Mouse scrolling not working about imgui

[ocornut]

You will need to provide more details.
First try in to see if it happens official unmodified examples.

[Thalenberghen]

I compiled the unmodified opengl3/sdl2 example.
The behaviour is slightly different but still not working as expected.
Here is a video of what it looks like:
https://www.youtube.com/watch?v=dFMub49vs2g

The scrolling down produces some flickering as if it always resets to the top on the next frame.
Scrolling up instead directly jumps to the top.
I don't know if this information helps or what else I can/should provide.

[inobelar]

@Thalenberghen since you use SDL2 backend, you can try to add printf(stdout, "wheel x=%f, y=%f\n", wheel_x, wheel_y); fflush(stdout); to see what wheel x/y offsets passed into Dear ImGui. Put it before io.AddMouseWheelEvent(wheel_x, wheel_y) in imgui_impl_sdl2.cpp here:

imgui/backends/imgui_impl_sdl2.cpp

Lines 321 to 337 in 4bb7567

	case SDL_MOUSEWHEEL:
	{
	//IMGUI_DEBUG_LOG("wheel %.2f %.2f, precise %.2f %.2f\n", (float)event->wheel.x, (float)event->wheel.y, event->wheel.preciseX, event->wheel.preciseY);
	#if SDL_VERSION_ATLEAST(2,0,18) // If this fails to compile on Emscripten: update to latest Emscripten!
	float wheel_x = -event->wheel.preciseX;
	float wheel_y = event->wheel.preciseY;
	#else
	float wheel_x = -(float)event->wheel.x;
	float wheel_y = (float)event->wheel.y;
	#endif
	#ifdef __EMSCRIPTEN__
	wheel_x /= 100.0f;
	#endif
	io.AddMouseSourceEvent(event->wheel.which == SDL_TOUCH_MOUSEID ? ImGuiMouseSource_TouchScreen : ImGuiMouseSource_Mouse);
	io.AddMouseWheelEvent(wheel_x, wheel_y);
	return true;
	}

[Thalenberghen]

I have added the line, and interestingly it behaves like my program now, where nothing happens at all.
All the values it prints for wheel x and y are 0 or -0.

Edit:
I checked and the value for the event->wheel_y is showing +-1 as I would expect.
But the precise_y which it seems to pick up is 0 or a gigantic negative number.

[ocornut]

Use Demo>Debug Log>IO to visualize data received by dear imgui.

[Thalenberghen]

So what's the verdict?
If I uncomment the preciseX/Y stuff and use the standard one everything works.
Should I just do that?