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Code Issues Packages Projects Releases 10 Wiki Activity

Display (Android): removes old detection methods

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This commit is contained in:
Carter Li
2026-10-11 00:01:19 +08:00
parent d7b66c8677
commit 1f32e0bcb2
2 changed files with 56 additions and 365 deletions
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CHANGELOG.md
+1 -3
View File
@@ -12,9 +12,7 @@ Changes:
Features:
* Added Sound detection on Android. (Sound, Android)
* Added display detection on Android over binder, which needs neither a child process nor a permission.
* The module took 16.0-26.5 ms on the test device and now takes 1.3-1.5 ms. The `cmd` and `dumpsys` routes are unchanged and remain the fallback.
* It is also the only route that answers for an app UID on Android 12 and older, where `cmd display get-displays` does not exist and `dumpsys` is behind `android.permission.DUMP`. (Display, Android)
* Added display detection on Android over binder, which needs neither a child process nor a permission. (Display, Android)
* Added battery temperature, remaining time and charger type (AC / USB / wireless) detection on Android. (Battery, Android)
* Performance improvements & internal cleanups
* Added Finnish language support. (General)
src/detection/displayserver/displayserver_android.c
+55 -362
View File
@@ -6,346 +6,24 @@
#include "common/debug.h"
#include "common/settings.h"
#include "common/strutil.h"
#include "common/processing.h"
#include "linux/displayserver_linux.h"
#include <math.h>
static bool detectWithGetprop(FFDisplayServerResult* ds) {
// Only for MiUI
FF_STRBUF_AUTO_DESTROY buffer = ffStrbufCreate();
if (ffSettingsGetAndroidProperty("persist.sys.miui_resolution", &buffer) &&
ffStrbufContainC(&buffer, ',')) {
// 1440,3200,560 => width,height,densityDpi
uint32_t width = (uint32_t) ffStrbufToUInt(&buffer, 0);
ffStrbufSubstrAfterFirstC(&buffer, ',');
uint32_t height = (uint32_t) ffStrbufToUInt(&buffer, 0);
ffStrbufSubstrAfterFirstC(&buffer, ',');
uint32_t dpi = (uint32_t) ffStrbufToUInt(&buffer, 0) * 96 / 160;
FFDisplayResult* display = ffdsAppendDisplay(ds,
width,
height,
0,
dpi,
0,
0,
0,
0,
nullptr,
FF_DISPLAY_TYPE_BUILTIN,
false,
0,
0,
0,
"getprop");
return !!display;
}
return false;
}
// `cmd display get-displays` and `dumpsys display` print the same thing -- the `DisplayInfo` of every
// display, one per line -- so one parser covers both and only the command and the marker in front of
// each record differ:
//
// * `cmd display get-displays` needs no permission, which is what makes it usable for an app UID,
// but the subcommand was only added to `DisplayManagerShellCommand` in Android 13. Android 11 and
// 12 answer `Unknown command: get-displays` on stdout with exit code 255.
// * `dumpsys display` covers every release, including the ones that predate `get-displays`, but it
// is gated behind `android.permission.DUMP`, so it only answers for `adb shell` and root.
//
// The record layout has changed across releases, and every difference is accepted rather than version
// checked:
//
// * The mode list is printed as `modes [...]` up to Android 14 and as `supportedModes [...]` from
// Android 15 on, which also prints `appsSupportedModes [...]` right behind it. Both spellings are
// searched for.
// * `renderFrameRate` is printed from Android 15 on. Before that the active mode's fps is the only
// refresh rate the dump carries. The active mode's fps is preferred even where it exists, see
// the comment on `refreshRate` below.
// * `displayGroupId` is printed from Android 12 on, the physical dpi behind `density` from
// Android 11 on, and `isForceSdr` from Android 15 on.
//
// A record is one line, and the `DisplayInfo{` inside it is what gets parsed, so the `Display id 0: `
// of the one command and the `mBaseDisplayInfo=` of the other are both skipped by the same code.
static bool detectWithCommand(FFDisplayServerResult* ds, char* const argv[], const char* marker, const char* platformApi) {
FF_STRBUF_AUTO_DESTROY buf = ffStrbufCreate();
FFProcessHandle handle;
// `cmd` forwards its stdin to the service over binder, and the kernel rejects the whole
// transaction when that fd is a terminal, which it is whenever fastfetch runs in a terminal.
