Fixed assertion when transitioning from an active ID to another within a group, affecting ColorPicker (broken in 1.62). Made ActiveIdIsAlive track the actual ID to avoid incorrect polling in BeginGroup/EndGroup when the ID changes within the group. (#2023, #820, #956, #1875).

CHANGELOG.txt

@@ -63,6 +63,7 @@ Other Changes:
  - Misc: Added ImGuiMouseCursor_Hand cursor enum + corresponding software cursor. (#1913, 1914) [@aiekick, @ocornut] 
  - Misc: Tweaked software mouse cursor offset to match the offset of the corresponding Windows 10 cursors.
  - Made assertion more clear when trying to call Begin() outside of the NewFrame()..EndFrame() scope. (#1987)
+ - Fixed assertion when transitioning from an active ID to another within a group, affecting ColorPicker (broken in 1.62). (#2023, #820, #956, #1875).
  - Fixed PushID() from keeping alive the new ID Stack top value (if a previously active widget shared the ID it would be erroneously kept alive).  
  - Fixed horizontal mouse wheel not forwarding the request to the parent window if ImGuiWindowFlags_NoScrollWithMouse is set. (#1463, #1380, #1502)
  - Fixed a include build issue for Cygwin in non-POSIX (Win32) mode. (#1917, #1319, #276)

imgui.cpp

@@ -2271,7 +2271,7 @@ void ImGui::SetActiveID(ImGuiID id, ImGuiWindow* window)
     g.ActiveIdWindow = window;
     if (id)
     {
-        g.ActiveIdIsAlive = true;
+        g.ActiveIdIsAlive = id;
         g.ActiveIdSource = (g.NavActivateId == id || g.NavInputId == id || g.NavJustTabbedId == id || g.NavJustMovedToId == id) ? ImGuiInputSource_Nav : ImGuiInputSource_Mouse;
     }
 }
@@ -2322,7 +2322,7 @@ void ImGui::KeepAliveID(ImGuiID id)
 {
     ImGuiContext& g = *GImGui;
     if (g.ActiveId == id)
-        g.ActiveIdIsAlive = true;
+        g.ActiveIdIsAlive = id;
     if (g.ActiveIdPreviousFrame == id)
         g.ActiveIdPreviousFrameIsAlive = true;
 }
@@ -3934,7 +3934,7 @@ void ImGui::NewFrame()
     g.HoveredIdPreviousFrame = g.HoveredId;
     g.HoveredId = 0;
     g.HoveredIdAllowOverlap = false;
-    if (!g.ActiveIdIsAlive && g.ActiveIdPreviousFrame == g.ActiveId && g.ActiveId != 0)
+    if (g.ActiveIdIsAlive != g.ActiveId && g.ActiveIdPreviousFrame == g.ActiveId && g.ActiveId != 0)
         ClearActiveID();
     if (g.ActiveId)
         g.ActiveIdTimer += g.IO.DeltaTime;
@@ -3942,7 +3942,8 @@ void ImGui::NewFrame()
     g.ActiveIdPreviousFrame = g.ActiveId;
     g.ActiveIdPreviousFrameWindow = g.ActiveIdWindow;
     g.ActiveIdPreviousFrameValueChanged = g.ActiveIdValueChanged;
-    g.ActiveIdIsAlive = g.ActiveIdPreviousFrameIsAlive = false;
+    g.ActiveIdIsAlive = 0;
+    g.ActiveIdPreviousFrameIsAlive = false;
     g.ActiveIdIsJustActivated = false;
     if (g.ScalarAsInputTextId && g.ActiveId != g.ScalarAsInputTextId)
         g.ScalarAsInputTextId = 0;
@@ -13155,7 +13156,7 @@ void ImGui::EndGroup()
     // If the current ActiveId was declared within the boundary of our group, we copy it to LastItemId so IsItemActive(), IsItemDeactivated() etc. will be functional on the entire group.
     // It would be be neater if we replaced window.DC.LastItemId by e.g. 'bool LastItemIsActive', but put a little more burden on individual widgets.
     // (and if you grep for LastItemId you'll notice it is only used in that context.
-    if (!group_data.BackupActiveIdIsAlive && g.ActiveIdIsAlive && g.ActiveId) // && g.ActiveIdWindow->RootWindow == window->RootWindow)
+    if ((group_data.BackupActiveIdIsAlive != g.ActiveId) && (g.ActiveIdIsAlive == g.ActiveId) && g.ActiveId) // && g.ActiveIdWindow->RootWindow == window->RootWindow)
         window->DC.LastItemId = g.ActiveId;
     else if (!group_data.BackupActiveIdPreviousFrameIsAlive && g.ActiveIdPreviousFrameIsAlive) // && g.ActiveIdPreviousFrameWindow->RootWindow == window->RootWindow)
         window->DC.LastItemId = g.ActiveIdPreviousFrame;

imgui_internal.h

@@ -408,7 +408,7 @@ struct ImGuiGroupData
     float       BackupCurrentLineHeight;
     float       BackupCurrentLineTextBaseOffset;
     float       BackupLogLinePosY;
-    bool        BackupActiveIdIsAlive;
+    ImGuiID     BackupActiveIdIsAlive;
     bool        BackupActiveIdPreviousFrameIsAlive;
     bool        AdvanceCursor;
 };
@@ -637,8 +637,8 @@ struct ImGuiContext
     float                   HoveredIdTimer;
     ImGuiID                 ActiveId;                           // Active widget
     ImGuiID                 ActiveIdPreviousFrame;
+    ImGuiID                 ActiveIdIsAlive;                    // Active widget has been seen this frame (we can't use a bool as the ActiveId may change within the frame)
     float                   ActiveIdTimer;
-    bool                    ActiveIdIsAlive;                    // Active widget has been seen this frame
     bool                    ActiveIdIsJustActivated;            // Set at the time of activation for one frame
     bool                    ActiveIdAllowOverlap;               // Active widget allows another widget to steal active id (generally for overlapping widgets, but not always)
     bool                    ActiveIdValueChanged;
@@ -784,8 +784,8 @@ struct ImGuiContext
         HoveredIdTimer = 0.0f;
         ActiveId = 0;
         ActiveIdPreviousFrame = 0;
+        ActiveIdIsAlive = 0;
         ActiveIdTimer = 0.0f;
-        ActiveIdIsAlive = false;
         ActiveIdIsJustActivated = false;
         ActiveIdAllowOverlap = false;
         ActiveIdValueChanged = false;