Readd media keys for Windows

This intentionally does not compile on Linux.

src/media_keys/media_keys.cpp

@@ -1,26 +1,94 @@
 #include "media_keys.h"
 #include "src/keyboard_input/input_sender.h"
+#include <Windows.h>
 
 namespace keyboardinput
 {
+INPUT createInputStruct( const WORD virtualKeyCode,
+                         const KeyStatus keyStatus ) noexcept
+{
+    INPUT input = {};
+
+    input.type = INPUT_KEYBOARD;
+
+    input.ki.wVk = virtualKeyCode;
+
+    if ( keyStatus == KeyStatus::Up )
+    {
+        input.ki.dwFlags = KEYEVENTF_KEYUP;
+    }
+    else if ( keyStatus == KeyStatus::Down )
+    {
+        input.ki.dwFlags = 0;
+    }
+
+    return input;
+}
+
+void sendKeyboardInputRaw( std::vector<INPUT> inputs )
+{
+    const auto success = SendInput( static_cast<unsigned int>( inputs.size() ),
+                                    inputs.data(),
+                                    sizeof( INPUT ) );
+
+    if ( ( inputs.size() > 0 ) && !success )
+    {
+        char* err;
+        auto errCode = GetLastError();
+        if ( !FormatMessage( FORMAT_MESSAGE_ALLOCATE_BUFFER
+                                 | FORMAT_MESSAGE_FROM_SYSTEM,
+                             nullptr,
+                             errCode,
+                             MAKELANGID( LANG_NEUTRAL,
+                                         SUBLANG_DEFAULT ), // default language
+                             reinterpret_cast<LPTSTR>( &err ),
+                             0,
+                             nullptr ) )
+        {
+            LOG( ERROR )
+                << "Error calling SendInput(): Could not get error message ("
+                << errCode << ")";
+        }
+        else
+        {
+            LOG( ERROR ) << "Error calling SendInput(): " << err;
+        }
+    }
+}
+
 void sendMediaNextSong()
 {
-    // noop
+    std::vector<INPUT> inputs = {};
+    inputs.push_back(
+        createInputStruct( VK_MEDIA_NEXT_TRACK, KeyStatus::Down ) );
+    inputs.push_back( createInputStruct( VK_MEDIA_NEXT_TRACK, KeyStatus::Up ) );
+    sendKeyboardInputRaw( inputs );
 }
 
 void sendMediaPreviousSong()
 {
-    // noop
+    std::vector<INPUT> inputs = {};
+    inputs.push_back(
+        createInputStruct( VK_MEDIA_PREV_TRACK, KeyStatus::Down ) );
+    inputs.push_back( createInputStruct( VK_MEDIA_PREV_TRACK, KeyStatus::Up ) );
+    sendKeyboardInputRaw( inputs );
 }
 
 void sendMediaPausePlay()
 {
-    // noop
+    std::vector<INPUT> inputs = {};
+    inputs.push_back(
+        createInputStruct( VK_MEDIA_PLAY_PAUSE, KeyStatus::Down ) );
+    inputs.push_back( createInputStruct( VK_MEDIA_PLAY_PAUSE, KeyStatus::Up ) );
+    sendKeyboardInputRaw( inputs );
 }
 
 void sendMediaStopSong()
 {
-    // noop
+    std::vector<INPUT> inputs = {};
+    inputs.push_back( createInputStruct( VK_MEDIA_STOP, KeyStatus::Down ) );
+    inputs.push_back( createInputStruct( VK_MEDIA_STOP, KeyStatus::Up ) );
+    sendKeyboardInputRaw( inputs ); // noop
 }
 
 } // namespace keyboardinput