Add --graph-style option and Unicode graph drawing

And also adjust the graph width calculation to do a better job when the
largest item is smaller than the number of columns used for the graph,
which would previously draw either nothing (if size = 0) or a full bar
(if size > 0).

Fixes #172.

ncdu.pod

@@ -227,6 +227,14 @@ browser with the 'g' key.
 Show (default) or hide the relative size percent column. Can also be toggled in
 the browser with the 'g' key.
 
+=item B<--graph-style> I<OPTION>
+
+Change the way that the relative size bar column is drawn. Recognized values
+are I<hash> to draw ASCII C<#> characters (most portable), I<half-block> to use
+half-block drawing characters (the default) or I<eigth-block> to use
+eigth-block drawing characters. Eigth-block characters are the most precise but
+may not render correctly in all terminals.
+
 =item B<--shared-column> I<OPTION>
 
 Set to I<off> to disable the shared size column for directories, I<shared>

src/browser.zig

@@ -224,14 +224,23 @@ const Row = struct {
         }
         if (main.config.show_graph and main.config.show_percent) ui.addch(' ');
         if (main.config.show_graph) {
-            const perblock = std.math.divFloor(u64, if (main.config.show_blocks) dir_max_blocks else dir_max_size, bar_size) catch unreachable;
-            const num = if (main.config.show_blocks) item.blocks else item.size;
+            var max = if (main.config.show_blocks) dir_max_blocks else dir_max_size;
+            var num = if (main.config.show_blocks) item.blocks else item.size;
+            if (max < bar_size) {
+                max *= bar_size;
+                num *= bar_size;
+            }
+            const perblock = std.math.divFloor(u64, max, bar_size) catch unreachable;
             var i: u32 = 0;
-            var siz: u64 = 0;
             self.bg.fg(.graph);
             while (i < bar_size) : (i += 1) {
-                siz = siz +| perblock;
-                ui.addch(if (siz <= num) '#' else ' ');
+                const frac = std.math.min(8, (num *| 8) / perblock);
+                ui.addstr(switch (main.config.graph_style) {
+                    .hash  => ([_][:0]const u8{ " ", " ", " ", " ", " ", " ", " ", " ", "#" })[frac],
+                    .half  => ([_][:0]const u8{ " ", " ", " ", " ", "▌", "▌", "▌", "▌", "█" })[frac],
+                    .eigth => ([_][:0]const u8{ " ", "▏", "▎", "▍", "▌", "▋", "▊", "▉", "█" })[frac],
+                });
+                num -|= perblock;
             }
         }
         self.bg.fg(.default);

src/main.zig

@@ -61,6 +61,7 @@ pub const config = struct {
     pub var show_mtime: bool = false;
     pub var show_graph: bool = true;
     pub var show_percent: bool = false;
+    pub var graph_style: enum { hash, half, eigth } = .half;
     pub var sort_col: SortCol = .blocks;
     pub var sort_order: SortOrder = .desc;
     pub var sort_dirsfirst: bool = false;
@@ -181,7 +182,13 @@ fn argConfig(args: *Args, opt: Args.Option) bool {
     else if (opt.is("--hide-percent")) config.show_percent = false
     else if (opt.is("--group-directories-first")) config.sort_dirsfirst = true
     else if (opt.is("--no-group-directories-first")) config.sort_dirsfirst = false
-    else if (opt.is("--sort")) {
+    else if (opt.is("--graph-style")) {
+        const val = args.arg();
+        if (std.mem.eql(u8, val, "hash")) config.graph_style = .hash
+        else if (std.mem.eql(u8, val, "half-block")) config.graph_style = .half
+        else if (std.mem.eql(u8, val, "eigth-block")) config.graph_style = .eigth
+        else ui.die("Unknown --graph-style option: {s}.\n", .{val});
+    } else if (opt.is("--sort")) {
         var val: []const u8 = args.arg();
         var ord: ?config.SortOrder = null;
         if (std.mem.endsWith(u8, val, "-asc")) {