953f9c5c3c
Guru and SchCotie are gone. Shift is the only mark, and the crash screen draws it where the face used to be. Guru was an icon -- a pictogram with a face, denoting one state -- that lived on the crash screen and nowhere else. Its argument was identity: `:(` is recognisably Microsoft's, and a crash screen is the single screenshot most likely to leave the machine, so it is the worst place to be wearing somebody else's face. That part holds, and it is kept in the branding README because it is the argument against any second mark. What does not follow is that the answer is a *new* mark. Shift already signs the system, it is already what the machine drew on the splash it started with, and a reader who has seen it twice before the crash recognises it faster than a face they have never seen. SchCotie was a mascot, and never existed: the file said so itself under "what this does not cover". A brief for a character nobody is about to draw is not worth carrying. So `draw_guru()` and its SVG-space geometry leave panic.c, the two `guru.svg` files are deleted, and PSOGM calls gfx_draw_logo() -- the same include/logo.h mask the loader splash and the boot console composite. At its native 128 px: there is no resampler in the crash path, and the face was scalable in a place that only ever drew it at one size. The name stays. "Purple Screen of Guru Meditation" is the Amiga nod, which panic.c's own header already called out as a separate thing from the mark. **And taking the screenshot to check it caught a regression from the TTF console work.** `gfx_draw_char()` -- the pixel-positioned path, which only PSOGM uses -- still walked `font_data[c][row]` for `row < CHAR_HEIGHT`. font_data has exactly 16 rows per glyph; CHAR_HEIGHT is the *TrueType* cell height now, about 21. So every line of the crash report drew five rows of the next character's bitmap underneath itself, and it looked like each line had been printed twice. The grid path had been updated when the cell size stopped being a constant; this one had not, because nothing routine draws text in pixel coordinates. Both go through one draw_glyph_px() now, and the bitmap's own geometry is spelled BITMAP_W/BITMAP_H so it cannot be mistaken for a cell size again. Two stale claims corrected while in there, in panic.c's header and in graphics.md: PSOGM has not dimmed-and-floated over the old screen for a while -- it clears to full purple, and the file's own code comment says why -- and there is no longer "a face that is obviously a cartoon". The website's crash section shows the mark in flat white rather than its own violets, which is what the kernel actually draws: PSOGM composites a coverage mask in one colour, and those violets sit close enough to #4B1D9A to half-disappear against it. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
143 lines
6.6 KiB
Markdown
143 lines
6.6 KiB
Markdown
# SchOS documentation
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Four kinds of document, kept in four directories, because they answer four
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different questions and go stale at four different rates.
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| **[architecture/](architecture/)** | *What SchOS is* | Present tense. Describes what is built and working. |
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| **[plan/](plan/)** | *What SchOS will be* | Future tense. Everything here is unbuilt. |
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| **[guides/](guides/)** | *How to work on it* | Imperative. Build it, test it, add to it. |
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| **[history/](history/)** | *Why it is the way it is* | Past tense. Bugs whose cause is not visible from the fix. |
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Plus two that belong to no category and apply to everything:
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**[licensing.md](licensing.md)** — read it before copying anyone else's code in —
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and **[branding/](branding/)**, which holds the marks and the rules for using
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them.
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---
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## The rule that keeps this from rotting
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> **When something is finished, it moves from `plan/` to `architecture/` and is
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> rewritten as a description of the thing rather than a record of building it.**
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A completed item is not a ticked checkbox. A ticked checkbox says the work
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happened; it does not say what the work *produced*, and six months later the
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checkbox is the only thing left and it explains nothing.
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So finishing a piece of work has three steps, and the third is not optional:
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1. The code works and is tested.
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2. The plan entry is deleted.
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3. A description exists in `architecture/` written for somebody who was not
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there — what it does, what shape it has, what it costs, and what it still
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does not do.
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This is not bookkeeping. The tree has already proved it necessary: the network
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stack was finished, verified end to end, and for a month afterwards the only
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description of it anywhere was a checkbox in a roadmap, four levels of
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indentation deep, written in the past tense of somebody arguing for the work
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rather than explaining the result.
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**The "what it does not do" section is the one that pays.** Every description in
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`architecture/` ends with one. A document that only lists a subsystem's
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strengths is marketing, and the reader who most needs the document is the one
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about to trip over a limitation nobody wrote down.
