maintain keyboard flags/led states in interrupt handler

report additional "modifier state" in keyboard events. can be used to
help translate key events to string/characters for text input

DGLEVENT.H

@@ -20,6 +20,7 @@ typedef byte EVENT_ACTION;
 typedef struct {
     KEY key;
     EVENT_ACTION action;
+    uword mod;
 } INPUTEVENT_KEYBOARD;
 
 typedef struct {

DGLKBRD.C

@@ -1,4 +1,5 @@
 #include "dglkbrd.h"
+#include "dglcmn.h"
 #include "dglevent.h"
 #include "dglutil.h"
 #include "dglerror.h"
@@ -22,6 +23,13 @@
 #define KEYBRD_LED_NUMLOCK     0x2
 #define KEYBRD_LED_CAPSLOCK    0x4
 
+#define KEYBRD_MOD_EXTENDED    0x1
+#define KEYBRD_MOD_SHIFT       0x2
+#define KEYBRD_MOD_NUMLOCK     0x4
+#define KEYBRD_MOD_CAPSLOCK    0x8
+
+#define KEY_EXTENDED           ((KEY)0xe0)
+
 static boolean _installed = FALSE;
 static INPUTEVENT *keyboard_event;
 
@@ -29,12 +37,18 @@ volatile ubyte keys[128];
 
 volatile KEY _key_last_scan;
 volatile KEY _key_scan;
+volatile uword _key_flags;
+volatile uword _key_mod;
 
 uword _old_flags;
 
 void (interrupt far *_old_handler)();
 
 static void reset_key_states() {
+    _key_last_scan = 0;
+    _key_scan = 0;
+    _key_flags = 0;
+    _key_mod = 0;
     memset((void*)keys, 0, 128);
 }
 
@@ -65,48 +79,6 @@ static boolean send_kb_data(ubyte data) {
     return (result == 0xFA);
 }
 
-static void push_keyboard_event(KEY key, EVENT_ACTION action) {
-    if (_events_enabled) {
-        // HACK: skipping extended (?) key extra keyscan code.
-        //       we only actually care about the subsequent key code...
-        //       (this is a terrible way to do this, doesn't handle all cases)
-        if (key != 0x60) {
-            _events_push(&keyboard_event);
-            keyboard_event->type = EVENT_TYPE_KEYBOARD;
-            keyboard_event->keyboard.key = key;
-            keyboard_event->keyboard.action = action;
-        }
-    }
-}
-
-// keyboard interrupt handler
-void interrupt far kb_int_handler(void) {
-    // read scan code of key that was just pressed
-    _key_scan = inp(KEYBRD_DATA_PORT);
-    if (_key_scan & 0x80) {
-        // high bit set indicates key was released, clear high bit to get
-        // the actual key scan code
-        _key_scan &= 0x7f;
-        keys[(int)_key_scan] = 0;
-        push_keyboard_event(_key_scan, EVENT_ACTION_RELEASED);
-    } else {
-        if (keys[(int)_key_scan])
-            push_keyboard_event(_key_scan, EVENT_ACTION_HELD);
-        else {
-            keys[(int)_key_scan] = 1;
-            push_keyboard_event(_key_scan, EVENT_ACTION_PRESSED);
-        }
-    }
-
-    _key_last_scan = _key_scan;
-
-    // indicate key event was processed to keyboard controller
-    _key_scan = inp(KEYBRD_CTRL_PORT) | 0x82;
-    outp(KEYBRD_CTRL_PORT, _key_scan);
-    outp(KEYBRD_CTRL_PORT, _key_scan & 0x7f);
-    outp(PIC_CTRL_PORT, 0x20);
-}
-
 static uword get_kb_flags(void) {
     return *((uword*)KEYBRD_FLAGS_ADDR);
 }
@@ -119,20 +91,11 @@ static void set_kb_flags(uword flags) {
 // set in the passed keyboard flags. returns FALSE if the LEDs could not
 // be updated (if keyboard data write did not succeed)
 static boolean update_kb_led(byte flags) {
-    ubyte led = 0;
-
-    if (flags & KEYBRD_FLAGS_SCROLLOCK)
-        led |= KEYBRD_LED_SCROLLOCK;
-    if (flags & KEYBRD_FLAGS_NUMLOCK)
-        led |= KEYBRD_LED_NUMLOCK;
-    if (flags & KEYBRD_FLAGS_CAPSLOCK)
-        led |= KEYBRD_LED_CAPSLOCK;
-
     if (!send_kb_data(KEYBRD_CMD_SET_LED)) {
         dgl_set_error(DGL_KEYBOARD_UPDATE_LED_FAILURE);
         return FALSE;
     }
-    if (!send_kb_data(led)) {
+    if (!send_kb_data((flags >> 4) & 3)) {
         dgl_set_error(DGL_KEYBOARD_UPDATE_LED_FAILURE);
         return FALSE;
     }
@@ -140,23 +103,126 @@ static boolean update_kb_led(byte flags) {
     return TRUE;
 }
 
