Allow calling BackendBase::open multiple times on playback devices

It will not be called while the device is running. If the first call succeeds,
a subsequent call that happens to fail must leave the existing device state as
it was so it can be resumed.

This is a rough first pass. It will fail when trying to re-open the same device
which can only be opened once (for instance, with direct hardware access, on
hardware that doesn't do its own mixing). Some backends won't guarantee the new
device is usable until the reset() or start() call.

1 files changed, 20 insertions, 15 deletions

diff --git a/alc/backends/portaudio.cpp b/alc/backends/portaudio.cpp
index d2e6a5a4..188f72f2 100644
--- a/alc/backends/portaudio.cpp
+++ b/alc/backends/portaudio.cpp
@@ -123,53 +123,58 @@ void PortPlayback::open(const char *name)
         throw al::backend_exception{al::backend_error::NoDevice, "Device name \"%s\" not found",
             name};
 
-    mUpdateSize = mDevice->UpdateSize;
-
+    PaStreamParameters params{};
     auto devidopt = ConfigValueInt(nullptr, "port", "device");
-    if(devidopt && *devidopt >= 0) mParams.device = *devidopt;
-    else mParams.device = Pa_GetDefaultOutputDevice();
-    mParams.suggestedLatency = mDevice->BufferSize / static_cast<double>(mDevice->Frequency);
-    mParams.hostApiSpecificStreamInfo = nullptr;
+    if(devidopt && *devidopt >= 0) params.device = *devidopt;
+    else params.device = Pa_GetDefaultOutputDevice();
+    params.suggestedLatency = mDevice->BufferSize / static_cast<double>(mDevice->Frequency);
+    params.hostApiSpecificStreamInfo = nullptr;
 
-    mParams.channelCount = ((mDevice->FmtChans == DevFmtMono) ? 1 : 2);
+    params.channelCount = ((mDevice->FmtChans == DevFmtMono) ? 1 : 2);
 
     switch(mDevice->FmtType)
     {
     case DevFmtByte:
-        mParams.sampleFormat = paInt8;
+        params.sampleFormat = paInt8;
         break;
     case DevFmtUByte:
-        mParams.sampleFormat = paUInt8;
+        params.sampleFormat = paUInt8;
         break;
     case DevFmtUShort:
         /* fall-through */
     case DevFmtShort:
-        mParams.sampleFormat = paInt16;
+        params.sampleFormat = paInt16;
         break;
     case DevFmtUInt:
         /* fall-through */
     case DevFmtInt:
-        mParams.sampleFormat = paInt32;
+        params.sampleFormat = paInt32;
         break;
     case DevFmtFloat:
-        mParams.sampleFormat = paFloat32;
+        params.sampleFormat = paFloat32;
         break;
     }
 
 retry_open:
-    PaError err{Pa_OpenStream(&mStream, nullptr, &mParams, mDevice->Frequency, mDevice->UpdateSize,
+    PaStream *stream{};
+    PaError err{Pa_OpenStream(&stream, nullptr, &params, mDevice->Frequency, mDevice->UpdateSize,
         paNoFlag, &PortPlayback::writeCallbackC, this)};
     if(err != paNoError)
     {
-        if(mParams.sampleFormat == paFloat32)
+        if(params.sampleFormat == paFloat32)
         {
-            mParams.sampleFormat = paInt16;
+            params.sampleFormat = paInt16;
             goto retry_open;
         }
         throw al::backend_exception{al::backend_error::NoDevice, "Failed to open stream: %s",
             Pa_GetErrorText(err)};
     }
 
+    Pa_CloseStream(mStream);
+    mStream = stream;
+    mParams = params;
+    mUpdateSize = mDevice->UpdateSize;
+
     mDevice->DeviceName = name;
 }