tui: Improve scrolling mechanism.

Respect the BGE flag from terminfo rather than guessing that it is
always off. Emit DECLRMM and DECSLRM (or equivalent) to properly define
the scroll rectangle.

1 files changed, 93 insertions, 15 deletions

diff --git a/src/nvim/tui/tui.c b/src/nvim/tui/tui.c
index 5614a1738f..736d50ee8b 100644
--- a/src/nvim/tui/tui.c
+++ b/src/nvim/tui/tui.c
@@ -83,6 +83,9 @@ typedef struct {
   kvec_t(Rect) invalid_regions;
   int out_fd;
   bool scroll_region_is_full_screen;
+  bool can_change_scroll_region;
+  bool can_set_lr_margin;
+  bool can_set_left_right_margin;
   bool mouse_enabled;
   bool busy;
   cursorentry_T cursor_shapes[SHAPE_IDX_COUNT];
@@ -92,6 +95,7 @@ typedef struct {
   struct {
     int enable_mouse, disable_mouse;
     int enable_bracketed_paste, disable_bracketed_paste;
+    int enable_lr_margin, disable_lr_margin;
     int set_rgb_foreground, set_rgb_background;
     int set_cursor_color;
     int enable_focus_reporting, disable_focus_reporting;
@@ -157,6 +161,8 @@ static void terminfo_start(UI *ui)
   data->unibi_ext.set_cursor_color = -1;
   data->unibi_ext.enable_bracketed_paste = -1;
   data->unibi_ext.disable_bracketed_paste = -1;
+  data->unibi_ext.enable_lr_margin = -1;
+  data->unibi_ext.disable_lr_margin = -1;
   data->unibi_ext.enable_focus_reporting = -1;
   data->unibi_ext.disable_focus_reporting = -1;
   data->unibi_ext.resize_screen = -1;
@@ -171,6 +177,13 @@ static void terminfo_start(UI *ui)
     data->ut = unibi_dummy();
   }
   fix_terminfo(data);
+  data->can_change_scroll_region =
+    !!unibi_get_str(data->ut, unibi_change_scroll_region);
+  data->can_set_lr_margin =
+    !!unibi_get_str(data->ut, unibi_set_lr_margin);
+  data->can_set_left_right_margin =
+    !!unibi_get_str(data->ut, unibi_set_left_margin_parm)
+    && !!unibi_get_str(data->ut, unibi_set_right_margin_parm);
   // Set 't_Co' from the result of unibilium & fix_terminfo.
   t_colors = unibi_get_num(data->ut, unibi_max_colors);
   // Enter alternate screen and clear
@@ -426,9 +439,46 @@ static void clear_region(UI *ui, int top, int bot, int left, int right)
   unibi_goto(ui, grid->row, grid->col);
 }
 
+static bool can_use_scroll(UI * ui)
+{
+  TUIData *data = ui->data;
+  UGrid *grid = &data->grid;
+
+  return data->scroll_region_is_full_screen
+    || (data->can_change_scroll_region
+        && ((grid->left == 0 && grid->right == ui->width - 1)
+            || data->can_set_lr_margin
+            || data->can_set_left_right_margin));
+}
+
+static void set_scroll_region(UI *ui)
+{
+  TUIData *data = ui->data;
+  UGrid *grid = &data->grid;
+
+  data->params[0].i = grid->top;
+  data->params[1].i = grid->bot;
+  unibi_out(ui, unibi_change_scroll_region);
+  if (grid->left != 0 || grid->right != ui->width - 1) {
+    unibi_out(ui, data->unibi_ext.enable_lr_margin);
+    if (data->can_set_lr_margin) {
+      data->params[0].i = grid->left;
+      data->params[1].i = grid->right;
+      unibi_out(ui, unibi_set_lr_margin);
+    } else {
+      data->params[0].i = grid->left;
+      unibi_out(ui, unibi_set_left_margin_parm);
+      data->params[0].i = grid->right;
+      unibi_out(ui, unibi_set_right_margin_parm);
+    }
+  }
+  unibi_goto(ui, grid->row, grid->col);
+}
+
 static void reset_scroll_region(UI *ui)
 {
   TUIData *data = ui->data;
+  UGrid *grid = &data->grid;
 
   if (0 <= data->unibi_ext.reset_scroll_region) {
     unibi_out(ui, data->unibi_ext.reset_scroll_region);
@@ -437,6 +487,20 @@ static void reset_scroll_region(UI *ui)
     data->params[1].i = ui->height - 1;
     unibi_out(ui, unibi_change_scroll_region);
   }
+  if (grid->left != 0 || grid->right != ui->width - 1) {
+    if (data->can_set_lr_margin) {
+      data->params[0].i = 0;
+      data->params[1].i = ui->width - 1;
+      unibi_out(ui, unibi_set_lr_margin);
+    } else {
+      data->params[0].i = 0;
+      unibi_out(ui, unibi_set_left_margin_parm);
+      data->params[0].i = ui->width - 1;
+      unibi_out(ui, unibi_set_right_margin_parm);
+    }
+    unibi_out(ui, data->unibi_ext.disable_lr_margin);
+  }
+  unibi_goto(ui, grid->row, grid->col);
 }
 
 static void tui_resize(UI *ui, Integer width, Integer height)
@@ -650,19 +714,22 @@ static void tui_scroll(UI *ui, Integer count)
   int clear_top, clear_bot;
   ugrid_scroll(grid, (int)count, &clear_top, &clear_bot);
 
