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Code Issues Activity Actions

Piano: Use a secondary thread to write the audio stream.

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This frees up the main thread to draw the GUI. The secondary thread uses
a pipe to trick the main thread's event loop to break out of select() and
update() the PianoWidget. :^)
This commit is contained in:
Andreas Kling 2019-07-13 20:20:08 +02:00
parent dcfa93e71f
commit eec9666735
3 changed files with 88 additions and 54 deletions
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43
Applications/Piano/main.cpp
View file

@ -1,20 +1,19 @@
#include "Music.h"
#include "PianoWidget.h"
#include <LibCore/CFile.h>
#include <LibCore/CNotifier.h>
#include <LibGUI/GApplication.h>
#include <LibGUI/GEventLoop.h>
#include <LibGUI/GWindow.h>
static int s_pipefds[2];
int main(int argc, char** argv)
{
CFile audio("/dev/audio");
if (!audio.open(CIODevice::WriteOnly)) {
dbgprintf("Can't open audio device: %s", audio.error_string());
return 1;
}
GApplication app(argc, argv);
pipe(s_pipefds);
auto* window = new GWindow;
window->set_title("Piano");
window->set_rect(100, 100, 512, 512);
@ -24,12 +23,30 @@ int main(int argc, char** argv)
window->show();
for (;;) {
GEventLoop::current().pump(GEventLoop::WaitMode::PollForEvents);
u8 buffer[4096];
piano_widget->fill_audio_buffer(buffer, sizeof(buffer));
audio.write(buffer, sizeof(buffer));
}
CNotifier notifier(s_pipefds[0], CNotifier::Read);
notifier.on_ready_to_read = [&] {
char buffer[32];
read(s_pipefds[1], buffer, sizeof(buffer));
piano_widget->update();
};
return 0;
create_thread([](void* context) -> int {
auto* piano_widget = (PianoWidget*)context;
CFile audio("/dev/audio");
if (!audio.open(CIODevice::WriteOnly)) {
dbgprintf("Can't open audio device: %s", audio.error_string());
return 1;
}
for (;;) {
u8 buffer[4096];
piano_widget->fill_audio_buffer(buffer, sizeof(buffer));
audio.write(buffer, sizeof(buffer));
char ch = '!';
write(s_pipefds[0], &ch, 1);
}
}, piano_widget);
return app.exec();
}