wayland: Refactor time fields in SDL_WaylandKeyboardRepeat

Refactorization with no functional changes.

Instead of `next_repeat_ms` containing a timestamp based on SDL ticks, we make
it zero-based relative to the key press time, and we store the key press time in
SDL ticks in a new field.

This refactorization is groundwork for future commits which need to use the
key press and release timestamps provided by the Wayland API, which are also
expressed in milliseconds, but whose base does not match the one for SDL ticks.

Signed-off-by: Joan Bruguera <joanbrugueram@gmail.com>

src/video/wayland/SDL_waylandevents.c

@@ -204,13 +204,10 @@ touch_surface(SDL_TouchID id)
 
 /* Returns SDL_TRUE if a key repeat event was due */
 static SDL_bool
-keyboard_repeat_handle(SDL_WaylandKeyboardRepeat* repeat_info, uint32_t now)
+keyboard_repeat_handle(SDL_WaylandKeyboardRepeat* repeat_info, uint32_t elapsed)
 {
     SDL_bool ret = SDL_FALSE;
-    if (!repeat_info->is_key_down || !repeat_info->is_initialized) {
-        return ret;
-    }
-    while ((now - repeat_info->next_repeat_ms) < 0x80000000U) {
+    while ((elapsed - repeat_info->next_repeat_ms) < 0x80000000U) {
         if (repeat_info->scancode != SDL_SCANCODE_UNKNOWN) {
             SDL_SendKeyboardKey(SDL_PRESSED, repeat_info->scancode);
         }
@@ -238,7 +235,8 @@ keyboard_repeat_set(SDL_WaylandKeyboardRepeat* repeat_info,
         return;
     }
     repeat_info->is_key_down = SDL_TRUE;
-    repeat_info->next_repeat_ms = SDL_GetTicks() + repeat_info->repeat_delay;
+    repeat_info->sdl_press_time = SDL_GetTicks();
+    repeat_info->next_repeat_ms = repeat_info->repeat_delay;
     repeat_info->scancode = scancode;
     if (has_text) {
         SDL_memcpy(repeat_info->text, text, 8);
@@ -247,6 +245,10 @@ keyboard_repeat_set(SDL_WaylandKeyboardRepeat* repeat_info,
     }
 }
 
+static SDL_bool keyboard_repeat_is_set(SDL_WaylandKeyboardRepeat* repeat_info) {
+    return repeat_info->is_initialized && repeat_info->is_key_down;
+}
+
 void
 Wayland_SendWakeupEvent(_THIS, SDL_Window *window)
 {
@@ -273,13 +275,13 @@ Wayland_WaitEventTimeout(_THIS, int timeout)
 #endif
 
     /* If key repeat is active, we'll need to cap our maximum wait time to handle repeats */
-    if (input && input->keyboard_repeat.is_initialized && input->keyboard_repeat.is_key_down) {
-        uint32_t now = SDL_GetTicks();
-        if (keyboard_repeat_handle(&input->keyboard_repeat, now)) {
+    if (input && keyboard_repeat_is_set(&input->keyboard_repeat)) {
+        uint32_t elapsed = SDL_GetTicks() - input->keyboard_repeat.sdl_press_time;
+        if (keyboard_repeat_handle(&input->keyboard_repeat, elapsed)) {
             /* A repeat key event was already due */
             return 1;
         } else {
-            uint32_t next_repeat_wait_time = (input->keyboard_repeat.next_repeat_ms - now) + 1;
+            uint32_t next_repeat_wait_time = (input->keyboard_repeat.next_repeat_ms - elapsed) + 1;
             if (timeout >= 0) {
                 timeout = SDL_min(timeout, next_repeat_wait_time);
             } else {
@@ -305,8 +307,8 @@ Wayland_WaitEventTimeout(_THIS, int timeout)
 
             /* If key repeat is active, we might have woken up to generate a key event */
             if (key_repeat_active) {
-                uint32_t now = SDL_GetTicks();
-                if (keyboard_repeat_handle(&input->keyboard_repeat, now)) {
+                uint32_t elapsed = SDL_GetTicks() - input->keyboard_repeat.sdl_press_time;
+                if (keyboard_repeat_handle(&input->keyboard_repeat, elapsed)) {
                     return 1;
                 }
             }
@@ -346,9 +348,9 @@ Wayland_PumpEvents(_THIS)
     }
 #endif
 
-    if (input) {
-        uint32_t now = SDL_GetTicks();
-        keyboard_repeat_handle(&input->keyboard_repeat, now);
+    if (input && keyboard_repeat_is_set(&input->keyboard_repeat)) {
+        uint32_t elapsed = SDL_GetTicks() - input->keyboard_repeat.sdl_press_time;
+        keyboard_repeat_handle(&input->keyboard_repeat, elapsed);
     }
 
     /* wl_display_prepare_read() will return -1 if the default queue is not empty.

src/video/wayland/SDL_waylandevents_c.h

@@ -36,6 +36,7 @@ typedef struct {
     SDL_bool is_initialized;
 
     SDL_bool is_key_down;
+    uint32_t sdl_press_time; // Key press time expressed in SDL ticks
     uint32_t next_repeat_ms;
     uint32_t scancode;
     char text[8];