+static void push_keyboard_event(KEY key, EVENT_ACTION action) {
+    if (_events_enabled) {
+        _events_push(&keyboard_event);
+        keyboard_event->type = EVENT_TYPE_KEYBOARD;
+        keyboard_event->keyboard.key = key;
+        keyboard_event->keyboard.action = action;
+        keyboard_event->keyboard.mod = _key_mod;
+    }
+}
+
+static boolean handler_filter_keys(void) {
+    if (BIT_ISSET(KEYBRD_MOD_EXTENDED, _key_mod)) {
+        // extended key + leftshift comes with cursor key presses when
+        // numlock is enabled
+        if ((_key_scan & 0x7f) == (KEY)KEY_LEFTSHIFT)
+            return TRUE;
+    }
+    return FALSE;
+}
+
+static void handler_update_flags_and_leds(void) {
+    switch (_key_scan) {
+        case (KEY)KEY_CAPSLOCK:
+            BIT_TOGGLE(KEYBRD_FLAGS_CAPSLOCK, _key_flags);
+            update_kb_led(_key_flags);
+            set_kb_flags(_key_flags);
+            break;
+        case (KEY)KEY_NUMLOCK:
+            BIT_TOGGLE(KEYBRD_FLAGS_NUMLOCK, _key_flags);
+            update_kb_led(_key_flags);
+            set_kb_flags(_key_flags);
+            break;
+        case (KEY)KEY_SCROLLLOCK:
+            BIT_TOGGLE(KEYBRD_FLAGS_SCROLLOCK, _key_flags);
+            update_kb_led(_key_flags);
+            set_kb_flags(_key_flags);
+            break;
+        default:
+            break;
+    }
+}
+
+static void handler_update_modifiers(void) {
+    if (BIT_ISSET(KEYBRD_FLAGS_NUMLOCK, _key_flags))
+        BIT_SET(KEYBRD_MOD_NUMLOCK, _key_mod);
+    else
+        BIT_CLEAR(KEYBRD_MOD_NUMLOCK, _key_mod);
+
+    if (BIT_ISSET(KEYBRD_FLAGS_CAPSLOCK, _key_flags))
+        BIT_SET(KEYBRD_MOD_CAPSLOCK, _key_mod);
+    else
+        BIT_CLEAR(KEYBRD_MOD_CAPSLOCK, _key_mod);
+
+    if (keys[KEY_LEFTSHIFT] || keys[KEY_RIGHTSHIFT])
+        BIT_SET(KEYBRD_MOD_SHIFT, _key_mod);
+    else
+        BIT_CLEAR(KEYBRD_MOD_SHIFT, _key_mod);
+}
+
+// keyboard interrupt handler
+void interrupt far kb_int_handler(void) {
+    // read scan code of key that was just pressed
+    _key_scan = inp(KEYBRD_DATA_PORT);
+    if (_key_scan == KEY_EXTENDED) {
+        // extended key scan
+        BIT_SET(KEYBRD_MOD_EXTENDED, _key_mod);
+
+    } else {
+        if (!handler_filter_keys()) {
+            if (_key_scan & 0x80) {
+                // high bit set indicates key was released, clear high bit
+                // to get the actual key scan code
+                _key_scan &= 0x7f;
+                keys[(int)_key_scan] = 0;
+                handler_update_modifiers();
+                push_keyboard_event(_key_scan, EVENT_ACTION_RELEASED);
+            } else {
+                if (keys[(int)_key_scan])
+                    push_keyboard_event(_key_scan, EVENT_ACTION_HELD);
+                else {
+                    keys[(int)_key_scan] = 1;
+                    handler_update_flags_and_leds();
+                    handler_update_modifiers();
+                    push_keyboard_event(_key_scan, EVENT_ACTION_PRESSED);
+                }
+            }
+            _key_last_scan = _key_scan;
+        }
+
+        BIT_CLEAR(KEYBRD_MOD_EXTENDED, _key_mod);
+    }
+
+    // indicate key event was processed to keyboard controller
+    _key_scan = inp(KEYBRD_CTRL_PORT) | 0x82;
+    outp(KEYBRD_CTRL_PORT, _key_scan);
+    outp(KEYBRD_CTRL_PORT, _key_scan & 0x7f);
+    outp(PIC_CTRL_PORT, 0x20);
+}
+
 boolean keyboard_init(void) {
     if (_installed) {
         dgl_set_error(DGL_KEYBOARD_ALREADY_INITIALIZED);
         return FALSE;
     }
 
+    reset_key_states();
+
     // preserve old flags
     _old_flags = get_kb_flags();
+    _key_flags = _old_flags;
+
+    handler_update_modifiers();
 
-    reset_key_states();
     _old_handler = _dos_getvect(9);
     _dos_setvect(9, kb_int_handler);
 
     // turn off keyboard LEDs since our interrupt handler does not currently
     // respect the num/caps/scroll lock statuses
     int_disable();
-    update_kb_led(0);
+    update_kb_led(_key_flags);
     int_enable();
 
     _installed = TRUE;
@@ -173,11 +239,12 @@ boolean keyboard_shutdown(void) {
     int_enable();
 
     _dos_setvect(9, _old_handler);
-    reset_key_states();
 
     // restore keyboard flags to previous state
     set_kb_flags(_old_flags);
 
+    reset_key_states();
+
     _installed = FALSE;
     return TRUE;
 }

TEST/EVENTS.C

@@ -29,9 +29,10 @@ void test_events(void) {
 
         switch (event->type) {
             case EVENT_TYPE_KEYBOARD:
-                printf("KEYBOARD: %2d - %d\n",
+                printf("KEYBOARD: %2d - %d (%d)\n",
                        event->keyboard.key,
-                       event->keyboard.action);
+                       event->keyboard.action,
+                       event->keyboard.mod);
                 break;
 
             case EVENT_TYPE_MOUSE_MOTION: