MenuItem, BeginMenu: Fix undesirable tall frames in horizontal layout context, which would be visible when trying to use rounded selectable/menus.

PushStyleVar: Added comments in the assert message.
Minor tweaks.

imgui.cpp

@@ -6006,7 +6006,7 @@ void ImGui::PushStyleVar(ImGuiStyleVar idx, float val)
         *pvar = val;
         return;
     }
-    IM_ASSERT(0); // Called function with wrong-type? Variable is not a float.
+    IM_ASSERT(0 && "Called PushStyleVar() float variant but variable is not a float!");
 }
 
 void ImGui::PushStyleVar(ImGuiStyleVar idx, const ImVec2& val)
@@ -6020,7 +6020,7 @@ void ImGui::PushStyleVar(ImGuiStyleVar idx, const ImVec2& val)
         *pvar = val;
         return;
     }
-    IM_ASSERT(0); // Called function with wrong-type? Variable is not a ImVec2.
+    IM_ASSERT(0 && "Called PushStyleVar() ImVec2 variant but variable is not a ImVec2!");
 }
 
 void ImGui::PopStyleVar(int count)

imgui_widgets.cpp

@@ -5405,7 +5405,7 @@ bool ImGui::Selectable(const char* label, bool selected, ImGuiSelectableFlags fl
         bb.Max.x -= (GetContentRegionMax().x - max_x);
     }
 
-    if (flags & ImGuiSelectableFlags_Disabled) PushStyleColor(ImGuiCol_Text, g.Style.Colors[ImGuiCol_TextDisabled]);
+    if (flags & ImGuiSelectableFlags_Disabled) PushStyleColor(ImGuiCol_Text, style.Colors[ImGuiCol_TextDisabled]);
     RenderTextClipped(bb_inner.Min, bb_inner.Max, label, NULL, &label_size, style.SelectableTextAlign, &bb);
     if (flags & ImGuiSelectableFlags_Disabled) PopStyleColor();
 
@@ -5877,10 +5877,11 @@ void ImGui::EndMenuBar()
         {
             // To do so we claim focus back, restore NavId and then process the movement request for yet another frame.
             // This involve a one-frame delay which isn't very problematic in this situation. We could remove it by scoring in advance for multiple window (probably not worth the hassle/cost)
-            IM_ASSERT(window->DC.NavLayerActiveMaskNext & 0x02); // Sanity check
+            const ImGuiNavLayer layer = ImGuiNavLayer_Menu;
+            IM_ASSERT(window->DC.NavLayerActiveMaskNext & (1 << layer)); // Sanity check
             FocusWindow(window);
-            SetNavIDWithRectRel(window->NavLastIds[1], 1, window->NavRectRel[1]);
-            g.NavLayer = ImGuiNavLayer_Menu;
+            SetNavIDWithRectRel(window->NavLastIds[layer], layer, window->NavRectRel[layer]);
+            g.NavLayer = layer;
             g.NavDisableHighlight = true; // Hide highlight for the current frame so we don't see the intermediary selection.
             g.NavMoveRequestForward = ImGuiNavForward_ForwardQueued;
             NavMoveRequestCancel();
@@ -5930,7 +5931,7 @@ bool ImGui::BeginMenu(const char* label, bool enabled)
         // For ChildMenu, the popup position will be overwritten by the call to FindBestWindowPosForPopup() in Begin()
         popup_pos = ImVec2(pos.x - 1.0f - (float)(int)(style.ItemSpacing.x * 0.5f), pos.y - style.FramePadding.y + window->MenuBarHeight());
         window->DC.CursorPos.x += (float)(int)(style.ItemSpacing.x * 0.5f);
-        PushStyleVar(ImGuiStyleVar_ItemSpacing, style.ItemSpacing * 2.0f);
+        PushStyleVar(ImGuiStyleVar_ItemSpacing, ImVec2(style.ItemSpacing.x * 2.0f, style.ItemSpacing.y));
         float w = label_size.x;
         pressed = Selectable(label, menu_is_open, ImGuiSelectableFlags_NoHoldingActiveID | ImGuiSelectableFlags_PressedOnClick | ImGuiSelectableFlags_DontClosePopups | (!enabled ? ImGuiSelectableFlags_Disabled : 0), ImVec2(w, 0.0f));
         PopStyleVar();
@@ -6074,7 +6075,7 @@ bool ImGui::MenuItem(const char* label, const char* shortcut, bool selected, boo
         // Note that in this situation we render neither the shortcut neither the selected tick mark
         float w = label_size.x;
         window->DC.CursorPos.x += (float)(int)(style.ItemSpacing.x * 0.5f);
-        PushStyleVar(ImGuiStyleVar_ItemSpacing, style.ItemSpacing * 2.0f);
+        PushStyleVar(ImGuiStyleVar_ItemSpacing, ImVec2(style.ItemSpacing.x * 2.0f, style.ItemSpacing.y));
         pressed = Selectable(label, false, flags, ImVec2(w, 0.0f));
         PopStyleVar();
         window->DC.CursorPos.x += (float)(int)(style.ItemSpacing.x * (-1.0f + 0.5f)); // -1 spacing to compensate the spacing added when Selectable() did a SameLine(). It would also work to call SameLine() ourselves after the PopStyleVar().