Fixed mouse click count for relative mode and multiple mice

We'll track the click count separately for each input source, and the click distance is calculated using a point on an infinite plane that is pushed around by mouse motion deltas, unclamped by the window edge.

src/events/SDL_mouse.c

@@ -337,6 +337,7 @@ void SDL_RemoveMouse(SDL_MouseID mouseID, bool send_event)
     for (int i = 0; i < mouse->num_sources; ++i) {
         SDL_MouseInputSource *source = &mouse->sources[i];
         if (source->mouseID == mouseID) {
+            SDL_free(source->clickstate);
             if (i != mouse->num_sources - 1) {
                 SDL_memcpy(&mouse->sources[i], &mouse->sources[i + 1], (mouse->num_sources - i - 1) * sizeof(mouse->sources[i]));
             }
@@ -728,6 +729,9 @@ static void SDL_PrivateSendMouseMotion(Uint64 timestamp, SDL_Window *window, SDL
         // Use unclamped values if we're getting events outside the window
         mouse->last_x = relative ? mouse->x : x;
         mouse->last_y = relative ? mouse->y : y;
+
+        mouse->click_motion_x += xrel;
+        mouse->click_motion_y += yrel;
     }
 
     // Move the mouse cursor, if needed
@@ -795,29 +799,29 @@ static SDL_MouseInputSource *GetMouseInputSource(SDL_Mouse *mouse, SDL_MouseID m
         mouse->sources = sources;
         ++mouse->num_sources;
         source = &sources[mouse->num_sources - 1];
+        SDL_zerop(source);
         source->mouseID = mouseID;
-        source->buttonstate = 0;
         return source;
     }
     return NULL;
 }
 
-static SDL_MouseClickState *GetMouseClickState(SDL_Mouse *mouse, Uint8 button)
+static SDL_MouseClickState *GetMouseClickState(SDL_MouseInputSource *source, Uint8 button)
 {
-    if (button >= mouse->num_clickstates) {
+    if (button >= source->num_clickstates) {
         int i, count = button + 1;
-        SDL_MouseClickState *clickstate = (SDL_MouseClickState *)SDL_realloc(mouse->clickstate, count * sizeof(*mouse->clickstate));
+        SDL_MouseClickState *clickstate = (SDL_MouseClickState *)SDL_realloc(source->clickstate, count * sizeof(*source->clickstate));
         if (!clickstate) {
             return NULL;
         }
-        mouse->clickstate = clickstate;
+        source->clickstate = clickstate;
 
-        for (i = mouse->num_clickstates; i < count; ++i) {
-            SDL_zero(mouse->clickstate[i]);
+        for (i = source->num_clickstates; i < count; ++i) {
+            SDL_zero(source->clickstate[i]);
         }
-        mouse->num_clickstates = count;
+        source->num_clickstates = count;
     }
-    return &mouse->clickstate[button];
+    return &source->clickstate[button];
 }
 
 static void SDL_PrivateSendMouseButton(Uint64 timestamp, SDL_Window *window, SDL_MouseID mouseID, Uint8 button, bool down, int clicks)
@@ -882,19 +886,19 @@ static void SDL_PrivateSendMouseButton(Uint64 timestamp, SDL_Window *window, SDL
     source->buttonstate = buttonstate;
 
     if (clicks < 0) {
-        SDL_MouseClickState *clickstate = GetMouseClickState(mouse, button);
+        SDL_MouseClickState *clickstate = GetMouseClickState(source, button);
         if (clickstate) {
             if (down) {
                 Uint64 now = SDL_GetTicks();
 
                 if (now >= (clickstate->last_timestamp + mouse->double_click_time) ||
-                    SDL_fabs((double)mouse->x - clickstate->last_x) > mouse->double_click_radius ||
-                    SDL_fabs((double)mouse->y - clickstate->last_y) > mouse->double_click_radius) {
+                    SDL_fabs(mouse->click_motion_x - clickstate->click_motion_x) > mouse->double_click_radius ||
+                    SDL_fabs(mouse->click_motion_y - clickstate->click_motion_y) > mouse->double_click_radius) {
                     clickstate->click_count = 0;
                 }
                 clickstate->last_timestamp = now;
-                clickstate->last_x = mouse->x;
-                clickstate->last_y = mouse->y;
+                clickstate->click_motion_x = mouse->click_motion_x;
+                clickstate->click_motion_y = mouse->click_motion_y;
                 if (clickstate->click_count < 255) {
                     ++clickstate->click_count;
                 }
@@ -1001,17 +1005,15 @@ void SDL_QuitMouse(void)
     mouse->cur_cursor = NULL;
 
     if (mouse->sources) {
+        for (int i = 0; i < mouse->num_sources; ++i) {
+            SDL_MouseInputSource *source = &mouse->sources[i];
+            SDL_free(source->clickstate);
+        }
         SDL_free(mouse->sources);
         mouse->sources = NULL;
     }
     mouse->num_sources = 0;
 
-    if (mouse->clickstate) {
-        SDL_free(mouse->clickstate);
-        mouse->clickstate = NULL;
-    }
-    mouse->num_clickstates = 0;
-
     SDL_RemoveHintCallback(SDL_HINT_MOUSE_DOUBLE_CLICK_TIME,
                         SDL_MouseDoubleClickTimeChanged, mouse);
 

src/events/SDL_mouse_c.h

@@ -39,17 +39,22 @@ struct SDL_Cursor
 
 typedef struct
 {
-    SDL_MouseID mouseID;
-    Uint32 buttonstate;
-} SDL_MouseInputSource;
-
-typedef struct
-{
-    float last_x, last_y;
     Uint64 last_timestamp;
+    double click_motion_x;
+    double click_motion_y;
     Uint8 click_count;
 } SDL_MouseClickState;
 
+typedef struct
+{
+    SDL_MouseID mouseID;
+    Uint32 buttonstate;
+
+    // Data for double-click tracking
+    int num_clickstates;
+    SDL_MouseClickState *clickstate;
+} SDL_MouseInputSource;
+
 typedef struct
 {
     // Create a cursor from a surface
@@ -93,6 +98,8 @@ typedef struct
     float x_accu;
     float y_accu;
     float last_x, last_y; // the last reported x and y coordinates
+    double click_motion_x;
+    double click_motion_y;
     bool has_position;
     bool relative_mode;
     bool relative_mode_warp_motion;
@@ -123,10 +130,6 @@ typedef struct
     int num_sources;
     SDL_MouseInputSource *sources;
 
-    // Data for double-click tracking
-    int num_clickstates;
-    SDL_MouseClickState *clickstate;
-
     SDL_Cursor *cursors;
     SDL_Cursor *def_cursor;
     SDL_Cursor *cur_cursor;