Disable cursor-pixel readout in CameraDisplay#1748
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The pixel-value readout added in e6813d8 ("Show pixel co-ordinate with their pixel value in image", ros2#1716) lives in ImageDisplay and maps cursor position to image pixel coordinates assuming the image fills the panel with plain aspect-preserving letterboxing. CameraDisplay inherits this mapping but lays out its background image rectangle differently — via calculateScreenCorners(), which scales the rectangle by the user-controlled "Zoom Factor", applies a FOV-derived (not pixel-derived) aspect ratio, and honors CameraInfo.roi. None of that is taken into account by the inherited mapping, so the reported pixel value is wrong whenever the zoom factor is not 1 (and slightly off in some other cases too). Rather than duplicate or generalize the mapping for CameraDisplay, disable the readout there by no longer populating last_msg_ in CameraDisplay::processMessage(). With last_msg_ left unset, mapWidgetPosToImagePixel() short-circuits and the tooltip/status stay empty — silence is better than a plausible-looking but incorrect value. ImageDisplay itself is unaffected. Fixes ros2#1747 Signed-off-by: Arne Baeyens <mail@arnebaeyens.com>
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Description
The pixel-value readout added in e6813d8 ("Show pixel co-ordinate with their pixel value in image", #1716) lives in ImageDisplay and maps cursor position to image pixel coordinates assuming the image fills the panel with plain aspect-preserving letterboxing. CameraDisplay inherits this mapping but lays out its background image rectangle differently — via calculateScreenCorners(), which scales the rectangle by the user-controlled "Zoom Factor", applies a FOV-derived (not pixel-derived) aspect ratio, and honors CameraInfo.roi. None of that is taken into account by the inherited mapping, so the reported pixel value is wrong whenever the zoom factor is not 1 (and slightly off in some other cases too).
Rather than duplicate or generalize the mapping for CameraDisplay, disable the readout there by no longer populating last_msg_ in CameraDisplay::processMessage(). With last_msg_ left unset, mapWidgetPosToImagePixel() short-circuits and the tooltip/status stay empty — silence is better than a plausible-looking but incorrect value. ImageDisplay itself is unaffected.
Fixes #1747
Is this user-facing behavior change?
Yes, this fixes a user-facing bug.
Did you use Generative AI?
Claude Opus 4.7