Add --prefer-text option

Expose an option to configure how key/text events are forwarded to the
Android device.

Enabling the option avoids issues when combining multiple keys to enter
special characters, but breaks the expected behavior of alpha keys in
games (typically WASD).

Fixes <https://github.com/Genymobile/scrcpy/issues/650>

app/scrcpy.1

@@ -61,6 +61,13 @@ Set the TCP port the client listens on.
 
 Default is 27183.
 
+.TP
+.B \-\-prefer\-text
+Inject alpha characters and space as text events instead of key events.
+
+This avoids issues when combining multiple keys to enter special characters,
+but breaks the expected behavior of alpha keys in games (typically WASD).
+
 .TP
 .BI "\-\-push\-target " path
 Set the target directory for pushing files to the device by drag & drop. It is passed as\-is to "adb push".

app/src/event_converter.c

@@ -75,7 +75,8 @@ convert_meta_state(SDL_Keymod mod) {
 }
 
 bool
-convert_keycode(SDL_Keycode from, enum android_keycode *to, uint16_t mod) {
+convert_keycode(SDL_Keycode from, enum android_keycode *to, uint16_t mod,
+                bool prefer_text) {
     switch (from) {
         MAP(SDLK_RETURN,       AKEYCODE_ENTER);
         MAP(SDLK_KP_ENTER,     AKEYCODE_NUMPAD_ENTER);
@@ -92,6 +93,12 @@ convert_keycode(SDL_Keycode from, enum android_keycode *to, uint16_t mod) {
         MAP(SDLK_DOWN,         AKEYCODE_DPAD_DOWN);
         MAP(SDLK_UP,           AKEYCODE_DPAD_UP);
     }
+
+    if (prefer_text) {
+        // do not forward alpha and space key events
+        return false;
+    }
+
     if (mod & (KMOD_LALT | KMOD_RALT | KMOD_LGUI | KMOD_RGUI)) {
         return false;
     }

app/src/event_converter.h

@@ -14,7 +14,8 @@ enum android_metastate
 convert_meta_state(SDL_Keymod mod);
 
 bool
-convert_keycode(SDL_Keycode from, enum android_keycode *to, uint16_t mod);
+convert_keycode(SDL_Keycode from, enum android_keycode *to, uint16_t mod,
+                bool prefer_text);
 
 enum android_motionevent_buttons
 convert_mouse_buttons(uint32_t state);

app/src/input_manager.c

@@ -214,12 +214,15 @@ clipboard_paste(struct controller *controller) {
 void
 input_manager_process_text_input(struct input_manager *im,
                                  const SDL_TextInputEvent *event) {
-    char c = event->text[0];
-    if (isalpha(c) || c == ' ') {
-        SDL_assert(event->text[1] == '\0');
-        // letters and space are handled as raw key event
-        return;
+    if (!im->prefer_text) {
+        char c = event->text[0];
+        if (isalpha(c) || c == ' ') {
+            SDL_assert(event->text[1] == '\0');
+            // letters and space are handled as raw key event
+            return;
+        }
     }
+
     struct control_msg msg;
     msg.type = CONTROL_MSG_TYPE_INJECT_TEXT;
     msg.inject_text.text = SDL_strdup(event->text);
@@ -234,7 +237,8 @@ input_manager_process_text_input(struct input_manager *im,
 }
 
 static bool
-convert_input_key(const SDL_KeyboardEvent *from, struct control_msg *to) {
+convert_input_key(const SDL_KeyboardEvent *from, struct control_msg *to,
+                  bool prefer_text) {
     to->type = CONTROL_MSG_TYPE_INJECT_KEYCODE;
 
     if (!convert_keycode_action(from->type, &to->inject_keycode.action)) {
@@ -242,7 +246,8 @@ convert_input_key(const SDL_KeyboardEvent *from, struct control_msg *to) {
     }
 
     uint16_t mod = from->keysym.mod;
-    if (!convert_keycode(from->keysym.sym, &to->inject_keycode.keycode, mod)) {
+    if (!convert_keycode(from->keysym.sym, &to->inject_keycode.keycode, mod,
+                         prefer_text)) {
         return false;
     }
 
