Rename "event" to "message"

After the recent refactorings, a "control event" is not necessarily an
"event" (it may be a "command"). Similarly, the unique "device event"
used to send the device clipboard content is more a "reponse" to the
request from the client than an "event".

Rename both to "message", and rename the message types to better
describe their intent.

app/src/control_msg.c

@@ -0,0 +1,83 @@
+#include "control_msg.h"
+
+#include <string.h>
+
+#include "buffer_util.h"
+#include "log.h"
+#include "str_util.h"
+
+static void
+write_position(uint8_t *buf, const struct position *position) {
+    buffer_write32be(&buf[0], position->point.x);
+    buffer_write32be(&buf[4], position->point.y);
+    buffer_write16be(&buf[8], position->screen_size.width);
+    buffer_write16be(&buf[10], position->screen_size.height);
+}
+
+// write length (2 bytes) + string (non nul-terminated)
+static size_t
+write_string(const char *utf8, size_t max_len, unsigned char *buf) {
+    size_t len = utf8_truncation_index(utf8, max_len);
+    buffer_write16be(buf, (uint16_t) len);
+    memcpy(&buf[2], utf8, len);
+    return 2 + len;
+}
+
+size_t
+control_msg_serialize(const struct control_msg *msg, unsigned char *buf) {
+    buf[0] = msg->type;
+    switch (msg->type) {
+        case CONTROL_MSG_TYPE_INJECT_KEYCODE:
+            buf[1] = msg->inject_keycode.action;
+            buffer_write32be(&buf[2], msg->inject_keycode.keycode);
+            buffer_write32be(&buf[6], msg->inject_keycode.metastate);
+            return 10;
+        case CONTROL_MSG_TYPE_INJECT_TEXT: {
+            size_t len = write_string(msg->inject_text.text,
+                                      CONTROL_MSG_TEXT_MAX_LENGTH, &buf[1]);
+            return 1 + len;
+        }
+        case CONTROL_MSG_TYPE_INJECT_MOUSE_EVENT:
+            buf[1] = msg->inject_mouse_event.action;
+            buffer_write32be(&buf[2], msg->inject_mouse_event.buttons);
+            write_position(&buf[6], &msg->inject_mouse_event.position);
+            return 18;
+        case CONTROL_MSG_TYPE_INJECT_SCROLL_EVENT:
+            write_position(&buf[1], &msg->inject_scroll_event.position);
+            buffer_write32be(&buf[13],
+                             (uint32_t) msg->inject_scroll_event.hscroll);
+            buffer_write32be(&buf[17],
+                             (uint32_t) msg->inject_scroll_event.vscroll);
+            return 21;
+        case CONTROL_MSG_TYPE_SET_CLIPBOARD: {
+            size_t len = write_string(msg->inject_text.text,
+                                      CONTROL_MSG_CLIPBOARD_TEXT_MAX_LENGTH,
+                                      &buf[1]);
+            return 1 + len;
+        }
+        case CONTROL_MSG_TYPE_BACK_OR_SCREEN_ON:
+        case CONTROL_MSG_TYPE_EXPAND_NOTIFICATION_PANEL:
+        case CONTROL_MSG_TYPE_COLLAPSE_NOTIFICATION_PANEL:
+        case CONTROL_MSG_TYPE_GET_CLIPBOARD:
+            // no additional data
+            return 1;
+        default:
+            LOGW("Unknown message type: %u", (unsigned) msg->type);
+            return 0;
+    }
+}
+
+void
+control_msg_destroy(struct control_msg *msg) {
+    switch (msg->type) {
+        case CONTROL_MSG_TYPE_INJECT_TEXT:
+            SDL_free(msg->inject_text.text);
+            break;
+        case CONTROL_MSG_TYPE_SET_CLIPBOARD:
+            SDL_free(msg->set_clipboard.text);
+            break;
+        default:
+            // do nothing
+            break;
+    }
+}