add following of started collection

src/app.zig

@@ -62,6 +62,7 @@ pub const ChannelView = struct {
     y_range: RangeF64,
     sample_rate: ?f64 = null,
     unit: ?NIDaq.Unit = null,
+    follow: bool = false,
 
     source: union(enum) {
         file: usize,
@@ -338,6 +339,7 @@ pub fn startDeviceChannelReading(self: *App, channel_view: *ChannelView) void {
     };
 
     device_channel.active_task = task;
+    channel_view.follow = true;
 }
 
 pub fn appendChannelFromFile(self: *App, path: []const u8) !void {

src/graph.zig

@@ -27,19 +27,24 @@ pub const ViewOptions = struct {
 };
 
 pub const Cache = struct {
+    const Key = struct {
+        options: ViewOptions,
+        drawn_x_range: RangeF64
+    };
+
     texture: ?rl.RenderTexture2D = null,
-    options: ?ViewOptions = null,
+    key: ?Key = null,
 
     pub fn deinit(self: *Cache) void {
         if (self.texture) |texture| {
             texture.unload();
             self.texture = null;
         }
-        self.options = null;
+        self.key = null;
     }
 
     pub fn invalidate(self: *Cache) void {
-        self.options = null;
+        self.key = null;
     }
 
     pub fn draw(self: Cache, rect: rl.Rectangle) void {
@@ -178,7 +183,7 @@ pub fn drawCached(cache: *Cache, render_size: Vec2, options: ViewOptions, sample
         if (texure.width != render_width or texure.height != render_height) {
             render_texture.unload();
             cache.texture = null;
-            cache.options = null;
+            cache.key = null;
         }
     }
 
@@ -191,12 +196,17 @@ pub fn drawCached(cache: *Cache, render_size: Vec2, options: ViewOptions, sample
 
     const render_texture = cache.texture.?;
 
-    if (cache.options != null and std.meta.eql(cache.options.?, options)) {
+    const cache_key = Cache.Key{
+        .options = options,
+        .drawn_x_range = RangeF64.init(0, @max(@as(f64, @floatFromInt(samples.len)) - 1, 0)).intersectPositive(options.x_range)
+    };
+
+    if (cache.key != null and std.meta.eql(cache.key.?, cache_key)) {
         // Cached graph hasn't changed, no need to redraw.
         return;
     }
 
-    cache.options = options;
+    cache.key = cache_key;
 
     render_texture.begin();
     defer render_texture.end();

src/ni-daq/task-pool.zig

@@ -74,7 +74,6 @@ fn readAnalog(task_pool: *TaskPool, entry: *Entry, timeout: f64) !void {
     task_pool.mutex.lock();
     defer task_pool.mutex.unlock();
 
-
     if (entry.sampling.sample_count) |sample_count| {
         try entry.samples.ensureTotalCapacity(sample_count);
     } else {

src/screens/main_screen.zig

@@ -76,6 +76,7 @@ fn pushChannelMoveCommand(self: *MainScreen, channel_view: *ChannelView, x_range
 
     view_rect.x_range = x_range;
     view_rect.y_range = y_range;
+    channel_view.follow = false;
 }
 
 fn pushChannelMoveCommandAxis(self: *MainScreen, channel_view: *ChannelView, axis: UI.Axis, view_range: RangeF64) void {
@@ -100,6 +101,8 @@ fn showChannelViewGraph(self: *MainScreen, channel_view: *ChannelView) *UI.Box {
         .size_y = UI.Sizing.initGrowFull(),
         .background = srcery.black,
         .flags = &.{ .clickable, .draggable, .scrollable },
+        .align_x = .center,
+        .align_y = .center,
     });
     graph_box.beginChildren();
     defer graph_box.endChildren();
@@ -154,6 +157,15 @@ fn showChannelViewGraph(self: *MainScreen, channel_view: *ChannelView) *UI.Box {
         graph_box.texture = texture.texture;
     }
 
