Impl drag and drop in WebHEADdev

2 files changed, 345 insertions, 177 deletions

diff --git a/index.htm b/index.htm
index 18c110f..1207f79 100644
--- a/index.htm
+++ b/index.htm
@@ -76,7 +76,14 @@
 
                   this.sound_buffer_address = program.exports.js_sound_buffer();
                   this.pixels_address       = program.exports.js_pixels();
-                  this.frames               = new Float32Array(this.memory_buffer, this.sound_buffer_address, program.exports.js_max_num_sound_frames());
+                  this.max_drop_size        = program.exports.js_max_drop_size();
+                  this.drop_address         = program.exports.js_drop_buffer();
+
+                  this.frames = new Float32Array(
+                    this.memory_buffer,
+                    this.sound_buffer_address,
+                    program.exports.js_max_num_sound_frames()
+                  );
 
                   let title_address = program.exports.js_title();
 
@@ -160,6 +167,50 @@
 
                 this.program.exports.js_keydown(ev.key, ev.mod, ev.ch);
               },
+
+              dragenter : (ev) => {
+                if (this.program === undefined)
+                  return;
+
+                this.program.exports.js_dragenter();
+              },
+
+              dragleave : (ev) => {
+                if (this.program === undefined)
+                  return;
+
+                this.program.exports.js_dragenter();
+              },
+
+              drop : (ev) => {
+                if (this.program === undefined)
+                  return;
+
+                for (let f of ev.files) {
+                  if (f.name.byteLength + f.data.byteLength > this.max_drop_size) {
+                    console.error("File too big");
+                    continue;
+                  }
+
+                  new Uint8Array(
+                    this.memory_buffer,
+                    this.drop_address,
+                    f.name.byteLength
+                  ).set(
+                    new Uint8Array(f.name)
+                  );
+
+                  new Uint8Array(
+                    this.memory_buffer,
+                    this.drop_address + f.name.byteLength,
+                    f.data.byteLength
+                  ).set(
+                    new Uint8Array(f.data)
+                  );
+
+                  this.program.exports.js_drop(f.name.byteLength, f.data.byteLength);
+                }
+              },
             };
 
             this.port.onmessage = (ev) => {
@@ -223,35 +274,26 @@
         let program = await WebAssembly.instantiate(
           wasm,
           {
-            wasi_snapshot_preview1 : {
-              clock_time_get : () => {},
-              args_sizes_get : () => {},
-              args_get       : () => {},
-              proc_exit      : () => {},
-              fd_close       : () => {},
-              fd_write       : () => {},
-              fd_seek        : () => {},
-            },
             env : {
               p_clipboard_write_impl : () => {},
               p_time_impl            : () => {},
-
-              floor : () => {},
-              ceil  : () => {},
-              sqrt  : () => {},
-              cbrt  : () => {},
-              pow   : () => {},
-              log   : () => {},
-              log2  : () => {},
-              log10 : () => {},
-              exp   : () => {},
-              sin   : () => {},
-              cos   : () => {},
-              tan   : () => {},
-              asin  : () => {},
-              acos  : () => {},
-              atan  : () => {},
-              atan2 : () => {},
+              floor                  : () => {},
+              ceil                   : () => {},
+              trunc                  : () => {},
+              sqrt                   : () => {},
+              cbrt                   : () => {},
+              pow                    : () => {},
+              log                    : () => {},
+              log2                   : () => {},
+              log10                  : () => {},
+              exp                    : () => {},
+              sin                    : () => {},
+              cos                    : () => {},
+              tan                    : () => {},
+              asin                   : () => {},
+              acos                   : () => {},
+              atan                   : () => {},
+              atan2                  : () => {},
             },
           }
         );
@@ -568,7 +610,6 @@
         });
 
         window.addEventListener("wheel", (ev) => {
-          ev.preventDefault();
           if (!sound_ready)
             return;
 
