wemeet: fix camera crash on Wayland (#522135)

2026-06-18 02:57:33 +00:00
parent 300ecf86e9 7a32f4395d
commit 7890ba0a99
2 changed files with 194 additions and 1 deletions
@@ -20,6 +20,7 @@
  systemd,
  udev,
  libGL,
+  libglvnd,
  fontconfig,
  freetype,
  openssl,
@@ -173,6 +174,44 @@ let
    };
  };

+  wemeet-camera-fix = stdenv.mkDerivation {
+    pname = "wemeet-camera-fix";
+    version = "0-unstable-2026-05-20";
+
+    src = ./wemeet-camera-fix.c;
+
+    dontUnpack = true;
+    dontWrapQtApps = true;
+
+    buildInputs = [
+      libglvnd
+      libx11
+    ];
+
+    buildPhase = ''
+      runHook preBuild
+
+      $CC $CFLAGS -Wall -Wextra -fPIC -shared \
+        -o libwemeet-camera-fix.so $src \
+        -ldl -lEGL -lX11
+
+      runHook postBuild
+    '';
+
+    installPhase = ''
+      runHook preInstall
+
+      install -Dm755 ./libwemeet-camera-fix.so $out/lib/libwemeet-camera-fix.so
+
+      runHook postInstall
+    '';
+
+    meta = {
+      description = "Fix for WeMeet Wayland camera preview rendering";
+      license = lib.licenses.mit;
+    };
+  };
+
  selectSystem =
    attrs:
    attrs.${stdenv.hostPlatform.system}
@@ -284,7 +323,7 @@ stdenv.mkDerivation {
        "--prefix QT_PLUGIN_PATH : $out/app/wemeet/plugins"
      ];
      commonWrapperArgs = baseWrapperArgs ++ [
-        "--prefix LD_PRELOAD : ${libwemeetwrap}/lib/libwemeetwrap.so:${wemeet-x11-fix}/lib/libwemeet-x11-fix.so"
+        "--prefix LD_PRELOAD : ${libwemeetwrap}/lib/libwemeetwrap.so:${wemeet-x11-fix}/lib/libwemeet-x11-fix.so:${wemeet-camera-fix}/lib/libwemeet-camera-fix.so"
        "--run 'if [[ $XDG_SESSION_TYPE == \"wayland\" ]]; then export LD_PRELOAD=${wemeet-wayland-screenshare}/lib/wemeet/libhook.so\${LD_PRELOAD:+:$LD_PRELOAD}; fi'"
      ];
      xwaylandWrapperArgs = baseWrapperArgs ++ [
@@ -0,0 +1,154 @@
+/*
+ * LD_PRELOAD shim for WeMeet's camera preview on Wayland.
+ *
+ * WeMeet's libxcast.so uses EGL to render the local camera preview. It links
+ * against libEGL and libX11, and later passes X11 native windows to EGL. In a
+ * Wayland session, Mesa can choose the Wayland EGL platform for
+ * eglGetDisplay(NULL), which makes libxcast.so hand an X11 XID to the Wayland
+ * platform path when creating its window surface. The camera still opens and
+ * remote participants can see it, but the local preview fails to render or may
+ * crash.
+ *
+ * Only for calls originating in libxcast.so, force EGL display creation through
+ * the X11 platform. Qt/QtWebEngine and other callers continue to use their
+ * normal EGL path.
