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# Cthulhu Development Guide
This document applies to the Cthulhu fork maintained by Storm Dragon.
Cthulhu is forked from Orca; prior Orca maintainers and contributors are part
of the upstream history, but they are not current maintainers of this fork.
## Local Development Build
To develop Cthulhu without overwriting your system installation, use the provided build scripts:
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# Cthulhu Remote Controller (D-Bus Interface)
This documentation covers the Cthulhu fork maintained by Storm Dragon.
Cthulhu is forked from Orca; former Orca maintainers and contributors are part
of the project's upstream history, but they are not current maintainers of
this fork.
> **⚠️⚠️ WORK IN PROGRESS**: This D-Bus interface is brand new and not yet feature complete.
Low-risk feature additions will continue to be made. The API may be
modified beyond bug fixes in future versions based on feedback from consumers of this support.
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## Note
Cthulhu is a fork of the Orca screen reader. Project home: https://git.stormux.org/storm/cthulhu. Cthulhu is currently a supplemental screen reader that fills a nitch for some advanced users. E.g. some older QT based programs may work with Cthulhu, and if you use certain window managers like i3, Mozilla applications like Firefox and Thunderbird may work better.
Cthulhu is a fork of the Orca screen reader. Project home: https://git.stormux.org/storm/cthulhu. Cthulhu is currently a supplemental screen reader that fills a niche for some advanced users. For example, some older Qt-based programs may work with Cthulhu, and if you use certain window managers like i3, Mozilla applications like Firefox and Thunderbird may work better.
## Current Maintenance
Cthulhu is currently maintained by Storm Dragon.
Current contributors called out in this fork's documentation:
- Hunter Joziak
- Harley Richardson (`destructatron`)
## Project History
Cthulhu is forked from Orca and builds on many years of upstream work by the Orca community, including former maintainers and contributors such as Joanmarie Diggs and others.
Those upstream maintainers and contributors are part of the project's history, but they are not current maintainers of this fork unless explicitly noted elsewhere.
## Introduction
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# Cthulhu Remote Controller - Available Commands
This documentation covers the Cthulhu fork maintained by Storm Dragon.
Cthulhu is forked from Orca; former Orca maintainers and contributors are part
of the project's upstream history, but they are not current maintainers of
this fork.
This document lists the currently available D-Bus commands in Cthulhu's Remote Controller interface.
> **Note**: This is a work-in-progress. As more modules are exposed via D-Bus, this document will be expanded. Eventually this will be auto-generated using `tools/generate_dbus_documentation.py`.
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<programming-language>Python</programming-language>
<maintainer>
<foaf:Person>
<foaf:name>Joanmarie Diggs</foaf:name>
<foaf:mbox rdf:resource="mailto:jdiggs@igalia.com" />
<gnome:userid>joanied</gnome:userid>
</foaf:Person>
</maintainer>
<maintainer>
<foaf:Person>
<foaf:name>Federico Mena Quintero</foaf:name>
<foaf:mbox rdf:resource="mailto:federico@gnome.org" />
<gnome:userid>federico</gnome:userid>
<foaf:name>Storm Dragon</foaf:name>
<foaf:mbox rdf:resource="mailto:storm_dragon@stormux.org" />
</foaf:Person>
</maintainer>
</Project>
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Cthulhu is a screen reader for individuals who are blind or visually impaired,
forked from Orca. It provides access to applications and toolkits that support
the AT-SPI (e.g., the GNOME desktop).
the AT-SPI (e.g., GNOME and other Linux desktop environments).
This fork is currently maintained by Storm Dragon. It builds on upstream Orca
work, but former Orca maintainers and contributors are not current maintainers
of this fork.
This screen reader helps users navigate their desktop environment and applications
through speech synthesis and braille output.
After installation, you can start Cthulhu through the GNOME desktop environment
After installation, you can start Cthulhu through your desktop environment
or by running 'cthulhu' from the command line.
DEPENDENCIES:
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.\" along with this; if not write to the Free Software Foundation, Inc.
.\" 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA
'\"
.TH cthulhu 1 "20 September 2013" "GNOME"
.TH cthulhu 1 "10 April 2026" "Stormux"
.SH NAME
cthulhu \- a scriptable screen reader
.SH SYNOPSIS
@@ -26,13 +26,17 @@ is a screen reader for people with visual impairments,
it provides alternative access to the desktop by using speech synthesis and braille.
