Use Ctrl+/ as shortcut in Delphi program

Question

Is this even possible? Notepad++ for example does it, but simply trying to assign it to components like actions or menu items doesn't work. The event it is assigned to simply doesn't trigger.

So, I took my question to Google. Nada. Then, I tried stepping through the various shortcut functions, in this case TextToShortCut and ShortCutToText.

The first one, TextToShortCut, converts stuff like 'Ctrl+A' (a string) to the following 16bit value:

(uint)A | (uint)Ctrl

Works fine, mostly. However, I observed the following weirdness:

// Try converting back and forward...
TextToShortCut('Ctrl+/') = 16495

// That's incorrect. It should be:
Ord('/') or scCtrl = 16431

// Incorrect too
ShortCutToText(16495) = 'Ctrl+/'

// This is the shortcut the first line actually creates (Ctrl+o)
Ord('o') or scCtrl = 16495 // wut?

// Which is invalid, cause only caps are used
ShortCutToText(16431) = ''

What's going on here? For now, I believe the error lies in the final part of TextToShortCut: after handling the part before the + sign ("Ctrl" in this case), it will try to find a shortcut for the remaining part ("/"). However, in its current form the part after + must be a valid shortcut on its own too.

for Key := $08 to $255 do { Copy range from table in ShortCutToText }
  if AnsiCompareText(Text, ShortCutToText(Key)) = 0 then
  begin
    Result := Key or Shift;
    Exit;
  end;

So, because:

ShortCutToText('/') = 0 (failure)
MapVirtualKey('/',MAPVK_VK_TO_VSC) = 0 (failure)

... the loop fails to detect '/' as a valid shortcut.

Is this some VCL bug or am I missing something?

Here's a proof of concept (yes, I'm taking screenshots of code, but mashing this together with the Component Palette is faster than using this code directly):

Edit 1:

Edit 2:

Manually assigning 16431 to the menu item does not work.

Greatcoat

Works fine here. Although only on the / key that is part of the numpad. But then that's what npp does. Its restore zoom shortcut is mapped to Ctrl+Num / – Precipitation

Notepad++ uses the regular one (left of Shift on US International) for stepping to the beginning of the word at the caret too. – Greatcoat

Answer 1

If you assign an OnShortCut event handler to your menu's parent TForm, you will see that pressing Ctrl+/ results in a TShortCut value of 16575 from Menus.ShortCutFromMessage(), which is the function that the VCL uses internally when dispatching keystrokes for shortcut handling.

Both ShortCutToText(16495) and ShortCutToText(16575) return 'Ctrl+/', so lets break it down:

scCtrl = $4000
16495 = $406F
16575 = $40BF

Both shortcuts have the scCtrl flag present.

ShortCutToText($6F) and ShortCutToText($BF) both return '/'. This is because MapVirtualKey() returns the same scan code ($350000) for both virtual keys $6F (VK_DIVIDE) and $BF (VK_OEM_2 - the /? key for US keyboards).

When dispatching a shortcut, the VCL does exact comparisons of TShortCut values. So when you have 16495 assigned as your shortcut, it will not trigger because the system is reporting a shortcut of 16575 instead, even though they both map to Ctrl+/.

When I assign 16575 to the ShortCut property of a TMenuItem or TAction, pressing Ctrl+/ triggers the item, as expected.

So the trick is that the system is reporting a shortcut that uses the VK_OEM_2 virtual key for /, but you are expecting it to use the VK_DIVIDE virtual key instead.

Gordon

Answer 2

A simple investigation of Key from an OnKeyDown event handler shows two different kind of forward slashes:

• / on the numerical keypad = 111 (combined with CTRL = 16575)
• / next to the shift key = 191 (combined with CTRL = 16495)

It is not possible to create a single shortcut which responds to both.

But instead of setting the shortcut on the memu item, you could attach an action which has a SecondaryShortCuts property. Then use:

procedure TForm1.FormCreate(Sender: TObject);
begin
  Action1.ShortCut := 16575;
  Action1.SecondaryShortCuts.Add('Ctrl+/');
end;

Lubbi

There's always the SecondaryShortCuts property – Precipitation

I'm not trying to bind to both, I'm just trying to bind to the 191 one. Thanks for answering though. – Greatcoat

I'm just trying to bind to the 191 one. Why doesn't the question state that? Are we meant to guess? – Precipitation

@DavidHeffernan: I completely forgot about the existence of the Numpad version of / when I wrote it. Sorry about that. – Greatcoat

That's understandable. But your comment doesn't sound very grateful. Thanks for answering though. But what you did not like about the answer was really a result of that omission. I guess that's why I reacted. Sticking up for my fellow answerer!! – Precipitation