Show a more useful error when a Nikon High Efficiency NEF fails to load - #812
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marcinz606 merged 3 commits intoAug 12, 2026
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Reported as "NegPy won't open this NEF" on a Z 8 file. It is not a NEF fault: the camera recorded it in High Efficiency (HE / HE*), which is intoPIX TicoRAW under a licensed codec. Nothing in the tags gives it away. The TIFF Compression reads 34713, "Nikon NEF Compressed" -- the same value a lossless NEF carries -- so libraw parses the file, reports the full 8280x5520 sensor and a valid crop, and only fails when the payload is unpacked, with "Unsupported file format or not RAW file". To someone whose other NEFs all work, that reads as a corrupt file. Only the payload distinguishes them: the strip opens with a plain-text intoPIX vendor marker, and the ratio is 0.357 against ~0.55-0.70 for lossless. `unsupported_raw_reason` recognises that marker and returns wording that says what to do -- re-shoot Lossless Compressed, or convert to DNG. The loader stays lazy: the check runs only once a decode has already failed, so a file that works never pays for it (measured 1.5 ms on a lossless NEF, which is 1.5 ms saved on every decode of every good file). Anything it does not recognise keeps libraw's own message, which is the honest answer for a genuinely corrupt or unknown file. Ruled out on the way: stripped MakerNotes (intact, 67 KB across 77 Nikon tags) and a truncated file (every other IFD reads, including a full-resolution JPEG preview). Verified through the app headless -- the status line, the error signal and load_failed all carry the new wording -- and the detector is tested against a byte-built synthetic HE NEF as well as the real one, so it does not depend on a single sample.
The toast was an unwrapped QLabel. Fine for "merging exposures"; not for a message that has to say what went wrong and what to do about it, which ran off both edges. It now wraps within a share of the canvas width. Two bounds, because one is not enough: the maximum keeps it clear of the edges, and the minimum stops Qt's wrapping sizeHint -- which aims for a squarish block -- folding a sentence into five narrow lines when it has the width for two. Short toasts keep their natural size. The bounds are applied when the message is posted as well as on resize, since a load failure can post one before the HUD has ever been resized. Measured at 1400px canvas: the unsupported-raw message goes from one overflowing line to 770x52, and "merging exposures" is unchanged at 327x34. The NEF message is shortened to suit, saying the same thing in half the words. Noted while rendering it, not changed: showMessage lowercases every toast, so this one reads "nikon high efficiency (he) raw -- negpy cannot decode this format ... convert to dng". That is a good voice for activity toasts and it flattens the acronyms in anything the user has to act on. Left alone because it is a house-style decision rather than a fault, and it predates this change; worth a look if error toasts become common.
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We can't load Nikon High Efficiency NEF files because libraw doesn't support the codec. This creates a more useful error message if someone tries to open one (and also fixes wrapping in the toast, so the whole message is visible).
Related to #808