@@ -592,6 +633,68 @@
             ch    : paste_ch,
           });
         });
+
+        canvas.addEventListener("dragover", (ev) => {
+          ev.preventDefault();
+          if (!sound_ready) {
+            ev.dataTransfer.dropEffect = "none";
+            return;
+          }
+
+          if (ev.clientX != undefined && ev.clientY != undefined)
+            sound_node.port.postMessage({
+              id : "mousemove",
+              x  : ev.clientX,
+              y  : ev.clientY,
+            });
+        });
+
+        canvas.addEventListener("dragenter", (ev) => {
+          ev.preventDefault();
+          if (!sound_ready)
+            return;
+
+          sound_node.port.postMessage({
+            id : "dragenter",
+          });
+        });
+
+        canvas.addEventListener("dragleave", (ev) => {
+          ev.preventDefault();
+          if (!sound_ready)
+            return;
+
+          sound_node.port.postMessage({
+            id : "dragleave",
+          });
+        });
+
+        canvas.addEventListener("drop", (ev) => {
+          ev.preventDefault();
+          if (!sound_ready)
+            return;
+
+          (async () => {
+            let files = [];
+
+            for (let f of ev.dataTransfer.files) {
+              //  Copy the buffer in case the underlaying buffer's size is larger.
+              let bytes  = await f.bytes();
+              let buffer = new ArrayBuffer(bytes.length);
+              new Uint8Array(buffer).set(bytes);
+
+              files.push({
+                name : new TextEncoder("utf8").encode(f.name),
+                data : buffer,
+              });
+            }
+
+            sound_node.port.postMessage({
+              id    : "drop",
+              files : files,
+            });
+          })();
+        });
       }
 
       run({
diff --git a/reduced_system_layer.c b/reduced_system_layer.c
index 6032ee3..a1bac25 100644
--- a/reduced_system_layer.c
+++ b/reduced_system_layer.c
@@ -176,6 +176,7 @@ i32 main(i32 argc, c8 **argv);
 #endif
 
 #ifndef MAX_INPUT_SIZE
+//  How many input events can be buffered during one frame.
 #define MAX_INPUT_SIZE 256
 #endif
 
@@ -203,22 +204,29 @@ i32 main(i32 argc, c8 **argv);
 #define MAX_PIXEL_SIZE (16.0)
 #endif
 
-#ifndef PIXEL_SIZE_DELTA
-#define PIXEL_SIZE_DELTA (0.1)
+#ifndef DEFAULT_PIXEL_SIZE
+#define DEFAULT_PIXEL_SIZE (8.0)
 #endif
 
-#ifndef DEFAULT_PIXEL_SIZE
-#define DEFAULT_PIXEL_SIZE (3.0)
+#ifndef PIXEL_SIZE_DELTA
+#define PIXEL_SIZE_DELTA (0.05)
 #endif
 
 #ifndef MIN_FRAME_DURATION
+//  The pixel size will decrease when the frame duration is lower.
 #define MIN_FRAME_DURATION 17
 #endif
 
 #ifndef MAX_FRAME_DURATION
+//  The pixel size will increaseo when the frame duration is higher.
 #define MAX_FRAME_DURATION 34
 #endif
 
+#ifndef FRAME_DURATION_HARD_LIMIT
+//  The pixel size value will reset if the frame duration is higher.
+#define FRAME_DURATION_HARD_LIMIT 500
+#endif
+
 #ifndef NUM_FRAMES_AVERAGED
 #define NUM_FRAMES_AVERAGED 400
 #endif
@@ -924,7 +932,7 @@ static void drop_files_set_data_(i64 index, i64 data_size) {
   g_platform.drop_files[index].data      = _drop_files_buffer + offset;
 }
 
-i8 pixel_size_update_(i32 real_width, i32 real_height) {
+static i8 pixel_size_update_(i32 real_width, i32 real_height) {
   i8 size_changed = 0;
 
   i32 width  = real_width;
@@ -954,13 +962,15 @@ i8 pixel_size_update_(i32 real_width, i32 real_height) {
   return size_changed;
 }
 
-void pixel_size_calubrate_(i64 current_frame_duration) {
+static void pixel_size_calubrate_(i64 current_frame_duration) {
   if (g_platform.exact_resolution)
     return;
 
   i64 frame_duration = average_frame_duration_(current_frame_duration);
 
-  if (g_platform.pixel_size < MAX_PIXEL_SIZE && frame_duration > MAX_FRAME_DURATION)
+  if (current_frame_duration > FRAME_DURATION_HARD_LIMIT)
+    g_platform.pixel_size = MAX_PIXEL_SIZE;
+  else if (g_platform.pixel_size < MAX_PIXEL_SIZE && frame_duration > MAX_FRAME_DURATION)
     g_platform.pixel_size += PIXEL_SIZE_DELTA * (frame_duration - MAX_FRAME_DURATION);
   else if (g_platform.pixel_size > MIN_PIXEL_SIZE && frame_duration < MIN_FRAME_DURATION)
     g_platform.pixel_size -= PIXEL_SIZE_DELTA * (MIN_FRAME_DURATION - frame_duration);
@@ -2223,7 +2233,134 @@ void p_clipboard_write(i64 size, c8 *data) {
 
