[Part 1] SDL3: event: runtime issue fixes #3576
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📝 WalkthroughWalkthroughIntroduces an SDL3-compatible gesture subsystem via a new header/implementation, integrates gesture lifecycle (init/quit) and event translation into the event module, updates event and window event enumerations with SDL3-aware guards, and adjusts constants mapping for MULTIGESTURE and JOYBALLMOTION to SDL values. Changes
Sequence Diagram(s)sequenceDiagram
autonumber
participant App
participant Pygame as Pygame Event Module
participant SDL as SDL Core
participant Gesture as Gesture Subsystem
App->>Pygame: import/init
Pygame->>Gesture: Gesture_Init() [SDL3+]
Gesture-->>Pygame: init result
note right of Pygame: Event filters and proxy mappings set
App->>Pygame: quit
Pygame->>Gesture: Gesture_Quit() [SDL3+]
Gesture-->>Pygame: cleanup done
sequenceDiagram
autonumber
participant Touch as Touch Device
participant SDL as SDL Event Loop
participant Gesture as Gesture Subsystem
participant Pygame as Pygame Event Module
participant Py as Python
Touch->>SDL: Finger events (down/move/up)
SDL->>Gesture: Feed raw touch data [SDL3+ impl]
Gesture-->>SDL: Emit GESTURE_MULTIGESTURE / GESTURE_DOLLARGESTURE / GESTURE_DOLLARRECORD
SDL->>Pygame: SDL_* gesture/touch events
Pygame->>Pygame: Translate to dict (SDL2/SDL3 paths)
Pygame-->>Py: Post event objects
Estimated code review effort🎯 5 (Critical) | ⏱️ ~120+ minutes ✨ Finishing Touches
🧪 Generate unit tests
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Actionable comments posted: 4
🧹 Nitpick comments (3)
src_c/event.c (2)
493-506: Typo: _pg_event_psuedo_block → _pg_event_pseudo_blockMinor spelling fix improves searchability and consistency.
-static bool -_pg_event_psuedo_block(SDL_Event *event) +static bool +_pg_event_pseudo_block(SDL_Event *event) @@ - return true; + return true; @@ - return false; + return false;And update call sites:
- if (_pg_event_psuedo_block(event)) { + if (_pg_event_pseudo_block(event)) {(Apply in Line 514 and Line 748.)
818-822: Improve error reporting on Gesture_Init failureIf Gesture_Init doesn't set an SDL error, the raised message may be empty. Consider a fallback string.
- if (Gesture_Init() != 0) { - return RAISE(pgExc_SDLError, SDL_GetError()); - } + if (Gesture_Init() != 0) { + const char *err = SDL_GetError(); + return RAISE(pgExc_SDLError, (err && *err) ? err : "Gesture_Init failed"); + }src_c/include/SDL_gesture.h (1)
878-900: Consider cleaning up commented debug code.This section contains extensive commented-out debug code. Consider removing it entirely if it's no longer needed, or moving it to a debug-only block.
Either remove the commented code or wrap it in a debug macro:
- /* inTouch->gestureLast[j].dDist = dDist; - inTouch->gestureLast[j].dtheta = dtheta; - - printf("dDist = %f, dTheta = %f\n",dDist,dtheta); - gdtheta = gdtheta*.9 + dtheta*.1; - gdDist = gdDist*.9 + dDist*.1 - knob.r += dDist/numDownFingers; - knob.ang += dtheta; - printf("thetaSum = %f, distSum = %f\n",gdtheta,gdDist); - printf("id: %i dTheta = %f, dDist = %f\n",j,dtheta,dDist); */ +#ifdef DEBUG_GESTURES + /* Debug output for gesture processing */ + printf("dDist = %f, dTheta = %f\n", dDist, dtheta); +#endif
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📒 Files selected for processing (4)
src_c/_pygame.h(4 hunks)src_c/constants.c(2 hunks)src_c/event.c(7 hunks)src_c/include/SDL_gesture.h(1 hunks)
🧰 Additional context used
🧠 Learnings (1)
📚 Learning: 2025-08-31T06:44:48.360Z
Learnt from: ankith26
PR: pygame-community/pygame-ce#3427
File: src_c/_sdl2/touch.c:99-103
Timestamp: 2025-08-31T06:44:48.360Z
Learning: SDL_GetNumTouchFingers() returns 0 on failure, not as a valid "no fingers" state. A return value of 0 should be treated as an error condition and SDL_GetError() should be called to get the error message.
Applied to files:
src_c/include/SDL_gesture.h
🧬 Code graph analysis (1)
src_c/event.c (1)
src_c/include/SDL_gesture.h (3)
SDLCALL(204-209)Gesture_Quit(313-321)Gesture_Init(211-217)
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🔇 Additional comments (12)
src_c/constants.c (1)
263-263: Switch to SDL-native JOYBALLMOTION/MULTIGESTURE — verify SDL3 aliases existDEC_CONST maps to SDL_JOYBALLMOTION/SDL_MULTIGESTURE. Please confirm these are defined for SDL3 builds via pgcompat/pygame.h (or equivalent). Otherwise this will fail to compile on SDL3 and/or diverge from prior PG* placeholders. Also verify docs/tests no longer reference PG_JOYBALLMOTION/PG_MULTIGESTURE.
