docs: 0.2.6.3 — what was measured, the manual, and Sunday's checks

Why black and white is made with Ghostscript and how close it is to what Elmer prints; why Print image goes through the engine's copy image, with the table of what each other way failed on; what it cannot reach (a CSS background picture) and what it costs (the clipboard lives in Wonder Ink afterwards). The manual says Print page and Print image, and that the preview turns grey. Sunday's paper checks for both, in testing.md. Co-Authored-By: Claude Opus 5.5 <[email protected]>
2026-09-26 16:34:38 -05:00
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 # Backlog — 0.3.0 and later
 Recorded after hands-on testing of 0.2.6.1 in September 2026. **None of
-this is in 0.2.6.2**, which is limited to picture printing, the
+this is in 0.2.6.2 or 0.2.6.3**: 0.2.6.2 is limited to picture printing,
-Presentations memory failure and the settings lockdown. Each item says
+the Presentations memory failure and the settings lockdown, and 0.2.6.3
-what was observed, so whoever picks it up starts from the evidence.
+to the black-and-white preview and Print image. Each item says what was
 observed, so whoever picks it up starts from the evidence.
 ## Wonder Ink
@@ -23,6 +24,15 @@ what was observed, so whoever picks it up starts from the evidence.
 - **Readable worksheet names.** Tabs show the downloaded file's name,
  which for many worksheets is a long generated prefix. Strip it, or take
  the name from the PDF's own title.
 - **Print image and CSS background pictures** (from 0.2.6.3). The engine's
  hit test does not call a CSS background a picture, so right-click there
  offers only Print page. Only worth doing if Sunday's testing finds
  Wonder Ink's site draws artwork that way; the lab has no account to
  tell. See wonder-ink.md, *Print image*.
 - **The clipboard after Print image** (from 0.2.6.3). It is put back, but
  owned by Wonder Ink afterwards, so text copied elsewhere before is gone
  once Wonder Ink closes — there is no clipboard manager in the session.
  Measured, and judged smaller than leaving the picture there.
 - **A speaker on the tab that is playing sound** (`QWebEnginePage.recentlyAudible`).
 - **Linked lesson text opens an intermediate popup** instead of following
  the link, where Chrome follows it directly. Investigate: probably a
@@ -32,18 +32,28 @@ The size applies to every tab and is remembered next time.
 ## Printing
 Press **Ctrl** and **P**, click **Print** at the top right, or right-click
-and choose **Print…**. You will see the pages exactly as they will print.
+and choose **Print page…**. You will see the pages exactly as they will
 print.
 * Choose **Only some pages** to print, for example, `2` or `1-3`.
 * Set **Copies** for the number of children.
-* Choose **Black and white** to save color ink.
+* Choose **Black and white** to save color ink. The preview turns grey,
  so you see what will come out; choose **Color** to go back.
-**Printing a picture.** When the tab is a picture on its own, the
+**Printing a picture from the lesson.** Right-click the picture and
-preview also shows **Picture**: choose its **Size** (for example 50%),
+choose **Print image…**. Only that picture prints, not the page around
-click one of the nine **Position** squares to put it in a corner or the
+it. This works for pictures you cannot open by themselves.
-middle, and choose **Paper** upright or sideways. The preview changes as
+
-you choose, and shows exactly what will print. **Fill the whole page**
+In the preview for a picture, also under **Picture**: choose its
-makes it cover the paper but cuts off the edges.
+**Size** (for example 50%), click one of the nine **Position** squares to
 put it in a corner or the middle, and choose **Paper** upright or
 sideways. The preview changes as you choose, and shows exactly what will
 print. **Fill the whole page** makes it cover the paper but cuts off the
 edges. A picture that is open in a tab by itself prints the same way.
 If Wonder Ink says a picture *could not be taken from the page*, it had
 not finished loading: close the preview and try again, or choose **Print
 page…** to print the whole page instead.
 Click **Print**. Wonder Ink says when the printer has it and goes back to
 the lesson. **Cancel** prints nothing.
@@ -149,6 +149,17 @@ nothing else about the room's locks moves.
 | `notif-13pt`, `notif-15pt` | the two font sizes that were weighed for it |
 | `pc-typed-layer` | the card gone: the lab's keyboard tool closes it, which is why typing is still a bench test |
 ## Wonder Ink printing
 Under the lab's real Plasma session, driven with the pointer. See
 [wonder-ink.md](../wonder-ink.md), *Printing*.