 //  ================================================================
 //
-//  WebAssembly
+//  Web startup options
+//
+//  ================================================================
+
+#if defined(__wasm__)
+
+static u16 _key_map[MAX_NUM_KEYS] = {0};
+
+__attribute__((export_name("js_max_num_keys"))) i32 js_max_num_keys(void) {
+  return MAX_NUM_KEYS;
+}
+
+__attribute__((export_name("js_key_map"))) void *js_key_map(void) {
+  i32 n = 0;
+
+  _key_map[n++] = KEY_BACKSPACE;
+  _key_map[n++] = KEY_TAB;
+  _key_map[n++] = KEY_ENTER;
+  _key_map[n++] = KEY_LCTRL;
+  _key_map[n++] = KEY_RCTRL;
+  _key_map[n++] = KEY_LSHIFT;
+  _key_map[n++] = KEY_RSHIFT;
+  _key_map[n++] = KEY_LALT;
+  _key_map[n++] = KEY_RALT;
+  _key_map[n++] = KEY_LEFT;
+  _key_map[n++] = KEY_RIGHT;
+  _key_map[n++] = KEY_UP;
+  _key_map[n++] = KEY_DOWN;
+  _key_map[n++] = KEY_PAUSE;
+  _key_map[n++] = KEY_INSERT;
+  _key_map[n++] = KEY_HOME;
+  _key_map[n++] = KEY_END;
+  _key_map[n++] = KEY_PAGEUP;
+  _key_map[n++] = KEY_PAGEDOWN;
+  _key_map[n++] = KEY_ESCAPE;
+  _key_map[n++] = KEY_PRINTSCREEN;
+  _key_map[n++] = KEY_SPACE;
+  _key_map[n++] = KEY_LMETA;
+  _key_map[n++] = KEY_RMETA;
+  _key_map[n++] = KEY_QUOTE;
+  _key_map[n++] = KEY_COMMA;
+  _key_map[n++] = KEY_MINUS;
+  _key_map[n++] = KEY_PERIOD;
+  _key_map[n++] = KEY_SLASH;
+  _key_map[n++] = KEY_0;
+  _key_map[n++] = KEY_1;
+  _key_map[n++] = KEY_2;
+  _key_map[n++] = KEY_3;
+  _key_map[n++] = KEY_4;
+  _key_map[n++] = KEY_5;
+  _key_map[n++] = KEY_6;
+  _key_map[n++] = KEY_7;
+  _key_map[n++] = KEY_8;
+  _key_map[n++] = KEY_9;
+  _key_map[n++] = KEY_COLON;
+  _key_map[n++] = KEY_EQUAL;
+  _key_map[n++] = KEY_LBRACE;
+  _key_map[n++] = KEY_BACKSLASH;
+  _key_map[n++] = KEY_RBRACE;
+  _key_map[n++] = KEY_TILDE;
+  _key_map[n++] = KEY_A;
+  _key_map[n++] = KEY_B;
+  _key_map[n++] = KEY_C;
+  _key_map[n++] = KEY_D;
+  _key_map[n++] = KEY_E;
+  _key_map[n++] = KEY_F;
+  _key_map[n++] = KEY_G;
+  _key_map[n++] = KEY_H;
+  _key_map[n++] = KEY_I;
+  _key_map[n++] = KEY_J;
+  _key_map[n++] = KEY_K;
+  _key_map[n++] = KEY_L;
+  _key_map[n++] = KEY_M;
+  _key_map[n++] = KEY_N;
+  _key_map[n++] = KEY_O;
+  _key_map[n++] = KEY_P;
+  _key_map[n++] = KEY_Q;
+  _key_map[n++] = KEY_R;
+  _key_map[n++] = KEY_S;
+  _key_map[n++] = KEY_T;
+  _key_map[n++] = KEY_U;
+  _key_map[n++] = KEY_V;
+  _key_map[n++] = KEY_W;
+  _key_map[n++] = KEY_X;
+  _key_map[n++] = KEY_Y;
+  _key_map[n++] = KEY_Z;
+  _key_map[n++] = KEY_DELETE;
+  _key_map[n++] = KEY_F1;
+  _key_map[n++] = KEY_F2;
+  _key_map[n++] = KEY_F3;
+  _key_map[n++] = KEY_F4;
+  _key_map[n++] = KEY_F5;
+  _key_map[n++] = KEY_F6;
+  _key_map[n++] = KEY_F7;
+  _key_map[n++] = KEY_F8;
+  _key_map[n++] = KEY_F9;
+  _key_map[n++] = KEY_F10;
+  _key_map[n++] = KEY_F11;
+  _key_map[n++] = KEY_F12;
+  _key_map[n++] = KEY_F13;
+  _key_map[n++] = KEY_F14;
+  _key_map[n++] = KEY_F15;
+  _key_map[n++] = KEY_F16;
+  _key_map[n++] = KEY_F17;
+  _key_map[n++] = KEY_F18;
+  _key_map[n++] = KEY_F19;
+  _key_map[n++] = KEY_F20;
+  _key_map[n++] = KEY_F21;
+  _key_map[n++] = KEY_F22;
+  _key_map[n++] = KEY_F23;
+  _key_map[n++] = KEY_F24;
+
+  return _key_map;
+}
+
+__attribute__((export_name("js_sound_sample_rate"))) f64 js_sound_sample_rate(void) {
+  return (f64) SOUND_SAMPLE_RATE;
+}
+
+__attribute__((export_name("js_num_sound_channels"))) i32 js_num_sound_channels(void) {
+  return NUM_SOUND_CHANNELS;
+}
+
+#endif // defined(__wasm__)
+
+//  ================================================================
+//
+//  Web
 //
 //  ================================================================
 
