Martino Ferrari
c1460a6977
The help was 14 Pango-markup `.txt` bodies in a second GResource, drawn into a paged `GtkWindow` built in `help_window.cpp`. That made F1 a viewer of ours with no search index, no cross-references and no translation, and it kept the manual in the *binary* when every other desktop application's is a document on disk. It is now a real Mallard set: help/C/org.udpscope.app/ index.page + 14 topic pages + figures/*.png and `show_help()` hands `help:org.udpscope.app` to whatever the desktop registered for the `help:` scheme -- Yelp on GNOME -- through a `GtkUriLauncher`, reporting a launch failure with a `GtkAlertDialog` rather than a click that silently does nothing. The paged window's builder, the page table and `help_self_check()`'s markup validation are gone with the resource. The document identifier is the desktop file's own basename (its desktop-file id), derived in CMakeLists from `data/org.udpscope.app.desktop.in`, so the same string is the `.desktop` name, the GApplication id and the install directory at once. The set is installed by a new `install()` rule to `<datadir>/help/C/org.udpscope.app/` -- where the freedesktop Help System Specification's `help:` URI resolves `help:<id>` -- so the manual is read from a datadir by another process even though the binary has no install step. `UDPSCOPE_HELP_NAME` and `UDPSCOPE_HELP_DIR` are compiled in from that one place. The 14 pages were migrated fact for fact, but restructured the Mallard way: a `<desc>` per page (what a search result shows), `<steps>` for procedures, `<terms>` for option lists, `<gui>`/`<key>`/`<keyseq>` for interface words and keys, `<note>` for the asides, and a topic graph via `<link type="guide" xref="index#main"/>`. The figures are annotated screenshots produced by `tools/make-help-shots.sh`, which drives the app headlessly against `tools/mock_udpstreamer.py` and draws the boxes with ImageMagick; the side panel's box is measured from the app's own `side=NNNx` dump reading, the header and status bands come from a documented table, and a crop whose standard deviation is 0 fails the script. `cmake --build build --target test-help` checks the set the way `test-ui` checks the `.ui` files: `yelp-check`'s offline subcommands (links, media, orphans, ids) and a `yelp-build html` render. `yelp-check validate` is deliberately absent -- it fetches the Mallard RelaxNG schema over the network and fails offline for that reason, not for a fault in the pages. The `[help]` probe reading changes with the resource it was written for. `parsed == pages` over in-binary markup cannot exist now, so `help_self_check()` scans `UDPSCOPE_HELP_DIR` and the line reads `topics=14 index=1 figures=3`; `topics=0 index=0` is the manual missing from the tree, which is the finding the old count named. Verified: clean build with the documented three warnings (the help bundle's `-Woverlength-strings` is gone, so the baseline moves from four to three); test-ui 14/14; test-help clean (the four subcommands and 15 pages rendered); a temp-prefix install lands 15 `.page` files and 3 figures at `share/help/C/org.udpscope.app/`; the headless run reads `[help] topics=14 index=1 figures=3 dir=...` with 0 Gtk-CRITICAL. Yelp's own window could not be exercised on this box -- it starts under Xvfb, activates its portals and never maps, the same WebKit/portal limitation that stops a grab -- so its rendering and its search index are unverified here; the content pipeline was (`yelp-build` renders the whole set). Docs: the manual's build/install/open story in `build-and-run.md` and README; the warning baseline in `verification.md`/CLAUDE.md; the help bullets in `invariants-gtk-and-chrome.md`; the `[help]` line in `probe-readings.md`.
67 lines
2.9 KiB
Plaintext
67 lines
2.9 KiB
Plaintext
<page xmlns="http://projectmallard.org/1.0/"
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type="topic" style="task"
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id="window">
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<info>
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<link type="guide" xref="index#viewing"/>
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<link type="seealso" xref="navigate"/>
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<desc>The time window control: how to set it, and why a long window is decimated rather
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than refused.</desc>
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<credit type="author copyright">
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<name>Martino Ferrari</name>
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</credit>
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</info>
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<title>Time window</title>
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<p>The window is how much time the plot shows. Every row shares one window: the figure has
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a single x link group, so the rows cannot drift apart. The trigger's event span follows it,
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and the pre-trigger share is a share of <em>this</em> window.</p>
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<section id="reach">
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<title>How to reach it</title>
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<steps>
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<item>
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<p>The header bar's window button opens a popover: type a number, pick a unit under
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it, or step a decade with the arrows.</p>
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</item>
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<item>
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<p>The button's own label is a reading of the current window in a natural unit,
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width-locked so a change of window cannot widen the header bar.</p>
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</item>
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</steps>
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</section>
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<section id="knowing">
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<title>Worth knowing</title>
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<list>
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<item><p>A window too long to store at the wire rate is <em>decimated, not refused</em>.
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The shared clock takes a power-of-two stride, and each group of samples is
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<em>averaged</em> rather than strided, so a tone above the stored Nyquist is attenuated
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instead of aliasing to a false low frequency.</p></item>
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<item><p>The stamp stored for a group is the group's <em>mean</em>, which is where the
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averaging puts the value. Stamping at the end of a group would shift every trace half a
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stored sample late.</p></item>
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<item><p>Moving the window across a decimation boundary rebuilds the buffer and drops
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the history. Walking it inside one decade is free.</p></item>
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<item><p><em>This control is the only thing that changes the window.</em> A zoom, a pan
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or a fit moves the view <em>inside</em> it and leaves it alone — which is the point of
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the previous bullet: a wheel notch that redefined the window could re-plan the buffer
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and throw your samples away.</p></item>
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<item><p>The trigger sees the <em>stored</em> (filtered) signal, not the wire signal,
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because an edge found on a sample that is not in the buffer could not be cut out of
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it.</p></item>
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</list>
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</section>
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<section id="example">
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<title>Example</title>
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<p>1 MS/s with 200 MB of buffer. A 2 s window stores every sample
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(<code>time x1</code>). Widen it to 600 s and the stride becomes <code>x16</code>: 625 S/s
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stored, anti-aliased at 312.5 Hz. A 2 kHz sine seen through that window reads
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<code>y=[-0.059, 0.079]</code> — attenuated to about 6%, not folded down to a
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full-amplitude 125 Hz one.</p>
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</section>
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</page>
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