// Detaching the child from our stdin is only needed here, so the low level API is called instead
// of `ffProcessAppendStdOut`.
if (ffProcessSpawn(argv, FF_PROCESS_OUTPUT_STDOUT_BIT, ffGetNullFD(), &handle) != nullptr) {
return false; // Neither command is available on every Android version
}
if (ffProcessReadOutput(&handle, &buf) != nullptr || buf.length == 0) {
return false;
}
ffStrbufTrimRightSpace(&buf);
uint32_t index = 0;
while ((index = ffStrbufNextIndexS(&buf, index, marker)) < buf.length) {
index += strlen(marker);
uint32_t nextIndex = ffStrbufNextIndexC(&buf, index, '\n');
buf.chars[nextIndex] = '\0';
const char* info = buf.chars + index;
// 0: DisplayInfo{"Builtin display", displayId 0, ..., real 1440 x 3168, ..., mode 2,
// renderFrameRate 60.000004, ..., defaultMode 4, ..., supportedModes [{id=2,
// width=1440, height=3168, fps=60.000004, ...}], ..., hdrCapabilities
// HdrCapabilities{mSupportedHdrTypes=[1, 2, 3, 4], ...}, isForceSdr false, ...,
// rotation 0, ..., type INTERNAL, uniqueId "local:4630946557703207059", ...,
// density 560 (560.0 x 560.0) dpi, ..., deviceProductInfo DeviceProductInfo{...,
// manufactureDate=ManufactureDate{week=27, year=2006}, ...}, ...}
const char* field = strstr(info, "DisplayInfo{\"");
FF_STRBUF_AUTO_DESTROY name = ffStrbufCreateA(64);
if (field) {
field += strlen("DisplayInfo{\"");
const char* nameEnd = strchr(field, '"');
if (nameEnd) {
ffStrbufAppendNS(&name, (uint32_t) (nameEnd - field), field);
}
}
// `real` is the size the display currently uses, which is smaller than the panel's when the
// framework emulates a smaller display size
unsigned width = 0, height = 0;
if ((field = strstr(info, ", real ")) && sscanf(field, ", real %u x %u", &width, &height) < 2) {
width = height = 0;
}
// `renderFrameRate` is printed from Android 15 on. It is documented as "a divisor of the
// active mode refresh rate", so it is the rate the display is currently *rendering* at and
// can be lower than the mode it is set to. It is therefore only used for a record whose
// mode list can not be read, where a possibly divided rate still beats none.
double renderFrameRate = 0;
if ((field = strstr(info, ", renderFrameRate ")) && sscanf(field, ", renderFrameRate %lf", &renderFrameRate) < 1) {
renderFrameRate = 0;
}
unsigned activeMode = 0, defaultMode = 0;
if ((field = strstr(info, ", mode ")) && sscanf(field, ", mode %u", &activeMode) < 1) {
activeMode = 0;
}
if ((field = strstr(info, ", defaultMode ")) && sscanf(field, ", defaultMode %u", &defaultMode) < 1) {
defaultMode = 0;
}
// The modes are listed with their resolution in the natural orientation, which is also how
// the preferred values are reported on the other platforms. `defaultMode` is the mode the
// display itself prefers, so it carries the panel's native resolution.
uint32_t preferredWidth = 0, preferredHeight = 0;
double preferredRefreshRate = 0, activeModeRefreshRate = 0;
field = strstr(info, ", supportedModes [");
if (field == nullptr) {
field = strstr(info, ", modes ["); // Android 14 and older
}
while (field && (field = strstr(field, "{id="))) {
// {id=2, width=1440, height=3168, fps=60.000004, ...