@@ -2240,21 +2377,23 @@ static f64 _wheel_dy       = 0;
 static b8  _wait_events    = 0;
 static i64 _timeout        = 0;
 static i64 _sound_read     = 0;
+static b8  _files_dragged  = 0;
+static b8  _files_dropped  = 0;
 
-static u16 _key_map         [MAX_NUM_KEYS]         = {0};
-static c8  _href            [4096]                 = {0};
-static u32 _pixels_scaled   [MAX_NUM_PIXELS]       = {0};
-static u32 _pixels_internal [MAX_NUM_PIXELS]       = {0};
-static b8  _key_pressed     [MAX_NUM_KEYS]         = {0};
-static f32 _sound_buffer    [MAX_NUM_SOUND_FRAMES] = {0};
+static c8  _href            [4096]                   = {0};
+static u32 _pixels_scaled   [MAX_NUM_PIXELS]         = {0};
+static u32 _pixels_internal [MAX_NUM_PIXELS]         = {0};
+static b8  _key_pressed     [MAX_NUM_KEYS]           = {0};
+static f32 _sound_buffer    [MAX_NUM_SOUND_FRAMES]   = {0};
+static u8  _drop_buffer     [DROP_FILES_BUFFER_SIZE] = {0};
 
 i64 p_recv(u16 slot, IP_Address address, i64 size, u8 *data, u16 *local_port, IP_Address *remote_address) {
-  //  Not implemented
+  LOG_ERROR("Web sockets are not implemented.");
   return 0;
 }
 
 i64 p_send(u16 slot, IP_Address address, i64 size, u8 *data, u16 *local_port) {
-  //  Not implemented
+  LOG_ERROR("Web sockets are not implemented.");
   return 0;
 }
 
@@ -2288,17 +2427,27 @@ void p_init(void) {
 }
 
 i32 p_handle_events(void) {
-  g_platform.input_size = _input_size;
-  g_platform.cursor_dx  = _cursor_dx;
-  g_platform.cursor_dy  = _cursor_dy;
-  g_platform.wheel_dx   = _wheel_dx;
-  g_platform.wheel_dy   = _wheel_dy;
-
-  _input_size = 0;
-  _cursor_dx  = 0;
-  _cursor_dy  = 0;
-  _wheel_dx   = 0;
-  _wheel_dy   = 0;
+  if (g_platform.files_dropped)
+    drop_files_clean_();
+
+  g_platform.input_size    = _input_size;
+  g_platform.cursor_dx     = _cursor_dx;
+  g_platform.cursor_dy     = _cursor_dy;
+  g_platform.wheel_dx      = _wheel_dx;
+  g_platform.wheel_dy      = _wheel_dy;
+  g_platform.files_dragged = _files_dragged;
+  g_platform.files_dropped = _files_dropped;
+
+  _input_size    = 0;
+  _cursor_dx     = 0;
+  _cursor_dy     = 0;
+  _wheel_dx      = 0;
+  _wheel_dy      = 0;
+
+  if (_files_dropped) {
+    _files_dragged = 0;
+    _files_dropped = 0;
+  }
 
