Fix half-pixel offset on imported images

[Keavon]

Fixes #3670

[gemini-code-assist]

Summary of Changes

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This pull request resolves a visual bug where imported images would appear with a half-pixel offset, particularly when added through a non-mouse-driven workflow like a file open dialog. The changes refine the coordinate transformation logic to ensure that images are always precisely aligned within the viewport, improving the accuracy of image placement.

Highlights

• Image Import Alignment: Refactored the logic for positioning imported images, specifically addressing a half-pixel offset that occurred when images were imported without a specific mouse location.
• Viewport Centering Calculation: Modified the calculation of center_in_viewport_layerspace and center_in_viewport to ensure precise alignment, especially when importing images via the file-open flow where mouse input is None.

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[gemini-code-assist]

Code Review

This pull request fixes a half-pixel offset issue when importing images without a specific mouse position by using DAffine2::IDENTITY to default to the document origin. The change is applied to both PasteImage and PasteSvg message handlers. The fix appears correct. My only feedback is regarding code duplication between these two handlers, which could be refactored into a helper function to improve maintainability.

[gemini-code-assist]

This logic for calculating center_in_viewport is identical to the logic for center_in_viewport_layerspace in the PasteImage message handler above (lines 667-671). To improve maintainability and reduce code duplication, consider extracting this logic into a private helper function within DocumentMessageHandler.

For example:

impl DocumentMessageHandler {
    // ...

    fn get_document_space_transform_from_mouse(&self, mouse: Option<ViewportPosition>, viewport: &ViewportMessageHandler) -> DAffine2 {
        mouse.map_or(DAffine2::IDENTITY, |pos| {
            let viewport_location: DVec2 = pos.into();
            let document_to_viewport = self.navigation_handler.calculate_offset_transform(viewport.center_in_viewport_space().into(), &self.document_ptz);
            DAffine2::from_translation(document_to_viewport.inverse().transform_point2(viewport_location - viewport.offset().into_dvec2()))
        })
    }

    // ...
}

Then you could call self.get_document_space_transform_from_mouse(mouse, viewport) in both PasteImage and PasteSvg message handlers.

[cubic-dev-ai]

2 issues found across 1 file

Confidence score: 3/5

• There is a concrete regression risk in editor/src/messages/portfolio/document/document_message_handler.rs: both PasteImage and PasteSvg now fall back mouse: None to document origin, which can place pasted content far from the user’s current view.
• This is medium severity but high confidence (6/10, 8/10), so the PR likely remains workable yet carries noticeable user-facing paste behavior risk in existing documents.
• Pay close attention to editor/src/messages/portfolio/document/document_message_handler.rs - verify mouse: None paste placement logic so clipboard pastes stay visible in non-origin views.

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="editor/src/messages/portfolio/document/document_message_handler.rs">

<violation number="1" location="editor/src/messages/portfolio/document/document_message_handler.rs:667">
P2: `PasteImage` now treats `mouse: None` as document origin for all flows, which regresses clipboard paste placement in existing documents.</violation>

<violation number="2" location="editor/src/messages/portfolio/document/document_message_handler.rs:721">
P2: `PasteSvg` applies the same `mouse: None -> origin` fallback, causing clipboard SVG paste to appear off-screen in non-origin views.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}