Update Card Placement Keep In View Logic

[PauloMFJ]

Overview

Update placement logic to follow 3 steps:

1. If it already fits fully in the viewport, leave the camera be.
2. If we can zoom out to frame every card at once, do that so the new card shows up in the context of the whole set.
3. We couldn't fit everything without hitting the min-zoom cap, so just pan to the new card so it lands on-screen

[gemini-code-assist]

Code Review

This pull request updates the camera behavior when revealing a freshly placed card in the atlas scope. It introduces a canFitWithinZoomCap helper to determine if the entire page bounds can fit within the viewport without hitting the minimum zoom cap. If so, the camera zooms to fit; otherwise, it centers on the new card. The reviewer identified potential robustness issues in canFitWithinZoomCap related to NaN propagation from undefined padding and division by zero when bounds dimensions are non-positive, providing a code suggestion to address these edge cases.

[gemini-code-assist]

In canFitWithinZoomCap, there are two potential issues that could lead to unexpected behavior or NaN values:

1. Potential NaN from editor.options.zoomToFitPadding: If zoomToFitPadding is undefined or not set, Math.min(editor.options.zoomToFitPadding, ...) will return NaN. This propagates through the calculations, causing fitZoom to be NaN and the function to always return false (preventing step 2 from ever running).
2. Division by Zero: If bounds.w or bounds.h is 0 (e.g., if there are no shapes or the bounding box is empty), dividing by them will result in Infinity or NaN. We should guard against non-positive dimensions early.

Adding a fallback for zoomToFitPadding (defaulting to 128 as per tldraw's defaults) and a guard clause for non-positive bounds dimensions will make this logic much more robust.

const canFitWithinZoomCap = (editor: Editor, bounds: Box): boolean => {
  if (bounds.w <= 0 || bounds.h <= 0) return false;

  const screen = editor.getViewportScreenBounds();
  const zoomToFitPadding = editor.options.zoomToFitPadding ?? 128;
  const inset = Math.min(zoomToFitPadding, screen.width * 0.28);
  const fitZoom = Math.min(
    (screen.width - inset) / bounds.w,
    (screen.height - inset) / bounds.h,
  );

  const minZoomStep = editor.getCameraOptions().zoomSteps[0] ?? MIN_ZOOM;
  const minZoom = minZoomStep * editor.getBaseZoom();

  return fitZoom >= minZoom;
};