-  if (data->scroll_region_is_full_screen || 0 <= unibi_change_scroll_region) {
+  if (can_use_scroll(ui)) {
+    bool scroll_clears_to_current_colour =
+      unibi_get_bool(data->ut, unibi_back_color_erase);
+
     // Change terminal scroll region and move cursor to the top
     if (!data->scroll_region_is_full_screen) {
-      data->params[0].i = grid->top;
-      data->params[1].i = grid->bot;
-      unibi_out(ui, unibi_change_scroll_region);
+      set_scroll_region(ui);
     }
     unibi_goto(ui, grid->top, grid->left);
     // also set default color attributes or some terminals can become funny
-    HlAttrs clear_attrs = EMPTY_ATTRS;
-    clear_attrs.foreground = grid->fg;
-    clear_attrs.background = grid->bg;
-    update_attrs(ui, clear_attrs);
+    if (scroll_clears_to_current_colour) {
+      HlAttrs clear_attrs = EMPTY_ATTRS;
+      clear_attrs.foreground = grid->fg;
+      clear_attrs.background = grid->bg;
+      update_attrs(ui, clear_attrs);
+    }
 
     if (count > 0) {
       if (count == 1) {
@@ -686,11 +753,9 @@ static void tui_scroll(UI *ui, Integer count)
     }
     unibi_goto(ui, grid->row, grid->col);
 
-    if (grid->bg != -1) {
-      // Update the cleared area of the terminal if its builtin scrolling
-      // facility was used and the background color is not the default. This is
-      // required because scrolling may leave wrong background in the cleared
-      // area.
+    if (!scroll_clears_to_current_colour) {
+      // This is required because scrolling will leave wrong background in the
+      // cleared area on non-bge terminals.
       clear_region(ui, clear_top, clear_bot, grid->left, grid->right);
     }
   } else {
@@ -1025,13 +1090,21 @@ static void fix_terminfo(TUIData *data)
     unibi_set_if_empty(ut, unibi_cursor_invisible, "\x1b[?25l");
     unibi_set_if_empty(ut, unibi_flash_screen, "\x1b[?5h$<100/>\x1b[?5l");
     unibi_set_if_empty(ut, unibi_exit_attribute_mode, "\x1b(B\x1b[m");
+    unibi_set_if_empty(ut, unibi_set_tb_margin, "\x1b[%i%p1%d;%p2%dr");
+    unibi_set_if_empty(ut, unibi_set_lr_margin, "\x1b[%i%p1%d;%p2%ds");
+    unibi_set_if_empty(ut, unibi_set_left_margin_parm, "\x1b[%i%p1%ds");
+    unibi_set_if_empty(ut, unibi_set_right_margin_parm, "\x1b[%i;%p2%ds");
     unibi_set_if_empty(ut, unibi_change_scroll_region, "\x1b[%i%p1%d;%p2%dr");
     unibi_set_if_empty(ut, unibi_clear_screen, "\x1b[H\x1b[2J");
     unibi_set_if_empty(ut, unibi_from_status_line, "\x07");
-    data->unibi_ext.reset_scroll_region = (int)unibi_add_ext_str(ut, NULL,
-      "\x1b[r");
+    unibi_set_bool(ut, unibi_back_color_erase, true);
   }
 
+  data->unibi_ext.enable_lr_margin = (int)unibi_add_ext_str(ut, NULL,
+      "\x1b[?69h");
+  data->unibi_ext.disable_lr_margin = (int)unibi_add_ext_str(ut, NULL,
+      "\x1b[?69l");
+
   data->unibi_ext.enable_bracketed_paste = (int)unibi_add_ext_str(ut, NULL,
       "\x1b[?2004h");
   data->unibi_ext.disable_bracketed_paste = (int)unibi_add_ext_str(ut, NULL,
@@ -1068,6 +1141,11 @@ static void fix_terminfo(TUIData *data)
       "\x1b[8;%p1%d;%p2%dt");
   }
 
+  if (data->term == kTermXTerm || data->term == kTermRxvt) {
+    data->unibi_ext.reset_scroll_region = (int)unibi_add_ext_str(ut, NULL,
+      "\x1b[r");
+  }
+
 end:
   // Fill some empty slots with common terminal strings
   if (data->term == kTermiTerm) {