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feat(graphics): DisplayMirror for screen mirroring and remote input - #394
jamesarich wants to merge 24 commits into
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The title clearly and concisely describes the main change: adding DisplayMirror support for screen mirroring and remote input. |
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The failure is in generating This diff is five C++ files ( What it looks like instead: I have not proven it by reproducing locally, so treat that as a strong hypothesis rather than a finding. If it holds, it will redden every PR until Note #393, opened the same day, shows no |
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Correcting my own comment above: the timing evidence I gave for the I said the last green What still stands: this diff is five C++ files under I have re-triggered CI to get a second datapoint. Treat the cause as unknown until that comes back, not as diagnosed. |
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As a small hint: InputDriver is a base class, you won't put any implementation into here. Same goes for DisplayDriver. Please take more effort into your design choices before pushing PRs. What you probably want is a DisplayMirror class and put all implementation there. |
Appreciate the first look - this is draft specifically because of my non-confidence in the design choices 😅 . |
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CI resolved: So the |
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Extracted a What is left in existing files is 8 lines:
Everything else is Two things fell out of the move rather than being carried across:
Still draft, still a PoC. Thanks for the pointer, it is a much better shape. |
jamesarich
changed the title
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Though still draft but let me remark that the current design how the class is integrated is still bad as it introduces artificial dependencies which are not in line with the current architecture. Class DisplayMirror with its static methods should work behind the scenes with no dependencies to it. So this has to be removed (inversion of control): LGFXDriver is just one out of many other possible choices of subclasses of DisplayDriver (think of e.g. EInkDriver, eTFTDriver, AdafruitDriver) depending on the driver class which all could be mirrored to another display. Said that it make sense to add a protected generic flush Also note, that with your DisplayMirror header declaration |
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Good direction, thanks @mverch67 |
DisplayDriver gains a static flush observer invoked from the LGFX flush callback before the in-place panel byte-swap, so observers receive native little-endian RGB565 dirty rects (LVGL thread; copy and return), plus a thread-safe requestFullRefresh drained in task_handler so a newly attached observer can synchronize the full frame. Both flush variants stay in sync. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
lv_scr_act covers only the active screen; clock and notification overlays live on the top and system layers, so a full-frame sync for a flush observer must repaint those too. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
InputDriver gains injectTouch/injectKey statics callable from any thread: events land in lock-free SPSC rings drained by two always-present virtual LVGL devices created in the (previously empty) base init — a pointer whose read callback holds PRESSED for a requested duration (taps and synthesized long presses) and a keypad attached to the default group, which init now guarantees exists even on boards with no physical input so injected keys can navigate widgets. Mirrors the flush-observer pattern on the output side. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Two fixes for remote control. First: a slept panel swallowed injected input as a wake event, which is every event when nobody is physically at the device — inject* now raises a wake request drained on the UI thread (force wakeup when powersaving, otherwise reset the inactivity timer), distinct from toggleDisplay which would sleep an awake screen. Second: add a virtual encoder device, because LVGL moves focus between widgets on encoder rotation while keypad UP/DOWN go to the already-focused widget — so arrow keys silently did nothing while typed characters worked. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Creating the default input group unconditionally would enrol every focusable widget on touch-only boards that have no focus concept, so injection is now opt-in: a host calls enableInjection() before init(), and init() is otherwise inert as before. The flush observer becomes atomic with a documented detach-quiesce contract, its comment records that the tightly-packed pixel guarantee is PARTIAL-render-mode only and that LGFXDriver is the only driver honouring it, the injector contract narrows to single-producer (the rings are SPSC), and encoder steps clamp instead of truncating through int8. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
InputDriver and DisplayDriver are base classes, so the mirror had no business living in them. All of it - the flush observer, the wake and full-repaint requests, and the virtual pointer, keypad and encoder - now sits in DisplayMirror. Both base classes revert to master. What is left in existing files is two hook lines in LGFXDriver::display_flush and a DeviceScreen accessor for the display driver. DisplayMirror::start() replaces InputDriver::enableInjection(): a host calls it after DeviceScreen::init(), where LVGL is already up and the view has not built its widgets yet, so the ordering flag on InputDriver::init() is gone. The wake and repaint requests ride the LVGL read callbacks rather than DisplayDriver::task_handler, so the mirror adds no periodic work of its own.
It touches LVGL directly instead of hopping threads, so it has to run before the host's UI task exists. That was implicit in the ordering note; say it.
The driver framework no longer knows DisplayMirror exists. DisplayDriver gains a generic flush notification - a static FlushCallback plus a protected flush() - and DisplayMirror registers a lambda in start(). LGFXDriver drops the DisplayMirror include and calls the inherited hook instead, so any other DisplayDriver subclass gains mirroring by adding the same one line. The callback is static because the LVGL flush callbacks a subclass registers are plain C function pointers with no instance to hand back; every driver here already keeps a static self-pointer for that reason. Registered once in start() and never cleared: assigning a std::function while the LVGL thread may be calling it is not safe, so capture stays gated on the atomic observer and the render path stays a single acquire load. LVGL also leaves DisplayMirror's header. It is how the class is implemented, not part of what it offers, and firmware includes this header to reach start()/inject*(); the indev pointers, read callbacks and rings move into an anonymous namespace in the .cpp.
