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Detect pinch gesture in web target #15768

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Detect pinch gesture in web target #15768

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15 changes: 15 additions & 0 deletions src/video/emscripten/SDL_emscriptenevents.c
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Original file line number Diff line number Diff line change
Expand Up @@ -342,6 +342,21 @@ static EM_BOOL Emscripten_HandleWheel(int eventType, const EmscriptenWheelEvent
break;
}

if (wheelEvent->mouse.ctrlKey && SDL_EventEnabled(SDL_EVENT_PINCH_UPDATE)) {
// Browsers emit "wheel" event with "ctrlKey" flag active when the user does a pinch gesture.

// makes touch and wheel zoom events match better
double scale = SDL_sqrt(deltaY > 0 ? deltaY : -deltaY);
if (deltaY < 0) { scale *= -1.0; }
scale = SDL_pow(0.885, scale);

// We send all events as web target doesn't accumulate scale value like desktop targets.
SDL_SendPinch(SDL_EVENT_PINCH_BEGIN, 0, window_data->window, 0);
SDL_SendPinch(SDL_EVENT_PINCH_UPDATE, 0, window_data->window, scale);
SDL_SendPinch(SDL_EVENT_PINCH_END, 0, window_data->window, 0);
return true;
}

SDL_SendMouseWheel(0, window_data->window, SDL_DEFAULT_MOUSE_ID, deltaX, -deltaY, SDL_MOUSEWHEEL_NORMAL);
return SDL_EventEnabled(SDL_EVENT_MOUSE_WHEEL);
}
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