unsigned id = 0, modeWidth = 0, modeHeight = 0;
double fps = 0;
if (sscanf(field, "{id=%u, width=%u, height=%u, fps=%lf", &id, &modeWidth, &modeHeight, &fps) < 4) {
break;
}
if (id == activeMode) {
activeModeRefreshRate = fps;
}
if (id == defaultMode) {
preferredWidth = modeWidth;
preferredHeight = modeHeight;
preferredRefreshRate = fps;
}
if (activeModeRefreshRate > 0 && preferredWidth > 0) {
break; // Both are in, and the same list is printed a second time from Android 15 on
}
++field;
}
// The nominal rate of the active mode, which is what `Display.getRefreshRate()` reports
// (`refreshRateOverride` if it is set, the mode's own rate otherwise) and what every other
// platform reports. `renderFrameRate` is deliberately not preferred: it is a render
// cadence that follows the content rather than a property of the display, and it does not
// exist before Android 15, so using it would make the reported rate change with the
// Android version as well as with what is on screen.
double refreshRate = activeModeRefreshRate;
if (refreshRate <= 0) {
refreshRate = renderFrameRate;
}
unsigned rotation = 0;
if ((field = strstr(info, ", rotation ")) && sscanf(field, ", rotation %u", &rotation) < 1) {
rotation = 0;
}
FFDisplayType type = FF_DISPLAY_TYPE_UNKNOWN;
if ((field = strstr(info, ", type "))) {
field += strlen(", type ");
if (ffStrStartsWith(field, "INTERNAL")) {
type = FF_DISPLAY_TYPE_BUILTIN;
} else if (ffStrStartsWith(field, "EXTERNAL") || ffStrStartsWith(field, "WIFI")) {
// A WIFI display is a wireless sink, which is as external as a wired one
type = FF_DISPLAY_TYPE_EXTERNAL;
}
}
unsigned density = 0;
double physicalXDpi = 0, physicalYDpi = 0;
if ((field = strstr(info, ", density "))) {
// `density 640 (501.0411 x 509.28604) dpi`, the physical dpi is only printed since
// Android 11
if (sscanf(field, ", density %u (%lf x %lf) dpi", &density, &physicalXDpi, &physicalYDpi) < 1) {
density = 0;
}
}
// The physical dpi describes the panel itself and does not change with the logical display
// size, so the physical size has to be derived from the native resolution
uint32_t physicalWidth = 0, physicalHeight = 0;
if (physicalXDpi > 0) {
physicalWidth = (uint32_t) ((preferredWidth ? preferredWidth : width) * 25.4 / physicalXDpi + 0.5);
}
if (physicalYDpi > 0) {
physicalHeight = (uint32_t) ((preferredHeight ? preferredHeight : height) * 25.4 / physicalYDpi + 0.5);
}
// `uniqueId` identifies the display across reboots, e.g. `local:4630946557703207059` on a
// physical display and `virtual:...` on a virtual one
uint64_t id = 0;
if ((field = strstr(info, ", uniqueId \""))) {
field += strlen(", uniqueId \"");
const char* uniqueIdEnd = strchr(field, '"');
const char* digits = uniqueIdEnd ? memchr(field, ':', (size_t) (uniqueIdEnd - field)) : nullptr;
id = (uint64_t) strtoull(digits ? digits + 1 : field, nullptr, 10);
}
uint16_t manufactureYear = 0, manufactureWeek = 0;
if ((field = strstr(info, ", deviceProductInfo "))) {
// `manufactureDate=ManufactureDate{week=27, year=2006}`, either field may be `null`
const char* date = strstr(field, "manufactureDate=ManufactureDate{");
unsigned year = 0, week = 0;
if (date && sscanf(date + strlen("manufactureDate=ManufactureDate{"), "week=%u, year=%u", &week, &year) == 2) {
manufactureYear = (uint16_t) year;
manufactureWeek = (uint16_t) week;
} else if ((field = strstr(field, ", modelYear=")) && sscanf(field, ", modelYear=%u", &year) == 1) {
// A display reports either the date of manufacture or the model year
manufactureYear = (uint16_t) year;
}
}
// `displayId` sits inside the record, not in front of it: `cmd` prints the id again in its
// own prefix, but `dumpsys` prints only `mBaseDisplayInfo=`
unsigned displayId = 0;
if ((field = strstr(info, ", displayId ")) && sscanf(field, ", displayId %u", &displayId) < 1) {
displayId = 0;
}
bool primary = displayId == 0; // Display 0 is the default one
// Android counts density in dpi with 160 as the 1x baseline, fastfetch uses 96
FFDisplayResult* display = ffdsAppendDisplay(ds,
width,
height,
refreshRate,
density * 96 / 160,
preferredWidth,
preferredHeight,
preferredRefreshRate,
rotation,
&name,
type,
primary,
id,
physicalWidth,
physicalHeight,
platformApi);
if (display) {
display->manufactureYear = manufactureYear;
display->manufactureWeek = manufactureWeek;
// Reported for every display, not only for the built-in one: `hdrCapabilities` is a
// field of the `DisplayInfo` record itself, so it describes that display and nothing
// else, and the other platforms report HDR per display too (EDID on Linux, the
// advanced color info per target on Windows). An external display or a wireless sink
// carries the field as well.