 | | |
 | --- | --- |
 | `pic-preview-default`, `pic-preview-half-topleft` | a picture in a tab of its own, laid out on Letter: as large as fits, then 50% top left (0.2.6.2) |
 | `print-image-menu` | right-click on a picture inside a lesson: **Print image…** and **Print page…**; on the words there is only Print page (0.2.6.3) |
 | `print-image-bw-half-topleft` | Print image on a signed-in picture, 50% top left, Black and white — the preview grey, as the job CUPS kept was (0.2.6.3) |
 ## Failures, kept
 | | |
@@ -575,14 +575,14 @@ ifupdown stanza is already gone. **Do not run `--adopt` on it.**
      still reports `yes`
 - [ ] The laptop still reconnects after a reboot
-## Wonder Ink — 0.2.6.1 and 0.2.6.2, before either goes to stable
+## Wonder Ink — 0.2.6.1 to 0.2.6.3, before any goes to stable
 Everything below was done in the lab except what a lab cannot do: paper,
 a classroom's own graphics, a real keyboard, its network and its screen.
 Those are these checks. Stable stays on 0.2.2 until they pass.
 Before starting, on each machine: `dpkg-query -W ekklesia-classroom`
-must say `0.2.6.1`. The desktops only get it once stable is moved, so on
+must say `0.2.6.3`, which carries everything 0.2.6.1 and 0.2.6.2 did. The desktops only get it once stable is moved, so on
 a desktop install it by hand for the test:
 ```
@@ -600,14 +600,14 @@ after testing, either promote or reinstall 0.2.2 the same way.
 - [ ] Open Wonder Ink, sign in, open a lesson with a worksheet
 - [ ] Click the worksheet; it opens as a tab named after the file, with a
      document icon
- [ ] Ctrl+P (or right-click → Print…): the preview shows the worksheet's
+- [ ] Ctrl+P (or right-click → Print page…): the preview shows the worksheet's
      own pages, page count right, ‹ › turn them
 - [ ] Printer shows **Elmer**, preselected
 - [ ] Print → a notification "Sent to the printer — … — Elmer", Wonder Ink
      stays open on the lesson
 - [ ] **The worksheet comes out of Elmer**, every page, right size, in colour
- [ ] Pages `2`, Copies `2`, Black and white → exactly two grey copies of
+- [ ] Pages `2`, Copies `2`, Black and white → the preview turns grey,
-      page 2 come out
+      and exactly two grey copies of page 2 come out
 - [ ] Print a normal lesson page the same way; it comes out, Letter
 - [ ] Open the preview and press Cancel → nothing prints
 - [ ] Print three times in a row → three printouts, no crash
@@ -627,6 +627,43 @@ after testing, either promote or reinstall 0.2.2 the same way.
 - [ ] A worksheet PDF still prints with no Picture section
 - [ ] The print dialog says **Color**, not Colour
 ### Black and white, and Print image (0.2.6.3)
 The lab measured all of this on the files CUPS kept, and under the real
 Plasma session for the clipboard. What it cannot show is Wonder Ink's own
 site (no account), real paper, and a classroom's own keyboard and mouse.
 - [ ] A lesson page with colour on it: Ctrl+P, then **Black and white** →
      the preview says *Preparing black and white…* for a moment, then the
      page is **grey**. **Color** → colour again. Back and forth three
      times: it is instant after the first, and stays on the same page
 - [ ] Print it in black and white: **the paper matches the grey preview**
 - [ ] The same with a worksheet PDF (a few pages), in black and white
 - [ ] Choose Black and white, then Color, then Print → it comes out **in
      colour**
 - [ ] In a lesson, **right-click on a picture** (not the words): the menu
      has **Print image…** and **Print page…**. Right-click on the words:
      only **Print page…**
 - [ ] **Print image…** on a picture you cannot open in a tab by itself:
      the preview shows *that picture* on white, with the **Picture**
      section — not the lesson page
 - [ ] Size **50%**, the **top-left** square, Black and white → the preview
      shows a grey picture in the top-left quarter. Print it: **the paper
      matches the preview**
 - [ ] Print image on a picture with a transparent background (a clipart
      animal, a logo) → white around it on paper, not black
 - [ ] Print image, then **Cancel** → nothing prints
 - [ ] Copy some words in the browser, then use Print image in Wonder
      Ink, then paste in the browser → the words paste, not the picture
 - [ ] If any picture says *could not be taken from the page*: note which
      lesson and which picture. Right-click the same picture again once
      the page has finished loading. If it still says so, that picture is
      drawn in a way the engine does not treat as a picture — tell us
      where it is
 - [ ] If right-clicking an obvious picture offers **only** Print page, the
      site draws it as a background. Note which lesson — it is the one
      case Print image cannot reach
 ### Size and zoom
 - [ ] A lesson in Wonder Ink is the same size as the same page in the
@@ -695,4 +732,4 @@ classroom-wonderink --diagnose
      says `false`)
 If anything here fails, leave the desktops on stable 0.2.2 and fix it in
-0.2.6.2 on canary.
