render: add cli renderer

Add a renderer for applications running on the primary screen. This
renderer uses relative cursor positioning, and works with all the same
primitives as the alternate screen.

Fix a bug where repositioning was never turned back to false. This was a
nasty one with huge perf implications.

Set internal cells to a space and default on init. This prevents us from
writing them. As a result, we now issue a hardware clear on resize.

build.zig

@@ -38,6 +38,7 @@ pub fn build(b: *std.Build) void {
 
     // Examples
     const Example = enum {
+        cli,
         image,
         main,
         nvim,

examples/cli.zig

@@ -0,0 +1,106 @@
+const std = @import("std");
+const vaxis = @import("vaxis");
+const Cell = vaxis.Cell;
+const TextInput = vaxis.widgets.TextInput;
+
+const log = std.log.scoped(.main);
+pub fn main() !void {
+    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+    defer {
+        const deinit_status = gpa.deinit();
+        if (deinit_status == .leak) {
+            log.err("memory leak", .{});
+        }
+    }
+    const alloc = gpa.allocator();
+
+    var vx = try vaxis.init(alloc, .{});
+    defer vx.deinit(alloc);
+
+    var loop: vaxis.Loop(Event) = .{ .vaxis = &vx };
+
+    try loop.run();
+    defer loop.stop();
+
+    try vx.queryTerminal();
+
+    var text_input = TextInput.init(alloc, &vx.unicode);
+    defer text_input.deinit();
+
+    var selected_option: ?usize = null;
+
+    const options = [_][]const u8{
+        "option 1",
+        "option 2",
+        "option 3",
+    };
+
+    // The main event loop. Vaxis provides a thread safe, blocking, buffered
+    // queue which can serve as the primary event queue for an application
+    while (true) {
+        // nextEvent blocks until an event is in the queue
+        const event = loop.nextEvent();
+        // exhaustive switching ftw. Vaxis will send events if your Event
+        // enum has the fields for those events (ie "key_press", "winsize")
+        switch (event) {
+            .key_press => |key| {
+                if (key.codepoint == 'c' and key.mods.ctrl) {
+                    break;
+                } else if (key.matches(vaxis.Key.tab, .{})) {
+                    if (selected_option == null) {
+                        selected_option = 0;
+                    } else {
+                        selected_option.? = @min(options.len - 1, selected_option.? + 1);
+                    }
+                } else if (key.matches(vaxis.Key.tab, .{ .shift = true })) {
+                    if (selected_option == null) {
+                        selected_option = 0;
+                    } else {
+                        selected_option.? = selected_option.? -| 1;
+                    }
+                } else if (key.matches(vaxis.Key.enter, .{})) {
+                    if (selected_option) |i| {
+                        log.err("enter", .{});
+                        try text_input.insertSliceAtCursor(options[i]);
+                        selected_option = null;
+                    }
+                } else {
+                    if (selected_option == null)
+                        try text_input.update(.{ .key_press = key });
+                }
+            },
+            .winsize => |ws| {
+                try vx.resize(alloc, ws);
+            },
+            else => {},
+        }
+
+        const win = vx.window();
+        win.clear();
+
+        text_input.draw(win);
+
+        if (selected_option) |i| {
+            win.hideCursor();
+            for (options, 0..) |opt, j| {
+                log.err("i = {d}, j = {d}, opt = {s}", .{ i, j, opt });
+                var seg = [_]vaxis.Segment{.{
+                    .text = opt,
+                    .style = if (j == i) .{ .reverse = true } else .{},
+                }};
+                _ = try win.print(&seg, .{ .row_offset = j + 1 });
+            }
+        }
+        try vx.render();
+    }
+}
+
+// Our Event. This can contain internal events as well as Vaxis events.
+// Internal events can be posted into the same queue as vaxis events to allow
+// for a single event loop with exhaustive switching. Booya
+const Event = union(enum) {
+    key_press: vaxis.Key,
+    winsize: vaxis.Winsize,
+    focus_in,
+    foo: u8,
+};

src/InternalScreen.zig

@@ -16,7 +16,7 @@ pub const InternalCell = struct {
     uri_id: std.ArrayList(u8) = undefined,
     // if we got skipped because of a wide character
     skipped: bool = false,
-    default: bool = false,
+    default: bool = true,
 
