gst-play: Improve Win32 keyboard input handling

The console HANDLE will be keep signalled state unless application
reads console input buffer immediately. So we should read and flush
console input buffer from the thread where the event is signalled,
instead of GMain context thread.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/2058>

diff --git a/subprojects/gst-plugins-base/tools/gst-play-kb.c b/subprojects/gst-plugins-base/tools/gst-play-kb.c
index 9c6cf43..b056c20 100644 (file)
--- a/subprojects/gst-plugins-base/tools/gst-play-kb.c
+++ b/subprojects/gst-plugins-base/tools/gst-play-kb.c
@@ -145,37 +145,37 @@ typedef struct
 
 static Win32KeyHandler *win32_handler = NULL;
 
-static gboolean
-gst_play_kb_source_cb (Win32KeyHandler * handler)
+typedef struct
 {
-  HANDLE h_input = handler->console_handle;
-  INPUT_RECORD buffer;
-  DWORD n;
+  gboolean is_ascii;
+  WORD vkcode;
+  gchar key_val[2];
+} KbSourceData;
 
-  if (PeekConsoleInput (h_input, &buffer, 1, &n) && n == 1) {
-    ReadConsoleInput (h_input, &buffer, 1, &n);
-
-    if (buffer.EventType == KEY_EVENT && buffer.Event.KeyEvent.bKeyDown) {
-      gchar key_val[2] = { 0 };
-
-      switch (buffer.Event.KeyEvent.wVirtualKeyCode) {
-        case VK_RIGHT:
-          kb_callback (GST_PLAY_KB_ARROW_RIGHT, kb_callback_data);
-          break;
-        case VK_LEFT:
-          kb_callback (GST_PLAY_KB_ARROW_LEFT, kb_callback_data);
-          break;
-        case VK_UP:
-          kb_callback (GST_PLAY_KB_ARROW_UP, kb_callback_data);
-          break;
-        case VK_DOWN:
-          kb_callback (GST_PLAY_KB_ARROW_DOWN, kb_callback_data);
-          break;
-        default:
-          key_val[0] = buffer.Event.KeyEvent.uChar.AsciiChar;
-          kb_callback (key_val, kb_callback_data);
-          break;
-      }
+static gboolean
+gst_play_kb_source_cb (KbSourceData * data)
+{
+  if (!kb_callback)
+    return G_SOURCE_REMOVE;
+
+  if (data->is_ascii) {
+    kb_callback (data->key_val, kb_callback_data);
+  } else {
+    switch (data->vkcode) {
+      case VK_RIGHT:
+        kb_callback (GST_PLAY_KB_ARROW_RIGHT, kb_callback_data);
+        break;
+      case VK_LEFT:
+        kb_callback (GST_PLAY_KB_ARROW_LEFT, kb_callback_data);
+        break;
+      case VK_UP:
+        kb_callback (GST_PLAY_KB_ARROW_UP, kb_callback_data);
+        break;
+      case VK_DOWN:
+        kb_callback (GST_PLAY_KB_ARROW_DOWN, kb_callback_data);
+        break;
+      default:
+        break;
     }
   }
 
@@ -187,6 +187,8 @@ gst_play_kb_win32_thread (gpointer user_data)
 {
   Win32KeyHandler *handler = (Win32KeyHandler *) user_data;
   HANDLE handles[2];
+  INPUT_RECORD buffer;
+  DWORD n;
 
   handles[0] = handler->event_handle;
   handles[1] = handler->console_handle;
@@ -210,7 +212,30 @@ gst_play_kb_win32_thread (gpointer user_data)
     }
     g_mutex_unlock (&handler->lock);
 
-    g_idle_add ((GSourceFunc) gst_play_kb_source_cb, handler);
+    if (PeekConsoleInput (handler->console_handle, &buffer, 1, &n) && n == 1) {
+      if (ReadConsoleInput (handler->console_handle, &buffer, 1, &n) &&
+          buffer.EventType == KEY_EVENT && buffer.Event.KeyEvent.bKeyDown) {
+        KbSourceData *data = g_new0 (KbSourceData, 1);
+
+        switch (buffer.Event.KeyEvent.wVirtualKeyCode) {
+          case VK_RIGHT:
+          case VK_LEFT:
+          case VK_UP:
+          case VK_DOWN:
+            data->is_ascii = FALSE;
+            data->vkcode = buffer.Event.KeyEvent.wVirtualKeyCode;
+            break;
+          default:
+            data->is_ascii = TRUE;
+            data->key_val[0] = buffer.Event.KeyEvent.uChar.AsciiChar;
+            data->key_val[1] = '\0';
+            break;
+        }
+
+        g_idle_add_full (G_PRIORITY_DEFAULT_IDLE,
+            (GSourceFunc) gst_play_kb_source_cb, data, g_free);
+      }
+    }
   }
 
   return NULL;