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From: M. Soyka on 29 Jul 2010 20:42
Hello all,

I'm using the virtual event capability of Tk and noticed
an inconsistency in how Tk reports the event ID using the
%T descriptor. Specifically, I get one value when I use
mouse clicks to generate the event and another when I use
the "event generate" command.

To illustrate, consider the following code sequence:

canvas .c -width 100 -height 100
pack .c

event add <<V1>> <Double-Button-1>
bind .c <<V1>> {puts "mouse generates event Id %T"}

If you double-click in the canvas, you get the expected output
"mouse generates event Id 4"

Now change the bind to output a different message and invoke
event generate:

bind .c <<V1>> {puts "event command generates event Id %T"}
event generate .c <<V1>>

What comes out is:
"event command generates event Id 35"

So we have two different event IDs for the same virtual event.

I expected to see the same event ID so my question is why
is this correct or expected behavior?

Next, I noticed that "35" is one beyond the
highest-numbered X event ID and wondered if I were to
define an additional virtual event, would it generate 36.
Modifying the above code to use the right mouse button
instead of the left and proceeding exactly as above:

event add <<V3>> <Double-Button-3>
bind .c <<V3>> {puts "mouse generates event Id %T"}

"mouse generates event Id 4"

bind .c <<V3>> {puts "event command generates event Id %T"}
event generate .c <<V3>>

"event command generates event Id 35"

So the answer is no, it generates the same ID and leads
to two questions:

Q1. Why doesn't it generate 36?

Q2. How can a script that expects a %T argument and handles both
events distinguish between the two?

Thank you for the education I'm about to get!

Mike
From: Harald Oehlmann on 30 Jul 2010 02:41
Hello Mike,

On 30 Jul., 02:42, "M. Soyka" <mssr...(a)gmail.com> wrote:
> To illustrate, consider the following code sequence:
>
>      canvas .c -width 100 -height 100
>      pack .c
>
>      event add <<V1>>  <Double-Button-1>
>      bind .c <<V1>>  {puts "mouse generates event Id %T"}
>
> If you double-click in the canvas, you get the expected output
>      "mouse generates event Id 4"

When I read the docs of bind:
http://www.tcl.tk/man/tcl8.5/TkCmd/bind.htm#M51

The "Tag" %T is replaced by the event type.
In my understanding this should be "Button" in the upper example.
Why it returns 4 ? I don't know.

> event generate .c <<V1>>
>
> What comes out is:
> "event command generates event Id 35"

I suppose "35" is for virtual events.
The reason for the first event to fire was a Button-Event.
The reason for the second was an event generate on a virtual event.

If you do:
8 % event generate .c <Button-1>
9 % event generate .c <Button-1>
mouse generates event Id 4

Strange...

Sorry, no more knowledge on this side,
Harald
From: M. Soyka on 30 Jul 2010 07:05
On 7/30/2010 2:41 AM, Harald Oehlmann wrote:
> Hello Mike,
>
> On 30 Jul., 02:42, "M. Soyka"<mssr...(a)gmail.com> wrote:
>> To illustrate, consider the following code sequence:
>>
>> canvas .c -width 100 -height 100
>> pack .c
>>
>> event add<<V1>> <Double-Button-1>
>> bind .c<<V1>> {puts "mouse generates event Id %T"}
>>
>> If you double-click in the canvas, you get the expected output
>> "mouse generates event Id 4"
>
> When I read the docs of bind:
> http://www.tcl.tk/man/tcl8.5/TkCmd/bind.htm#M51
>
> The "Tag" %T is replaced by the event type.
> In my understanding this should be "Button" in the upper example.
> Why it returns 4 ? I don't know.

It is 4 because (I think) the X Window system defined button presses
to be event ID 4.
>
>> event generate .c<<V1>>
>>
>> What comes out is:
>> "event command generates event Id 35"
>
> I suppose "35" is for virtual events.
Seems plausible. Again, the X Window system defines event IDs up to
34 for events like "Enter", "Leave". I forget what #34 is but it makes
some sense that virtual events would be assigned 35 and up.
> The reason for the first event to fire was a Button-Event.
> The reason for the second was an event generate on a virtual event.
>
> If you do:
> 8 % event generate .c<Button-1>
> 9 % event generate .c<Button-1>
> mouse generates event Id 4
>
> Strange...
>
> Sorry, no more knowledge on this side,
> Harald

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