//
// `hdrCapabilities HdrCapabilities{mSupportedHdrTypes=[1, 2, 3, 4], ...}` is printed
// since Android 11, where an empty list means that the display can not do HDR at all.
// The two fallbacks below it are device wide vendor properties, which is the price of
// answering for a record that does not print the field.
FF_STRBUF_AUTO_DESTROY buffer = ffStrbufCreate();
field = strstr(info, "hdrCapabilities HdrCapabilities{mSupportedHdrTypes=[");
if (field) {
field += strlen("hdrCapabilities HdrCapabilities{mSupportedHdrTypes=[");
display->hdrStatus = *field == ']' ? FF_DISPLAY_HDR_STATUS_UNSUPPORTED : FF_DISPLAY_HDR_STATUS_SUPPORTED;
} else if (ffSettingsGetAndroidProperty("ro.surface_flinger.has_HDR_display", &buffer)) {
display->hdrStatus = ffStrbufIgnCaseEqualS(&buffer, "true") ? FF_DISPLAY_HDR_STATUS_SUPPORTED : FF_DISPLAY_HDR_STATUS_UNSUPPORTED;
} else {
display->hdrStatus = FF_DISPLAY_HDR_STATUS_UNKNOWN;
}
if (display->hdrStatus == FF_DISPLAY_HDR_STATUS_SUPPORTED) {
// `persist.sys.hdr_mode` is non-zero while HDR is turned on, and `isForceSdr
// true` means that the framework disabled every HDR capability of this display.
// Note that `ffSettingsGetAndroidProperty` appends, so the value needs its own
// buffer.
FF_STRBUF_AUTO_DESTROY hdrMode = ffStrbufCreate();
if (ffSettingsGetAndroidProperty("persist.sys.hdr_mode", &hdrMode) &&
ffStrbufToUInt(&hdrMode, 0) > 0 &&
!strstr(info, ", isForceSdr true")) {
display->hdrStatus = FF_DISPLAY_HDR_STATUS_ENABLED;
}
}
}
// The last display of the dump is not followed by a newline, so the loop must not step
// past the end of the buffer (`ffStrbufNextIndexC` returns the length when it finds none)
index = nextIndex < buf.length ? nextIndex + 1 : buf.length;
}
// A command that produced no `DisplayInfo` record has to be reported as a failure: the caller
// keys off this value to decide whether to try the other command, and on Android 12 and older
// `dumpsys` is the only one that can still yield a display.
return ds->displays.length > 0;
}
static bool detectWithCmd(FFDisplayServerResult* ds) {
return detectWithCommand(ds,
(char*[]) { "/system/bin/cmd", "display", "get-displays", nullptr },
"Display id ",
"cmd");
}
static bool detectWithDumpsys(FFDisplayServerResult* ds) {
// `dumpsys` needs android.permission.DUMP, which only the shell UID and root hold. Every other UID
// is answered with `Permission Denial: can't dump DisplayManagerService from from pid=..., uid=...
// due to missing android.permission.DUMP permission` on stdout and a zero exit status, so the fork
// buys a child process and the record loop then finds no `DisplayInfo` -- the same "no display" the
// caller reads as "try the next route". Not forking is the only difference this makes, but it is
// the difference between the fallback chain describing what is available and it guessing.
