Icod.DCurses

Icod.DCurses is a managed, cross-platform curses-like terminal UI library for .NET.

The library sits above Icod.TermInfo and Icod.Terminal. Icod.TermInfo remains the immutable terminal-capability authority; Icod.Terminal owns the live terminal session, host mode, dimensions, lifecycle, input decoding, and reversible presentation and input-protocol leases. Icod.DCurses owns curses-shaped events, virtual screens and windows, terminal cells and styles, rendition policy, and refresh/damage synchronization.

Status

Icod.DCurses 0.3.0 is the current published stable release.

The 0.4.0 window editing and composition contract is feature-frozen and has passed its release-candidate gate. The source version and package version are now stable 0.4.0; publication remains post-merge until the matching main commit passes the Release matrix and v0.4.0 is created.

T401-T403 established the 0.4 package foundation, explicit non-standard window repositioning, window-local cell inspection, rectangular fill, and clear-to-beginning-of-line.

T404 adds Unicode-safe cell and line insertion/deletion using snapshot-transform-commit semantics. T405 adds deterministic destructive copy and blank-transparent overlay, including same-window overlap. T406 adds geometric horizontal/vertical lines and explicit border construction while leaving capability-aware line-glyph selection to the planned 0.6 presentation release.

T407 completes the feature-side release with safe range-oriented damage marking and querying. A public untouch operation is deliberately omitted because arbitrarily clearing logical dirty state could suppress refresh work still required by retained physical-screen knowledge.

T408 is complete: the 0.4 public API, documentation, dependency boundary, and fresh package-consumer surface passed the regret gate. 0.4.0-rc.1 then passed Windows, Linux, macOS, and canonical package/fresh-consumer validation without a public-contract correction. T409 has promoted that unchanged contract to stable 0.4.0 source for one final PR validation before merge.

0.3.0 established the Unicode terminal-cell contract: malformed UTF-16 is normalized before segmentation; width decisions operate on complete text elements; Unicode 17.0.0 East Asian Width and Emoji-property data are generated and checked in; East Asian Ambiguous policy is explicit; and public column-measurement/truncation/slicing helpers share the same rules as window writes.

0.2.0 completed stable Icod.Terminal 1.0.0 semantic-input parity: the curses facade carries the complete stable key vocabulary, modifier state, press/repeat/release phases, modern character metadata, and optional keyboard reporting while keeping raw terminal decoding and protocol lifecycle in Icod.Terminal.

The dependency baseline remains:

• Icod.Terminal 1.0.0
• Icod.TermInfo 1.10.0

The retired DCurses backend, native mode, lifecycle-source, input-decoder, and pre-Terminal session implementations remain removed. DCurses does not add a mouse parser, paste reader, protocol escape emitter, keyboard decoder, or second input loop.

The first release line was driven by the requirements of top, slabtop, and watch. The 1.0 development train broadens that foundation into a general managed TUI contract.

See Icod.DCurses-1.0.0-Development-Roadmap.md for the authoritative release train through 1.0.0, and Icod.DCurses-0.4.0-Development-Roadmap.md for the window editing/composition tranche. The 0.4 checkpoints and release gates are recorded in:

• docs/T402-T403-Window-Geometry-and-Region-Editing.md
• docs/T405-Window-Composition.md
• docs/T406-Geometric-Line-and-Border-Drawing.md
• docs/T407-Damage-Ranges-and-Editing-Acceptance.md
• docs/T408-Public-API-Documentation-and-Package-Regret-Gate.md
• docs/T409-0.4.0-Stable-Release-Closure.md
• docs/Public-API-Baseline-0.4.md

The completed 0.3 Unicode release is recorded in Icod.DCurses-0.3.0-Development-Roadmap.md, its T302-T308 documents, and docs/Public-API-Baseline-0.3.md.

Icod.DCurses-0.2.0-Development-Roadmap.md and docs/Public-API-Baseline-0.2.md record the stable semantic-input release. docs/Dependency-Baseline-0.1.1.md retains the Terminal/TermInfo ownership baseline inherited by later releases.

Icod.DCurses-Development-Roadmap.md retains the original project roadmap and 0.1 development history. Historical integration checkpoints remain under docs/.

Architecture

top / slabtop / watch / other TUIs
                 |
            Icod.DCurses
     windows / cells / refresh
       rendition / curses events
                 |
            Icod.Terminal
 session / input / lifecycle / dimensions
 presentation / input-protocol leases
                 |
            Icod.TermInfo
      terminal capability model
                 |
            terminal / tty

Icod.DCurses does not hard-code one terminal family. Terminal-specific output continues to be selected through Icod.TermInfo, while live session ownership and reversible terminal state are centralized in Icod.Terminal.

