Improve large file support

Disable absolute line numbers for large files (currently
anything bigger than 32MiB). This speeds up moving around
with for example nn% since no new lines need to be calculated.

Of course movements like :nn will be unaffected.

The optimizations can be disabled by explicitly enabling
absolute line numbers as in :set number

4 files changed, 31 insertions, 8 deletions

diff --git a/ui-curses.c b/ui-curses.c
index 671fa61..1bc145a 100644
--- a/ui-curses.c
+++ b/ui-curses.c
@@ -619,7 +619,7 @@ static bool ui_window_draw_sidebar(UiCursesWin *win) {
 				if (win->options & UI_OPTION_LINE_NUMBERS_ABSOLUTE) {
 					mvwprintw(win->winside, i, 0, "%*u", sidebar_width-1, l->lineno);
 				} else if (win->options & UI_OPTION_LINE_NUMBERS_RELATIVE) {
-					size_t rel = l->lineno;
+					size_t rel = (win->options & UI_OPTION_LARGE_FILE) ? 0 : l->lineno;
 					if (l->lineno > cursor_lineno)
 						rel = l->lineno - cursor_lineno;
 					else if (l->lineno < cursor_lineno)
@@ -643,7 +643,6 @@ static void ui_window_draw_status(UiWin *w) {
 	bool focused = uic->selwin == win;
 	const char *filename = vis_file_name(win->file);
 	const char *status = vis_mode_status(vis);
-	CursorPos pos = view_cursor_getpos(win->view);
 	wattrset(win->winstatus, focused ? A_REVERSE|A_BOLD : A_REVERSE);
 	mvwhline(win->winstatus, 0, 0, ' ', win->width);
 	mvwprintw(win->winstatus, 0, 0, "%s %s %s %s",
@@ -651,11 +650,15 @@ static void ui_window_draw_status(UiWin *w) {
 	          filename ? filename : "[No Name]",
 	          text_modified(vis_file_text(win->file)) ? "[+]" : "",
 	          vis_macro_recording(vis) ? "recording": "");
-	char buf[win->width + 1];
-	int len = snprintf(buf, win->width, "%zd, %zd", pos.line, pos.col);
-	if (len > 0) {
-		buf[len] = '\0';
-		mvwaddstr(win->winstatus, 0, win->width - len - 1, buf);
+
+	if (!(win->options & UI_OPTION_LARGE_FILE)) {
+		CursorPos pos = view_cursor_getpos(win->view);
+		char buf[win->width + 1];
+		int len = snprintf(buf, win->width, "%zd, %zd", pos.line, pos.col);
+		if (len > 0) {
+			buf[len] = '\0';
+			mvwaddstr(win->winstatus, 0, win->width - len - 1, buf);
+		}
 	}
 }
 
diff --git a/ui.h b/ui.h
index 314bc9d..76de366 100644
--- a/ui.h
+++ b/ui.h
@@ -25,6 +25,7 @@ enum UiOption {
 	UI_OPTION_CURSOR_LINE = 1 << 7,
 	UI_OPTION_STATUSBAR = 1 << 8,
 	UI_OPTION_ONELINE = 1 << 9,
+	UI_OPTION_LARGE_FILE = 1 << 10,
 };
 
 enum UiStyles {
diff --git a/view.c b/view.c
index 4182cc5..abbc3a5 100644
--- a/view.c
+++ b/view.c
@@ -86,6 +86,7 @@ struct View {
 	lua_State *lua;     /* lua state used for syntax highlighting */
 	char *lexer_name;
 	bool need_update;   /* whether view has been redrawn */
+	bool large_file;    /* optimize for displaying large files */
 	int colorcolumn;
 };
 
@@ -305,7 +306,7 @@ static void view_clear(View *view) {
 
 	view->start_last = view->start;
 	view->topline = view->lines;
-	view->topline->lineno = text_lineno_by_pos(view->text, view->start);
+	view->topline->lineno = view->large_file ? 1 : text_lineno_by_pos(view->text, view->start);
 	view->lastline = view->topline;
 
 	size_t line_size = sizeof(Line) + view->width*sizeof(Cell);
@@ -1012,10 +1013,17 @@ void view_options_set(View *view, enum UiOption options) {
 		[SYNTAX_SYMBOL_EOL]      = UI_OPTION_SYMBOL_EOL,
 		[SYNTAX_SYMBOL_EOF]      = UI_OPTION_SYMBOL_EOF,
 	};
+
 	for (int i = 0; i < LENGTH(mapping); i++) {
 		view->symbols[i] = (options & mapping[i]) ? &symbols_default[i] :
 			&symbols_none[i];
 	}
+
+	if (options & UI_OPTION_LINE_NUMBERS_ABSOLUTE)
+		options &= ~UI_OPTION_LARGE_FILE;
+
+	view->large_file = (options & UI_OPTION_LARGE_FILE);
+
 	if (view->ui)
 		view->ui->options_set(view->ui, options);
 }
diff --git a/vis.c b/vis.c
index 4c5124a..32deb80 100644
--- a/vis.c
+++ b/vis.c
@@ -43,6 +43,9 @@
 #include "util.h"
 #include "vis-core.h"
 
+/* enable large file optimization for files larger than: */
+#define LARGE_FILE (1 << 25)
+
 static Macro *macro_get(Vis *vis, enum VisMacro m);
 static void macro_replay(Vis *vis, const Macro *macro);
 
@@ -180,6 +183,14 @@ Win *window_new_file(Vis *vis, File *file) {
 	}
 	file->refcount++;
 	view_tabwidth_set(win->view, vis->tabwidth);
+
+	if (text_size(file->text) > LARGE_FILE) {
+		enum UiOption opt = view_options_get(win->view);
+		opt |= UI_OPTION_LARGE_FILE;
+		opt &= ~UI_OPTION_LINE_NUMBERS_ABSOLUTE;
+		view_options_set(win->view, opt);
+	}
+
 	if (vis->windows)
 		vis->windows->prev = win;
 	win->next = vis->windows;