Added IsMousePosValid() helper.

imgui.cpp

@@ -2153,11 +2153,10 @@ void ImGui::NewFrame()
 
     // Update mouse input state
     // If mouse just appeared or disappeared (usually denoted by -FLT_MAX component, but in reality we test for -256000.0f) we cancel out movement in MouseDelta
-    const float MOUSE_INVALID = -256000.0f;
-    if ((g.IO.MousePos.x < MOUSE_INVALID && g.IO.MousePos.y < MOUSE_INVALID) || (g.IO.MousePosPrev.x < MOUSE_INVALID && g.IO.MousePosPrev.y < MOUSE_INVALID))
-        g.IO.MouseDelta = ImVec2(0.0f, 0.0f);
-    else
+    if (IsMousePosValid(&g.IO.MousePos) && IsMousePosValid(&g.IO.MousePosPrev))
         g.IO.MouseDelta = g.IO.MousePos - g.IO.MousePosPrev;
+    else
+        g.IO.MouseDelta = ImVec2(0.0f, 0.0f);
     g.IO.MousePosPrev = g.IO.MousePos;
     for (int i = 0; i < IM_ARRAYSIZE(g.IO.MouseDown); i++)
     {
@@ -3228,6 +3227,15 @@ ImVec2 ImGui::GetMousePosOnOpeningCurrentPopup()
     return g.IO.MousePos;
 }
 
+// We typically use ImVec2(-FLT_MAX,-FLT_MAX) to denote an invalid mouse position
+bool ImGui::IsMousePosValid(const ImVec2* mouse_pos)
+{
+    if (mouse_pos == NULL)
+        mouse_pos = &GImGui->IO.MousePos;
+    const float MOUSE_INVALID = -256000.0f;
+    return mouse_pos->x >= MOUSE_INVALID && mouse_pos->y >= MOUSE_INVALID;
+}
+
 ImVec2 ImGui::GetMouseDragDelta(int button, float lock_threshold)
 {
     ImGuiContext& g = *GImGui;

imgui.h

@@ -458,6 +458,7 @@ namespace ImGui
     IMGUI_API bool          IsMouseReleased(int button);                                        // did mouse button released (went from Down to !Down)
     IMGUI_API bool          IsMouseDragging(int button = 0, float lock_threshold = -1.0f);      // is mouse dragging. if lock_threshold < -1.0f uses io.MouseDraggingThreshold
     IMGUI_API bool          IsMouseHoveringRect(const ImVec2& r_min, const ImVec2& r_max, bool clip = true);  // is mouse hovering given bounding rect (in screen space). clipped by current clipping settings. disregarding of consideration of focus/window ordering/blocked by a popup.
+    IMGUI_API bool          IsMousePosValid(const ImVec2* mouse_pos = NULL);                    //
     IMGUI_API ImVec2        GetMousePos();                                                      // shortcut to ImGui::GetIO().MousePos provided by user, to be consistent with other calls
     IMGUI_API ImVec2        GetMousePosOnOpeningCurrentPopup();                                 // retrieve backup of mouse positioning at the time of opening popup we have BeginPopup() into
     IMGUI_API ImVec2        GetMouseDragDelta(int button = 0, float lock_threshold = -1.0f);    // dragging amount since clicking. if lock_threshold < -1.0f uses io.MouseDraggingThreshold