+the next maintenance release on canary.
@@ -71,7 +71,8 @@ wrong a teacher is standing in front of a class.
 The right-click menu is built rather than filtered, so a future Qt cannot
 grow view-source or save-page back into it without somebody noticing in
 the code: back, forward, reload, open in a new tab when there is a link,
-cut/copy/paste in a text field, print.
+cut/copy/paste in a text field, print image when there is a picture under
 the pointer, print page.
 Keys: Ctrl+W closes a tab, Alt+Left and Alt+Right navigate, Ctrl+P prints,
 Ctrl+Tab switches. Ctrl+T, Ctrl+N and Ctrl+L are deliberately unbound.
@@ -232,8 +233,9 @@ One dialog, for lessons and worksheets alike:
 * **Pages** — all, or some: `2`, `1-3`, `1, 3, 5-6`, checked against the
  document with the reason given if wrong;
 * **Copies** — 1 to 50;
-* **Colour** — colour or black and white, only where the printer's driver
+* **Color** — colour or black and white, only where the printer's driver
-  has a grey mode, and asked for in that driver's own terms;
+  has a grey mode, and asked for in that driver's own terms. Since 0.2.6.3
  the preview turns grey too (below);
 * **Cancel** sends nothing; **Print** returns to the lesson once CUPS has
  the job, and a notification says where it went. A refused job keeps the
  preview open with CUPS's reason.
@@ -280,6 +282,140 @@ background is left off, measured.
 Temporary PDFs live in the teacher's `$XDG_RUNTIME_DIR` and are removed
 when the preview closes.
 ### Black and white is shown as it prints (0.2.6.3)
 Printing through Elmer found that **Black and white** came out grey on
 paper while the preview stayed in colour. 0.2.6.2 only told the driver:
 the preview was the colour PDF, CUPS was given the colour PDF, and
 `ColorModel=Grayscale` turned it grey inside Elmer's filters.
 So black and white is now made before the preview, not after it. When it
 is chosen, the preview makes a grey copy of the document with
 Ghostscript, shows that copy, and Print hands CUPS that same file — still
 with `ColorModel=Grayscale`, so Elmer's generic PCL 6 driver prints it
 with `pxlmono` as before rather than as a colour job that happens to be
 grey. Choosing **Color** shows and prints the colour document again.
 Measured before building it (Ghostscript 10.05.1, in the lab):
 | | |
 | --- | --- |
 | a lesson page, a picture page, a leader guide, a fillable form | grey and only grey; same pages, page sizes and words; text still text; a filled-in form field and a drawn mark kept, in grey |
 | against what Elmer would have printed | Ghostscript's grey rendering of the colour original and of the grey copy give the **same greys**: within 1 level in 255 on every filled area and picture. Small text can land a fraction of a pixel over — on a real lesson page, 12 of 32,754 8×8 blocks, all on one line of body text, in pairs of opposite sign. Elmer's driver *is* Ghostscript. (poppler's own grey differs on 7% of a coloured page, which is why the copy is not made with poppler) |
 | how long | 0.05 s for a worksheet, 0.2 s for a text lesson page, 1.3 s for a full-page photograph, 2 s for 42 pages — and **4.4 s** for one lesson page with eleven full-size pictures, under the real Plasma session. `-dUseFastColor` saves 40% and changes the greys, so it is not used |
 | a PDF Ghostscript cannot read | exits 1 and **still leaves a file behind** |
 From those:
 * the copy is made in the background, the preview says *Preparing black
  and white…* and Print waits for it — four seconds is long enough to
  look like a frozen window. It has a minute before it is given up on,
  not the 20 s a page render has: a lesson of photographs on a slower
  laptop is slow, not stuck. Cancel stops it at once;
 * it is made once per document and kept, and each drawn page is kept, so
  turning Color and Black and white back and forth is instant after the
  first time, and stays on the page the teacher was looking at;
 * a conversion is judged by its exit status and its page count, never by
  whether a file appeared. If it fails the preview says so and offers
  Color. It **never prints the colour file in its place**: the teacher
  asked for black and white;
 * pages are never turned (pdfwrite otherwise rotates a page to match its
  text), and annotations are drawn into the page as they print, so no
  later filter can draw them again in colour;
 * a printer whose driver has no grey mode is not offered black and white,
  and choosing one returns the preview to colour.
 `tools/lab/wonderink-print-check` shows a colourful lesson in colour,
 turns it to black and white and back five times on page 2, and prints
 page 2 twice: every grey preview is grey pixel for pixel, every colour
 one is not, the grey copy is made once, and the job CUPS kept is
 **byte-for-byte the file the preview showed**, grey on every page, sent
 with `ColorModel=Grayscale` through `pxlmono`. The same for a worksheet,
 a 50% top-left picture, a return to Color (which prints in colour through
 `pxlcolor`), and Cancel.