+ */
+
+#define _GNU_SOURCE
+#include <dlfcn.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <EGL/egl.h>
+#include <EGL/eglext.h>
+#include <X11/Xlib.h>
+
+#ifndef EGL_PLATFORM_X11_KHR
+#define EGL_PLATFORM_X11_KHR 0x31D5
+#endif
+
+typedef EGLDisplay (*pfn_eglGetDisplay)(EGLNativeDisplayType);
+typedef EGLDisplay (*pfn_eglGetPlatformDisplay)(EGLenum, void *, const EGLAttrib *);
+typedef EGLDisplay (*pfn_eglGetPlatformDisplayEXT)(EGLenum, void *, const EGLint *);
+
+static pfn_eglGetDisplay real_eglGetDisplay;
+static pfn_eglGetPlatformDisplay real_eglGetPlatformDisplay;
+static pfn_eglGetPlatformDisplayEXT real_eglGetPlatformDisplayEXT;
+
+static EGLDisplay x11_egl_display = EGL_NO_DISPLAY;
+static Display *x_display;
+static pthread_once_t once_resolve = PTHREAD_ONCE_INIT;
+static pthread_once_t once_x11 = PTHREAD_ONCE_INIT;
+
+static int debug_enabled(void)
+{
+    static int value = -1;
+    if (value < 0) {
+        value = getenv("WEMEET_CAMERA_FIX_DEBUG") != NULL;
+    }
+    return value;
+}
+
+#define LOG(...)                                                               \
+    do {                                                                       \
+        if (debug_enabled()) {                                                 \
+            fprintf(stderr, "[wemeet-camera-fix] " __VA_ARGS__);               \
+        }                                                                      \
+    } while (0)
+
+static void resolve_real_symbols(void)
+{
+    real_eglGetDisplay = (pfn_eglGetDisplay)dlsym(RTLD_NEXT, "eglGetDisplay");
+    real_eglGetPlatformDisplay =
+        (pfn_eglGetPlatformDisplay)dlsym(RTLD_NEXT, "eglGetPlatformDisplay");
+    real_eglGetPlatformDisplayEXT =
+        (pfn_eglGetPlatformDisplayEXT)dlsym(RTLD_NEXT, "eglGetPlatformDisplayEXT");
+}
+
+static void init_x11_egl_display(void)
+{
+    pthread_once(&once_resolve, resolve_real_symbols);
+
+    x_display = XOpenDisplay(NULL);
+    if (!x_display) {
+        fprintf(stderr, "[wemeet-camera-fix] XOpenDisplay(NULL) failed; DISPLAY=%s\n",
+                getenv("DISPLAY") ? getenv("DISPLAY") : "(unset)");
+        return;
+    }
+
+    if (real_eglGetPlatformDisplay) {
+        x11_egl_display =
+            real_eglGetPlatformDisplay(EGL_PLATFORM_X11_KHR, x_display, NULL);
+    } else if (real_eglGetPlatformDisplayEXT) {
+        x11_egl_display =
+            real_eglGetPlatformDisplayEXT(EGL_PLATFORM_X11_KHR, x_display, NULL);
+    } else if (real_eglGetDisplay) {
+        x11_egl_display = real_eglGetDisplay((EGLNativeDisplayType)x_display);
+    }
+
+    LOG("initialized X11 EGLDisplay=%p for X Display*=%p\n",
+        (void *)x11_egl_display, (void *)x_display);
+}
+
+static int caller_is_xcast(void *caller)
+{
+    Dl_info info;
+
+    if (!caller) {
+        return 0;
+    }
+    memset(&info, 0, sizeof(info));
+    if (!dladdr(caller, &info) || !info.dli_fname) {
+        return 0;
+    }
+    return strstr(info.dli_fname, "libxcast.so") != NULL;
+}
+
+EGLDisplay eglGetDisplay(EGLNativeDisplayType display_id)
+{
+    pthread_once(&once_resolve, resolve_real_symbols);
+
+    if (caller_is_xcast(__builtin_return_address(0))) {
+        pthread_once(&once_x11, init_x11_egl_display);
+        LOG("eglGetDisplay from libxcast.so -> %p\n", (void *)x11_egl_display);
+        return x11_egl_display;
+    }
+
+    return real_eglGetDisplay ? real_eglGetDisplay(display_id) : EGL_NO_DISPLAY;
+}
+
+EGLDisplay eglGetPlatformDisplay(EGLenum platform, void *native_display,
+                                 const EGLAttrib *attrib_list)
+{
+    pthread_once(&once_resolve, resolve_real_symbols);
+
+    if (caller_is_xcast(__builtin_return_address(0))) {
+        pthread_once(&once_x11, init_x11_egl_display);
+        LOG("eglGetPlatformDisplay from libxcast.so -> %p\n",
+            (void *)x11_egl_display);
+        return x11_egl_display;
+    }
+
+    return real_eglGetPlatformDisplay
+               ? real_eglGetPlatformDisplay(platform, native_display, attrib_list)
+               : EGL_NO_DISPLAY;
+}
+
+EGLDisplay eglGetPlatformDisplayEXT(EGLenum platform, void *native_display,
+                                    const EGLint *attrib_list)
+{
+    pthread_once(&once_resolve, resolve_real_symbols);
+
+    if (caller_is_xcast(__builtin_return_address(0))) {
+        pthread_once(&once_x11, init_x11_egl_display);
+        LOG("eglGetPlatformDisplayEXT from libxcast.so -> %p\n",
+            (void *)x11_egl_display);
+        return x11_egl_display;
+    }
+
+    return real_eglGetPlatformDisplayEXT
+               ? real_eglGetPlatformDisplayEXT(platform, native_display, attrib_list)
+               : EGL_NO_DISPLAY;
+}