm *t);
 void runes_display_restore_cursor(RunesTerm *t);
+void runes_display_use_alternate_buffer(RunesTerm *t);
+void runes_display_use_normal_buffer(RunesTerm *t);
 
 #endif
diff --git a/parser.c b/parser.c
index 55e7482..ef95462 100644
--- a/parser.c
+++ b/parser.c
@@ -2330,6 +2330,9 @@ static void runes_parser_handle_sm(RunesTerm *t, char *buf, size_t len)
             case 25:
                 runes_display_show_cursor(t);
                 break;
+            case 1049:
+                runes_display_use_alternate_buffer(t);
+                break;
             default:
                 fprintf(
                     stderr, "unknown SM parameter: %c%d\n",
@@ -2359,6 +2362,9 @@ static void runes_parser_handle_rm(RunesTerm *t, char *buf, size_t len)
             case 25:
                 runes_display_hide_cursor(t);
                 break;
+            case 1049:
+                runes_display_use_normal_buffer(t);
+                break;
             default:
                 fprintf(
                     stderr, "unknown RM parameter: %c%d\n",
diff --git a/parser.l b/parser.l
index 0fb8c1d..2bf7206 100644
--- a/parser.l
+++ b/parser.l
@@ -359,6 +359,9 @@ static void runes_parser_handle_sm(RunesTerm *t, char *buf, size_t len)
             case 25:
                 runes_display_show_cursor(t);
                 break;
+            case 1049:
+                runes_display_use_alternate_buffer(t);
+                break;
             default:
                 fprintf(
                     stderr, "unknown SM parameter: %c%d\n",
@@ -388,6 +391,9 @@ static void runes_parser_handle_rm(RunesTerm *t, char *buf, size_t len)
             case 25:
                 runes_display_hide_cursor(t);
                 break;
+            case 1049:
+                runes_display_use_normal_buffer(t);
+                break;
             default:
                 fprintf(
                     stderr, "unknown RM parameter: %c%d\n",
diff --git a/term.h b/term.h
index 4813097..6bcc07c 100644
--- a/term.h
+++ b/term.h
@@ -7,6 +7,7 @@ struct runes_term {
 
     cairo_t *cr;
     cairo_t *backend_cr;
+    cairo_t *alternate_cr;
     uv_loop_t *loop;
 
     cairo_pattern_t *bgcolor;
@@ -21,6 +22,7 @@ struct runes_term {
 
     char show_cursor;
     char focused;
+    char alternate;
 
     cairo_pattern_t *colors[8];
 
-- 
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