fix: Crystal ball example dragging no longer causes camera to jump#3925
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The center-tap handler was converting canvas coordinates with CameraComponent.globalToLocal and using the resulting viewport Y (0-1600 range) directly as a world Y. Since the ball can be at world Y far from zero after bouncing, this caused a large camera jump on every click. Removed the broken center-tap camera movement and added DragCallbacks so clicking and dragging now smoothly pans the camera target via localDelta.
Directly modifying cameraTarget.position during drag was being overwritten each frame by the running MoveCameraTarget effect (e.g. the bounce animation), causing jank. Add CameraTarget.nudge() which shifts both _from and _to of the animation path alongside the position, so any active animation is preserved but offset by the drag delta instead of fighting it.
…ra move Only the left/right tap areas control the ball. The center-tap camera movement used viewport coordinates as world coordinates, causing large jumps, so it has been removed.
event.localPosition is in the InputHandler's local space (0 to size.x = 900), but the thresholds were comparing against game.size.x (the actual canvas width). On desktop this could exceed 900, making the right tap region unreachable and all taps fall in the dead center zone.
…ad zone The original third-based split left a center region that did nothing useful for ball control. Split at the midpoint so every tap moves the ball.
spydon
changed the title
wolfenrain
approved these changes
May 18, 2026
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Description
The center-tap handler in
InputHandlerwas usingCameraComponent.globalToLocal(event.canvasPosition)to obtain a Y coordinate, then passing it directly as a world-space target tocameraTarget.go(). However,globalToLocalreturns viewport-space coordinates (0-1600 range for a 900x1600 camera), not world-space coordinates. Since the ball can be at world Y far from zero after bouncing up, this caused a large camera jump every time the user clicked anywhere in the center area.The fix removes the broken center-tap camera movement and adds
DragCallbacksso that clicking and dragging smoothly pans the camera target usingevent.localDelta, which is already in world-space units.Checklist
docsand added dartdoc comments with///.examplesordocs.Breaking Change?
Testing instructions
cd examples/games/crystal_ball && flutter runRelated Issues