feat(#23): allow scrolling the list of candidates

When the list of candidates is larger than the terminal height or configured display lines (default 10), moving the selected line past the bottom will now scroll the list so any item can be selected with the arrow keys alone. Closes #23
natecraddock · Feb 24, 2023 · 4ea08e7 · 4ea08e7
1 parent 09996da
commit 4ea08e7
Showing 1 changed file with 12 additions and 4 deletions.
diff --git a/src/ui.zig b/src/ui.zig
@@ -16,6 +16,7 @@ const term = @import("term.zig");
 
 const State = struct {
     selected: usize,
+    offset: usize,
     prompt: []const u8,
     prompt_width: usize,
 };
@@ -158,7 +159,7 @@ fn draw(
     while (line < terminal.height) : (line += 1) {
         terminal.cursorDown(1);
         terminal.clearLine();
-        if (line < candidates.len) drawCandidate(terminal, candidates[line], tokens, width, line == state.selected, case_sensitive, plain);
+        if (line < candidates.len) drawCandidate(terminal, candidates[line + state.offset], tokens, width, line == state.selected, case_sensitive, plain);
     }
     terminal.sgr(.reset);
     terminal.cursorUp(terminal.height);
@@ -327,6 +328,7 @@ pub fn run(
 
     var state = State{
         .selected = 0,
+        .offset = 0,
         .prompt = prompt_str,
         .prompt_width = try dw.strWidth(try escapeANSI(allocator, prompt_str), .half),
     };
@@ -364,6 +366,7 @@ pub fn run(
             filtered = filter.rankCandidates(filtered_buf, candidates, tokens, keep_order, plain, case_sensitive);
             redraw = true;
             state.selected = 0;
+            state.offset = 0;
         }
 
         // do we need to redraw?
@@ -372,14 +375,15 @@ pub fn run(
             try draw(terminal, &state, &query, tokens, filtered, candidates.len, case_sensitive, plain);
         }
 
-        const visible_rows = @intCast(i64, std.math.min(terminal.height, filtered.len));
+        const visible_rows = std.math.min(terminal.height, filtered.len);
 
         var buf: [2048]u8 = undefined;
         const input = try terminal.read(&buf);
         const action = inputToAction(input, vi_mode);
 
         const last_cursor = query.cursor;
         const last_selected = state.selected;
+        const last_offset = state.offset;
 
         switch (action) {
             .str => |str| try query.insert(str),
@@ -390,23 +394,27 @@ pub fn run(
             .delete => query.delete(1, .right),
             .line_up => if (state.selected > 0) {
                 state.selected -= 1;
+            } else if (state.offset > 0) {
+                state.offset -= 1;
             },
             .line_down => if (state.selected < visible_rows - 1) {
                 state.selected += 1;
+            } else if (state.offset < filtered.len - visible_rows) {
+                state.offset += 1;
             },
             .cursor_left => query.moveCursor(1, .left),
             .cursor_leftmost => query.setCursor(0),
             .cursor_rightmost => query.setCursor(query.len),
             .cursor_right => query.moveCursor(1, .right),
             .select => {
                 if (filtered.len == 0) break;
-                return filtered[state.selected].str;
+                return filtered[state.selected + state.offset].str;
             },
             .close => break,
             .pass => {},
         }
 
-        redraw = last_cursor != query.cursor or last_selected != state.selected;
+        redraw = last_cursor != query.cursor or last_selected != state.selected or last_offset != state.offset;
     }
 
     return null;