Internals: Added ImLinearSweep() helper.

TODO.txt

@@ -236,6 +236,7 @@ It's mostly a bunch of personal notes, probably incomplete. Feel free to query i
  - misc: provide a way to compile out the entire implementation while providing a dummy API (e.g. #define IMGUI_DUMMY_IMPL)
  - misc: provide HoveredTime and ActivatedTime to ease the creation of animations.
  - misc: fix for compilation settings where stdcall isn't the default (e.g. vectorcall) (#1230)
+ - misc: detect user not calling Render() and suggest to call EndFrame()?
  - remote: make a system like RemoteImGui first-class citizen/project (#75)
 
  - demo: add vertical separator demo

imgui_internal.h

@@ -154,6 +154,7 @@ static inline float  ImFloor(float f)
 static inline ImVec2 ImFloor(const ImVec2& v)                                   { return ImVec2((float)(int)v.x, (float)(int)v.y); }
 static inline float  ImDot(const ImVec2& a, const ImVec2& b)                    { return a.x * b.x + a.y * b.y; }
 static inline ImVec2 ImRotate(const ImVec2& v, float cos_a, float sin_a)        { return ImVec2(v.x * cos_a - v.y * sin_a, v.x * sin_a + v.y * cos_a); }
+static inline float  ImLinearSweep(float current, float target, float speed)    { if (current < target) return ImMin(current + speed, target); if (current > target) return ImMax(current - speed, target); return current; }
 
 // We call C++ constructor on own allocated memory via the placement "new(ptr) Type()" syntax.
 // Defining a custom placement new() with a dummy parameter allows us to bypass including <new> which on some platforms complains when user has disabled exceptions.