Also applies to: 305-305
src_c/event.c (5)
28-28: Single-TU gesture implementation — avoid duplicate definitionsDefining SDL_GESTURE_IMPLEMENTATION here compiles the implementation into this TU. Please verify no other TU defines it to prevent duplicate symbols at link time.
507-518: Event filter split looks goodReturn type gating for SDL2/SDL3 and delegating pseudo-block decisions is appropriate.
741-749: Correct: do not hard-block window events hereEarly return keeps window events visible to watchers; actual blocking is handled later.
783-786: Proper lifecycle: Gesture_Quit on AutoQuitGood pairing with init; avoids leaking the event watch/touch state.
1310-1341: Casting SDL_Event to Gesture_MultiGestureEvent risks UB; prefer copy/accessor**Strict-aliasing/ABI assumptions can break under optimization or platform ABIs. Please either memcpy into a local Gesture_MultiGestureEvent or add an accessor helper in SDL_gesture.h that fills an out struct. Add a size check, too.
Suggested patch for safer read (SDL3 branch):
- _pg_insobj(dict, "touch_id", - PyLong_FromLongLong( - ((Gesture_MultiGestureEvent *)event)->touchID)); - _pg_insobj( - dict, "x", - PyFloat_FromDouble(((Gesture_MultiGestureEvent *)event)->x)); - _pg_insobj( - dict, "y", - PyFloat_FromDouble(((Gesture_MultiGestureEvent *)event)->y)); - _pg_insobj(dict, "rotated", - PyFloat_FromDouble( - ((Gesture_MultiGestureEvent *)event)->dTheta)); - _pg_insobj(dict, "pinched", - PyFloat_FromDouble( - ((Gesture_MultiGestureEvent *)event)->dDist)); - _pg_insobj(dict, "num_fingers", - PyLong_FromLong( - ((Gesture_MultiGestureEvent *)event)->numFingers)); + Gesture_MultiGestureEvent ge; + memcpy(&ge, event, sizeof(ge)); + _pg_insobj(dict, "touch_id", PyLong_FromLongLong(ge.touchID)); + _pg_insobj(dict, "x", PyFloat_FromDouble(ge.x)); + _pg_insobj(dict, "y", PyFloat_FromDouble(ge.y)); + _pg_insobj(dict, "rotated", PyFloat_FromDouble(ge.dTheta)); + _pg_insobj(dict, "pinched", PyFloat_FromDouble(ge.dDist)); + _pg_insobj(dict, "num_fingers", PyLong_FromLong(ge.numFingers));Additionally, near the top of this file (or in SDL_gesture.h), add:
#if SDL_VERSION_ATLEAST(3, 0, 0) _Static_assert(sizeof(Gesture_MultiGestureEvent) <= sizeof(SDL_Event), "Gesture_MultiGestureEvent must fit into SDL_Event"); #endifsrc_c/_pygame.h (2)
53-59: SDL3 gesture aliases look goodIncluding SDL_gesture.h and aliasing SDL_* to GESTURE_* ensures the rest of the code can stay SDL2-style.
425-445: Verify WINDOWSIZECHANGED mapping semanticsPGE_WINDOWSIZECHANGED → SDL_EVENT_WINDOW_PIXEL_SIZE_CHANGED: confirm this matches prior behavior (logical vs pixel size). If callers expect logical size changes, consider documenting or mapping accordingly.
src_c/include/SDL_gesture.h (4)
1-24: LGTM! Proper licensing and context documentation.The file correctly includes the SDL license header and clearly documents that this is the SDL2 gesture implementation vendored for SDL3 compatibility.
872-876: Good defensive programming for division by zero.The code properly handles the edge case where
lDist == 0to avoid division by zero and resulting NaN values.
454-454: Verify SDL_TouchID signedness and use of sentinel
SDL_TouchID is defined in the external SDL2 headers, so please confirm whether it’s a signed type (e.g. Sint64) and adjust theif (touchID >= 0)check to explicitly compare against the proper invalid sentinel (negative) or use an SDL-defined invalid touch-ID constant rather than relying on signedness.
283-293: Confirm SDL_GetTouchDevices(NULL) API usage: Per SDL3 docs,SDL_GetTouchDevices(NULL)returns a 0-terminatedSDL_TouchIDarray (or NULL on failure), accepts a NULL count pointer, and must be freed withSDL_free(); the code correctly checks for NULL, iterates until the zero terminator, and frees the array (wiki.libsdl.org)
SDL_gesture.h