   for (i64 i = 0; i < MAX_NUM_KEYS; ++i)
     g_platform.key_pressed[i] = _key_pressed[i];
@@ -2370,8 +2519,10 @@ void p_queue_sound(i64 delay_in_samples, i64 num_samples, f32 *frames) {
     return;
 
   i64 num_frames = num_samples * NUM_SOUND_CHANNELS;
-  if (num_frames > MAX_NUM_SOUND_FRAMES)
+  if (num_frames > MAX_NUM_SOUND_FRAMES) {
+    LOG_ERROR("Sound buffer overflow.");
     return;
+  }
 
   i64 begin = (_sound_position + delay_in_samples * NUM_SOUND_CHANNELS) % MAX_NUM_SOUND_FRAMES;
 
@@ -2389,121 +2540,6 @@ void p_queue_sound(i64 delay_in_samples, i64 num_samples, f32 *frames) {
   }
 }
 
-__attribute__((export_name("js_max_num_keys"))) i32 js_max_num_keys(void) {
-  return MAX_NUM_KEYS;
-}
-
-__attribute__((export_name("js_key_map"))) void *js_key_map(void) {
-  i32 n = 0;
-
-  _key_map[n++] = KEY_BACKSPACE;
-  _key_map[n++] = KEY_TAB;
-  _key_map[n++] = KEY_ENTER;
-  _key_map[n++] = KEY_LCTRL;
-  _key_map[n++] = KEY_RCTRL;
-  _key_map[n++] = KEY_LSHIFT;
-  _key_map[n++] = KEY_RSHIFT;
-  _key_map[n++] = KEY_LALT;
-  _key_map[n++] = KEY_RALT;
-  _key_map[n++] = KEY_LEFT;
-  _key_map[n++] = KEY_RIGHT;
-  _key_map[n++] = KEY_UP;
-  _key_map[n++] = KEY_DOWN;
-  _key_map[n++] = KEY_PAUSE;
-  _key_map[n++] = KEY_INSERT;
-  _key_map[n++] = KEY_HOME;
-  _key_map[n++] = KEY_END;
-  _key_map[n++] = KEY_PAGEUP;
-  _key_map[n++] = KEY_PAGEDOWN;
-  _key_map[n++] = KEY_ESCAPE;
-  _key_map[n++] = KEY_PRINTSCREEN;
-  _key_map[n++] = KEY_SPACE;
-  _key_map[n++] = KEY_LMETA;
-  _key_map[n++] = KEY_RMETA;
-  _key_map[n++] = KEY_QUOTE;
-  _key_map[n++] = KEY_COMMA;
-  _key_map[n++] = KEY_MINUS;
-  _key_map[n++] = KEY_PERIOD;
-  _key_map[n++] = KEY_SLASH;
-  _key_map[n++] = KEY_0;
-  _key_map[n++] = KEY_1;
-  _key_map[n++] = KEY_2;
-  _key_map[n++] = KEY_3;
-  _key_map[n++] = KEY_4;
-  _key_map[n++] = KEY_5;
-  _key_map[n++] = KEY_6;
-  _key_map[n++] = KEY_7;
-  _key_map[n++] = KEY_8;
-  _key_map[n++] = KEY_9;
-  _key_map[n++] = KEY_COLON;
-  _key_map[n++] = KEY_EQUAL;
-  _key_map[n++] = KEY_LBRACE;
-  _key_map[n++] = KEY_BACKSLASH;
-  _key_map[n++] = KEY_RBRACE;
-  _key_map[n++] = KEY_TILDE;
-  _key_map[n++] = KEY_A;
-  _key_map[n++] = KEY_B;
-  _key_map[n++] = KEY_C;
-  _key_map[n++] = KEY_D;
-  _key_map[n++] = KEY_E;
-  _key_map[n++] = KEY_F;
-  _key_map[n++] = KEY_G;
-  _key_map[n++] = KEY_H;
-  _key_map[n++] = KEY_I;
-  _key_map[n++] = KEY_J;
-  _key_map[n++] = KEY_K;
-  _key_map[n++] = KEY_L;
-  _key_map[n++] = KEY_M;
-  _key_map[n++] = KEY_N;
-  _key_map[n++] = KEY_O;
-  _key_map[n++] = KEY_P;
-  _key_map[n++] = KEY_Q;
-  _key_map[n++] = KEY_R;
-  _key_map[n++] = KEY_S;
-  _key_map[n++] = KEY_T;
-  _key_map[n++] = KEY_U;
-  _key_map[n++] = KEY_V;
-  _key_map[n++] = KEY_W;
-  _key_map[n++] = KEY_X;
-  _key_map[n++] = KEY_Y;
-  _key_map[n++] = KEY_Z;
-  _key_map[n++] = KEY_DELETE;
-  _key_map[n++] = KEY_F1;
-  _key_map[n++] = KEY_F2;
-  _key_map[n++] = KEY_F3;
-  _key_map[n++] = KEY_F4;
-  _key_map[n++] = KEY_F5;
-  _key_map[n++] = KEY_F6;
-  _key_map[n++] = KEY_F7;
-  _key_map[n++] = KEY_F8;
-  _key_map[n++] = KEY_F9;
-  _key_map[n++] = KEY_F10;
-  _key_map[n++] = KEY_F11;
-  _key_map[n++] = KEY_F12;
-  _key_map[n++] = KEY_F13;
-  _key_map[n++] = KEY_F14;
-  _key_map[n++] = KEY_F15;
-  _key_map[n++] = KEY_F16;
-  _key_map[n++] = KEY_F17;
-  _key_map[n++] = KEY_F18;
-  _key_map[n++] = KEY_F19;
-  _key_map[n++] = KEY_F20;
-  _key_map[n++] = KEY_F21;
-  _key_map[n++] = KEY_F22;
-  _key_map[n++] = KEY_F23;
-  _key_map[n++] = KEY_F24;
-
-  return _key_map;
-}
-
-__attribute__((export_name("js_sound_sample_rate"))) f64 js_sound_sample_rate(void) {
-  return (f64) SOUND_SAMPLE_RATE;
-}
-
-__attribute__((export_name("js_num_sound_channels"))) i32 js_num_sound_channels(void) {
-  return NUM_SOUND_CHANNELS;
-}
-
 __attribute__((export_name("js_max_num_sound_frames"))) i32 js_max_num_sound_frames(void) {
   return MAX_NUM_SOUND_FRAMES;
 }
@@ -2521,11 +2557,6 @@ __attribute__((export_name("js_href_size"))) i32 js_href_size(void) {
 }
 
