Easy way to get a windowID from a SDL_Event

[madebr]

I think it would be useful if SDL would get an api to easy extract the windowID from a SDL_Event.
For example, right now you'd need to a big switch or complicated if-else to only keep those event types that have a windowID.

A use case could be filtering events of different windows, and deliver only those events of a specific window.
Example use case: imgui

I prototyped a patch that does that.
It creates an enum that bundles event types into groups (SDL_EVENTGROUP_*)
Using those groups, I can more easily extract the windowID of an event.

Patch

diff --git a/include/SDL3/SDL_events.h b/include/SDL3/SDL_events.h
index 7dda52410..f7caa353d 100644
--- a/include/SDL3/SDL_events.h
+++ b/include/SDL3/SDL_events.h
@@ -919,6 +919,284 @@ typedef union SDL_Event
 /* Make sure we haven't broken binary compatibility */
 SDL_COMPILE_TIME_ASSERT(SDL_Event, sizeof(SDL_Event) == sizeof(((SDL_Event *)NULL)->padding));
 
+/**
+ * Groups of event types
+ *
+ * \since This enum is available since SDL 3.0.0.
+ */
+typedef enum SDL_EventTypeGroup
+{
+    SDL_EVENTGROUP_SYSTEM,              /**< System-wide events can access SDL_Event.common */
+    SDL_EVENTGROUP_DISPLAY,             /**< Events of this group can access SDL_Event.display */
+    SDL_EVENTGROUP_WINDOW,              /**< Events of this group can access SDL_Event.window */
+    SDL_EVENTGROUP_KDEVICE,             /**< Events of this group can access SDL_Event.kdevice */
+    SDL_EVENTGROUP_KEY,                 /**< Events of this group can access SDL_Event.key */
+    SDL_EVENTGROUP_EDIT,                /**< Events of this group can access SDL_Event.edit */
+    SDL_EVENTGROUP_EDIT_CANDIDATES,     /**< Events of this group can access SDL_Event.edit_candidates */
+    SDL_EVENTGROUP_TEXT,                /**< Events of this group can access SDL_Event.text */
+    SDL_EVENTGROUP_MDEVICE,             /**< Events of this group can access SDL_Event.mdevice */
+    SDL_EVENTGROUP_MOTION,              /**< Events of this group can access SDL_Event.motion */
+    SDL_EVENTGROUP_BUTTON,              /**< Events of this group can access SDL_Event.button */
+    SDL_EVENTGROUP_WHEEL,               /**< Events of this group can access SDL_Event.wheel */
+    SDL_EVENTGROUP_JDEVICE,             /**< Events of this group can access SDL_Event.jdevice */
+    SDL_EVENTGROUP_JAXIS,               /**< Events of this group can access SDL_Event.jaxis */
+    SDL_EVENTGROUP_JBALL,               /**< Events of this group can access SDL_Event.jball */
+    SDL_EVENTGROUP_JHAT,                /**< Events of this group can access SDL_Event.jhat */
+    SDL_EVENTGROUP_JBUTTON,             /**< Events of this group can access SDL_Event.jbutton */
+    SDL_EVENTGROUP_JBATTERY,            /**< Events of this group can access SDL_Event.jbattery */
+    SDL_EVENTGROUP_GDEVICE,             /**< Events of this group can access SDL_Event.gdevice */
+    SDL_EVENTGROUP_GAXIS,               /**< Events of this group can access SDL_Event.gaxis */