     pub fn eql(self: InternalCell, cell: Cell) bool {
         // fastpath when both cells are default
@@ -55,6 +55,7 @@ pub fn init(alloc: std.mem.Allocator, w: usize, h: usize) !InternalScreen {
             .uri = std.ArrayList(u8).init(alloc),
             .uri_id = std.ArrayList(u8).init(alloc),
         };
+        try screen.buf[i].char.append(' ');
     }
     screen.width = w;
     screen.height = h;

src/Tty.zig

@@ -32,6 +32,10 @@ state: struct {
     kitty_keyboard: bool = false,
     bracketed_paste: bool = false,
     mouse: bool = false,
+    cursor: struct {
+        row: usize = 0,
+        col: usize = 0,
+    } = .{},
 } = .{},
 
 /// initializes a Tty instance by opening /dev/tty and "making it raw"

src/Vaxis.zig

@@ -94,7 +94,8 @@ pub fn deinit(self: *Vaxis, alloc: ?std.mem.Allocator) void {
 
 /// resize allocates a slice of cells equal to the number of cells
 /// required to display the screen (ie width x height). Any previous screen is
-/// freed when resizing
+/// freed when resizing. The cursor will be sent to it's home position and a
+/// hardware clear-below-cursor will be sent
 pub fn resize(self: *Vaxis, alloc: std.mem.Allocator, winsize: Winsize) !void {
     log.debug("resizing screen: width={d} height={d}", .{ winsize.cols, winsize.rows });
     self.screen.deinit(alloc);
@@ -105,7 +106,18 @@ pub fn resize(self: *Vaxis, alloc: std.mem.Allocator, winsize: Winsize) !void {
     // every cell
     self.screen_last.deinit(alloc);
     self.screen_last = try InternalScreen.init(alloc, winsize.cols, winsize.rows);
-    // try self.screen_last.resize(alloc, winsize.cols, winsize.rows);
+    var tty = self.tty orelse return;
+    if (tty.state.alt_screen)
+        _ = try tty.write(ctlseqs.home)
+    else {
+        _ = try tty.buffered_writer.write("\r");
+        var i: usize = 0;
+        while (i < tty.state.cursor.row) : (i += 1) {
+            _ = try tty.buffered_writer.write(ctlseqs.ri);
+        }
+    }
+    _ = try tty.write(ctlseqs.erase_below_cursor);
+    try tty.flush();
 }
 
 /// returns a Window comprising of the entire terminal screen
@@ -216,7 +228,15 @@ pub fn render(self: *Vaxis) !void {
     // this if we have an update to make. We also need to hide cursor
     // and then reshow it if needed
     _ = try tty.write(ctlseqs.hide_cursor);
-    _ = try tty.write(ctlseqs.home);
+    if (tty.state.alt_screen)
+        _ = try tty.write(ctlseqs.home)
+    else {
+        _ = try tty.write("\r");
+        var i: usize = 0;
+        while (i < tty.state.cursor.row) : (i += 1) {
+            _ = try tty.write(ctlseqs.ri);
+        }
+    }
     _ = try tty.write(ctlseqs.sgr_reset);
 
     // initialize some variables
@@ -225,6 +245,10 @@ pub fn render(self: *Vaxis) !void {
     var col: usize = 0;
     var cursor: Style = .{};
     var link: Hyperlink = .{};
+    var cursor_pos: struct {
+        row: usize = 0,
+        col: usize = 0,
+    } = .{};
 
     // Clear all images
     _ = try tty.write(ctlseqs.kitty_graphics_clear);
@@ -232,8 +256,6 @@ pub fn render(self: *Vaxis) !void {
     var i: usize = 0;
     while (i < self.screen.buf.len) {
         const cell = self.screen.buf[i];
-        defer {
-            // advance by the width of this char mod 1
         const w = blk: {
             if (cell.char.width != 0) break :blk cell.char.width;
 
@@ -241,6 +263,8 @@ pub fn render(self: *Vaxis) !void {
             const width = gwidth.gwidth(cell.char.grapheme, method, &self.unicode.width_data) catch 1;
             break :blk @max(1, width);
         };
+        defer {
+            // advance by the width of this char mod 1
             std.debug.assert(w > 0);
             var j = i + 1;
             while (j < i + w) : (j += 1) {
@@ -277,7 +301,24 @@ pub fn render(self: *Vaxis) !void {
 
