Tidying up BeginMenu() code + comments.

imgui.cpp

@@ -7034,8 +7034,9 @@ void ImGui::ClosePopupsOverWindow(ImGuiWindow* ref_window, bool restore_focus_to
             // Trim the stack when popups are not direct descendant of the reference window (the reference window is often the NavWindow)
             bool popup_or_descendent_is_ref_window = false;
             for (int m = popup_count_to_keep; m < g.OpenPopupStack.Size && !popup_or_descendent_is_ref_window; m++)
-                if (g.OpenPopupStack[m].Window && g.OpenPopupStack[m].Window->RootWindow == ref_window->RootWindow)
-                    popup_or_descendent_is_ref_window = true;
+                if (ImGuiWindow* popup_window = g.OpenPopupStack[m].Window)
+                    if (popup_window->RootWindow == ref_window->RootWindow)
+                        popup_or_descendent_is_ref_window = true;
             if (!popup_or_descendent_is_ref_window)
                 break;
         }

imgui_widgets.cpp

@@ -5947,31 +5947,36 @@ bool ImGui::BeginMenu(const char* label, bool enabled)
     if (menuset_is_open)
         g.NavWindow = backed_nav_window;
 
-    bool want_open = false, want_close = false;
+    bool want_open = false;
+    bool want_close = false;
     if (window->DC.LayoutType == ImGuiLayoutType_Vertical) // (window->Flags & (ImGuiWindowFlags_Popup|ImGuiWindowFlags_ChildMenu))
     {
+        // Close menu when not hovering it anymore unless we are moving roughly in the direction of the menu
         // Implement http://bjk5.com/post/44698559168/breaking-down-amazons-mega-dropdown to avoid using timers, so menus feels more reactive.
-        bool moving_within_opened_triangle = false;
-        if (g.HoveredWindow == window && g.OpenPopupStack.Size > g.BeginPopupStack.Size && g.OpenPopupStack[g.BeginPopupStack.Size].SourceWindow == window && !(window->Flags & ImGuiWindowFlags_MenuBar))
+        bool moving_toward_other_child_menu = false;
+
+        ImGuiWindow* child_menu_window = (g.BeginPopupStack.Size < g.OpenPopupStack.Size && g.OpenPopupStack[g.BeginPopupStack.Size].SourceWindow == window) ? g.OpenPopupStack[g.BeginPopupStack.Size].Window : NULL;
+        if (g.HoveredWindow == window && child_menu_window != NULL && !(window->Flags & ImGuiWindowFlags_MenuBar))
         {
-            if (ImGuiWindow* next_window = g.OpenPopupStack[g.BeginPopupStack.Size].Window)
-            {
-                // FIXME-DPI: Values should be derived from a master "scale" factor.
-                ImRect next_window_rect = next_window->Rect();
-                ImVec2 ta = g.IO.MousePos - g.IO.MouseDelta;
-                ImVec2 tb = (window->Pos.x < next_window->Pos.x) ? next_window_rect.GetTL() : next_window_rect.GetTR();
-                ImVec2 tc = (window->Pos.x < next_window->Pos.x) ? next_window_rect.GetBL() : next_window_rect.GetBR();
-                float extra = ImClamp(ImFabs(ta.x - tb.x) * 0.30f, 5.0f, 30.0f); // add a bit of extra slack.
-                ta.x += (window->Pos.x < next_window->Pos.x) ? -0.5f : +0.5f;    // to avoid numerical issues
-                tb.y = ta.y + ImMax((tb.y - extra) - ta.y, -100.0f);             // triangle is maximum 200 high to limit the slope and the bias toward large sub-menus // FIXME: Multiply by fb_scale?
-                tc.y = ta.y + ImMin((tc.y + extra) - ta.y, +100.0f);
-                moving_within_opened_triangle = ImTriangleContainsPoint(ta, tb, tc, g.IO.MousePos);
-                //window->DrawList->PushClipRectFullScreen(); window->DrawList->AddTriangleFilled(ta, tb, tc, moving_within_opened_triangle ? IM_COL32(0,128,0,128) : IM_COL32(128,0,0,128)); window->DrawList->PopClipRect(); // Debug
-            }
+            // FIXME-DPI: Values should be derived from a master "scale" factor.
+            ImRect next_window_rect = child_menu_window->Rect();
+            ImVec2 ta = g.IO.MousePos - g.IO.MouseDelta;
+            ImVec2 tb = (window->Pos.x < child_menu_window->Pos.x) ? next_window_rect.GetTL() : next_window_rect.GetTR();
+            ImVec2 tc = (window->Pos.x < child_menu_window->Pos.x) ? next_window_rect.GetBL() : next_window_rect.GetBR();
+            float extra = ImClamp(ImFabs(ta.x - tb.x) * 0.30f, 5.0f, 30.0f);    // add a bit of extra slack.
+            ta.x += (window->Pos.x < child_menu_window->Pos.x) ? -0.5f : +0.5f; // to avoid numerical issues
+            tb.y = ta.y + ImMax((tb.y - extra) - ta.y, -100.0f);                // triangle is maximum 200 high to limit the slope and the bias toward large sub-menus // FIXME: Multiply by fb_scale?
+            tc.y = ta.y + ImMin((tc.y + extra) - ta.y, +100.0f);
+            moving_toward_other_child_menu = ImTriangleContainsPoint(ta, tb, tc, g.IO.MousePos);
+            //GetForegroundDrawList()->AddTriangleFilled(ta, tb, tc, moving_within_opened_triangle ? IM_COL32(0,128,0,128) : IM_COL32(128,0,0,128)); // [DEBUG]
         }
+        if (menu_is_open && !hovered && g.HoveredWindow == window && g.HoveredIdPreviousFrame != 0 && g.HoveredIdPreviousFrame != id && !moving_toward_other_child_menu)
+            want_close = true;
 
-        want_close = (menu_is_open && !hovered && g.HoveredWindow == window && g.HoveredIdPreviousFrame != 0 && g.HoveredIdPreviousFrame != id && !moving_within_opened_triangle);
-        want_open = (!menu_is_open && hovered && !moving_within_opened_triangle) || (!menu_is_open && hovered && pressed);
+        if (!menu_is_open && hovered && pressed) // Click to open
+            want_open = true;
+        else if (!menu_is_open && hovered && !moving_toward_other_child_menu) // Hover to open
+            want_open = true;
 
         if (g.NavActivateId == id)
         {