Serial Plotter sometimes doesn't provide values on hover

[per1234]

Describe the bug

When Serial Plotter is in "STOP" mode, hovering the mouse pointer near a data point results in a popup that shows its value.

🐛 Sometimes this does not work.

I have not managed to figure out what are the exact conditions that cause it, but I can reliably reproduce it.

To Reproduce

1. Upload the following sketch to an Arduino board:

   void setup() {
     Serial.begin(9600);
     while (!Serial) {}
     delay(1000);  // Needed due to bug in IDE2 that causes loss of data received immediately after opening SP/SM
     for (byte x=0;x<100;x++){
       Serial.println(random(10));
     }
   }
   void loop() {}

2. Select Tools > Serial Plotter from the Arduino IDE menus.
3. Wait for the data to be plotted.
4. Click the STOP button.
5. Hover the mouse pointer over the plotted data.
   🐛 The values are not shown:
   
   If you do see values, Click the RUN button, reset the board, and repeat the instructions from step (2).
6. Resize the window.
7. Hover the mouse pointer over the plotted data.
   🙂 The values are now shown as expected:
   

Expected behavior

Plotted values are always shown on hover when Serial Plotter is in "STOP" mode.

Desktop

• OS: Windows 10
• Version: 2.0.0-beta.12-snapshot.20f7712
  Date: 2021-11-23T17:19:15.791Z
  CLI Version: 0.19.1 alpha [718bbbf2]

Additional context

In addition to the window resizing used in the demo, hover values also start working after any of the following UI actions:

• Switching the "Interpolate" setting.
• Hiding and then unhiding the plot line.

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Note: the demonstration sketch will only output data once after the program starts. If you are using a board with native USB capability (e.g., MKR, Leonardo, Nano 33), reset the board to get additional data output if you want to try the demo multiple times.