From c27b597951820961e65d01a0651469568aad2a12 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Fri, 19 May 2017 19:25:41 +0530
Subject: [PATCH] Fix incorrect implementation of the CSI scroll commands

I was lazy and just assumed they were n indexes, but they actually
scroll the screen without moving the cursor. Fixes #76
---
 kitty/data-types.h |  2 ++
 kitty/parser.c     |  8 ++-----
 kitty/screen.c     | 56 ++++++++++++++++++++++++++++++++++------------
 3 files changed, 46 insertions(+), 20 deletions(-)

diff --git a/kitty/data-types.h b/kitty/data-types.h
index 1306b6b8a..0f6137ef4 100644
--- a/kitty/data-types.h
+++ b/kitty/data-types.h
@@ -376,6 +376,8 @@ void screen_change_default_color(Screen *self, unsigned int which, uint32_t col)
 void screen_alignment_display(Screen *self);
 void screen_reverse_index(Screen *self);
 void screen_index(Screen *self);
+void screen_scroll(Screen *self, unsigned int count);
+void screen_reverse_scroll(Screen *self, unsigned int count);
 void screen_reset(Screen *self);
 void screen_set_tab_stop(Screen *self);
 void screen_tab(Screen *self);
diff --git a/kitty/parser.c b/kitty/parser.c
index b3530a182..ca6195535 100644
--- a/kitty/parser.c
+++ b/kitty/parser.c
@@ -335,11 +335,7 @@ screen_cursor_up2(Screen *s, unsigned int count) { screen_cursor_up(s, count, fa
 static inline void 
 screen_cursor_back1(Screen *s, unsigned int count) { screen_cursor_back(s, count, -1); }
 static inline void 
-screen_indexn(Screen *s, unsigned int count) { for (index_type i=0; i < MAX(1, count); i++) screen_index(s); }
-static inline void 
 screen_tabn(Screen *s, unsigned int count) { for (index_type i=0; i < MAX(1, count); i++) screen_tab(s); }
-static inline void 
-screen_reverse_indexn(Screen *s, unsigned int count) { for (index_type i=0; i < count; i++) screen_reverse_index(s); }
 static inline void
 save_cursor(Screen *s, unsigned int UNUSED param, bool private) {
     if (private) fprintf(stderr, "%s %s", ERROR_PREFIX, "CSI s in private mode not supported");
@@ -488,9 +484,9 @@ dispatch_csi(Screen *screen, PyObject DUMP_UNUSED *dump_callback) {
         case DECSCUSR: 
             CALL_CSI_HANDLER1M(screen_set_cursor, 1); 
         case SU:
-            CALL_CSI_HANDLER1(screen_indexn, 1); 
+            CALL_CSI_HANDLER1(screen_scroll, 1); 
         case SD:
-            CALL_CSI_HANDLER1(screen_reverse_indexn, 1); 
+            CALL_CSI_HANDLER1(screen_reverse_scroll, 1); 
         case DECSTR:
             if (end_modifier == '$') {
                 // DECRQM
diff --git a/kitty/screen.c b/kitty/screen.c
index 4af72edcd..a71880eb5 100644
--- a/kitty/screen.c
+++ b/kitty/screen.c
@@ -582,36 +582,64 @@ screen_cursor_to_column(Screen *self, unsigned int column) {
     }
 }
 
+#define INDEX_UP \
+    linebuf_index(self->linebuf, top, bottom); \
+    if (self->linebuf == self->main_linebuf && bottom == self->lines - 1) { \
+        /* Only add to history when no page margins have been set */ \
+        linebuf_init_line(self->linebuf, bottom); \
+        historybuf_add_line(self->historybuf, self->linebuf->line); \
+        tracker_line_added_to_history(self->change_tracker); \
+    } \
+    linebuf_clear_line(self->linebuf, bottom); \
+    if (bottom - top > self->lines - 1) tracker_update_screen(self->change_tracker); \
+    else tracker_update_line_range(self->change_tracker, top, bottom); 
+
 void 
 screen_index(Screen *self) {
     // Move cursor down one line, scrolling screen if needed
     unsigned int top = self->margin_top, bottom = self->margin_bottom;
     if (self->cursor->y == bottom) {
-        linebuf_index(self->linebuf, top, bottom);
-        if (self->linebuf == self->main_linebuf && bottom == self->lines - 1) {
-            // Only add to history when no page margins have been set
-            linebuf_init_line(self->linebuf, bottom);
-            historybuf_add_line(self->historybuf, self->linebuf->line);
-            tracker_line_added_to_history(self->change_tracker);
-        }
-        linebuf_clear_line(self->linebuf, bottom);
-        if (bottom - top > self->lines - 1) tracker_update_screen(self->change_tracker);
-        else tracker_update_line_range(self->change_tracker, top, bottom);
+        INDEX_UP;
     } else screen_cursor_down(self, 1);
 }
 
+void 
+screen_scroll(Screen *self, unsigned int count) {
+    // Scroll the screen up by count lines, not moving the cursor
+    count = MIN(self->lines, count);
+    unsigned int top = self->margin_top, bottom = self->margin_bottom;
+    while (count > 0) {
+        count--;
+        INDEX_UP;
+    }
+}
+
+#define INDEX_DOWN \
+    linebuf_reverse_index(self->linebuf, top, bottom); \
+    linebuf_clear_line(self->linebuf, top); \
+    if (bottom - top > self->lines - 1) tracker_update_screen(self->change_tracker); \
+    else tracker_update_line_range(self->change_tracker, top, bottom);
+
 void 
 screen_reverse_index(Screen *self) {
     // Move cursor up one line, scrolling screen if needed
     unsigned int top = self->margin_top, bottom = self->margin_bottom;
     if (self->cursor->y == top) {
-        linebuf_reverse_index(self->linebuf, top, bottom);
-        linebuf_clear_line(self->linebuf, top);
-        if (bottom - top > self->lines - 1) tracker_update_screen(self->change_tracker);
-        else tracker_update_line_range(self->change_tracker, top, bottom);
+        INDEX_DOWN;
     } else screen_cursor_up(self, 1, false, -1);
 }
 
+void 
+screen_reverse_scroll(Screen *self, unsigned int count) {
+    // Scroll the screen down by count lines, not moving the cursor
+    count = MIN(self->lines, count);
+    unsigned int top = self->margin_top, bottom = self->margin_bottom;
+    while (count > 0) {
+        count--;
+        INDEX_DOWN;
+    }
+}
+
 
 void 
 screen_carriage_return(Screen *self) {