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Guarantee that pens are in proximity before motion and button events

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This also delays pen proximity out events to make sure that the pen is really gone before delivering them. On Android, you get a HOVER_EXIT event when the pen contacts the surface, which we don't want to treat as the pen leaving proximity.
This commit is contained in:
Sam Lantinga
2026-02-05 10:21:08 -08:00
parent cd7fc90c87
commit bddf6d3e2a
9 changed files with 77 additions and 25 deletions
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2
src/events/SDL_events.c
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@@ -1484,6 +1484,8 @@ void SDL_PumpEventMaintenance(void)
}
#endif
SDL_SendPendingPenProximity();
SDL_UpdateCursorAnimation();
SDL_UpdateTrays();

73
src/events/SDL_pen.c
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@@ -37,6 +37,8 @@ typedef struct SDL_Pen
float x;
float y;
SDL_PenInputFlags input_state;
bool pending_proximity_out;
SDL_WindowID pending_proximity_window_id;
void *driverdata;
} SDL_Pen;
@@ -45,6 +47,7 @@ typedef struct SDL_Pen
static SDL_RWLock *pen_device_rwlock = NULL;
static SDL_Pen *pen_devices SDL_GUARDED_BY(pen_device_rwlock) = NULL;
static int pen_device_count SDL_GUARDED_BY(pen_device_rwlock) = 0;
static SDL_AtomicInt pending_proximity_out;
// You must hold pen_device_rwlock before calling this, and result is only safe while lock is held!
// If SDL isn't initialized, grabbing the NULL lock is a no-op and there will be zero devices, so
@@ -248,8 +251,8 @@ SDL_PenID SDL_AddPenDevice(Uint64 timestamp, const char *name, SDL_Window *windo
SDL_free(namecpy);
}
if (result) {
SDL_SendPenProximity(timestamp, result, window, in_proximity);
if (result && in_proximity) {
SDL_SendPenProximity(timestamp, result, window, true, true);
}
return result;
@@ -261,7 +264,7 @@ void SDL_RemovePenDevice(Uint64 timestamp, SDL_Window *window, SDL_PenID instanc
return;
}
SDL_SendPenProximity(timestamp, instance_id, window, false); // bye bye
SDL_SendPenProximity(timestamp, instance_id, window, false, true); // bye bye
SDL_LockRWLockForWriting(pen_device_rwlock);
SDL_Pen *pen = FindPenByInstanceId(instance_id);
@@ -453,6 +456,15 @@ void SDL_SendPenAxis(Uint64 timestamp, SDL_PenID instance_id, SDL_Window *window
}
}
static void EnsurePenProximity(Uint64 timestamp, SDL_Pen *pen, SDL_Window *window)
{
if (pen->pending_proximity_out) {
pen->pending_proximity_out = false;
} else if (!(pen->input_state & SDL_PEN_INPUT_IN_PROXIMITY)) {
SDL_SendPenProximity(timestamp, pen->instance_id, window, true, true);
}
}
void SDL_SendPenMotion(Uint64 timestamp, SDL_PenID instance_id, SDL_Window *window, float x, float y)
{
bool send_event = false;
@@ -465,6 +477,8 @@ void SDL_SendPenMotion(Uint64 timestamp, SDL_PenID instance_id, SDL_Window *wind
SDL_LockRWLockForReading(pen_device_rwlock);
SDL_Pen *pen = FindPenByInstanceId(instance_id);
if (pen) {
EnsurePenProximity(timestamp, pen, window);
if ((pen->x != x) || (pen->y != y)) {
pen->x = x; // we could do an SDL_SetAtomicInt here if we run into trouble...
pen->y = y; // we could do an SDL_SetAtomicInt here if we run into trouble...
@@ -528,6 +542,8 @@ void SDL_SendPenButton(Uint64 timestamp, SDL_PenID instance_id, SDL_Window *wind
SDL_LockRWLockForReading(pen_device_rwlock);
SDL_Pen *pen = FindPenByInstanceId(instance_id);
if (pen) {
EnsurePenProximity(timestamp, pen, window);
input_state = pen->input_state;
const Uint32 flag = (Uint32) (1u << button);
const bool current = ((input_state & flag) != 0);
@@ -579,7 +595,7 @@ void SDL_SendPenButton(Uint64 timestamp, SDL_PenID instance_id, SDL_Window *wind
}
}
void SDL_SendPenProximity(Uint64 timestamp, SDL_PenID instance_id, SDL_Window *window, bool in)
void SDL_SendPenProximity(Uint64 timestamp, SDL_PenID instance_id, SDL_Window *window, bool in, bool immediate)
{
bool send_event = false;
SDL_PenInputFlags input_state = 0;
@@ -591,16 +607,23 @@ void SDL_SendPenProximity(Uint64 timestamp, SDL_PenID instance_id, SDL_Window *w
SDL_LockRWLockForReading(pen_device_rwlock);
SDL_Pen *pen = FindPenByInstanceId(instance_id);
if (pen) {
input_state = pen->input_state;
const bool in_proximity = ((input_state & SDL_PEN_INPUT_IN_PROXIMITY) != 0);
if (in_proximity != in) {
if (in) {
input_state |= SDL_PEN_INPUT_IN_PROXIMITY;
} else {
input_state &= ~SDL_PEN_INPUT_IN_PROXIMITY;
if (in || immediate) {
input_state = pen->input_state;
const bool in_proximity = ((input_state & SDL_PEN_INPUT_IN_PROXIMITY) != 0);
if (in_proximity != in) {
if (in) {
input_state |= SDL_PEN_INPUT_IN_PROXIMITY;
} else {
input_state &= ~SDL_PEN_INPUT_IN_PROXIMITY;
}
send_event = true;
pen->input_state = input_state; // we could do an SDL_SetAtomicInt here if we run into trouble...
}
send_event = true;
pen->input_state = input_state; // we could do an SDL_SetAtomicInt here if we run into trouble...
pen->pending_proximity_out = false;
} else {
pen->pending_proximity_out = true;
pen->pending_proximity_window_id = (window ? window->id : 0);
SDL_SetAtomicInt(&pending_proximity_out, true);
}
}
SDL_UnlockRWLock(pen_device_rwlock);
@@ -617,3 +640,27 @@ void SDL_SendPenProximity(Uint64 timestamp, SDL_PenID instance_id, SDL_Window *w
}
}
void SDL_SendPendingPenProximity(void)
{
if (SDL_CompareAndSwapAtomicInt(&pending_proximity_out, true, false)) {
SDL_LockRWLockForReading(pen_device_rwlock);
for (int i = 0; i < pen_device_count; i++) {
SDL_Pen *pen = &pen_devices[i];
if (pen->pending_proximity_out) {
pen->pending_proximity_out = false;
SDL_Window *window = NULL;
if (pen->pending_proximity_window_id) {
window = SDL_GetWindowFromID(pen->pending_proximity_window_id);
if (!window) {
// The window is already gone, ignore this event
continue;
}
}
SDL_SendPenProximity(0, pen->instance_id, window, false, true);
}
}
SDL_UnlockRWLock(pen_device_rwlock);
}
}