@@ -393,7 +398,7 @@ input_manager_process_key(struct input_manager *im,
     }
 
     struct control_msg msg;
-    if (convert_input_key(event, &msg)) {
+    if (convert_input_key(event, &msg, im->prefer_text)) {
         if (!controller_push_msg(controller, &msg)) {
             LOGW("Could not request 'inject keycode'");
         }

app/src/input_manager.h

@@ -14,6 +14,7 @@ struct input_manager {
     struct controller *controller;
     struct video_buffer *video_buffer;
     struct screen *screen;
+    bool prefer_text;
 };
 
 void

app/src/main.c

@@ -67,6 +67,13 @@ static void usage(const char *arg0) {
         "        Set the TCP port the client listens on.\n"
         "        Default is %d.\n"
         "\n"
+        "    --prefer-text\n"
+        "        Inject alpha characters and space as text events instead of\n"
+        "        key events.\n"
+        "        This avoids issues when combining multiple keys to enter a\n"
+        "        special character, but breaks the expected behavior of alpha\n"
+        "        keys in games (typically WASD).\n"
+        "\n"
         "    --push-target path\n"
         "        Set the target directory for pushing files to the device by\n"
         "        drag & drop. It is passed as-is to \"adb push\".\n"
@@ -300,6 +307,7 @@ guess_record_format(const char *filename) {
 #define OPT_ALWAYS_ON_TOP         1003
 #define OPT_CROP                  1004
 #define OPT_RECORD_FORMAT         1005
+#define OPT_PREFER_TEXT           1006
 
 static bool
 parse_args(struct args *args, int argc, char *argv[]) {
@@ -321,6 +329,7 @@ parse_args(struct args *args, int argc, char *argv[]) {
         {"serial",                required_argument, NULL, 's'},
         {"show-touches",          no_argument,       NULL, 't'},
         {"turn-screen-off",       no_argument,       NULL, 'S'},
+        {"prefer-text",           no_argument,       NULL, OPT_PREFER_TEXT},
         {"version",               no_argument,       NULL, 'v'},
         {"window-title",          required_argument, NULL,
                                                      OPT_WINDOW_TITLE},
@@ -404,6 +413,9 @@ parse_args(struct args *args, int argc, char *argv[]) {
             case OPT_PUSH_TARGET:
                 opts->push_target = optarg;
                 break;
+            case OPT_PREFER_TEXT:
+                opts->prefer_text = true;
+                break;
             default:
                 // getopt prints the error message on stderr
                 return false;

app/src/scrcpy.c

@@ -42,6 +42,7 @@ static struct input_manager input_manager = {
     .controller = &controller,
     .video_buffer = &video_buffer,
     .screen = &screen,
+    .prefer_text = false, // initialized later
 };
 
 // init SDL and set appropriate hints
@@ -414,6 +415,8 @@ scrcpy(const struct scrcpy_options *options) {
         show_touches_waited = true;
     }
 
+    input_manager.prefer_text = options->prefer_text;
+
     ret = event_loop(options->display, options->control);
     LOGD("quit...");
 

app/src/scrcpy.h

@@ -5,6 +5,7 @@
 #include <stdint.h>
 
 #include "config.h"
+#include "input_manager.h"
 #include "recorder.h"
 
 struct scrcpy_options {
@@ -24,6 +25,7 @@ struct scrcpy_options {
     bool display;
     bool turn_screen_off;
     bool render_expired_frames;
+    bool prefer_text;
 };
 
 #define SCRCPY_OPTIONS_DEFAULT { \
@@ -43,6 +45,7 @@ struct scrcpy_options {
     .display = true, \
     .turn_screen_off = false, \
     .render_expired_frames = false, \
+    .prefer_text = false, \
 }
 
 bool