qtvcp probe help: fix broken/blurry images and typos

[PeterStolz]

Fixes the bundled help pages for the VersaProbe and Basic Probe dialogs in qtvcp. Three commits:

1. Fix broken image paths

The versaprobe (pages 4-7) and basic_probe (pages 7-8) help pages referenced their images through an absolute path baked into a developer's home directory (/home/chris/emc/share/qtvcp/images/...), so they rendered as broken-file icons on every install. basic_probe page 6 also omitted the .png extension. Pointed them at the existing assets via the relative ../images/ form the loader rewrites.

2. Render help diagrams crisp at display size

The help dialogs (QTextEdit) rescale images with no smoothing, so the diagrams looked soft or pixelated: most pages forced width=500 onto images of widely varying native sizes, and the versaprobe diagrams pointed at tiny 300px thumbnails. Shipped the diagrams pre-scaled to their 500px display width (Lanczos) in new probe_icons_help/ and basic_probe_help/ dirs and reference those, so Qt draws them 1:1 with no rescaling. Generalised the loader image-path rewrite from ../images/probe_icons/ to ../images/ so any image subdir resolves. Also centred the versaprobe page-4 image to match the other pages and dropped the width override on basic_probe page 4 (480px native, was being upscaled).

3. Fix typos in help text

Corrected several typos in the help text (then->than, imprial->imperial, clearence->clearance, a missing word, a garbled sentence rephrased to match the wording already used on page 1, and the stray EXTRA CLEARANCE references renamed to the actual field name EXTRA DEPTH).

No functional/behaviour changes - HTML, help images, and one loader string.

[BsAtHome]

Wouldn't it be better to replace the images, that are no screen-shots, to be SVG images? Or can't QtTextDocument render SVG images linked in html <img> tags?

[PeterStolz]

Good question — I looked into it properly. QTextDocument does render SVG via <img> (Qt's qsvg imageformat plugin, which qtvcp already pulls in for icons — I verified it draws vector-crisp even when upscaled), and you're right that the diagrams are vector at heart: the versaprobe ones carry Software: www.inkscape.org in their PNG metadata, so they were originally drawn in Inkscape.

The snag is that the .svg sources were never committed — only the PNG exports are in the tree (I checked the full history too), and a couple of the help images are actually gnome-screenshot captures of the panel, which can't be vectorised anyway.

So instead of bundling resized PNG copies, I switched the help-dialog loader to pre-scale each raster image to its display size with a smooth filter and register it as a document resource, so Qt draws it 1:1 rather than nearest-neighbour (which was the cause of the jaggies). SVG <img> are passed straight through untouched, so if the original Inkscape sources ever surface they can just be dropped in with no further code change. Pushed as the latest commit — no new assets added.

[PeterStolz]

For scope, while it's fresh: because this fix lives in the VersaProbe/BasicProbe widgets themselves, it lands everywhere those are embedded: qtaxis, qtdragon, qtdragon_hd/qtdragon_hd_vert, qtdragon_lathe, woodpecker, x1mill, plus the standalone panels/versaprobe (which embeds into any GUI, including AXIS/gmoccapy), not just one screen.

One thing I noticed in there: the two HelpDialog classes in versa_probe.py and basic_probe.py are ~80% identical (they differ only in title, page list, preference key, page step, and one fallback string). They could be collapsed into a single shared HelpDialog base, which would also let this scaling helper live in one place instead of being duplicated. Happy to do that as a follow up if there's interest.

[c-morley]

Thanks for work. More pull requests will be happily welcomed.