5
src/events/SDL_pen_c.h
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@@ -82,7 +82,10 @@ extern void SDL_SendPenAxis(Uint64 timestamp, SDL_PenID instance_id, SDL_Window
extern void SDL_SendPenButton(Uint64 timestamp, SDL_PenID instance_id, SDL_Window *window, Uint8 button, bool down);
// Backend calls this when a pen's proximity changes, to generate events and update state.
extern void SDL_SendPenProximity(Uint64 timestamp, SDL_PenID instance_id, SDL_Window *window, bool in);
extern void SDL_SendPenProximity(Uint64 timestamp, SDL_PenID instance_id, SDL_Window *window, bool in, bool immediate);
// Pumping events calls this to generate pending pen proximity events
extern void SDL_SendPendingPenProximity(void);
// Backend can optionally use this to find the SDL_PenID for the `handle` that was passed to SDL_AddPenDevice.
extern SDL_PenID SDL_FindPenByHandle(void *handle);

4
src/video/android/SDL_androidpen.c
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@@ -78,12 +78,12 @@ void Android_OnPen(SDL_Window *window, int pen_id_in, SDL_PenDeviceType device_t
// we don't compare tip flags above because MotionEvent.getButtonState doesn't return stylus tip/eraser state.
switch (action) {
case ACTION_HOVER_ENTER:
SDL_SendPenProximity(0, pen, window, true);
SDL_SendPenProximity(0, pen, window, true, true);
break;
case ACTION_CANCEL:
case ACTION_HOVER_EXIT: // strictly speaking, this can mean both "proximity out" and "left the View" but close enough.
SDL_SendPenProximity(0, pen, window, false);
SDL_SendPenProximity(0, pen, window, false, false);
break;
case ACTION_DOWN:

4
src/video/cocoa/SDL_cocoapen.m
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@@ -87,7 +87,7 @@ static void Cocoa_HandlePenProximityEvent(SDL_CocoaWindowData *_data, NSEvent *e
Cocoa_PenHandle *handle = Cocoa_FindPenByDeviceID(devid, toolid);
if (handle) {
handle->is_eraser = is_eraser; // in case this changed.
SDL_SendPenProximity(Cocoa_GetEventTimestamp([event timestamp]), handle->pen, _data.window, true);
SDL_SendPenProximity(Cocoa_GetEventTimestamp([event timestamp]), handle->pen, _data.window, true, true);
return; // already have this one.
}
@@ -116,7 +116,7 @@ static void Cocoa_HandlePenProximityEvent(SDL_CocoaWindowData *_data, NSEvent *e
if (handle) {
// We never remove pens (until shutdown), since Apple gives no indication when they are actually gone.
// But unless you are plugging and unplugging a tablet millions of times, generating new device IDs, this shouldn't be a massive memory drain.
SDL_SendPenProximity(Cocoa_GetEventTimestamp([event timestamp]), handle->pen, _data.window, false);
SDL_SendPenProximity(Cocoa_GetEventTimestamp([event timestamp]), handle->pen, _data.window, false, false);
}
}
}

