Nav: Fixed an assert in certain circumstance (mostly when using popups) when mouse positions stop being valid. (#2168) + adding a else block to make NavCalcPreferredRefPos() more explicit.

docs/CHANGELOG.txt

@@ -46,6 +46,7 @@ Other Changes:
   accidental alteration of window position. We now round the provided size. (#2067)
 - Nav, Focus: Fixed ImGuiWindowFlags_NoBringToFrontOnFocus windows not being restoring focus
   properly after the main menu bar or last focused window is deactivated.
+- Nav: Fixed an assert in certain circumstance (mostly when using popups) when mouse positions stop being valid. (#2168)
 - DragFloat: Fixed a situation where dragging with value rounding enabled or with a power curve 
   erroneously wrapped the value to one of the min/max edge. (#2024, #708, #320, #2075).
 - DragFloat: Disabled using power curve when one edge is FLT_MAX (broken in 1.61). (#2024)

imgui.cpp

@@ -2966,7 +2966,7 @@ static void ImGui::UpdateMouseInputs()
 
     // Round mouse position to avoid spreading non-rounded position (e.g. UpdateManualResize doesn't support them well)
     if (IsMousePosValid(&g.IO.MousePos))
-        g.IO.MousePos = ImFloor(g.IO.MousePos);
+        g.IO.MousePos = g.LastValidMousePos = ImFloor(g.IO.MousePos);
 
     // If mouse just appeared or disappeared (usually denoted by -FLT_MAX components) we cancel out movement in MouseDelta
     if (IsMousePosValid(&g.IO.MousePos) && IsMousePosValid(&g.IO.MousePosPrev))
@@ -6415,8 +6415,8 @@ void ImGui::OpenPopupEx(ImGuiID id)
     popup_ref.ParentWindow = parent_window;
     popup_ref.OpenFrameCount = g.FrameCount;
     popup_ref.OpenParentId = parent_window->IDStack.back();
-    popup_ref.OpenMousePos = g.IO.MousePos;
     popup_ref.OpenPopupPos = NavCalcPreferredRefPos();
+    popup_ref.OpenMousePos = IsMousePosValid(&g.IO.MousePos) ? g.IO.MousePos : popup_ref.OpenPopupPos;
 
     //printf("[%05d] OpenPopupEx(0x%08X)\n", g.FrameCount, id);
     if (g.OpenPopupStack.Size < current_stack_size + 1)
@@ -7093,13 +7093,20 @@ static ImVec2 ImGui::NavCalcPreferredRefPos()
 {
     ImGuiContext& g = *GImGui;
     if (g.NavDisableHighlight || !g.NavDisableMouseHover || !g.NavWindow)
-        return ImFloor(g.IO.MousePos);
-
-    // When navigation is active and mouse is disabled, decide on an arbitrary position around the bottom left of the currently navigated item
-    const ImRect& rect_rel = g.NavWindow->NavRectRel[g.NavLayer];
-    ImVec2 pos = g.NavWindow->Pos + ImVec2(rect_rel.Min.x + ImMin(g.Style.FramePadding.x*4, rect_rel.GetWidth()), rect_rel.Max.y - ImMin(g.Style.FramePadding.y, rect_rel.GetHeight()));
-    ImRect visible_rect = GetViewportRect();
-    return ImFloor(ImClamp(pos, visible_rect.Min, visible_rect.Max));   // ImFloor() is important because non-integer mouse position application in back-end might be lossy and result in undesirable non-zero delta.
+    {
+        // Mouse (we need a fallback in case the mouse becomes invalid after being used)
+        if (IsMousePosValid(&g.IO.MousePos))
+            return g.IO.MousePos;
+        return g.LastValidMousePos;
+    }
+    else
+    {
+        // When navigation is active and mouse is disabled, decide on an arbitrary position around the bottom left of the currently navigated item.
+        const ImRect& rect_rel = g.NavWindow->NavRectRel[g.NavLayer];
+        ImVec2 pos = g.NavWindow->Pos + ImVec2(rect_rel.Min.x + ImMin(g.Style.FramePadding.x * 4, rect_rel.GetWidth()), rect_rel.Max.y - ImMin(g.Style.FramePadding.y, rect_rel.GetHeight()));
+        ImRect visible_rect = GetViewportRect();
+        return ImFloor(ImClamp(pos, visible_rect.Min, visible_rect.Max));   // ImFloor() is important because non-integer mouse position application in back-end might be lossy and result in undesirable non-zero delta.
+    }
 }
 
 float ImGui::GetNavInputAmount(ImGuiNavInput n, ImGuiInputReadMode mode)

imgui_internal.h

@@ -687,8 +687,9 @@ struct ImGuiContext
     ImGuiInputSource        ActiveIdSource;                     // Activating with mouse or nav (gamepad/keyboard)
     ImGuiID                 LastActiveId;                       // Store the last non-zero ActiveId, useful for animation.
     float                   LastActiveIdTimer;                  // Store the last non-zero ActiveId timer since the beginning of activation, useful for animation.
+    ImVec2                  LastValidMousePos;
     ImGuiWindow*            MovingWindow;                       // Track the window we clicked on (in order to preserve focus). The actually window that is moved is generally MovingWindow->RootWindow.
-    ImVector<ImGuiColorMod>   ColorModifiers;                     // Stack for PushStyleColor()/PopStyleColor()
+    ImVector<ImGuiColorMod> ColorModifiers;                     // Stack for PushStyleColor()/PopStyleColor()
     ImVector<ImGuiStyleMod> StyleModifiers;                     // Stack for PushStyleVar()/PopStyleVar()
     ImVector<ImFont*>       FontStack;                          // Stack for PushFont()/PopFont()
     ImVector<ImGuiPopupRef> OpenPopupStack;                     // Which popups are open (persistent)
@@ -833,6 +834,7 @@ struct ImGuiContext
         ActiveIdSource = ImGuiInputSource_None;
         LastActiveId = 0;
         LastActiveIdTimer = 0.0f;
+        LastValidMousePos = ImVec2(0.0f, 0.0f);
         MovingWindow = NULL;
         NextTreeNodeOpenVal = false;
         NextTreeNodeOpenCond = 0;