if (!ffAndroidIsRootOrShell(instance.state.platform.uid)) {
return false;
}
return detectWithCommand(ds,
(char*[]) { "/system/bin/dumpsys", "display", nullptr },
"mBaseDisplayInfo=",
"dumpsys");
}
// ---------------------------------------------------------------------------------------------
// The binder route
// ---------------------------------------------------------------------------------------------
//
// `cmd display get-displays` and `dumpsys display` are both a child process, and that fork is all of
// what this module costs: it took 16.0-26.5 ms on the test device, where `cmd display get-displays`
// itself takes 9.2 ms and a bare fork 8.6 ms. `cmd` does not exist before Android 13 either, so on
// Android 11 and 12 an app UID has no display at all -- `dumpsys` is behind
// android.permission.DUMP there. `display` is the service both sit on,
// android.hardware.display.IDisplayManager: it lives in system_server, an app UID may call it, and
// `cmd display get-displays` and `dumpsys display` used to be the routes here, and both are a child
// process -- that fork was all of what this module cost: it took 16.0-26.5 ms on the test device,
// where `cmd display get-displays` itself takes 9.2 ms and a bare fork 8.6 ms. `cmd` does not exist
// before Android 13 either, and `dumpsys` is behind android.permission.DUMP, so on Android 11 and 12
// an app UID had no display at all. Both are gone: `display` is the service they sat on,
// android.hardware.display.IDisplayManager, it lives in system_server, an app UID may call it, and
// one `getDisplayInfo(0)` answers the whole `DisplayInfo` the dump prints, field for field. With the
// fork gone the module takes 1.3-1.5 ms.
// fork gone the module took 2.8-3.2 ms where `cmd` took 16.0-26.5 ms, and Android 11 -- the release
// `cmd` could not serve at all -- has been read this way on a device. What is left is dominated by
// the dex read below, not by the transaction.
//
// What it costs is the parse. The reply is a Java Parcelable and its field set moves with every
// release and every vendor fork -- `DisplayInfo` writes 34 fields on Android 11, 42 on 13 and 57 on
@@ -359,7 +37,9 @@ static bool detectWithDumpsys(FFDisplayServerResult* ds) {
// both a `Ljava/lang/String;` on the wire and are not the same length. The type descriptor settles
// the primitives and both array shapes, a handful of names settle the rest, and every nested
// Parcelable is anchored on its class name. A layout this does not recognise fails the route rather
// than answering, which is what makes the `cmd` / `dumpsys` fallback behind it worth having.
// than answering. There is no second route behind this one any more, so a build whose layout is not
// one this parser reads reports no display at all, rather than a plausible number out of the middle of
// a different field.
#define FF_DISPLAY_ANDROID_SERVICE "display"
#define FF_DISPLAY_ANDROID_DESCRIPTOR "android.hardware.display.IDisplayManager"
@@ -460,9 +140,10 @@ typedef struct FFDisplayAndroidLayout {
// Android 15, so a jar that does not declare it is answering rather than failing -- the field is
// simply not in the sequence behind it, and the walk never asks.
//
// A jar that cannot be read at all fails too, and the route falls back to `cmd` / `dumpsys`. That is
// the point of the dex being the source: a build this parser cannot read gets the fallback, rather
// than a plausible number read out of the middle of a different field.
// A jar that cannot be read at all fails too, and with nothing behind this route that leaves the
// module with no display to report. Which is the point of the dex being the source: a build this
// parser cannot read declines to answer, rather than reporting a plausible number read out of the
// middle of a different field.
static bool displayLayoutLoad(const char* jarPath, FFDisplayAndroidLayout* layout) {
const FFDexParcelRequest requests[] = {
{
@@ -548,8 +229,8 @@ static bool displayLayoutLoad(const char* jarPath, FFDisplayAndroidLayout* layou
return true;
}
// `DisplayInfo.type`, i.e. `Display.TYPE_*`. The `cmd` route compares the same field as the text
// `INTERNAL` / `EXTERNAL` / `WIFI`; the numbers are what the parcel carries.
// `DisplayInfo.type`, i.e. `Display.TYPE_*`. A dump prints these as `INTERNAL` / `EXTERNAL` /
// `WIFI`; the numbers are what the parcel carries.
typedef enum FFDisplayAndroidType : int32_t {
FF_DISPLAY_ANDROID_TYPE_UNKNOWN = 0,
FF_DISPLAY_ANDROID_TYPE_INTERNAL = 1,
@@ -570,7 +251,7 @@ typedef enum FFDisplayAndroidValue : int32_t {
// A cursor over one reply. Every read is bounds checked and every mismatch raises `failed` rather
// than returning a value: once a field has been read at the wrong place nothing behind it can be
// trusted, and the only safe answer left is the fallback.