+    SDL_EVENTGROUP_GBUTTON,             /**< Events of this group can access SDL_Event.gbutton */
+    SDL_EVENTGROUP_GTOUCHPAD,           /**< Events of this group can access SDL_Event.gtouchpad */
+    SDL_EVENTGROUP_GSENSOR,             /**< Events of this group can access SDL_Event.gsensor */
+    SDL_EVENTGROUP_ADEVICE,             /**< Events of this group can access SDL_Event.adevice */
+    SDL_EVENTGROUP_CDEVICE,             /**< Events of this group can access SDL_Event.cdevice */
+    SDL_EVENTGROUP_SENSOR,              /**< Events of this group can access SDL_Event.sensor */
+    SDL_EVENTGROUP_QUIT,                /**< Events of this group can access SDL_Event.quit */
+    SDL_EVENTGROUP_USER,                /**< Events of this group can access SDL_Event.user */
+    SDL_EVENTGROUP_TFINGER,             /**< Events of this group can access SDL_Event.tfinger */
+    SDL_EVENTGROUP_PTIP,                /**< Events of this group can access SDL_Event.ptip */
+    SDL_EVENTGROUP_PMOTION,             /**< Events of this group can access SDL_Event.pmotion */
+    SDL_EVENTGROUP_PBUTTON,             /**< Events of this group can access SDL_Event.pbutton */
+    SDL_EVENTGROUP_DROP,                /**< Events of this group can access SDL_Event.drop */
+    SDL_EVENTGROUP_CLIPBOARD,           /**< Events of this group can access SDL_Event.clipboard */
+} SDL_EventTypeGroup;
+
+/**
+ * Get the group to which an event type belongs.
+ *
+ * \param type Event type of type SDL_EventType
+ *
+ * \returns SDL_EventTypeGroup on success or -1 if there was an error;
+ *          call SDL_GetError() for more information.
+ *
+ * \since This enum is available since SDL 3.0.0.
+ */
+static SDL_EventTypeGroup SDL_GetEventGroupType(Uint32 type) {
+    if (type >= SDL_EVENT_USER && type <= SDL_EVENT_LAST) {
+        return SDL_EVENTGROUP_USER;
+    }
+    switch (type) {
+    default:
+        return SDL_SetError("Unknown event type");
+
+    case SDL_EVENT_KEYMAP_CHANGED:
+    case SDL_EVENT_TERMINATING:
+    case SDL_EVENT_LOW_MEMORY:
+    case SDL_EVENT_WILL_ENTER_BACKGROUND:
+    case SDL_EVENT_DID_ENTER_BACKGROUND:
+    case SDL_EVENT_WILL_ENTER_FOREGROUND:
+    case SDL_EVENT_DID_ENTER_FOREGROUND:
+    case SDL_EVENT_LOCALE_CHANGED:
+    case SDL_EVENT_SYSTEM_THEME_CHANGED:
+    case SDL_EVENT_RENDER_TARGETS_RESET:
+    case SDL_EVENT_RENDER_DEVICE_RESET:
+        return SDL_EVENTGROUP_SYSTEM;
+
+    case SDL_EVENT_QUIT:
+        return SDL_EVENTGROUP_QUIT;
+
+    case SDL_EVENT_DISPLAY_ORIENTATION:
+    case SDL_EVENT_DISPLAY_ADDED:
+    case SDL_EVENT_DISPLAY_REMOVED:
+    case SDL_EVENT_DISPLAY_MOVED:
+    case SDL_EVENT_DISPLAY_DESKTOP_MODE_CHANGED:
+    case SDL_EVENT_DISPLAY_CURRENT_MODE_CHANGED:
+    case SDL_EVENT_DISPLAY_CONTENT_SCALE_CHANGED:
+        return SDL_EVENTGROUP_DISPLAY;
+
+    case SDL_EVENT_WINDOW_SHOWN:
+    case SDL_EVENT_WINDOW_HIDDEN:
+    case SDL_EVENT_WINDOW_EXPOSED:
+    case SDL_EVENT_WINDOW_MOVED:
+    case SDL_EVENT_WINDOW_RESIZED:
