Transition effect and animation in imGui

[coderboyisongithub]

I am trying to do is when i hover my mouse over a histogram it should change its color but with transition,like fade_in,fade_out something like that how shall i do it?

[ocornut]

It's not easily possible at imgui level but you can do it as user code level. You would need to track hover-state and a timer for each ID you want to involve in the animation (e.g. map<id, float>) and manually update those timers. Say, you could store a 0.0..1.0 float per ID, make this float grow toward 1.0 on hover and go back toward 0.0 otherwise.

Something like this pseudo-code:
(untested, I'm just typing code in the reply here)

ImGuiID item_id = ImGui::GetID("label");
auto it = my_map.find(item_id);
float value = (it != my_map.end()) ? it->second : 0.0f;
PushStyleCol(...., lerp(saturate(value), color, color_hovered);
PlotHistogram();
if (IsItemHovered())
    value = min(value + io.DeltaTime * fade_in_speed, 1.0f);
else
   value = max(value - io.DeltaTime * fade_in_speed, 0.0f);
if (it != my_map.end())
   it->second = value;
else if (value > 0.0f)
  my_insert.insert(pair(id, value));
PopStyleCol();

Also see #1537 for inspiration.