perf: optimize viewport to skip redundant refreshes

[rm-hull]

Introduces a _dirty flag and an optional force parameter to the viewport.refresh method. This ensures that the underlying device's display method is only invoked when content has actually changed, reducing unnecessary I/O and CPU usage.

Changes include:

• Tracking a _dirty state when hotspots are removed.
• Adding a force flag to refresh() to allow explicit overrides.
• Updating display() and set_position() to trigger a forced refresh.
• Skipping the device.display() call if no redraw is required and no state changes are detected.

sequenceDiagram
    participant App
    participant Viewport
    participant Hotspot
    participant Device

    App->>Viewport: refresh(force)
    Viewport->>Hotspot: should_redraw()
    Hotspot-->>Viewport: redraw_needed

    alt force or redraw_needed or dirty
        Viewport->>Device: display(image)
        Note over Viewport: Set dirty = False
    else no changes
        Note over Viewport: Skip display update
    end

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Fixes #280

[gemini-code-assist]

Summary of Changes

Hello @rm-hull, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the performance of the viewport component by introducing an intelligent refresh mechanism. By tracking content changes with a _dirty flag and allowing explicit forced refreshes, it ensures that the display is only updated when absolutely necessary, thereby reducing unnecessary I/O and CPU cycles and addressing a known issue with redundant refreshes.

Highlights

• Optimized Viewport Refresh Logic: Implemented a _dirty flag and a force parameter in the viewport.refresh method to prevent redundant calls to the underlying device's display method, significantly reducing unnecessary I/O and CPU usage.
• Explicit Refresh Triggers: Modified display() and set_position() methods to explicitly call refresh(force=True), ensuring updates are propagated to the device when the content or position of the viewport changes.
• Hotspot Removal Tracking: The remove_hotspot() method now sets the _dirty flag, indicating that the viewport content has changed and requires a refresh on the next refresh() call.
• New Test Case for Optimization: Added tests/test_issue_280.py to thoroughly validate the new refresh optimization logic, covering various scenarios like initial state, forced updates, and hotspot interactions to ensure correctness and prevent regressions.

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[gemini-code-assist]

Code Review

This pull request introduces a well-thought-out performance optimization for the viewport class by skipping redundant refreshes. The introduction of a _dirty flag and a force parameter in the refresh method is implemented correctly and logically. The changes ensure that the underlying device's display method is invoked only when necessary, which should reduce I/O and CPU usage as intended. The new test file provides excellent coverage, validating the behavior in various scenarios, including initial state, forced updates, and state changes from hotspot management. The code is clean, and the changes are effective. Overall, this is a high-quality contribution.