+    case SDL_EVENT_WINDOW_PIXEL_SIZE_CHANGED:
+    case SDL_EVENT_WINDOW_METAL_VIEW_RESIZED:
+    case SDL_EVENT_WINDOW_MINIMIZED:
+    case SDL_EVENT_WINDOW_MAXIMIZED:
+    case SDL_EVENT_WINDOW_RESTORED:
+    case SDL_EVENT_WINDOW_MOUSE_ENTER:
+    case SDL_EVENT_WINDOW_MOUSE_LEAVE:
+    case SDL_EVENT_WINDOW_FOCUS_GAINED:
+    case SDL_EVENT_WINDOW_FOCUS_LOST:
+    case SDL_EVENT_WINDOW_CLOSE_REQUESTED:
+    case SDL_EVENT_WINDOW_HIT_TEST:
+    case SDL_EVENT_WINDOW_ICCPROF_CHANGED:
+    case SDL_EVENT_WINDOW_DISPLAY_CHANGED:
+    case SDL_EVENT_WINDOW_DISPLAY_SCALE_CHANGED:
+    case SDL_EVENT_WINDOW_SAFE_AREA_CHANGED:
+    case SDL_EVENT_WINDOW_OCCLUDED:
+    case SDL_EVENT_WINDOW_ENTER_FULLSCREEN:
+    case SDL_EVENT_WINDOW_LEAVE_FULLSCREEN:
+    case SDL_EVENT_WINDOW_DESTROYED:
+    case SDL_EVENT_WINDOW_PEN_ENTER:
+    case SDL_EVENT_WINDOW_PEN_LEAVE:
+    case SDL_EVENT_WINDOW_HDR_STATE_CHANGED:
+        return SDL_EVENTGROUP_WINDOW;
+
+    case SDL_EVENT_KEY_DOWN:
+    case SDL_EVENT_KEY_UP:
+        return SDL_EVENTGROUP_KEY;
+
+    case SDL_EVENT_TEXT_EDITING:
+        return SDL_EVENTGROUP_EDIT;
+
+    case SDL_EVENT_TEXT_INPUT:
+        return SDL_EVENTGROUP_TEXT;
+
+    case SDL_EVENT_KEYBOARD_ADDED:
+    case SDL_EVENT_KEYBOARD_REMOVED:
+        return SDL_EVENTGROUP_KDEVICE;
+
+    case SDL_EVENT_TEXT_EDITING_CANDIDATES:
+        return SDL_EVENTGROUP_EDIT_CANDIDATES;
+
+    case SDL_EVENT_MOUSE_MOTION:
+        return SDL_EVENTGROUP_MOTION;
+
+    case SDL_EVENT_MOUSE_BUTTON_DOWN:
+    case SDL_EVENT_MOUSE_BUTTON_UP:
+        return SDL_EVENTGROUP_BUTTON;
+
+    case SDL_EVENT_MOUSE_WHEEL:
+        return SDL_EVENTGROUP_WHEEL;
+
+    case SDL_EVENT_MOUSE_ADDED:
+    case SDL_EVENT_MOUSE_REMOVED:
+        return SDL_EVENTGROUP_MDEVICE;
+
+    case SDL_EVENT_JOYSTICK_AXIS_MOTION:
+        return SDL_EVENTGROUP_JAXIS;
+
+    case SDL_EVENT_JOYSTICK_BALL_MOTION:
+        return SDL_EVENTGROUP_JBALL;
+
+    case SDL_EVENT_JOYSTICK_HAT_MOTION:
+        return SDL_EVENTGROUP_JHAT;
+
+    case SDL_EVENT_JOYSTICK_BUTTON_DOWN:
+    case SDL_EVENT_JOYSTICK_BUTTON_UP:
+        return SDL_EVENTGROUP_JBUTTON;
+
+    case SDL_EVENT_JOYSTICK_ADDED:
+    case SDL_EVENT_JOYSTICK_REMOVED:
+    case SDL_EVENT_JOYSTICK_UPDATE_COMPLETE:
+        return SDL_EVENTGROUP_JDEVICE;
+
+    case SDL_EVENT_JOYSTICK_BATTERY_UPDATED:
+        return SDL_EVENTGROUP_JBATTERY;
+
+    case SDL_EVENT_GAMEPAD_AXIS_MOTION:
+        return SDL_EVENTGROUP_GAXIS;
+
+    case SDL_EVENT_GAMEPAD_BUTTON_DOWN:
+    case SDL_EVENT_GAMEPAD_BUTTON_UP:
+        return SDL_EVENTGROUP_GBUTTON;
+
+    case SDL_EVENT_GAMEPAD_ADDED:
+    case SDL_EVENT_GAMEPAD_REMOVED:
+    case SDL_EVENT_GAMEPAD_REMAPPED:
+    case SDL_EVENT_GAMEPAD_UPDATE_COMPLETE:
+    case SDL_EVENT_GAMEPAD_STEAM_HANDLE_UPDATED:
+        return SDL_EVENTGROUP_GDEVICE;
+
+    case SDL_EVENT_GAMEPAD_TOUCHPAD_DOWN:
+    case SDL_EVENT_GAMEPAD_TOUCHPAD_MOTION:
+    case SDL_EVENT_GAMEPAD_TOUCHPAD_UP:
+        return SDL_EVENTGROUP_GTOUCHPAD;
+
+    case SDL_EVENT_GAMEPAD_SENSOR_UPDATE:
