Fix fluidsynth backend

backends/playback/fluidsynth/fluidsynth_backend.cpp

@@ -91,10 +91,34 @@ void FluidSynthBackend::load(const char *filename) {
     delete file;
     file_data = realloc(file_data, file_len);
     fluid_player_add_mem(player, file_data, file_len);
+    fluid_player_set_loop(player, -1);
+    fluid_player_play(player);
+    size_t prev_pos = 0;
+    size_t cur_pos = 0;
+    size_t samples = 0;
+    sample_positions.push_back({0, 0});
+    float fakebuf;
+    fluid_player_seek(player, 0);
+    while (prev_pos <= cur_pos) {
+        size_t samples_to_add = std::floor((96000.0 * 60.0) / fluid_player_get_bpm(player));
+        fluid_synth_write_float(synth, samples_to_add, &fakebuf, 0, 0, &fakebuf, 0, 0);
+        samples += samples_to_add;
+        prev_pos = cur_pos;
+        while (prev_pos == cur_pos) {
+            cur_pos = fluid_player_get_current_tick(player);
+            if (prev_pos == cur_pos) {
+                fluid_synth_write_float(synth, 1, &fakebuf, 0, 0, &fakebuf, 0, 0);
+                samples++;
+            }
+        }
+        sample_positions.push_back({samples, cur_pos});
+    }
+    this->length = ((double)samples) / 96000.0;
 }
 extern SDL_AudioSpec obtained;
 void FluidSynthBackend::switch_stream(int idx) {
-    fluid_player_play(player);
+    fluid_player_seek(player, 0);
+    open = true;
 }
 void FluidSynthBackend::cleanup() {
     delete_fluid_player(player);
@@ -106,14 +130,33 @@ void FluidSynthBackend::cleanup() {
     file_len = 0;
     free(file_data);
     file_data = nullptr;
+    open = false;
 }
 size_t FluidSynthBackend::render(void *buf, size_t maxlen) {
     size_t sample_type_len = sizeof(float);
     maxlen /= sample_type_len * 2;
+    position += ((double)maxlen) / 96000.0;
     maxlen *= sample_type_len * 2;
     if (fluid_synth_write_float(synth, maxlen / 2 / sample_type_len, buf, 0, 2, buf, 1, 2) == FLUID_FAILED) {
         return 0;
     }
+    if (position >= length) {
+            int tick = fluid_player_get_current_tick(player);
+            int prev_sample = 0;
+            int cur_sample = 0;
+            for (auto &pair : sample_positions) {
+                    prev_sample = cur_sample;
+                    cur_sample = pair.first;
+                    if (pair.second > tick) {
+                            position = ((double)prev_sample) / 96000.0;
+                            break;
+                    } else if (pair.second == tick) {
+                            position = ((double)cur_sample) / 96000.0;
+                            break;
+                    }
+            }
+    }
+    
     return maxlen;
 }
 bool FluidSynthBackend::is_fluidsynth_setting(std::string path) {
@@ -122,10 +165,31 @@ bool FluidSynthBackend::is_fluidsynth_setting(std::string path) {
     return path.substr(0, strlen(prefix)) == std::string(prefix);
 }
 void FluidSynthBackend::seek(double position) {
-    fluid_player_seek(player, position);
+    size_t tick = 0;
+    size_t sample = position * 96000;
+    size_t prev_sample = 0;
+    size_t next_sample = 0;
+    for (auto &pair : sample_positions) {
+        prev_sample = next_sample;
+        next_sample = pair.first;
+        if (next_sample > sample) {
+            tick = pair.second - 1;
+            this->position = ((double)prev_sample) / 96000.0;
+            break;
+        } else if (next_sample == sample) {
+            tick = pair.second;
+            this->position = ((double)next_sample) / 96000.0;
+	    prev_sample = next_sample;
+            break;
+        }
+    }
+    fluid_player_seek(player, tick);
+    float fakebuf;
+    if (sample > prev_sample) fluid_synth_write_float(synth, sample - prev_sample, &fakebuf, 0, 0, &fakebuf, 0, 0);
+    this->position = position;
 }
 double FluidSynthBackend::get_position() {
-    return fluid_player_get_current_tick(player);
+    return position;
 }
 int FluidSynthBackend::get_stream_idx() {
     return 0;

backends/playback/fluidsynth/fluidsynth_backend.hpp

@@ -12,6 +12,7 @@
 #include <SDL.h>
 #include "file_backend.hpp"
 #include <fluidsynth.h>
+#include <vector>
 class FluidSynthBackend : public PlaybackBackend {
     void *file_data;
     size_t file_len;
@@ -20,6 +21,7 @@ class FluidSynthBackend : public PlaybackBackend {
     fluid_settings_t *settings;
     fluid_synth_t *synth;
     fluid_player_t *player;
+    std::vector<std::pair<size_t, size_t>> sample_positions;
     void fluidsynth_get_property_list(const char *name, int type);
     public:
     void set_fluidsynth_property_str(std::string path, std::string val);
@@ -132,8 +134,5 @@ class FluidSynthBackend : public PlaybackBackend {
     int get_stream_idx() override;
     size_t render(void *buf, size_t maxlen) override;
     double get_position() override;
-    inline double get_length() override {
-        return 0.0;
-    }
     inline ~FluidSynthBackend() override { }
 };