Draft: Migrate from SDL2 to SDL3

.github/workflows/release.yml

@@ -80,8 +80,16 @@ jobs:
              libavutil-dev libswresample-dev libusb-1.0-0 libusb-1.0-0-dev \
              libv4l-dev
 
+        # SDL3 is not available in Ubuntu yet
+      - name: Install SDL3
+        run: |
+          app/deps/sdl.sh linux native shared
+
       - name: Test
-        run: release/test_client.sh
+        run: |
+          export PKG_CONFIG_PATH="$PWD"/app/deps/work/install/linux-native-shared/lib/pkgconfig
+          export LD_LIBRARY_PATH="$PWD"/app/deps/work/install/linux-native-shared/lib
+          release/test_client.sh
 
   build-linux-x86_64:
     runs-on: ubuntu-22.04

app/deps/sdl.sh

@@ -5,10 +5,10 @@ cd "$DEPS_DIR"
 . common
 process_args "$@"
 
-VERSION=2.32.8
+VERSION=3.2.18
 FILENAME=SDL-$VERSION.tar.gz
 PROJECT_DIR=SDL-release-$VERSION
-SHA256SUM=dd35e05644ae527848d02433bec24dd0ea65db59faecf1a0e5d1880c533dac2c
+SHA256SUM=51539fa13e546bc50c632beed3f34257de2baa38a4c642048de56377903b4265
 
 cd "$SOURCES_DIR"
 
@@ -35,45 +35,48 @@ else
     cd "$DIRNAME"
 
     conf=(
-        --prefix="$INSTALL_DIR/$DIRNAME"
+        -DCMAKE_INSTALL_PREFIX="$INSTALL_DIR/$DIRNAME"
     )
 
     if [[ "$HOST" == linux ]]
     then
         conf+=(
-            --enable-video-wayland
-            --enable-video-x11
+            -DSDL_WAYLAND=ON
+            -DSDL_X11=ON
         )
     fi
 
     if [[ "$LINK_TYPE" == static ]]
     then
         conf+=(
-            --enable-static
-            --disable-shared
+            -DBUILD_SHARED_LIBS=OFF
         )
     else
         conf+=(
-            --disable-static
-            --enable-shared
+            -DBUILD_SHARED_LIBS=ON
         )
     fi
 
     if [[ "$BUILD_TYPE" == cross ]]
     then
+        if [[ "$HOST" = win32 ]]
+        then
+            TOOLCHAIN_FILENAME="cmake-toolchain-mingw64-i686.cmake"
+        elif [[ "$HOST" = win64 ]]
+        then
+            TOOLCHAIN_FILENAME="cmake-toolchain-mingw64-x86_64.cmake"
+        else
+            echo "Unsupported cross-build to host: $HOST" >&2
+            exit 1
+        fi
+
         conf+=(
-            --host="$HOST_TRIPLET"
+            -DCMAKE_TOOLCHAIN_FILE="$SOURCES_DIR/$PROJECT_DIR/build-scripts/$TOOLCHAIN_FILENAME"
         )
     fi
 
-    "$SOURCES_DIR/$PROJECT_DIR"/configure "${conf[@]}"
+    cmake "$SOURCES_DIR/$PROJECT_DIR" "${conf[@]}"
 fi
 
-make -j
-# There is no "make install-strip"
-make install
-# Strip manually
-if [[ "$LINK_TYPE" == shared && "$HOST" == win* ]]
-then
-    ${HOST_TRIPLET}-strip "$INSTALL_DIR/$DIRNAME/bin/SDL2.dll"
-fi
+cmake --build .
+cmake --install .

app/meson.build

@@ -63,6 +63,7 @@ src = [
     'src/util/thread.c',
     'src/util/tick.c',
     'src/util/timeout.c',
+    'src/util/window.c',
 ]
 
 conf = configuration_data()
@@ -117,7 +118,7 @@ dependencies = [
     dependency('libavcodec', version: '>= 57.37', static: static),
     dependency('libavutil', static: static),
     dependency('libswresample', static: static),
-    dependency('sdl2', version: '>= 2.0.5', static: static),
+    dependency('sdl3', version: '>= 3.2.0', static: static),
 ]
 
 if v4l2_support

app/src/audio_player.c

@@ -1,23 +1,40 @@
 #include "audio_player.h"
 