+    if (view_rect.x_range.size() == 0 or view_rect.y_range.size() == 0) {
+        graph_box.setText("<Empty>");
+        graph_box.text_color = srcery.hard_black;
+        graph_box.font = .{
+            .variant = .bold_italic,
+            .size = ui.rem(3)
+        };
+    }
+
     return graph_box;
 }
 
@@ -513,6 +525,8 @@ fn showRuler(self: *MainScreen, ruler: *UI.Box, graph_box: *UI.Box, channel_view
 fn showChannelView(self: *MainScreen, channel_view: *ChannelView, height: UI.Sizing) !void {
     var ui = &self.app.ui;
 
+    const show_ruler = true;
+
     const channel_view_box = ui.createBox(.{
         .key = UI.Key.initPtr(channel_view),
         .layout_direction = .top_to_bottom,
@@ -522,7 +536,34 @@ fn showChannelView(self: *MainScreen, channel_view: *ChannelView, height: UI.Siz
     channel_view_box.beginChildren();
     defer channel_view_box.endChildren();
 
-    const show_ruler = true;
+    const toolbar = ui.createBox(.{
+        .layout_direction = .left_to_right,
+        .layout_gap = 16,
+        .background = srcery.hard_black,
+        .size_x = UI.Sizing.initGrowFull(),
+        .size_y = UI.Sizing.initFixed(.{ .pixels = ui.rem(2) })
+    });
+    {
+        toolbar.beginChildren();
+        defer toolbar.endChildren();
+
+        if (self.app.getChannelSourceDevice(channel_view)) |device_channel| {
+            _ = device_channel;
+
+            const follow = ui.button("Follow");
+            follow.background = srcery.hard_black;
+            if (channel_view.follow) {
+                follow.borders = UI.Borders.bottom(.{
+                    .color = srcery.green,
+                    .size = 4
+                });
+            }
+            if (ui.signal(follow).clicked()) {
+                channel_view.follow = !channel_view.follow;
+            }
+        }
+    }
+
 
     if (!show_ruler) {
         _ = self.showChannelViewGraph(channel_view);
@@ -645,16 +686,18 @@ pub fn tick(self: *MainScreen) !void {
     if (self.app.started_collecting) {
         for (self.app.listChannelViews()) |*channel_view| {
             const device_channel = self.app.getChannelSourceDevice(channel_view) orelse continue;
+            if (!channel_view.follow) continue;
 
             const sample_rate = device_channel.active_task.?.sampling.sample_rate;
-            const samples = device_channel.samples.items;
+            const sample_count: f32 = @floatFromInt(device_channel.samples.items.len);
-            const sample_count: f32 = @floatFromInt(samples.len);
+
+            channel_view.view_rect.y_range = channel_view.y_range;
 
             channel_view.view_rect.x_range.lower = 0;
             if (sample_count > channel_view.view_rect.x_range.upper) {
                 channel_view.view_rect.x_range.upper = sample_count + @as(f32, @floatCast(sample_rate)) * 10;
             }
-            channel_view.view_cache.invalidate();
+            // channel_view.view_cache.invalidate();
         }
     }
 
@@ -665,6 +708,7 @@ pub fn tick(self: *MainScreen) !void {
         const scroll_area = ui.beginScrollbar(ui.keyFromString("Channels"));
         defer ui.endScrollbar();
         scroll_area.layout_direction = .top_to_bottom;
+        scroll_area.layout_gap = 4;
 
         for (self.app.listChannelViews()) |*channel_view| {
             try self.showChannelView(channel_view, UI.Sizing.initFixed(.{ .pixels = channel_view.height }));

src/ui.zig

@@ -420,6 +420,12 @@ pub const Borders = struct {
             .right = border,
         };
     }
+
+    pub fn bottom(border: Border) Borders {
+        return Borders{
+            .bottom = border,
+        };
+    }
 };
 
 const BoxIndex = std.math.IntFittingRange(0, max_boxes);