Target

The implementation targets:

• .NET 8
• .NET 9
• .NET 10
• C# 13
• Windows
• Linux
• macOS

Installation

The current published stable package is:

dotnet add package Icod.DCurses --version 0.3.0

Quick start

using Icod.DCurses;

await using CursesSession session = await CursesSession.OpenAsync();
CursesWindow screen = session.StandardScreen;

screen.Clear();
screen.Move(
    0,
    0
);
screen.Write(
    "Hello from Icod.DCurses",
    new CursesStyle(
        CursesColor.Default,
        CursesColor.Default,
        CursesTextAttributes.Bold
    )
);
await session.RefreshAsync();

CursesEvent terminalEvent = await session.ReadEventAsync();

The session owns the presentation state it enters and restores that state when disposed. Applications should consume terminal input and lifecycle activity through CursesSession rather than adding a parallel terminal reader.

Window editing and composition (0.4)

The 0.4 line adds window-local editing and composition while retaining the shared-view model:

CursesScreen logical = new( 80, 24 );
CursesWindow editor = logical.CreateWindow( 2, 4, 18, 60 );

editor.Reposition( 3, 5 );
editor.FillRectangle( 0, 0, 18, 60, CursesCell.Blank() );
editor.Move( 1, 2 );
editor.Write( "A界B" );
editor.InsertCells( 2 );

CursesWindow status = logical.CreateWindow( 21, 5, 1, 60 );
editor.CopyRectangleTo( status, 1, 0, 1, 20, 0, 0 );

editor.DrawHorizontalLine( 16, 1, 58, new CursesCell( "-" ) );
editor.TouchRegion( 0, 0, 18, 60 );
bool needsRefresh = editor.IsRegionTouched( 0, 0, 18, 60 );

CopyRectangleTo includes source blanks; OverlayRectangleTo treats ordinary source blanks as transparent. Overlapping copies snapshot the source before any destination write. Editing and drawing preserve the cursor and retain the 0.3 wide-cell invariants.

Drawing methods accept caller-supplied one-column cells in 0.4. Capability-aware Unicode/alternate-character-set line-glyph selection is intentionally deferred to the 0.6 presentation tranche.

Unicode column helpers (0.3)

Applications can measure or trim printable text using the same terminal-column contract as window writes:

int columns = CursesText.MeasureColumns( "A界B" );
string prefix = CursesText.TruncateToColumns( "A界B", 3 );
string slice = CursesText.SliceByColumns( "A界B", 1, 2 );

The default provider uses Unicode 17.0.0 data and treats East Asian Ambiguous characters as narrow. Applications that deliberately require wide-Ambiguous semantics can pass UnicodeCursesTextWidthProvider.WideAmbiguousInstance to a CursesScreen or to the CursesText helpers.

Column helpers normalize malformed UTF-16 before text-element segmentation, reject terminal controls, and never return half of a two-column text element.

Modern keyboard input (0.2)

Applications which want key-event phases can request them through the curses protocol lease without using Terminal protocol types directly:

var keyboard = await session.AcquireInputProtocolsAsync(
    new CursesInputProtocolOptions {
        KeyboardReportingMode = CursesKeyboardReportingMode.EventTypes
    }
);

if ( keyboard.IsAvailable ) {
    await using CursesInputProtocolLease lease = keyboard.GetRequiredValue();
    CursesEvent current = await session.ReadEventAsync();

    if ( current.Input is {
        Kind: CursesInputEventKind.Key
    } input ) {
        CursesKey key = input.Key;
        CursesKeyEventPhase? phase = input.KeyPhase;
        CursesKeyModifiers modifiers = input.Modifiers;
    }
}

Keyboard reporting is optional. A terminal which cannot provide the requested mode returns a controlled unavailable result; applications can continue using the ordinary curses input stream.

Build

From the repository root:

build.cmd

or:

./build.sh

Both wrappers delegate to packaging/Invoke-Build.ps1 and use the Debug configuration for local development. With no section argument they perform restore, build, test, pack, and package validation. They also accept clean, restore, build, test, pack, or validate; prerequisite phases are run automatically where needed.

Pull-request validation promotes the build to Staging. Pushes to main and release tags use Release. Package validation exercises the packed artifact and a fresh package-only consumer rather than relying only on the repository project references.

The Unicode width-data generator is a maintainer tool outside the solution. See tools/unicode-width-generator/README.md; normal builds do not fetch Unicode data from the network.

Authors

Timothy J. Bruce.

Copyright

Copyright (c) 2026 Timothy J. Bruce

License

Licensed under the GNU Lesser General Public License v3.0 or later. See LICENSE.

The NuGet package declares license acceptance as required. Package clients which honor NuGet's requireLicenseAcceptance metadata must obtain acceptance of the license terms before installation.