4
src/video/emscripten/SDL_emscriptenevents.c
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@@ -868,7 +868,7 @@ static void Emscripten_HandlePenEnter(SDL_WindowData *window_data, const Emscrip
SDL_PenID pen = SDL_FindPenByHandle((void *) (size_t) 1); // something > 0 for the single pen handle.
if (pen) {
SDL_SendPenProximity(0, pen, window_data->window, true);
SDL_SendPenProximity(0, pen, window_data->window, true, true);
} else {
// Web browsers offer almost none of this information as specifics, but can without warning offer any of these specific things.
SDL_PenInfo peninfo;
@@ -902,7 +902,7 @@ static void Emscripten_HandlePenLeave(SDL_WindowData *window_data, const Emscrip
const SDL_PenID pen = SDL_FindPenByHandle((void *) (size_t) 1); // something > 0 for the single pen handle.
if (pen) {
Emscripten_UpdatePointerFromEvent(window_data, event); // last data updates?
SDL_SendPenProximity(0, pen, window_data->window, false);
SDL_SendPenProximity(0, pen, window_data->window, false, false);
}
}

4
src/video/wayland/SDL_waylandevents.c
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@@ -3471,7 +3471,7 @@ static void tablet_tool_handle_frame(void *data, struct zwp_tablet_tool_v2 *tool
SDL_Window *window = sdltool->focus ? sdltool->focus->sdlwindow : NULL;
if (sdltool->frame.have_proximity && sdltool->frame.in_proximity) {
SDL_SendPenProximity(timestamp, instance_id, window, true);
SDL_SendPenProximity(timestamp, instance_id, window, true, true);
Wayland_TabletToolUpdateCursor(sdltool);
}
@@ -3510,7 +3510,7 @@ static void tablet_tool_handle_frame(void *data, struct zwp_tablet_tool_v2 *tool
}
if (sdltool->frame.have_proximity && !sdltool->frame.in_proximity) {
SDL_SendPenProximity(timestamp, instance_id, window, false);
SDL_SendPenProximity(timestamp, instance_id, window, false, false);
sdltool->focus = NULL;
Wayland_TabletToolUpdateCursor(sdltool);
}

4
src/video/windows/SDL_windowsevents.c
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@@ -1282,7 +1282,7 @@ LRESULT CALLBACK WIN_WindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lPara
void *hpointer = (void *)(size_t)1; // just something > 0. We're using this one ID any possible pen.
const SDL_PenID pen = SDL_FindPenByHandle(hpointer);
if (pen) {
SDL_SendPenProximity(WIN_GetEventTimestamp(), pen, data->window, true);
SDL_SendPenProximity(WIN_GetEventTimestamp(), pen, data->window, true, true);
} else {
// one can use GetPointerPenInfo() to get the current state of the pen, and check POINTER_PEN_INFO::penMask,
// but the docs aren't clear if these masks are _always_ set for pens with specific features, or if they
@@ -1323,7 +1323,7 @@ LRESULT CALLBACK WIN_WindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lPara
// if this just left the _window_, we don't care. If this is no longer visible to the tablet, time to remove it!
if ((msg == WM_POINTERCAPTURECHANGED) || !IS_POINTER_INCONTACT_WPARAM(wParam)) {
// technically this isn't just _proximity_ but maybe just leaving the window. Good enough. WinTab apparently has real proximity info.
SDL_SendPenProximity(WIN_GetEventTimestamp(), pen, data->window, false);
SDL_SendPenProximity(WIN_GetEventTimestamp(), pen, data->window, false, false);
}
returnCode = 0;
} break;

2
src/video/x11/SDL_x11pen.c
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@@ -328,7 +328,7 @@ void X11_NotifyPenProximityChange(SDL_VideoDevice *_this, SDL_Window *window, in
bool in_proximity;
X11_PenHandle *pen = X11_FindPenByDeviceID(deviceid);
if (pen && X11_XInput2PenIsInProximity(_this, deviceid, &in_proximity)) {
SDL_SendPenProximity(0, pen->pen, window, in_proximity);
SDL_SendPenProximity(0, pen->pen, window, in_proximity, in_proximity);
}
}