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meshtastic#401 renders straight into RGB565_SWAPPED and adds the DMA and direct-mode flush variants, so the mirror can no longer observe native pixels ahead of an in-place swap. Each variant now calls DisplayDriver::flush, the callback gains a stride for direct mode's whole-frame buffer, and DisplayMirror::pixelsByteSwapped() reports the display's byte order so the host converts while it copies.
DisplayDriver::flush now takes the LVGL flush arguments and reads the stride from the active draw buffer, offsetting into the frame outside partial mode, so the four LGFX variants make one identical call. The callback is a member like the rest of DisplayDriver's state, and DisplayMirror::start registers it once. DisplayMirror drops its InputDriver dependency (every input driver already sets the default group), gives the virtual pointer the physical touch's long-press time, follows the repo's snake_case LVGL callback names, removes stop() in favour of setFrameObserver(nullptr), and trims its comments.
injectLongPress and injectLongPressKey hold past the virtual device's own long-press threshold plus two refresh periods, so a host no longer hard-codes a duration that can drift from it. The keypad can now hold a key, which LVGL needs to send LONG_PRESSED for LV_KEY_ENTER. injectTouch is a plain tap.
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Inline comments:
Review comments at @source/graphics/DisplayMirror.cpp:
- Line 179: In `start()`, bind each virtual input device, including `keypad`, to
the supplied display returned by `driver->getDisplay()` rather than relying on
LVGL’s default display. In `service_requests()`, invalidate that display’s
screen and layers instead of using default-display calls.
Review comments at @source/graphics/driver/DisplayDriver.cpp:
- Line 77: Update the pixel-position calculation in the flush callback to
subtract the LVGL display offsets from area->x1 and area->y1 before indexing the
full-frame buffer. Keep the reported flush coordinates unchanged.
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include/graphics/DeviceScreen.hinclude/graphics/DisplayMirror.hinclude/graphics/driver/DisplayDriver.hinclude/graphics/driver/LGFXDriver.hsource/graphics/DisplayMirror.cppsource/graphics/driver/DisplayDriver.cpp
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…d unshift offset flush areas
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@jamesarich Is this ready for merging or does it depend on firmware PRs? |
no firmware dependency - device-ui goes first, then firmware#11681 picks it up |
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In the meantime the input policy classes (#314) have been merged into the main branch of this repo. You defined the DisplayMirror indev as keypad which has probably very poor usability (compared to pointer) to navigate the UI. That's where the input policy handler kicks in. It can perform context aware key inputs that get injected before lvgl takes over the handling. Though, it's very well possible to navigate the UI with a simple encoder with single/long press button but it requires the input policy handlers for usability. BTW: what is the framework to test the DisplayMirror? I mean how to see it in action? |
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It also registers a pointer and an encoder: taps hit the pointer, remote up/down turn the encoder, and only left/right, enter, back and typed characters reach the keypad. I'll send the whole D-pad through the #314 pipeline as a keypad source with its own capabilities and drop the encoder cross-map, or rework it off your branch if you'd prefer. To see it: meshtastic/firmware#11681 |
How does this work with Android? You cannot have MUI and another BLE client active at the same time! |
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ye - ble is a no-go, usb-serial was what i tested on. wifi/tcp may work too haven't tested. |
LVGL's X11 driver installs its own flush callback, so DisplayDriver::flush never ran and a Portduino MUI build mirrored nothing. Wrap it and forward each area first.
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To see it without hardware: meshtastic/firmware#11681 now has a temporary git clone -b screen-mirror-poc https://github.com/meshtastic/firmware && cd firmware
git submodule update --init
pio run -e native-tft-mirror
cat > config.yaml <<'Y'
Lora:
Module: sim
General:
MACAddress: AA:BB:CC:4D:49:52
Display:
Panel: X11
Width: 320
Height: 240
Config:
DisplayMode: COLOR
Y
.pio/build/native-tft-mirror/meshtasticd --config=config.yamlKeep I ran exactly this under Xvfb: the MUI screen comes back over TCP and a remote tap navigates. MUI and the TCP client run side by side here, since MUI is in-process. |
I tested it but the navigation is incomplete: left/right keys are not mapped. It would need the input policy classes in Screencast.From.2026-11-02.11-47-53.mp4 |
Remote keys now pass the same policy chain as a physical D-pad, so UP/DOWN traverse focus outside maps and text areas and command keys dispatch.
The view moves only the physical driver's indevs when it switches groups, so the mirror's keypad and encoder kept driving the group they joined at start. They now follow the physical keypad's group.
X11 adds its own keypad that the view never regroups, so following the first keypad picked the wrong group there. Take InputDriver's keyboard or encoder, then the default group.
