Padding of `wxMenu` and `wxMenuItem` is too small in high DPI

[taler21]

The padding of wxMenu and wxMenuItem doesn't seem to grow with DPI scaling.

At 100% DPI scaling:

At 200% DPI scaling:

At 300% DPI scaling:

I don't know if this can be fixed as the text editor of Windows (notepad.exe) has the same issue.

Platform and version information

• wxWidgets version you use: 3.2.6
• wxWidgets port you use: wxMSW
• OS and its version: Windows 10

[vadz]

AFAIK it's a Windows bug and there is indeed not much we can do about it (well, short of making all our menus owner-drawn), sorry.

I wonder if it's even possible to report bugs to Microsoft nowadays...

[taler21]

Theoretically, as a workaround, the undocumented message WM_UAHMEASUREMENUITEM mentioned in this comment could be used to adjust the sizes of menu bar menus and menu items.

In dark mode, the menu bar is already custom drawn. See 1bfdd58 (Use custom draw for the menu bar in dark mode, 2022-12-25).
So the workaround would be relatively simple for this case:

diff --git "a/src/msw/darkmode.cpp" "b/src/msw/darkmode.cpp"
index 7bfdfa0c9c..51a27992bb 100644
--- "a/src/msw/darkmode.cpp"
+++ "b/src/msw/darkmode.cpp"
@@ -534,6 +534,7 @@ namespace wxMSWMenuImpl
 // Definitions for undocumented messages and structs used in this code.
 constexpr int WM_MENUBAR_DRAWMENU = 0x91;
 constexpr int WM_MENUBAR_DRAWMENUITEM = 0x92;
+constexpr int WM_MENUBAR_MEASUREMENUITEM = 0x94;
 
 // This is passed via LPARAM of WM_MENUBAR_DRAWMENU.
 struct MenuBarDrawMenu
@@ -558,6 +559,13 @@ struct MenuBarDrawMenuItem
     MenuBarMenuItem mbmi;
 };
 
+struct MenuBarMeasureMenuItem
+{
+    MEASUREITEMSTRUCT mis;
+    MenuBarDrawMenu mbdm;
+    MenuBarMenuItem mbmi;
+};
+
 wxColour GetMenuColour(wxMenuColour which)
 {
     return wxDarkModeModule::GetSettings().GetMenuColour(which);
@@ -721,6 +729,36 @@ HandleMenuMessage(WXLRESULT* result,
                                   &textOpts);
             }
             return true;
+
+        case WM_MENUBAR_MEASUREMENUITEM:
+            if ( auto* const measureMenuItem = (MenuBarMeasureMenuItem*)lParam )
+            {
+                MEASUREITEMSTRUCT& mis = measureMenuItem->mis;
+
+                // Just a sanity check.
+                if ( mis.CtlType != ODT_MENU )
+                    break;
+
+                HWND hwnd = GetHwndOf(w);
+
+                WinStruct<MENUBARINFO> mbi;
+                if ( !::GetMenuBarInfo(hwnd, OBJID_MENU, 0, &mbi) )
+                {
+                    wxLogLastError("GetMenuBarInfo");
+                    break;
+                }
+
+                *result = w->MSWDefWindowProc(nMsg, wParam, lParam);
+
+                // Scale the horizontal padding of menu bar menus and the
+                // vertical padding of menu items with the DPI scaling factor
+                // as Windows doesn't do it.
+                if ( mbi.hMenu == measureMenuItem->mbdm.hmenu )
+                    mis.itemWidth += w->FromDIP(14) - 14;
+                else
+                    mis.itemHeight += w->FromDIP(6) - 6;
+            }
+            return true;
     }
 
     return false;

Unfortunately, adjusting the sizes of the menu bar menus via WM_UAHMEASUREMENUITEM alone is not enough to work around the issue also in light mode.
It seems that it would be necessary to custom draw the menu bar in light mode too. At least when the DPI scaling is greater than 100%.
Because if only the size of the menu bar menus is adjusted, their text will not be displayed centered.

[vadz]

Thanks for looking at this! Fixing it only for the dark mode is strictly better than leaving it wrong for both dark and light mode, so I guess the real question here is whether we want to make the menu bar always owner-drawn. I used to be categorically against it, as I was pretty sure that we'd start having problems due to doing this when some Windows version changes the menus in an incompatible way, but they haven't done it since a very long time — and, of course, we already do it anyhow in the dark mode. But it's not for nothing that we warn people that dark mode is experimental...

So still on the fence about this one. Any thoughts from the others?

[taler21]

If you want to avoid a custom drawn menu bar in light mode, only adjusting the sizes of the menu bar menus in this mode would be an option.
Left-aligned text in menu bar menus of correct size is, in my opinion, less bad than a padding that is much too small.
Such a partial workaround in light mode would at least somewhat improve the menu bar in high DPI.

[taler21]

I have created PR #25117 to improve the padding at high DPI, not only for dark mode but also for light mode.
Because, as I said before, left-aligned text in menu bar menus of correct size is less bad than a padding that is much too small.

[dsa-t]

Because, as I said before, left-aligned text in menu bar menus of correct size is less bad than a padding that is much too small.

I'm not sure that left-aligned text looks better than minimal padding. But also I don't use display scaling normally.