Flow and algorithm

Platform spec article

Flow and algorithm

Back to Console capabilities ◎ Open feature in platform map

Spec standingStandard

Owner

Piotr Mikstacki pmikstacki@cybernomad.it

Submitter

Piotr Mikstacki pmikstacki@cybernomad.it

Current document

ADRs (3)

1. 0020-no-color-semantics NO_COLOR disables color Accepted

   Any non-empty NO_COLOR strips ANSI emission.

   Context

   Users and CI expect no-color.org semantics for accessibility and logs.

   Decision

   Rule	Detail
   NO_COLOR	Non-empty value must force ShouldEmitAnsi() false
   Reference	no-color.org

   Consequences

   Capability probes and markup render paths consult the same gate.

   Verification anchors

   CapabilitiesTests.bd; Console/Capabilities.bd.

   Open full ADR page

2. 0021-colorterm-truecolor-upgrade COLORTERM upgrades to TrueColor Accepted

   COLORTERM presence selects TrueColor when color allowed.

   Context

   Modern terminals advertise truecolor via COLORTERM without breaking NO_COLOR.

   Decision

   Rule	Detail
   Probe	COLORTERM set → TrueColor when color not stripped
   FORCE_COLOR	May enable emission on non-TTY stdout

   Consequences

   EffectiveColorModel reflects env probes before SGR downgrade (see D-CORE-TERM-0003).

   Verification anchors

   CapabilitiesTests.bd.

   Open full ADR page

3. 0022-lossy-color-downgrade Lossy color downgrade Accepted

   RGB downgrades through palette ladders automatically.

   Context

   Callers should not manually pick CSI color modes per terminal.

   Decision

   Rule	Detail
   Downgrade	RGB → indexed → basic is lossy
   API	No per-sequence model selector on public helpers

   Consequences

   Styled output remains readable on Basic16 hosts without author branches.

   Verification anchors

   AnsiSgrGoldenTests.bd; capability + SGR integration.

   Open full ADR page

Articles

• Contracts and edge cases MUST rules for capability probing and color stripping. article Standard Reviewed Thu May 21
• Design model Capability record, color models, and environment-driven probing. article Standard Reviewed Thu May 21
• Examples Checking capabilities before custom styling. article Standard Reviewed Thu May 21
• Flow and algorithm Probe and strip algorithms for terminal capabilities. article Standard Reviewed Thu May 21
• Verification and traceability Tests and sources for capability probing. article Standard Reviewed Thu May 21

History

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Completeness

OKfeature · 3 SpecSection(s) · 1 H2 heading(s)

Section id	Required	Found
what-this-feature-specifies	yes	yes
implementation-anchors	yes	yes

Full tree: run pnpm verify:platform-spec-layout (writes src/generated/platform-spec-layout-report.json).

Related spec docs

• Feature
  Console capabilities

  Parent feature hub

Purpose

Document flow and algorithm for the Console Capabilities feature: role-specific normative detail beyond the feature hub.

Canonical references

• Feature hub: Console Capabilities
• Sibling articles in this bundle (design model, contracts, flow, examples, verification)

Detailed behavior

ProbeStdout algorithm

1. isTty ← Terminal.IsAtty(1) != 0
2. colorDisabled ← EnvFlagSet("NO_COLOR")
3. colorForced ← EnvFlagSet("FORCE_COLOR")
4. model ← Terminal.ProbeColorModel() (honors ForcePlainText internally)
5. Return Capabilities { ... }

ShouldStripColor decision tree

1. If colorDisabled → strip
2. Else if colorForced → do not strip
3. Else if !isTty → strip
4. Else → do not strip

ProbeColorModel (platform)

1. If ForcePlainText() → Basic16
2. Else if COLORTERM set → TrueColor
3. Else match TERM (xterm-256color, xterm-color, …)
4. Default → Indexed256

Downstream Ansi.Sgr reads the model once per IntoPrefix / RGB call path.

Verification

See the verification and traceability article in this bundle and compiler/corelib/beskid_corelib/tests/corelib_tests/src/console/.

Related topics

• Parent feature hub and Terminal and console area