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Two causes: firmware mapped LEFT/RIGHT to The client only sent taps when |
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Looks PhoneAPI is broken now (endless polling loop) and as a consequence the UI doesn't refresh properly: Screencast.From.2026-11-02.20-03-37.mp4 |
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Reproduced on Portduino at 480x480 - a full repaint is 460 KB against the firmware's 192 KB MUI rect pool, so |
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Ran it on a T-Deck: remote UP/DOWN walk the button menu and open panels, and ENTER enters them, so the A remote key that lands on a slept panel is spent waking it (3 of 3 runs), despite the wake handling in |
The driver leaves powersave on its next task_handler pass, so input read in the same cycle as the wake request landed on the blank screen and was spent waking it. Queued touches, keys and encoder steps now wait while the driver is still powersaving.
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Wake fix is in |
Adds
DisplayMirror: a self-contained class that streams the rendered screen out to a host and feeds the host's input back into LVGL. Inert unless a host callsstart(), so no default build changes behaviour.This is the missing piece of the screen-mirroring stack. firmware consumes it today through a
symlink://override inplatformio.ini, because no released device-ui carries it. Until this lands and a pin bumps, the whole MUI/colour path in meshtastic/firmware#11681 compiles out (HAS_MUI_MIRRORis 0) and only the 1bpp mono path works.What this adds
include/graphics/DisplayMirror.handsource/graphics/DisplayMirror.cpp. All of it lives there.Frame capture.
setFrameObserver()takes a dirty-rect sink called on every LVGL flush with(x, y, w, h), a pointer to the rect's top-left pixel and a row stride, which differs fromwonly in direct render mode, where the rect sits inside the whole frame. Pixels come in the display's byte order andpixelsByteSwapped()says which, since master renders straight intoRGB565_SWAPPEDunless a build setsLV_COLOR_FORMAT_NO_RGB_SWAP. Null by default, loaded with acquire semantics on the flush path.A full-repaint request. A host attaching mid-session needs a whole frame, not whatever changes next.
requestFullRefresh()is callable from any thread and invalidates the active screen pluslv_layer_top()andlv_layer_sys(): overlay content (clock, notifications) lives on those layers, so a client would otherwise see a stale overlay.Remote input.
start()registers three LVGL virtual input devices, a pointer, a keypad and an encoder, fed from 16-entry single-producer rings.injectLongPress()andinjectLongPressKey()hold past the virtual device's own long-press threshold, which the pointer copies from the physical touch, so a host never times a long-press itself. Injected keys run through the same input policy pipeline as a physical D-pad, so arrows traverse focus per context, and the virtual keypad and encoder follow the group ofInputDriver's keyboard or encoder (the default group without one), since the view only regroups those.A panel wake. Injected input has to wake a slept panel and still act, or the first remote event is swallowed as a wake, which is every event when nobody is physically at the device. The wake and repaint requests are drained on the LVGL thread from the read callbacks, so the mirror adds no periodic work of its own.
What it touches outside itself
DisplayDriver, a protectedflush(disp, area, px_map)that reads the stride from LVGL's active draw buffer and forwards to a per-instance callback set throughsetFlushCB().DisplayMirror::start()sets it once, so no driver names the mirror.LGFXDriver::display_flush, the sameflush(disp, area, px_map)call in each of the four variants (plain, shared-SPI DMA, DMA, direct-mode double buffer); in the non-shared DMA variant it runs after the transfer starts.DeviceScreen::getDisplayDriver(), a one-line accessor, so a host can hand the mirror the driver it needs for panel wake.Scope and safety
start()nothing is allocated, no input device is registered, and a flush costs one acquire load.<atomic>and<functional>are the only added includes.FromRadioand honouring a remote arm would stream the screen to whatever local client happens to be attached.Feature stack
Five repos, and the release order runs top to bottom. Nothing below can ship until the piece above it lands.
DisplayMirror: frame capture + remote inputDisplayFrame/DisplayPalette/DisplayInfo+ the two admin verbscapture_displaytoolingdevice-ui#394 is the current blocker: without it the MUI/colour path compiles out of every committed firmware configuration, leaving only the 1bpp mono path.
Testing
Exercised on a LILYGO T-Deck via meshtastic/firmware#11681 with a local
symlink://override: live mirror plus D-pad, keyboard and touch control from Meshtastic-Android.At this head it also runs without hardware: firmware
native-tft(MUI on X11) under Xvfb, mirrored over TCP with meshtastic-mcpcapture_display, and a remote tap lands.X11Drivernow passes LVGL's flush through to the frame observer, which it skipped before.Frames go out only from RGB565 displays: any other colour format logs a warning and mirrors nothing, so the 32 bpp Linux framebuffer driver stays unhooked.
That bench run predates the
DisplayMirrorextraction. The refactor itself is verified only by host-compiling the new translation unit against the pinned LVGL 9.3 and by CI here, so the T-Deck pass needs redoing before this leaves draft.Summary by CodeRabbit