Capture mouse wheel event

[raunakshrivastava7]

Hi,

I want to capture the event when mouse is hovered and mouse wheel is scrolled on a rectangle in a window. Based on the mouse wheel event, I have to increment or decrement text value.

The red circled portion in the below image is the rectangle. When the user moves mouse wheel over that rectangle, I want to increment or decrement the value '1150' depending upon direction of wheel movement.

I am developing this on Windows 10 and using v1.82 of Dear ImGUI.
P.S. : I am new to c++ and ImGUI.

// Here's the code snippet

 draw_list->AddRectFilled(ImVec2(p.x + 6, p.y + 161), ImVec2(p.x + 64, p.y + 479), col_black);

if(ImGui::IsItemClicked() || ImGui::IsItemHovered()) 
{

    mouseFloat += ImGui::GetIO().MouseWheel;

}


std::stringstream ss;
ss << mouseFloat;
mouseString = ss.str();
const char* floatval = mouseString.c_str();

draw_list->AddText(ImVec2(p.x+44, p.y + 45), IM_COL32_WHITE, floatval); 

[PathogenDavid]

AddRectFilled only draws a rectangle on screen, it doesn't create an item. So IsItemClicked/IsItemHovered won't work on it.

The easiest solution would probably be to add an InvisibleButton item that covers your rectangle.

There are some examples for using it this way in the examples. In particular the clipping sample and the canvas sample.

[ocornut]

In addition, note that by default mouse wheel will trigger scrolling.
To claim the mouse wheel you'll need to use SetItemUsingMouseWheel() currently declared in imgui_internal.h, you can call that function after your item. As suggested if you are drawing all elements yourself you'll probably want to use InvisibleButton(), so you would do:

InvisibleButton(...)
SetItemUsingMouseWheel(....)
if (ImGui::IsItemHovered())
{
    // use io.MouseWheel
}

(linking to #4207, #3281, #2891)

[raunakshrivastava7]

Thank you so much. It worked.

[moneyharassment]

Wouldn't it be better to use ImGui::IsMouseHoveringRect()?