Mon 21 Jul 22:43:21 CEST 2025

js/x11/examples/key-recognition.js

@@ -0,0 +1,69 @@
+var x11 = require('..');
+
+// The list provided by GetKeyboardMapping has sublists where each position
+// represents the result for some key composition.
+keyComposition = [
+  'Key',
+  'shift + Key',
+  'modeSwitch + Key',
+  'modeSwitch + shift + Key',
+  'altGr + Key',
+  'altGr + shift + Key'
+]
+
+x11.createClient(function(err, display){
+  if (err) throw err
+
+  var min = display.min_keycode,  // TODO: explain min_keycode
+      max = display.max_keycode,  // TODO: explain max_keycode
+      chr2Data = [],              // allow us to find a char by the charcode
+      key2Data = [];              // associate chars to a keycode
+
+  // The keySyms is a hash of mnemonic char names, associated to an integer
+  // charcode and its description.
+  for (codeName in x11.keySyms) {
+    keyData = x11.keySyms[codeName];
+    chr2Data[keyData.code] = { codeName: codeName, description: keyData.description };
+  }
+
+  var X = display.client,
+      wid = X.AllocID(),                     // Get a free integer id to a new window.
+      root = display.screen[0].root,         // The mother window. Like your window manager.
+      evKeyPress = x11.eventMask.KeyPress,   // Allow to filter for KeyPress events.
+      white = display.screen[0].white_pixel; // Will paint the window.
+
+  // Get the local key mapping to build key2Data.
+  X.GetKeyboardMapping(min, max-min, function(err, list) {
+    for (var i=0; i < list.length; ++i) {
+      var name = key2Data[i+min] = [];
+      var sublist = list[i];
+      for (var j=0; j < sublist.length; ++j)
+        name.push(chr2Data[sublist[j]]);
+    }
+  });
+
+  // Launch a window to listen by key events:
+  X.CreateWindow(wid, root, 0, 0, 100, 100, 0, 0, 0, 0, { backgroundPixel: white, eventMask: evKeyPress });
+  X.MapWindow(wid);
+
+  X.on('event', function(ev) {
+    if (ev.type == 2) {  // filter by KeyPress. Useful if you have a more open eventMask.
+      var key = key2Data[ev.keycode];  // key is a list of chars related to the pressed key.
+      if (key) {
+        console.log('\n>> key pressed:', ev.keycode);
+        for (var i=0; i<key.length; i++) // Describe each related char
+          if (key[i])
+            console.log(
+              key[i].codeName, '\t', (
+                key[i].description ? key[i].description : 'no description'
+              ), (
+                keyComposition[i] ? '\t' + keyComposition[i] : ''
+              )
+            );
+      }
+      else
+        console.log('>> keyCode '+ ev.keycode +' was not recognized.');
+    }
+  });
+
+});