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---
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## Start here
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**New to the tree** → [architecture/README.md](architecture/README.md), the
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system layer by layer, then [guides/layout.md](guides/layout.md) for where the
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files are.
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**Trying to build it** → [guides/building.md](guides/building.md).
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**Wondering what happens next** → [plan/1.0.md](plan/1.0.md), which is the finish
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line *and* the register of everything half-built. Then
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[plan/README.md](plan/README.md) for the order.
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**About to start something new** → the register, first. Nothing new starts while
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it has rows in it, and a row leaves only by being finished or deleted.
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**Something is broken and it feels familiar** → [history/](history/). There is a
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good chance it is in there.
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---
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## architecture/ — what SchOS is
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| [README](architecture/README.md) | The system, layer by layer. Read first. |
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| [boot.md](architecture/boot.md) | Firmware to the first userspace process. |
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| [kernel.md](architecture/kernel.md) | SchIFT: memory, processes, scheduling, traps, signals, SMP. |
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| [syscalls.md](architecture/syscalls.md) | The call table, and the Linux personality that lets real software run. |
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| [filesystem.md](architecture/filesystem.md) | The VFS, the buffer cache, procfs, mounts. |
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| [schfs.md](architecture/schfs.md) | SchFS: the copy-on-write root filesystem. |
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| [devices.md](architecture/devices.md) | The device model, driver binding, the class vtables. |
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| [usb.md](architecture/usb.md) | xHCI, the USB core, and the class drivers. |
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| [graphics.md](architecture/graphics.md) | Framebuffer, text rendering, console, and the crash screen. |
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| [terminals.md](architecture/terminals.md) | The six virtual terminals, and how one is switched to. |
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| [networking.md](architecture/networking.md) | Drivers, lwIP, sockets — Unix and INET. |
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| [init.md](architecture/init.md) | `schinit`, PID 1 as a role, and the job manifests. |
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## plan/ — what SchOS will be
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| [README](plan/README.md) | The three current decisions and the order they happen in. |
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| [1.0.md](plan/1.0.md) | **The finish line, and the freeze.** What 1.0 contains, what is deferred, and the register of every half-built thing in the tree. |
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| [foundations.md](plan/foundations.md) | The kernel work everything else is blocked on. |
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| [wayland.md](plan/wayland.md) | The GUI stack, and what gets deleted to make room. |
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| [hybrid.md](plan/hybrid.md) | Moving drivers out of the kernel. |
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| [schapi.md](plan/schapi.md) | The long-term API layering, and the compatibility promise. |
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| [roadmap.md](plan/roadmap.md) | Everything else still open. |
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## guides/ — how to work on it
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| [building.md](guides/building.md) | Prerequisites and the build, per host. |
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| [testing.md](guides/testing.md) | The harnesses, and what each one actually proves. |
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| [layout.md](guides/layout.md) | Repository map, and how to add a program or a port. |
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| [adding-a-driver.md](guides/adding-a-driver.md) | Writing one, binding it, publishing its class vtable. |
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## branding/ — the marks
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| [README](branding/README.md) | Shift, the one mark: what it is for, the colour rule, why an icon and a mascot were removed, and why a raster is committed next to its SVG. |
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## history/ — why it is the way it is
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| [README](history/README.md) | What belongs in here and what does not. |
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| [kernel.md](history/kernel.md) | Bugs whose cause was nowhere near their symptom. |
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| [schfs.md](history/schfs.md) | The filesystem's own, from the same period as its design. |
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| [moving-to-linux.md](history/moving-to-linux.md) | The Windows-to-Fedora move, kept for the parts that recur. |
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---
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## Writing one of these
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Four conventions, all of them observable in the existing files:
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**State the cost.** Every design choice gave something up. A document that does
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not say what is a document that will be argued with later by somebody who only
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sees the downside.
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**Prefer the measured number to the remembered one.** "500 of 3565 files carry
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the advertising clause" is worth more than "some do", and it was worth the
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minute it took to count.
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**Write down the bug that shaped it.** Half the non-obvious code in this tree is
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non-obvious because something failed once. If a design is strange, the strangeness
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is load-bearing and the reader deserves to know why before changing it.
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**No dates in headings.** A date in a heading turns a description into a
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changelog, and the description is the thing with a long life. Dates belong in
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`history/`, where they mean something.
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