.P
.B cthulhu
is maintained in this fork by Storm Dragon. It is forked from Orca and builds
on upstream work by former Orca maintainers and contributors, who are part of
the project's history but are not current maintainers of this fork.
.P
.B cthulhu
works with applications and toolkits that support
the Assistive Technology Service Provider Interface (AT-SPI), which
is the primary assistive technology infrastructure for Linux and
Solaris. Applications and toolkits supporting the AT-SPI include the
GNOME Gtk+ toolkit, the Java platform's Swing toolkit, LibreOffice,
Gecko, and WebKitGtk. AT-SPI support for the KDE Qt toolkit is being
pursued.
Gecko, WebKitGtk, and the KDE Qt toolkit.
.SH OPTIONS
.TP
.B \-s, --setup
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in laptop keyboard layout.
.B Cthulhu
uses default GNOME keyboard shortcuts to navigate the desktop and interact with various applications. The flat review commands provide an alternative method of interaction in certain inaccessible applications. It should not be confused with flat review functionality provided by other screen readers.
uses its configured keyboard shortcuts to navigate the desktop and interact with various applications. The flat review commands provide an alternative method of interaction in certain inaccessible applications. It should not be confused with flat review functionality provided by other screen readers.
.SH Desktop Mode
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# Tolk NVDA Presence Compatibility Design
## Goal
Allow applications running under Wine or Proton to use the official upstream `Tolk.dll` unchanged while routing Tolk speech through the existing Linux NVDA-to-Cthulhu path.
The compatibility layer must satisfy only the checks that Tolk performs when selecting its NVDA driver. It must not require replacing `Tolk.dll`, patching Tolk, or using a Tolk-specific DLL override.
## Confirmed Constraints
- The shipped `Tolk.dll` must remain the official upstream binary.
- The existing `wine2speechd` package already provides replacement `nvdaControllerClient32.dll` and `nvdaControllerClient64.dll` implementations for Linux.
- The current blocker is Tolk detection, not the downstream speech transport.
- Scope is limited to making Tolk believe NVDA is present; broader NVDA emulation is out of scope.
## Current Tolk Behavior
From `tolk/src/ScreenReaderDriverNVDA.cpp`, Tolk considers NVDA active only when both of the following succeed:
1. `nvdaController_testIfRunning() == 0`
2. `FindWindow(L"wxWindowClassNR", L"NVDA")` returns a window handle
If either check fails, Tolk will not select the NVDA driver and speech output through Tolk will fail.
## Recommended Approach
Extend the existing Wine NVDA compatibility stack with a minimal NVDA presence helper. The solution has two parts:
1. The existing custom NVDA controller DLLs continue handling `nvdaController_*` API calls and forwarding them into the Linux bridge.
2. A lightweight Windows helper process running inside Wine creates the exact window Tolk expects for NVDA detection.
This keeps the official `Tolk.dll` untouched and confines the compatibility contract to Tolk's actual checks.
## Architecture
### 1. NVDA controller DLLs
The custom `nvdaControllerClient32.dll` and `nvdaControllerClient64.dll` remain the Wine-visible implementation that applications and Tolk load.
Required behavior:
- `nvdaController_speakText` forwards speech to the existing Linux bridge.
- `nvdaController_brailleMessage` continues current behavior.
- `nvdaController_cancelSpeech` continues current behavior.
- `nvdaController_testIfRunning` returns success only when the Linux bridge is reachable and the compatibility environment is operational.
`nvdaController_testIfRunning` must not return success solely because the DLL loaded. It is the main guard against false positive Tolk detection.
### 2. NVDA presence helper
A small Windows executable is added to the Wine-side compatibility package. Its only job is to create and maintain a top-level window with:
- class name: `wxWindowClassNR`
- window title: `NVDA`
Required behavior:
- starts quickly and remains idle
- single-instance per Wine prefix or session
- exits cleanly without user interaction
- does not present visible UI unless Wine forces a window surface
- can be launched independently or on demand by the controller DLL
### 3. Startup coordination
The presence helper must be running before Tolk calls `FindWindow`, or Tolk detection will fail.
