Description

A description of the change and what it does. If relevant, please provide screenshots of what results from the change:

The goal of this refactor is to help reduce some duplicated code, and make it easier to add new widgets as required. To start, this will mostly be targeting scrollable table widgets, since they're some of the more complicated widgets in terms of state management and user interaction.

The main idea behind this change is to move on from the current system of each widget having three separated parts:

• State management
• Drawing management
• Event management (managed mostly within app.rs)

The biggest issue was that adding a new widget was painful to say the least - you would have to create a new state manager, write new code to handle events, and then write drawing code! To address this, I was planning on refactoring this AFTER 0.5.0 released, but given how much trouble this was giving me during the config implementation planning, I decided to do some of this now.

The new concept planned (and implemented for scrollable tables for now) is:

• Introduce "components" that represent base parts of a widget. So for things like processes, disks, etc., these are all scrollable tables. As such, the ScrollableTable trait would represent the base methods we want all scrollable tables to have. This means I don't have to have 5 different implementations of how to increment the table scroll cursor.

• Unify widget state management and drawing together. Since we already keep track of all these widget states within the overarching app state, we can just simply call the widget's drawing function.

Type of change

Remove the irrelevant ones:

• Refactoring (a change that doesn't change application functionality)

Test methodology

If relevant, please state how this was tested:

Furthermore, please tick which platforms this change was tested on:

• Windows
• macOS
• Linux

If relevant, all of these platforms should be tested.

Checklist

If relevant, ensure the following have been met:

• Change has been tested to work, and does not cause new breakage unless intended
• Code has been self-reviewed
• Documentation has been added/updated if needed (README, help menu, etc.)
• Passes Travis tests (clippy check and cargo test check)
• Areas your change affects have been linted using rustfmt (cargo fmt)
• No merge conflicts arise from the change