+        return SDL_EVENTGROUP_GSENSOR;
+
+    case SDL_EVENT_FINGER_DOWN:
+    case SDL_EVENT_FINGER_UP:
+    case SDL_EVENT_FINGER_MOTION:
+        return SDL_EVENTGROUP_TFINGER;
+
+    case SDL_EVENT_CLIPBOARD_UPDATE:
+        return SDL_EVENTGROUP_CLIPBOARD;
+
+    case SDL_EVENT_DROP_FILE:
+    case SDL_EVENT_DROP_TEXT:
+    case SDL_EVENT_DROP_BEGIN:
+    case SDL_EVENT_DROP_COMPLETE:
+    case SDL_EVENT_DROP_POSITION:
+        return SDL_EVENTGROUP_DROP;
+
+    case SDL_EVENT_AUDIO_DEVICE_ADDED:
+    case SDL_EVENT_AUDIO_DEVICE_REMOVED:
+    case SDL_EVENT_AUDIO_DEVICE_FORMAT_CHANGED:
+        return SDL_EVENTGROUP_ADEVICE;
+
+    case SDL_EVENT_SENSOR_UPDATE:
+        return SDL_EVENTGROUP_SENSOR;
+
+    case SDL_EVENT_PEN_DOWN:
+    case SDL_EVENT_PEN_UP:
+        return SDL_EVENTGROUP_PTIP;
+
+    case SDL_EVENT_PEN_MOTION:
+        return SDL_EVENTGROUP_PMOTION;
+
+    case SDL_EVENT_PEN_BUTTON_DOWN:
+    case SDL_EVENT_PEN_BUTTON_UP:
+        return SDL_EVENTGROUP_PBUTTON;
+
+    case SDL_EVENT_CAMERA_DEVICE_ADDED:
+    case SDL_EVENT_CAMERA_DEVICE_REMOVED:
+    case SDL_EVENT_CAMERA_DEVICE_APPROVED:
+    case SDL_EVENT_CAMERA_DEVICE_DENIED:
+        return SDL_EVENTGROUP_CDEVICE;
+    }
+}
+
+/**
+ * Get the associated window id of an event.
+ *
+ * \param event SDL event of which to get the window id
+ *
+ * \returns the associated window id on success or 0 if there is no assocated id
+ *
+ * \since This enum is available since SDL 3.0.0.
+ *
+ * \sa SDL_PollEvent
+ * \sa SDL_WaitEvent
+ * \sa SDL_WaitEventTimeout
+ */
+static int SDL_GetWindowIDFromEvent(const SDL_Event *event) {
+    switch (SDL_GetEventGroupType(event->type)) {
+    case SDL_EVENTGROUP_USER:
+        return event->user.windowID;
+    case SDL_EVENTGROUP_WINDOW:
+        return event->window.windowID;
+    case SDL_EVENTGROUP_KEY:
+        return event->key.windowID;
+    case SDL_EVENTGROUP_EDIT:
+        return event->edit.windowID;
+    case SDL_EVENTGROUP_TEXT:
+        return event->text.windowID;
+    case SDL_EVENTGROUP_EDIT_CANDIDATES:
+        return event->edit_candidates.windowID;
+    case SDL_EVENTGROUP_MOTION:
+        return event->motion.windowID;
+    case SDL_EVENTGROUP_BUTTON:
+        return event->button.windowID;
+    case SDL_EVENTGROUP_WHEEL:
+        return event->wheel.windowID;
+    case SDL_EVENTGROUP_TFINGER:
+        return event->tfinger.windowID;
+    case SDL_EVENTGROUP_PTIP:
+        return event->ptip.windowID;
+    case SDL_EVENTGROUP_PMOTION:
+        return event->pmotion.windowID;
+    case SDL_EVENTGROUP_PBUTTON:
+        return event->pbutton.windowID;
+    case SDL_EVENTGROUP_DROP:
+        return event->drop.windowID;
+    default:
+        return 0;
+    }
+}
 
 /* Function prototypes */
 

[slime73]

Related: #6869 (comment)

[slouken]

I don't think we want the event groups, but a function to get the window from an event seems useful. Feel free to create a PR that uses the event groups internally and have the function return SDL_Window * instead of an ID?