 __attribute__((export_name("js_main"))) void js_main(void) {
-  (void) drop_files_clean_;
-  (void) drop_files_set_num_;
-  (void) drop_files_set_name_;
-  (void) drop_files_set_data_;
-
   main(1, (c8 *[1]) { _href });
 }
 
@@ -2545,7 +2576,7 @@ __attribute__((export_name("js_frame"))) void js_frame(i32 frame_width, i32 fram
     _frame_height = frame_height;
   }
 
-  _num_size += pixel_size_update_(_frame_width, _frame_height);
+  _num_events += pixel_size_update_(_frame_width, _frame_height);
 
   g_platform.done = 0;
 
@@ -2642,6 +2673,40 @@ __attribute__((export_name("js_clipboard_buffer"))) void *js_clipboard_buffer(i3
   return g_platform.clipboard;
 }
 
+__attribute__((export_name("js_dragenter"))) void js_dragenter(void) {
+  _files_dragged = 1;
+}
+
+__attribute__((export_name("js_dragleave"))) void js_dragleave(void) {
+  _files_dragged = 0;
+}
+
+__attribute__((export_name("js_max_drop_size"))) i32 js_max_drop_size(void) {
+  return sizeof _drop_buffer;
+}
+
+__attribute__((export_name("js_drop_buffer"))) void *js_drop_buffer(void) {
+  return _drop_buffer;
+}
+
+__attribute__((export_name("js_drop"))) void js_drop(i32 name_len, i32 data_size) {
+  if (name_len + data_size > sizeof _drop_buffer) {
+    LOG_ERROR("File too big.");
+    return;
+  }
+
+  i64 n = g_platform.num_drop_files;
+
+  drop_files_set_num_(n + 1);
+  drop_files_set_name_(n, name_len, (c8 *) _drop_buffer);
+  drop_files_set_data_(n, data_size);
+
+  for (i64 i = 0; i < data_size; ++i)
+    g_platform.drop_files[n].data[i] = _drop_buffer[name_len + i];
+
+  _files_dropped = 1;
+}
+
 #endif // defined(__wasm__)
 
 //  ================================================================