some starting work on a temp graph widget; I'll do disk in a separate PR

src/app/data/time_series.rs

@@ -55,6 +55,10 @@ pub struct TimeSeriesData {
     #[cfg(feature = "gpu")]
     /// GPU memory data.
     pub gpu_mem: HashMap<String, Values>,
+
+    /// Temperature data, if needed. A mapping of sensor names to
+    /// their temperature values.
+    pub temp: HashMap<String, Values>,
 }
 
 impl TimeSeriesData {

src/widgets/disk_graph.rs

@@ -1 +1,3 @@
 //! Code for a disk graph widget.
+
+// TODO: Implement this.

src/widgets/mod.rs

@@ -19,3 +19,9 @@ pub use network_graph::*;
 pub use process_table::*;
 pub use temperature_graph::*;
 pub use temperature_table::*;
+
+/// Whether an event is handled by the current element or not.
+pub enum EventHandled {
+    Handled,
+    NotHandled,
+}

src/widgets/temperature_graph.rs

@@ -1 +1,57 @@
 //! Code for a temperature graph widget.
+
+use std::time::Instant;
+
+use crossterm::event::{KeyEvent, MouseEvent};
+use tui::{Frame, layout::Rect};
+
+use crate::app::{App, data::TemperatureType};
+
+use super::EventHandled;
+
+/// A temperature graph widget.
+///
+/// The current implementation of this uses tuine-style code; this will
+/// become the standard later on for all widgets.
+#[derive(Default)]
+pub struct TemperatureGraph {
+    current_display_time: u64,
+    autohide_timer: Option<Instant>,
+    current_max_temperature: u32,
+    temperature_unit: TemperatureType,
+}
+
+impl TemperatureGraph {
+    pub fn temperature_unit(mut self, unit: TemperatureType) -> Self {
+        self.temperature_unit = unit;
+        self
+    }
+
+    /// How this widget handles key events.
+    ///
+    /// TODO: This may merge with [`Self::handle_mouse_event`] in the future.
+    pub fn handle_key_event(event: KeyEvent) -> EventHandled {
+        EventHandled::NotHandled
+    }
+
+    /// How this widget handles mouse events.
+    ///
+    /// TODO: This may merge with [`Self::handle_key_event`] in the future.
+    pub fn handle_mouse_event(event: MouseEvent) -> EventHandled {
+        EventHandled::NotHandled
+    }
+
+    // /// How to lay out this widget in terms of sizing.
+    //
+    // For now, this is not implemented, and we will directly give sizes.
+    // pub fn layout() {}
+
+    /// How to draw this widget.
+    ///
+    /// This implementation is a bit of a hack/placeholder, in the future we don't want to bring in stuff like [`App`].
+    pub fn draw(&mut self, frame: &mut Frame<'_>, app_state: &mut App, draw_area: Rect) {
+        let data = &app_state.data_store.get_data().timeseries_data.temp;
+
+        // Inspect the newest entry of each sensor to determine the current max temperature.
+    }
+}