Fix the UI scaling factor invalidating the render cache

[TrueDoctor]

Fixes regression from #3722.

[gemini-code-assist]

Summary of Changes

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This pull request resolves an issue where UI scaling led to incorrect render caching. The solution involves enhancing the CacheKey to include the current UI scale, thereby making cached renders specific to the scaling factor. Additionally, the viewport bounds used for rendering are now correctly adjusted based on the device's display scale, ensuring visual consistency and preventing artifacts when UI scaling is active.

Highlights

• Render Cache Key Update: Modified the CacheKey struct to incorporate the UI scale, ensuring that the render cache can distinguish between different UI scaling levels and prevent incorrect cache hits.
• Viewport Bounds Adjustment: Adjusted the calculation of viewport_bounds within the render_output_cache function to correctly account for the device's display scale, resolving issues where UI scaling would distort cached renders.

Changelog

• node-graph/nodes/gstd/src/render_cache.rs
  • Added DAffine2 import from the glam crate.
  • Introduced a scale field of type u64 to the CacheKey struct.
  • Updated the CacheKey::new constructor to accept a scale: f64 argument and store its bit representation.
  • Modified the Default implementation for CacheKey to initialize the new scale field to 0.
  • Adjusted the viewport_bounds calculation in render_output_cache to divide the size by device_scale.
  • Passed render_params.scale to the CacheKey::new constructor in render_output_cache.

Activity

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[gemini-code-assist]

Code Review

This pull request addresses an issue with the render cache when UI scaling is active. The fix involves two main changes: including the device scale in the cache key to differentiate renders at different UI scales, and correcting the calculation of viewport bounds which was previously incorrect due to mixing logical and physical scales. The changes appear to correctly solve the problem. I've provided one suggestion to improve the clarity and maintainability of the viewport bounds calculation.

[gemini-code-assist]

This recalculation of viewport_bounds is a bit indirect. It relies on the implicit knowledge that viewport_bounds_in_local_space returns a bounding box with a correct start position but a size that is too large by a factor of device_scale. This happens because it's called with a physical resolution while the transform only accounts for logical scale.

For better clarity and maintainability, it would be better to calculate the bounds directly using the correct logical resolution.

Suggested change

	let viewport_bounds = footprint.viewport_bounds_in_local_space();
	let viewport_bounds = AxisAlignedBbox {
	start: viewport_bounds.start,
	end: viewport_bounds.start + viewport_bounds.size() / device_scale,
	};
	let inverse_transform = footprint.transform.inverse();
	let logical_resolution = footprint.resolution.as_dvec2() / device_scale;
	let viewport_bounds = AxisAlignedBbox {
	start: inverse_transform.transform_point2(DVec2::ZERO),
	end: inverse_transform.transform_point2(logical_resolution),
	};