87 lines
3.3 KiB
Rust
87 lines
3.3 KiB
Rust
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//! Selection-transform preview invalidation utilities.
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//!
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//! **Purpose:** Computes canvas-clipped dirty bounds for floating selection
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//! previews so both their previous and current positions can be uploaded to the
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//! persistent GPU texture during interactive movement.
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//!
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//! **Logic & Workflow:** Preview geometry is rounded exactly like the CPU
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//! compositor, clamped to the canvas origin, and clipped at the right and
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//! bottom canvas edges. Empty or fully out-of-canvas rectangles return `None`.
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//!
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//! **Side Effects / Dependencies:** The module is deterministic and has no I/O,
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//! global state, allocation, engine dependency, or GPU dependency.
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/// Calculates the clipped pixel bounds occupied by a transform preview.
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///
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/// **Purpose:** Produces the dirty rectangle that must be restored or redrawn
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/// when a floating selection changes position or dimensions.
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///
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/// **Logic & Workflow:** Delegates to the shared rotated-corner AABB calculation
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/// used by both preview and apply, clips it to the canvas, and rejects empty rectangles.
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///
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/// **Arguments:**
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/// - `transform`: Floating selection source and affine geometry.
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/// - `canvas_width`, `canvas_height`: Clipping dimensions of the document.
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///
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/// **Returns:** `Some([x0, y0, x1, y1])` for a non-empty clipped rectangle, or
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/// `None` when the preview cannot affect the canvas.
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///
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/// **Side Effects / Dependencies:** None.
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pub(crate) fn preview_bounds(
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transform: &crate::selection::SelectionTransform,
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canvas_width: u32,
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canvas_height: u32,
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) -> Option<[u32; 4]> {
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crate::selection::transform::transformed_bounds(transform, canvas_width, canvas_height)
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}
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#[cfg(test)]
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mod tests {
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use crate::selection::SelectionTransform;
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use iced::Vector;
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use super::preview_bounds;
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fn transform(x: f32, y: f32) -> SelectionTransform {
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SelectionTransform {
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pixels: vec![255; 30 * 40 * 4],
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width: 30,
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height: 40,
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pos: Vector::new(x, y),
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size: Vector::new(30.0, 40.0),
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rotation: 0.0,
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}
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}
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/// Verifies that consecutive preview positions expose both the old and new
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/// rectangles needed by the caller's dirty-region union.
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///
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/// **Purpose:** Guards against stale GPU pixels remaining at an old drag
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/// position when only the current preview rectangle is uploaded.
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///
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/// **Logic & Workflow:** Computes two partially overlapping positions and
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/// confirms their bounds preserve the complete restoration/redraw extent.
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///
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/// **Arguments & Returns:** Takes no arguments and returns nothing;
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/// assertion failures identify incorrect transform bounds.
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///
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/// **Side Effects / Dependencies:** None.
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#[test]
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fn consecutive_positions_retain_old_and_new_extents() {
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let previous = preview_bounds(&transform(10.0, 20.0), 100, 100).unwrap();
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let current = preview_bounds(&transform(25.0, 30.0), 100, 100).unwrap();
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assert_eq!(previous, [10, 20, 40, 60]);
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assert_eq!(current, [25, 30, 55, 70]);
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assert_eq!(
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[
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previous[0].min(current[0]),
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previous[1].min(current[1]),
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previous[2].max(current[2]),
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previous[3].max(current[3]),
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],
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[10, 20, 55, 70],
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);
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}
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}
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