 #include "util/log.h"
+#include "SDL3/SDL_hints.h"
 
 /** Downcast frame_sink to sc_audio_player */
 #define DOWNCAST(SINK) container_of(SINK, struct sc_audio_player, frame_sink)
 
-#define SC_SDL_SAMPLE_FMT AUDIO_F32
+#define SC_SDL_SAMPLE_FMT SDL_AUDIO_F32LE
 
 static void SDLCALL
-sc_audio_player_sdl_callback(void *userdata, uint8_t *stream, int len_int) {
-    struct sc_audio_player *ap = userdata;
+sc_audio_player_stream_callback(void *userdata, SDL_AudioStream *stream,
+                                int additional_amount, int total_amount) {
+    (void) total_amount;
 
-    assert(len_int > 0);
-    size_t len = len_int;
+    struct sc_audio_player *ap = userdata;
 
+    size_t len = additional_amount;
     assert(len % ap->audioreg.sample_size == 0);
-    uint32_t out_samples = len / ap->audioreg.sample_size;
 
-    sc_audio_regulator_pull(&ap->audioreg, stream, out_samples);
+    // The requested amount may exceed the internal aout_buffer size.
+    // In this (unlikely) case, send the data to the stream in multiple chunks.
+    while (len) {
+        size_t chunk_size = MIN(ap->aout_buffer_size, len);
+        uint32_t out_samples = chunk_size / ap->audioreg.sample_size;
+        sc_audio_regulator_pull(&ap->audioreg, ap->aout_buffer,
+                                out_samples);
+
+        assert(chunk_size <= len);
+        len -= chunk_size;
+        bool ok =
+            SDL_PutAudioStreamData(stream, ap->aout_buffer, chunk_size);
+        if (!ok) {
+            LOGW("Audio stream error: %s", SDL_GetError());
+            return;
+        }
+    }
 }
 
 static bool
@@ -61,23 +78,45 @@ sc_audio_player_frame_sink_open(struct sc_frame_sink *sink,
                                                        / SC_TICK_FREQ;
     assert(aout_samples <= 0xFFFF);
 
-    SDL_AudioSpec desired = {
+    char str[5 + 1]; // max 65535
+    int r = snprintf(str, sizeof(str), "%" PRIu16, (uint16_t) aout_samples);
+    assert(r >= 0 && (size_t) r < sizeof(str));
+    (void) r;
+    if (!SDL_SetHint(SDL_HINT_AUDIO_DEVICE_SAMPLE_FRAMES, str)) {
+        LOGE("Could not set audio output buffer");
+        sc_audio_regulator_destroy(&ap->audioreg);
+        return false;
+    }
+
+    // Make the buffer at least 1024 samples long (the hint is not always
+    // honored)
+    uint64_t aout_buffer_samples = MAX(1024, aout_samples);
+    ap->aout_buffer_size = aout_buffer_samples * sample_size;
+    ap->aout_buffer = malloc(ap->aout_buffer_size);
+    if (!ap->aout_buffer) {
+        sc_audio_regulator_destroy(&ap->audioreg);
+        return false;
+    }
+
+    SDL_AudioSpec spec = {
         .freq = ctx->sample_rate,
         .format = SC_SDL_SAMPLE_FMT,
         .channels = nb_channels,
-        .samples = aout_samples,
-        .callback = sc_audio_player_sdl_callback,
-        .userdata = ap,
     };
-    SDL_AudioSpec obtained;
 
-    ap->device = SDL_OpenAudioDevice(NULL, 0, &desired, &obtained, 0);
-    if (!ap->device) {
+    ap->stream = SDL_OpenAudioDeviceStream(SDL_AUDIO_DEVICE_DEFAULT_PLAYBACK,
+                                           &spec,
+                                           sc_audio_player_stream_callback, ap);
+    if (!ap->stream) {
         LOGE("Could not open audio device: %s", SDL_GetError());
+        free(ap->aout_buffer);
         sc_audio_regulator_destroy(&ap->audioreg);
         return false;
     }
 