Acceptable coordination strategies:
- preferred: launch the helper as part of the existing Wine accessibility startup path
- acceptable: lazily launch the helper the first time the custom NVDA DLL is loaded, then wait briefly for the window to appear
The preferred strategy is external startup rather than in-DLL process creation because it separates concerns and avoids loader-time side effects.
## Detection Contract
Tolk compatibility is considered successful only when all of the following are true:
- official `Tolk.dll` loads normally
- Tolk loads the custom NVDA controller DLL
- `nvdaController_testIfRunning()` returns `0`
- `FindWindow(L"wxWindowClassNR", L"NVDA")` succeeds
- `Tolk_DetectScreenReader()` returns `NVDA`
- `Tolk_Output()` delivers speech through the existing Linux bridge
If the Linux bridge is unavailable, the compatibility layer must fail closed:
- `nvdaController_testIfRunning()` returns failure
- Tolk does not report NVDA as active
The dummy NVDA window alone must never make Tolk think speech is available.
## Packaging
The compatibility feature belongs with the Wine NVDA compatibility stack, not in Tolk itself.
Expected package contents:
- `nvdaControllerClient32.dll`
- `nvdaControllerClient64.dll`
- `nvda-presence-helper.exe` or similarly named helper
- startup integration so the helper is available in Wine and Proton environments where Tolk-based games run
No `Tolk.dll` replacement or override is added.
## Error Handling
### Bridge unavailable
- `nvdaController_testIfRunning` returns failure
- speech-related entry points return the existing failure behavior
- Tolk should not detect NVDA
### Helper missing or failed to start
- `FindWindow` fails
- Tolk should not detect NVDA
- logging should identify missing helper startup distinctly from bridge connectivity failures
### Duplicate helper instances
- duplicates must resolve harmlessly, preferably by allowing one owner and exiting the rest
## Logging
Add targeted logging in the compatibility layer only. Logging should make these states distinguishable:
- controller DLL loaded
- bridge connectivity check succeeded or failed
- presence helper started
- presence window created
- Tolk compatibility ready
No Tolk-side logging changes are needed because Tolk is not being modified.
## Testing
### Functional test
Create or reuse a small Wine test application that:
1. calls `Tolk_Load()`
2. calls `Tolk_DetectScreenReader()`
3. calls `Tolk_Output(L\"test\", false)`
Expected result with bridge and helper active:
- `Tolk_DetectScreenReader()` returns `NVDA`
- speech reaches Cthulhu through the existing NVDA path
### Negative tests
1. Bridge down, helper up:
`Tolk_DetectScreenReader()` must not return `NVDA`
2. Bridge up, helper down:
`Tolk_DetectScreenReader()` must not return `NVDA`
3. Both down:
`Tolk_DetectScreenReader()` must not return `NVDA`
### Regression check
Verify that existing non-Tolk NVDA speech consumers continue using the current `wine2speechd` path without requiring Tolk-specific configuration.
## Out of Scope
- adding a plugin mechanism to Tolk
- maintaining a Tolk fork
- broader NVDA desktop emulation beyond what Tolk checks
- compatibility with applications that perform additional NVDA-specific probing outside the current `wine2speechd` contract
- anti-cheat or anti-tamper guarantees beyond avoiding Tolk replacement
## Risks
### Wine window behavior
The helper must create a window that `FindWindow` can discover reliably under Wine and Proton. If Wine normalizes or alters class registration behavior, the helper may need adjustment.
### Timing
If a game calls Tolk very early, helper startup races could cause intermittent detection failure. This is why pre-starting the helper is preferred.
### Split responsibility
The controller DLL and helper must agree on readiness. If they drift apart, Tolk may see the window but still fail to speak. The fail-closed `testIfRunning` check is the protection against this.
## Recommendation
Implement the feature in the existing Wine NVDA compatibility stack, not in Tolk and not in Cthulhu core.
The smallest correct implementation is:
1. fix or confirm `nvdaController_testIfRunning()` behavior in the custom DLL
2. add a minimal Wine helper that exposes the NVDA window Tolk checks for
3. wire startup so the helper is available before Tolk detection occurs
4. verify with a small Tolk test program under Wine