Add rendering hint to snap y axis

bare-metrics-gui/src/config.rs

@@ -21,6 +21,8 @@ pub struct GraphConfig {
     pub kind: MetricKind,
     #[serde(default)]
     pub transform: Option<MetricTransform>,
+    #[serde(default)]
+    pub rendering: GraphRenderingHints,
 }
 
 #[derive(Clone, Debug, Hash, Eq, PartialEq)]
@@ -29,3 +31,9 @@ pub struct GraphRequest {
     pub metric_labels: BTreeMap<String, String>,
     pub derivation: Option<MetricTransform>,
 }
+
+#[derive(Clone, Debug, Default, Deserialize)]
+pub struct GraphRenderingHints {
+    /// The view will be forced to include this range.
+    pub include_y_range: Option<(f64, f64)>,
+}

bare-metrics-gui/src/graph.rs

@@ -1,5 +1,5 @@
 use crate::background_loader::MetricsLogReadingRequester;
-use crate::config::GraphRequest;
+use crate::config::{GraphRenderingHints, GraphRequest};
 use bare_metrics_core::structures::UnixTimestampMilliseconds;
 use eframe::egui::{
     Color32, Frame as EguiFrame, PointerButton, Pos2, Rect, Sense, Stroke, TextStyle, Ui, Vec2,
@@ -64,7 +64,12 @@ impl Mul<(f64, f64)> for GraphTransform {
 }
 
 impl Graph {
-    pub fn draw(ui: &mut Ui, graph_request: &GraphRequest, reader: &MetricsLogReadingRequester) {
+    pub fn draw(
+        ui: &mut Ui,
+        graph_request: &GraphRequest,
+        render_hint: &GraphRenderingHints,
+        reader: &MetricsLogReadingRequester,
+    ) {
         let context_menu_id = ui.id().with("context menu");
 
         EguiFrame::dark_canvas(ui.style()).show(ui, |ui| {
@@ -101,13 +106,25 @@ impl Graph {
 
             // This range is reversed because screen coordinates go down, but we'd like them to go
             // up since this is more of a mathematical graph.
-            let y_axis = if let Some(histogram) = current_window.histograms.get(graph_request) {
+            let mut y_axis = if let Some(histogram) = current_window.histograms.get(graph_request) {
                 histogram.y_axis.clone().into_inner()
             } else if let Some(scalar) = current_window.scalars.get(graph_request) {
                 scalar.y_axis.clone().into_inner()
             } else {
                 (0.0, 10.0)
             };
+
+            if let Some((a, b)) = render_hint.include_y_range {
+                // Force the y-axis to contain a range. Useful if you like 0 to be anchored on a
+                // rate graph or something like that.
+                if y_axis.0 > a {
+                    y_axis.0 = a;
+                }
+                if y_axis.1 < b {
+                    y_axis.1 = b;
+                }
+            }
+
             let y_axis = (y_axis.1)..=(y_axis.0);
 
             // let display_transform =

bare-metrics-gui/src/main.rs

@@ -1,7 +1,7 @@
 use crate::background_loader::{
     MetricsLogReaderMessage, MetricsLogReaderNotification, MetricsLogReadingRequester,
 };
-use crate::config::{DashboardConfig, GraphRequest};
+use crate::config::{DashboardConfig, GraphRenderingHints, GraphRequest};
 use crate::graph::Graph;
 
 use bare_metrics_reader::MetricsLogReader;
@@ -23,7 +23,8 @@ pub struct MetricsGui {
     requester: MetricsLogReadingRequester,
 
     dashboard: Option<DashboardConfig>,
-    graph_requests: Vec<GraphRequest>,
+    // TODO we may want multiple graphs on the same pane, somehow.
+    graph_requests: Vec<(GraphRequest, GraphRenderingHints)>,
 }
 
 impl App for MetricsGui {
@@ -39,13 +40,13 @@ impl App for MetricsGui {
             egui::ScrollArea::new([false, true]).show(ui, |ui| {
                 if let Some(_dashboard) = dashboard {
                     let window = requester.shared.current_window.read().unwrap();
-                    for graph in graph_requests.iter() {
-                        ui.label(&graph.metric_name);
+                    for (request, render_hint) in graph_requests.iter() {
+                        ui.label(&request.metric_name);
 
-                        if window.scalars.contains_key(graph)
-                            || window.histograms.contains_key(graph)
+                        if window.scalars.contains_key(request)
+                            || window.histograms.contains_key(request)
                         {
-                            Graph::draw(ui, graph, requester);
+                            Graph::draw(ui, request, render_hint, requester);
                         } else {
                             // TODO clarify
                             ui.label("(loading or missing ...)");
@@ -104,12 +105,15 @@ impl MetricsGui {
         if let Some(dashboard) = self.dashboard.as_ref() {
             for graph in dashboard.graphs.iter() {
                 // TODO frankly we should maybe be using metric IDs in the graph requests
-                self.graph_requests.push(GraphRequest {
+                self.graph_requests.push((
+                    GraphRequest {
                         metric_name: graph.name.clone(),
                         // TODO we need something better about the metric labels
                         metric_labels: BTreeMap::new(),
                         derivation: graph.transform.clone(),
-                });
+                    },
+                    graph.rendering.clone(),
+                ));
             }
         } else {
             // TODO Build some stuff automatically based on alphabetical ordering
@@ -120,7 +124,12 @@ impl MetricsGui {
             .send(MetricsLogReaderMessage::LoadNewWindow {
                 new_time_range: f64::NEG_INFINITY..=f64::INFINITY,
                 new_wanted_time_points: 512,
-                requests: self.graph_requests.clone(),
+                requests: self
+                    .graph_requests
+                    .iter()
+                    .map(|(a, _)| a)
+                    .cloned()
+                    .collect(),
             })
             .unwrap();
     }