+    ap->device = SDL_GetAudioStreamDevice(ap->stream);
+    assert(ap->device);
+
     // The thread calling open() is the thread calling push(), which fills the
     // audio buffer consumed by the SDL audio thread.
     ok = sc_thread_set_priority(SC_THREAD_PRIORITY_TIME_CRITICAL);
@@ -86,7 +125,14 @@ sc_audio_player_frame_sink_open(struct sc_frame_sink *sink,
         (void) ok; // We don't care if it worked, at least we tried
     }
 
-    SDL_PauseAudioDevice(ap->device, 0);
+    ok = SDL_ResumeAudioDevice(ap->device);
+    if (!ok) {
+        LOGE("Could not resume audio device: %s", SDL_GetError());
+        SDL_DestroyAudioStream(ap->stream);
+        free(ap->aout_buffer);
+        sc_audio_regulator_destroy(&ap->audioreg);
+        return false;
+    }
 
     return true;
 }
@@ -95,11 +141,16 @@ static void
 sc_audio_player_frame_sink_close(struct sc_frame_sink *sink) {
     struct sc_audio_player *ap = DOWNCAST(sink);
 
+    assert(ap->stream);
     assert(ap->device);
-    SDL_PauseAudioDevice(ap->device, 1);
-    SDL_CloseAudioDevice(ap->device);
+    SDL_PauseAudioDevice(ap->device);
+
+    // ap->device is owned by ap->stream
+    SDL_DestroyAudioStream(ap->stream);
 
     sc_audio_regulator_destroy(&ap->audioreg);
+
+    free(ap->aout_buffer);
 }
 
 void

app/src/audio_player.h

@@ -3,7 +3,7 @@
 
 #include "common.h"
 
-#include <SDL2/SDL_audio.h>
+#include <SDL3/SDL_audio.h>
 
 #include "audio_regulator.h"
 #include "trait/frame_sink.h"
@@ -22,7 +22,11 @@ struct sc_audio_player {
     // SDL audio output buffer size
     sc_tick output_buffer_duration;
 
-    SDL_AudioDeviceID device;
+    uint8_t *aout_buffer;
+    size_t aout_buffer_size;
+
+    SDL_AudioStream *stream;
+    SDL_AudioDeviceID device; // owned by the audio stream
     struct sc_audio_regulator audioreg;
 };
 

app/src/compat.h

@@ -6,7 +6,7 @@
 #include <libavcodec/version.h>
 #include <libavformat/version.h>
 #include <libavutil/version.h>
-#include <SDL2/SDL_version.h>
+#include <SDL3/SDL_version.h>
 
 #ifndef _WIN32
 # define PRIu64_ PRIu64
@@ -61,28 +61,6 @@
 # define SCRCPY_LAVC_HAS_CODECPAR_CODEC_SIDEDATA
 #endif
 
-#if SDL_VERSION_ATLEAST(2, 0, 6)
-// <https://github.com/libsdl-org/SDL/commit/d7a318de563125e5bb465b1000d6bc9576fbc6fc>
-# define SCRCPY_SDL_HAS_HINT_TOUCH_MOUSE_EVENTS
-#endif
-
-#if SDL_VERSION_ATLEAST(2, 0, 8)
-// <https://hg.libsdl.org/SDL/rev/dfde5d3f9781>
-# define SCRCPY_SDL_HAS_HINT_VIDEO_X11_NET_WM_BYPASS_COMPOSITOR
-#endif
-
-#if SDL_VERSION_ATLEAST(2, 0, 16)
-# define SCRCPY_SDL_HAS_THREAD_PRIORITY_TIME_CRITICAL
-#endif
-
-#if SDL_VERSION_ATLEAST(2, 0, 18)
-# define SCRCPY_SDL_HAS_HINT_APP_NAME
-#endif
-
-#if SDL_VERSION_ATLEAST(2, 0, 14)
-# define SCRCPY_SDL_HAS_HINT_AUDIO_DEVICE_APP_NAME
-#endif
-
 #ifndef HAVE_STRDUP
 char *strdup(const char *s);
 #endif