Behavior of clicking in scrollbar

[m9710797]

Version/Branch of Dear ImGui:

Version 1.90.3, Branch: docking

Back-ends:

imgui_impl_opengl3.cpp + imgui_impl_sdl2.cpp

Compiler, OS:

Linux + GCC 13

Full config/build information:

No response

Details:

Hi,

Applications typically react in one of two ways when clicking in a scrollbar:

• The scrollbar-slider is immediately moved to that position. This is the behavior that Dear ImGui currently implements. And for example visual studio code does the same.
• Clicking above or below the slider scrolls up/down one page. Clicking on the slider allows to drag it up/down. For example firefox and chrome implement this behavior (or does it depend on the OS and/or window-manager?).

Depending on the situation one or the other can be better.

For example in my application (using Dear ImGui) I have a debugger with a disassembly view. This view literally contains tens of thousands of instructions (thanks a lot for ImGuiListClipper!). Trying to accurately scroll in this view using the scrollbar is difficult. And therefor some of our users requested the alternative scrollbar behavior.

The current workaround (for positioning the view using the mouse) is to approximately scroll via clicking the scrollbar and then fine-tune via the scroll-wheel. Though that's not ideal. Allowing to scroll per-page with the mouse (like in firefox/chrome) would mitigate this problem.

My question: would it be possible to have this alternative behavior for ImGui scrollbars?

• Either by manually coding/customizing the behavior. Could you then give some hints for how this could be done?
• Or by implementing this behavior in Dear ImGui itself. And then either have this globally selectable or per child window via a new ImGuiChildFlag? (Though I've not yet encountered an application that uses a mix of both behaviors).

An orthogonal though related question:
Some application use CTRL+scroll-wheel to scroll per page instead of per line. Could that be added in Dear ImGui? Though this behavior seems less universal, some applications instead zoom in/out when using CTRL+scroll-wheel.

Thanks for considering this.

Wouter

Screenshots/Video:

No response

Minimal, Complete and Verifiable Example code:

No response

[ocornut]

I have reworked the scrollbar behavior as suggested, doing a page by page scroll when clicking outside the grab: 5cbc34a

Some application use CTRL+scroll-wheel to scroll per page instead of per line. Could that be added in Dear ImGui? Though this > behavior seems less universal, some applications instead zoom in/out when using CTRL+scroll-wheel.

That may be implemented on your end:

if (ImGui::Shortcut(ImGuiMod_Ctrl | ImGuiKey_MouseWheelY))
{
    float v = ImGui::GetKeyData(ImGuiKey_MouseWheelY)->AnalogValue;
    ImGui::SetScrollY(ImGui::GetScrollY() + -v * ImGui::GetCurrentWindow()->InnerRect.GetHeight());
}

HOWEVER, it won't work as expected/desired with OS and drivers emitting smooth scrolling values for wheel (such as OS X, and some mouse setups/drivers on Windows).

[m9710797]

Thanks!
I'll try it soon.

[m9710797]

It's working great. Thanks!