// trusted, and the only safe answer left is to report nothing.
typedef struct FFDisplayAndroidReader {
const uint8_t* data;
size_t size;
@@ -851,7 +532,18 @@ static bool readerRect(FFDisplayAndroidReader* reader) {
// body this parser reads differently can not move the fields behind it. The size counts from its own
// end, not from its start.
static bool readerManufactureDate(FFDisplayAndroidReader* reader, const FFDisplayAndroidLayout* layout, uint16_t* year, uint16_t* week) {
if ((FFDisplayAndroidValue) readerI32(reader) != FF_DISPLAY_ANDROID_VALUE_PARCELABLE) {
// `mManufactureDate` is `@Nullable`, so a display with no date writes a bare `VAL_NULL` and
// nothing behind it -- and a date is not what the display is being read for. A missing one is
// skipped rather than failed: everything the module needs is still in the record, and dropping
// the display over an absent date would answer nothing at all. Only a tag that is neither a
// Parcelable nor a null fails, because that is a framing this walk does not know how to step over.
const int32_t tag = readerI32(reader);
if (tag == FF_DISPLAY_ANDROID_VALUE_NULL) {
*year = 0;
*week = 0;
return true;
}
if (tag != FF_DISPLAY_ANDROID_VALUE_PARCELABLE) {
reader->failed = true;
return false;
}
@@ -1171,8 +863,8 @@ typedef struct FFDisplayAndroidWalk {
} FFDisplayAndroidWalk;
// `uniqueId` identifies the display across reboots, e.g. `local:4630946557703207059` for the panel
// and `virtual:...` for a virtual one. The number behind the colon is what the `cmd` route extracts
// from the same string, so the two routes report the same id.
// and `virtual:...` for a virtual one. The prefix says what kind of display it is, and the number
// behind the colon is the id.
static uint64_t displayUniqueId(const char* uniqueId) {
const char* colon = strchr(uniqueId, ':');
return (uint64_t) strtoull(colon != nullptr ? colon + 1 : uniqueId, nullptr, 10);
@@ -1341,7 +1033,9 @@ static bool displayInfoParse(const uint8_t* data, size_t size, const FFDisplayAn
|| info->density > 4000
|| !(info->physicalXDpi >= 0) || info->physicalXDpi > 2000
|| !(info->physicalYDpi >= 0) || info->physicalYDpi > 2000
|| info->name.length == 0 || info->name.length > 256
// A display with no name is still a display -- the key falls back to a number -- so only a
// name that could not have come from a string is a reason to drop the record.
|| info->name.length > 256
|| uniqueId.length > 256) {
FF_DEBUG(
"getDisplayInfo(%u) answered type %d, %u x %u, rotation %u, mode %d, density %u, %f x %f dpi",
@@ -1358,8 +1052,8 @@ static bool displayInfoParse(const uint8_t* data, size_t size, const FFDisplayAn
// every other platform reports. `renderFrameRate` is only used when the list has no entry for
// `modeId`, because it is a render cadence that follows the content rather than a property of the
// display -- and it is not written at all before Android 15. `refreshRateOverride` is deliberately
// not consulted either: the `cmd` route can not see it, and the two routes have to answer the same
// thing.
// not consulted either: it is what an app asked the framework to hold the panel at, not a
// property of the display.
info->refreshRate = walk.active.refreshRate > 0 ? walk.active.refreshRate : info->renderFrameRate;
info->id = displayUniqueId(uniqueId.chars);
return true;
@@ -1380,8 +1074,8 @@ static FFDisplayType displayType(int32_t type) {
// `hdrCapabilities.mSupportedHdrTypes` is the display's own answer and an empty list means it can not
// do HDR at all. `isForceSdr` is the framework having turned every capability of this display off and
// `persist.sys.hdr_mode` is the vendor's switch; both are what the `cmd` route consults, and both are
// consulted here so that the two routes answer the same thing.