         // reposition the cursor, if needed
         if (reposition) {
-            try std.fmt.format(tty.buffered_writer.writer(), ctlseqs.cup, .{ row + 1, col + 1 });
+            reposition = false;
+            if (tty.state.alt_screen)
+                try std.fmt.format(tty.buffered_writer.writer(), ctlseqs.cup, .{ row + 1, col + 1 })
+            else {
+                if (cursor_pos.row == row) {
+                    const n = col - cursor_pos.col;
+                    try std.fmt.format(tty.buffered_writer.writer(), ctlseqs.cuf, .{n});
+                } else {
+                    const n = row - cursor_pos.row;
+                    var _i: usize = 0;
+                    _ = try tty.buffered_writer.write("\r");
+                    while (_i < n) : (_i += 1) {
+                        _ = try tty.buffered_writer.write("\n");
+                    }
+                    if (col > 0)
+                        try std.fmt.format(tty.buffered_writer.writer(), ctlseqs.cuf, .{col});
+                }
+            }
         }
 
         if (cell.image) |img| {
@@ -433,8 +474,12 @@ pub fn render(self: *Vaxis) !void {
             try std.fmt.format(writer, ctlseqs.osc8, .{ ps, cell.link.uri });
         }
         _ = try tty.write(cell.char.grapheme);
+        cursor_pos.col = col + w;
+        cursor_pos.row = row;
+        log.debug("cursor: row: {}, col: {}, grapheme: '{s}'", .{ cursor_pos.row, cursor_pos.col, cell.char.grapheme });
     }
     if (self.screen.cursor_vis) {
+        if (tty.state.alt_screen) {
             try std.fmt.format(
                 tty.buffered_writer.writer(),
                 ctlseqs.cup,
@@ -443,7 +488,29 @@ pub fn render(self: *Vaxis) !void {
                     self.screen.cursor_col + 1,
                 },
             );
+        } else {
+            // TODO: position cursor relative to current location
+            _ = try tty.write("\r");
+            var r: usize = 0;
+            if (self.screen.cursor_row >= cursor_pos.row) {
+                while (r < (self.screen.cursor_row - cursor_pos.row)) : (r += 1) {
+                    _ = try tty.write("\n");
+                }
+            } else {
+                while (r < (cursor_pos.row - self.screen.cursor_row)) : (r += 1) {
+                    _ = try tty.write(ctlseqs.ri);
+                }
+            }
+            if (self.screen.cursor_col > 0) {
+                try std.fmt.format(tty.buffered_writer.writer(), ctlseqs.cuf, .{self.screen.cursor_col});
+            }
+        }
+        self.tty.?.state.cursor.row = self.screen.cursor_row;
+        self.tty.?.state.cursor.col = self.screen.cursor_col;
         _ = try tty.write(ctlseqs.show_cursor);
+    } else {
+        self.tty.?.state.cursor.row = cursor_pos.row;
+        self.tty.?.state.cursor.col = cursor_pos.col;
     }
     if (self.screen.mouse_shape != self.screen_last.mouse_shape) {
         try std.fmt.format(
@@ -461,6 +528,7 @@ pub fn render(self: *Vaxis) !void {
         );
         self.screen_last.cursor_shape = self.screen.cursor_shape;
     }
+    log.debug("tty_cursor: row: {}, col: {}", .{ self.tty.?.state.cursor.row, self.tty.?.state.cursor.col });
 }
 
 fn enableKittyKeyboard(self: *Vaxis, flags: Key.KittyFlags) !void {

src/ctlseqs.zig

@@ -37,6 +37,13 @@ pub const cup = "\x1b[{d};{d}H";
 pub const hide_cursor = "\x1b[?25l";
 pub const show_cursor = "\x1b[?25h";
 pub const cursor_shape = "\x1b[{d} q";
+pub const ri = "\x1bM";
+pub const ind = "\n";
+pub const cuf = "\x1b[{d}C";
+pub const cub = "\x1b[{d}D";
+
+// Erase
+pub const erase_below_cursor = "\x1b[J";
 
 // alt screen
 pub const smcup = "\x1b[?1049h";