 ### Print image: a picture from inside a lesson (0.2.6.3)
 Right-clicking a picture in a lesson and choosing Print printed the whole
 page around it. Some of Wonder Ink's pictures cannot be opened on their
 own through the site at all, so a teacher had no way to give that
 picture the picture layout 0.2.6.2 introduced.
 The right-click menu now says what it will print. It asks the engine's
 own hit test what is under the pointer:
 | Under the pointer | Measured `mediaType` | The menu offers |
 | --- | --- | --- |
 | a picture (`<img>`, also inside a link, a frame, from `blob:` or `data:`) | Image | **Print image…** and **Print page…** |
 | a `<canvas>` | Canvas | **Print image…** and **Print page…** |
 | words, empty space, a CSS background picture | None | **Print page…** |
 Print page is always there. Ctrl+P and the Print button print the page,
 as before.
 **How the picture is taken** was measured before anything was built, on
 a lab site with each kind of picture a lesson might have, a real
 right-click on each, and the site logging every request:
 | | signed-in picture | hotlink-protected | one-time address | `blob:` / `data:` | another site's | canvas | WebP |
 | --- | --- | --- | --- | --- | --- | --- | --- |
 | engine's "download image" | ✓ | ✓ | **404** — fetched again | ✓ | ✓ | **nothing** | a file Qt cannot read |
 | `page.download(url)` | ✓ | **403** — no Referer | **404** | – | ✓ | – | the same |
 | `fetch()` from the page | ✓ | ✓ | ✓ | – | **refused** (CORS) | – | the same |
 | draw it on a canvas | ✓ | ✓ | ✓ | ✓ | **refused** (tainted) | – | ✓ |
 | **engine's "copy image"** | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
 Only the engine's own **copy image** hands over the picture in every
 case, and it is what Wonder Ink uses. It is the bitmap the page has
 already decoded — full size, transparency kept, any format Chromium
 reads (Qt itself cannot read WebP here) — and **it fetches nothing**: the
 site saw no request at all. So a picture behind the teacher's sign-in
 needs no sign-in again, and a picture the site hands out once is still
 there. 0.01 to 0.05 s in the lab.
 It goes through the clipboard, which is the teacher's. So what is on it
 is kept first and put back as soon as the picture arrives — whenever it
 arrives, even after Cancel. Measured under the real Plasma session
 (KWin, Wayland) with another program owning the clipboard: saved in
 0.002 s, the picture in 0.016 s, and that other program then pasted its
 own text again.
 The picture then goes into exactly the 0.2.6.2 picture preview — drawn on
 white, capped at 300 dpi across Letter, Size, Position, Paper, Fill the
 whole page, Color — named *Picture from* the lesson's title.
 **When it cannot be taken.** A picture that never loaded is still a
 picture to the hit test, and the engine then copies nothing. After three
 seconds the preview says *This picture could not be taken from the page*
 and that nothing was printed, with Print off. It does **not** fall back
 to printing the page; Print page is one right-click away and says what
 it does.
 What it cannot do, and says nothing about because it cannot know:
 * **a CSS background picture** is not a picture to the engine's hit
  test — Chrome's own menu has no "Save image" for one either. The menu
  offers only Print page. If Wonder Ink's site draws its artwork this
  way, that is the next thing to look at; nothing in the lab says it does;
 * **a video** frame is not offered;
 * **the teacher's clipboard is put back into Wonder Ink.** Under Wayland
  with no clipboard manager — this session has none — the clipboard
  belongs to whichever program last set it. After a Print image that is
  Wonder Ink, so text copied in another program before it can still be
  pasted while Wonder Ink is open, and is gone once Wonder Ink closes.
  Measured in the lab session. Leaving the picture there instead would
  lose it at once.
 `tools/lab/wonderink-print-check` runs a signed-in lesson site
 (`tools/lab/wonderink-lesson-site.py`: session cookie, one-time
 addresses, a second origin) and right-clicks for real: the words (Print
 page only, and the page prints), a JPEG, a PNG, a transparent PNG, a
 one-time picture, another site's, a `blob:`, a WebP, a canvas, a picture
 inside a link, a JPEG at 50% top left in black and white, a picture that
 never loaded, and Cancel. Each is judged on the job CUPS kept: where and
 how large, no ink elsewhere, the corner mark there — and **no request to
 the site** while it printed, and the teacher's clipboard theirs again.
 `tools/lab/wonderink-print-check` runs all of this against the installed
 command in the lab, and judges every scenario by what CUPS actually
 received. `tests/test-classroom-printing.sh` covers the CUPS side at every