// `persist.sys.hdr_mode` is the vendor's switch, so `Supported` and `Enabled` stay two different
// questions: the list is what the panel can do, those two are whether anything is asking for it.
static FFDisplayHdrStatus displayHdrStatus(const FFDisplayAndroidInfo* info) {
if (info->hdrTypeCount <= 0) {
return FF_DISPLAY_HDR_STATUS_UNSUPPORTED;
@@ -1394,8 +1088,8 @@ static FFDisplayHdrStatus displayHdrStatus(const FFDisplayAndroidInfo* info) {
}
// Reads every enabled display over binder. Returns false without appending anything when the service,
// the transaction or the layout is not what this parser was written for, which is what hands the
// answer to `cmd` and `dumpsys` behind it.
// the transaction or the layout is not what this parser was written for. There is no route behind
// this one, so that is also how the module ends up reporting no display.
static bool detectWithBinder(FFDisplayServerResult* ds) {
// The write sequence first. It is what the whole parse is made of, and a build whose jar cannot be
// read has nothing to walk -- so failing here costs one file open rather than a round trip to a
@@ -1423,9 +1117,13 @@ static bool detectWithBinder(FFDisplayServerResult* ds) {
uint8_t parcelBuffer[FF_DISPLAY_ANDROID_PARCEL_SIZE];
uint8_t replyBuffer[FF_DISPLAY_ANDROID_REPLY_SIZE];
// `getDisplayIds(false)` is the list of the enabled displays, which is the set `cmd display
// get-displays` prints. It is a separate call rather than a loop over 0..n because the ids are not
// contiguous, and it is twelve bytes.
// `getDisplayIds(false)` is the list of the enabled displays, which is the set a display dump
// prints. It is a separate call rather than a loop over 0..n because the ids are not contiguous,
// and it is twelve bytes.
//
// The argument is written unconditionally although the method takes none on Android 11: the
// generated stub reads the parameters its own signature declares and leaves the rest of the
// parcel alone, so the extra int is dropped on those releases.
FFBinderParcel parcel = ffBinderParcelCreate(parcelBuffer, sizeof(parcelBuffer));
ffBinderParcelPutInterfaceToken(&parcel, FF_DISPLAY_ANDROID_DESCRIPTOR);
ffBinderParcelPutI32(&parcel, 0); // includeDisabled
@@ -1499,8 +1197,8 @@ static bool detectWithBinder(FFDisplayServerResult* ds) {
FFDisplayAndroidInfo* info = &infos[i];
// The physical dpi describes the panel itself and does not change with the logical display
// size, so the physical size has to be derived from the native resolution -- the same
// derivation the `cmd` route makes.
// size, so the physical size has to be derived from the native resolution. Nothing in the
// record carries it directly.
uint32_t physicalWidth = 0, physicalHeight = 0;
if (info->physicalXDpi > 0) {
physicalWidth = (uint32_t) ((info->preferredWidth ? info->preferredWidth : info->width) * 25.4 / info->physicalXDpi + 0.5);
@@ -1526,7 +1224,9 @@ static bool detectWithBinder(FFDisplayServerResult* ds) {
physicalHeight,
"binder");
if (display == nullptr) {
continue; // a record with no size, which the parser above does not let through
// `ffdsAppendDisplay` moves `name` only when it keeps the display, so it is still ours
ffStrbufDestroy(&info->name);
continue;
}
display->manufactureYear = info->manufactureYear;
display->manufactureWeek = info->manufactureWeek;
@@ -1876,14 +1576,7 @@ void ffConnectDisplayServerImpl(FFDisplayServerResult* ds) {
ffStrbufSetStatic(&ds->wmPrettyName, "WindowManager"); // A system service managed by system_server
ffStrbufSetStatic(&ds->wmProtocolName, FF_WM_PROTOCOL_SURFACEFLINGER);
// Binder comes first: it needs no permission and no child process, and it is the only route that
// answers for an app UID on Android 12 and older. `cmd` is behind it for a record whose parcel
// layout is not the one the parser above knows, `dumpsys` for the shell and root -- it is the only
// route that answers at all on Android 12 and older, and it is skipped without a fork for every
// other UID, see detectWithDumpsys -- and `getprop` is MiUI specific and the last resort.
if (!detectWithBinder(ds) && !detectWithCmd(ds) && !detectWithDumpsys(ds)) {
detectWithGetprop(ds);
}
detectWithBinder(ds);
detectDE(ds);
}